Mo.'"'t.<o.l of

EQJ)INE FIE LD

SURGERY

Mc\~LAC\1 of

ECWINE FI E LD

SURGERY David A. Wilson, DVM

Associate Professor, Equine Surgery Department of Veterinary,Medicine and Surgery

University of Missouri Columbia, Missouri

Joanne Kramer, DVM Clinical Assistant Professor, Equine Surgery

Department of Veterinary Medicine and Surgery University of Missouri Columbia, Missouri

Gheorghe M. Constantinescu, DVM, PhD., Dr.h.c. Professpr, Anatomy

DepartrnentofBiomedical Sciences Ul'liversity of Missouri Columbia, Missouri

CHAPTER 1

Introduction David A. Wilson

"Chance favors the prepared mind." Louis Pasteur

This book is written for practitioners and veteri ­nary students attracted to and interested in equine surgery. Procedures are described and illustrated that can be performed in the field or basic prac­tice settings, require a minimum of additional equipment or assistance, generally take less than I hour of anesthesia, and do not involve entering a body cavity or joint. Although the procedures described in this book can be donf in the field by any qualified veterinarian, it is not the intention of this book to be the sole source of preparation or reference for the new or relatively inexperi­enced equine practitioner.

Performing surgery in the field has the poten­tial to be very rewarding but also the potential to be very unrewarding. If the procedure goes according to plan, the experience can be great. However, as with many things involving horses, there is a seemingly almost unlimited opportunity for fail ure. Preparation is the key to minimizing these opportunities for failure. A thorough under­standin g of the presenting problem, indicated surgical procedure, relevant anatomy, available facilities, equipment, and assistance, client expec­tations, and individual patient characteristics are important; these factors must be evaluated when considering surgery in the field.

With any surgical procedure, it is the responsi­bility of the surgeon to be thoroughly familiar with the pertinent anatomy as well as the poten­tial deviations from normal expected in health

2

and disease. Swelling and trauma can sign ificantly alter the anatomy such that previously well ­understood structures may be difficult to identify and in unexpected locations.

Once the anatomy is understood, the specific surgical procedure should be thoroughly reviewed. The surgeon should get in the habit of reviewing every procedure prior to performing the surgery to refresh the surgeon's memory of the specifics of the surgery. Equine practitioners are exposed to a wide range of disorders but do not often see many of anyone particular disorder. Therefore, it may be months or years between specific surgeries, and a procedure that was once very familiar may seem completely foreign after the first skin incision. Sur­gical procedures should be practiced on cadaver specimens prior to performing them for the first time on a client's animal. Practice surgeries on cadaver specimens to review the pertinent normal anatomy, confi rm the landmarks for the approach, and identify potentially difficult portions of the procedure and to develop familiarity with the particular instrument needs for the proposed surgery.

Practitioners or new graduates wanting to become more familiar with these procedures should consider working with or visiting an expe­rienced practitioner. In addition, many continu­ing education opportunities are available that provide in-depth reviews of these and similar pro­cedures. In particular, the annual meetings of the American College of Veterinary Surgeons and the American Association of Equine Practitioners are good sources of current surgical information.

CLIENT COMMUNICATION

Client communication is probably the most important factor in preventing misunderstand­ings and addressing problems when things do not go well. The owner (or trainer) should be informed of the options for therapy, costs, prog­nosis, potential complications and consequences, anticipated outcome, and recommendations prior to surgery. Ideally, this conversation should be with the person who will actually pay the bill and with the person responsible for the horse's care. However, in many insta nces in equine practke, the person paying the bill may not be available. Keeping good written notes of conversations and estimates and providing written discharge instructions concerning aftercare is essential. Ali communications should be as realistic and honest as possible. Clients must be warned of the poten­tial complications and expected outcome. General complications such as the development of rhab­domyolysis or colitis seen in horses stressed by transportation, anesthesia, and surgery should be communicated to the owner when appropriate. The specific complications associated with the procedure to be performed should also be dis­cussed. However, overstating the difficulty of the recommended surgery or the gravity of the poten­tial consequences to minimize client expectations is inappropriate.

INSURANCE

When contemplating surgery on an insured horse, the veterinarian should be aware that it is the client's responsibility to inform the insurance company of a pending su rgical procedure, partic­ularly for an elective procedure. which is the case for most procedures covered in this book. The veterinarian may choose to contact the insurance company, but it is the client's responsibility. The insurance company will then make a decision about whether to cover the an imal for the proce~ dure. These deliberations are between the owner and the company, but the veterinarian may be drawn into the process when decisions regarding treatment options, prognosis, and euthanasia are considered. Because of potential conflicts of inter­est, guidelines for those si tuations are available from the American Association of Equine Prac ti ­tioners Equine Insurance Committee. l

Introduction 3

DECISION FOR SURGERY

The decision to perform surgery on a specific case can be difficult. Is the surgery necessary? What are the best- and worst-case scenarios for a present­ing problem or specific procedure? The decision is complicated by adding the field scenario into the equation. The temperament of the horse, the potential surgical environment (i.e., facilities, terrain, weather, etc.), the availability of needed equipment, the availabil ity of trained assistants, the expectations of the client, the skill of the surgeon, and the ability to handle unforeseen developments aU enter into the decision. Certainly many clients have excellent facilities; however, there are other clients with facilities where field surgery may be a greater adventure than anyone needs. After considering the factors for a given cir­cumstance, the surgeon must decide whether to perform a particular procedure.

PATIENT EVALUATION

A thorough history should be gathered on all horses presented for elective surgery. Previous treatments, responses to treatment, potential ad­verse reactions to previously administered med­ications, and the genetic background (e.g., the potential for developing hyperkalemic periodic paralysis) should all be reviewed.

A thorough physical examination should be performed, concentrating on the rest of the animal prior to focusing on the potential reason for surgery. Blood should be submitted for evalu­ation including a complete blood cell count or at least a packed cell volume and total protein deter­mination prior to the time of the surgery. Serum chemistry evaluations are desirable but are not always necessary for elective procedures. If the horse's physical condition or laboratory values are abnormal, elective procedures should be postponed.

PATIENT PREPARATION PRIOR TO SURGERY

For most elective procedures, feed should be with­held about 6 hOllrs prior to surgery. Water should be allowed ad libitum. Withholding feed for up to 72 hours can be tolerated for elective proce­dures. However, it should be recognized and

4 PRESURGICAL PREPARATION AND ASSESSMENT

communicated to the owner that withholding feed will alter gastrointestinal flora and predispose the horse to colitis.

Tetanus vaccination status of the patient should be assessed and, if necessary, a tetanus booster should be administered. If the patient has never received tetanus toxoid and the surgery is an elective procedure, the procedure should be delayed until appropriate tetanus prophylaxis is established. Patients that have not received tetanus toxoid within the past 6 months, but are on a con­tinuing immunization program, should receive a tetanus booster.

Prophylactic and therapeutic antibiotics should be judiciously administered. When indi­cated, antibiotics should be administered imme­diately prior to surgery at the correct dosage and for the correct amount of time but should be dis­continued as soon as possible after surgery.

When possible, the surgical site should be clipped (size 40 clipper blades) and prepped before (within 2 hours) induction. Over smooth areas, the hair may be shaved with a disposable razor. A wide area surrounding the anticipated surgery site should be clipped and scrubbed in

order to be prepared for the unanticipated need to expand the surgical site.

Immediately prior to the operation, the pro­posed surgical site should undergo a surgical scrub consisting of at least 5 minutes' exposure to either povidone-iodine 7.5% surgical scrub (Betadine surgical scrub) or chlorhexidine glu­conate 4% antimicrobial skin cleanser (Hibiclens; Zeneca Pharmaceuticals Inc. , Wilmington, Del.). The final surgical preparation consists of alter­nating 70% alcohol or isotonic saline rinse with the surgical scrub using aseptic technique. Rinsing with saline or 70% isopropyl alcohol does not make a difference in the antimicrobial effect of povidone­iodine; however, alcohol reduces the residual effect and antiseptic quality of chlorhexidine.'

REFERENCES

I. American Association of Equine Practitioners: The veterillary role ill equille insurallce, Lexington, Ky, 2000, AAEP.

2. Stashak TS: Selected factors that affect wound healing. In Stashak TS, editor: Equine wound mall­

agement, Philadelphia, 1991, Lea & Febiger.

CHAPTER 2 •

Surgical Instruments David A. Wilson

This chapter serves as a reference for the various surgical instruments referred to throughout the book. The equine surgeon should become famil­iar with the instruments, how they handle, what procedures they should and should not be used for, and when they should be used. Using the right instrument at the right time is essential to good surgical technique. Selecting the appropriate instrument ensures minimal trauma to tissues and that the procedure will be performed in the least amount of time with the least harm to the patient. Handling the instruments in practice cadaver or laboratory settings is essential to become proficient enough to handle them effec­tively in surgical situations.

INSTRUMENTS

Scalpel blades used for the No.3 scalpel handle are sizes 10, II , 12, and 15 (Figure 2-1). Scalpel blade sizes 20, 21, and 22 are made for the No.4 scalpel handle (Figure 2-2). The No. 10 blade on a No.3 Bard-Parker handle is used for most equine su r­gical procedures. However, the No. 11 and No. 15 blades are useful when very precise or small inci­sions are required. The sharp tip on both the No. II and No. 12 blades is useful for lancing abscesses. Typically, the scalpel handle is held between the thumb and the third and fourth fingers, with the index finger placed over the back of the handle to apply pressure on the blade. When using the No. II and No. 15 blades, the

5

scalpel handle is usually held in a "pencil-grip" fashion to allow for finer motor control. The No. 4 handle and its associated blades are used for larger areas where precision is not a major concern.

Scissors

Many types of scissors are available depending on the job to be performed. These include scissors designed to cut various types of tissue and scis­sors designed to cut suture, wire, or bandage material. Operating scissors are classified accord­ing to the shape of the tips, for example, sharp­sharp, sharp-blunt, and blunt-blunt (Figure 2-3). When using the appropriate scissors, the tip of the scissors is used to cut tissue, the tip or body is used to cut sutures) and the heel is used to cut wire.

Metzenbaum scissors are relatively delicate and are made for precise dissection, whereas Mayo scissors are made for tissues with more substance. Mayo and Metzenbaum scissors are available with straight or curved blades. The straight blades are designed for working close to the surface of the wound, and the curved scissors are used for working deeper in the wound (Figu re 2-4). For blunt dissection, the closed tips of the scissors are inserted into the ti ssue and then opened to spread the tissue. Tissue scissors should not be used to cut suture or wire.

Bandage scissors are designed with angled blades, and the lower blade has a small "button" tip to protect the underlying structures and

6 PRESURGICAL PREPARATION AND A SSESSMENT

to allow easy entry under bandage material (Figu re 2-5) . If bandage scissors are used against contaminated wounds, the scissors should be sterilized after use to prevent transfer of infec­tion.

10 11 12 128 15 15C

Figure 2~ 1 Scalpel blades that fit the No.3 Bard­Parker handle. (Reprinted with permission from Miltex Instrument Company, Bethpage, N.Y., 2004. )

,

, ,

I ) 20 23 "

A B Figure 2·2 A, Bard-Parker No.4 handle. B, Va rious

shapes of scalpel blades that fit the No.4 scalpel handle. (Reprinted with permiss ion from Miltex Instrument Company. Bethpage. N.Y .• 2004. )

Needle Holders

The two primary types of needle holders used in large animal practice are the Mayo-Hegar and Olsen-Hegar needle holders (Figure 2-6). The Olsen-Hegar needle holders have a suture-cutting scissors built into the jaws, enabling the surgeon to cut suture without reaching for the suture-cutting scissors. A variety of other options for needle holders are available depending on the preference of the surgeon and the size of needle being held.

Thumb Forceps

Thumb fo rceps are used for grasping and holding tissues (Figure 2-7). Typically, the forceps are held in a "pencil" grip. Many types are available, and the selection is based on the type of tissue involved. Toothed fo rceps are commonly llsed for stabilization of tissue such as skin, fascia , or muscle while suturing. Theoretically, the presence of teeth on these forceps makes the grip required to hold the tissue less forceful than if there were no teeth, resulting in less tissue trauma. Fo rceps are often classified based on the number of inter­locking teeth on each head. For example 1 x 2 indicates there are two teeth on one side of the fo rceps and one on the other. The higher-number teeth are generally used for more robust tissues. Nontoothed forceps generally have ridges or grooves on the surface of the tip and are used for grasping visceral and serosal or adventitial tissues as the lack of teeth decreases the likelihood of puncture.

Hemostatic Forceps

Hemostatic forceps are primarily used to clamp the ends of vessels to establish hemostasis. Halstead mosquito forceps are used for clamping smaiJ vessels (Figure 2-8, A). Kelly forceps are used for clamping larger vessels and as a grasping forceps to hold tissue or stay sutures for manipulation

Figure 2-3 Operating scissors. (From Sonsthagen TF: Veterinary illstrllll1ellts alld

equipmel1t: a pocket guide, St Louis, 2006, Elsevier Inc.)

Sharp/sharp Sharplblunt BlunVbluntSharp/sharp Sharplblunt Blunt/blunt straight straight straight curved curved curved

A B c Figure 2-4 A. Straight Mayo scissors. S, Curved Mayo scissors. C, Curved Metzenbaum scissors. (Reprinted with permission from Miltex Instrument Company. Bethpage. N.Y .• 2004.)

Figure 2-5 Liste r bandage scissors. (From Sonsthagen TF: Veter;'lary imtrulllents and equipment: a pocket gil ide, St Louis, 2006, Elsevier Inc. )

Figure 2-8 A, Halstead mos­quito forceps. B, Kelly forceps. C. Crile fo rceps. (Reprinted with permission from Miltex Instru ­ment Company. Bethpage, N.Y., 2004.)

Yo

A

Surgicailnstruments 7

A B Figure 2-6 A, Mayo-Hegar needle holders. B, Olsen­Hegar needle holders. (Reprinted wi th permiss ion from Miltex Instrument Company, Bethpage. N.Y., 2004. )

~ " • • VI W •• ! Yo ,.

r;; •

2

@

<i!> ,

A B c Figure 2-7 Forceps. A. Brown-Adson forceps. B. Tissue forceps. C, Adson fo rceps. (Reprinted with per­mission from Miltex Instrument Company, Bethpage, N.Y .• 2004.)

Yo

B c

8 PRESU RGICAL PREPARATION AND ASSESSMENT

(Figure 2-8, B). When curved forceps are used, they should be applied such that the tip of the forceps is pointing upward.

Grasping Forceps

A variety of forceps with a ratchet device built into the handle are used to grasp. retract, or stabilize larger portions of tissue. Allis tissue forceps are probably one of the more common graspillg forceps (Figure 2-9). They have opposing edges with short teeth and relatively long "arms" and are used to grasp fasc ia, subcutaneous tissue, skin. tendon, etc. Because of their short teeth and

Figure 2-9 Al lis forceps. (Reprinted with permiss ion from Miltex Instrument Company, Bethpage. N.Y., 2004. )

i~

I

..... A B c D

potential for trauma, they should not be used on skin or viscera intended to remain with the patient. Sponge forceps are used to hold gauze or other sponges to blot tissues dry from blood or other fluid during dissection (Figure 2-10).

Retractors

Retractors are essential for the display of deep tissues during an operation. They may be hand­held or self-retracting. The retractors work by placing a blade in front of tissues that would oth­erwise reduce the visibility of the operative field (Figures 2-11 to 2-13). Great care must be taken

Figure 2·10 Forester sponge-holding forceps. (From Sonsthagen TF: Veterinary iflStrtlmellts alld equipmelll: a pocket guide, St Louis. 2006, Elsevier Inc.)

!

E

Figure 2-11 Finger-held retractors. A, Senn retractor. B, Mathieu retractor. C, Meyerding finger retractor with various blades for gripping (shown ver­ti cally). D, Farabeuf retractor. E, Parker retracto r. (Reprinted with permiss ion from Miltex Instrument Company, Bethpage, N.Y., 2004. )

f

I ~

10 b

B

o o c

, • •

.-

D

Surgical Instruments

• • • •

9

Figure 2-12 Hand-held retractors. A, Army-Navy retractor. B, Hohmann retractor wi th two different blades. C, Meyerding retractor. D, Ribbon maUeable retractor. (Reprinted with permission from Miltex Instrument Company, Bethpage, N.Y .. 2004.)

to ensure that damage is not caused to the struc­tures being retracted.

General Pack for Field Surgery

Box 2- J lists the contents of a typical general pack for field surgery. Throughout the remainder of the book, only the instruments needed in addi­tion to these are listed in the description of the procedure.

INSTRUMENT PREPARATION

Most of the procedures described in this book are classified as "clean" elective surgical proce­dures. Therefore, the instruments used should be wrapped and sterilized. Before sterilization, instruments are thoroughly cleaned, paying particular attention to box locks, hinges, and serrations, and disassembling instruments with multiple components. Common sterilization techniques include autoclaving, gas sterilization, plasma sterilization, and cold sterilization. Auto­c1aving, a technique using moist heat from steam, is the sterilization method of choice for preparing instruments for aseptic surgery. An indicator is placed in the pack with the instruments and should be checked by the surgeon to confirm the sterility of the instruments. The high heat and humidity effectively sterilize most instruments, but some surgical instruments and equipment

with delicate or heat-sensitive components cannot endure such an environment.

Gas sterilization usin g ethylene oxide is used for instruments that may be damaged by the heat of autoclaving. However, ethylene oxide produces noxious fumes that require special venting and

Figure 2-13 Self-retaining retractors. A, Weitlaner retractors. B, Gelpi retractors.

A

B

10 P RESURGICAL PREPARAT ION AND ASSESSM ENT

BOX 2-1

Contents of a Typical General Pack for Field Surgery

4 Towel clamps 2 Needle holders (Mayo-Hegar or Olsen-Hegar) I Brown-Adson thumb forceps I Rat tooth forceps (2 x 3 or I x 2) 2 Straight mosquito forceps (straight or curved) 2 Kelly forceps (straight or curved) 1 Suture scissors I Curved Metzenbaum scissors I Curved Mayo scissors I Straight Mayo scissors 2 Carma It or Oschsner forceps I NO.3 scalpel handle 30 Gauze sponges I Hand towel

Other Useful Equipment Battery-operated headlight or other light source Knee pads Glue to help hold drapes in place Ropes to assist in limb positioning Small fold-up camping table on which to place

instruments Towels

extensive aeration fo r at least 14 hours before the piece of equipment can be used again.

Hydrogen peroxide gas plasma is the latest tech­nique for low-temperatu re «50°C), low-moisture sterilization of sensitive surgical products. 1t is

suited for sterilizing heat- and moisture-sensi tive instruments and instruments with sharp edges. Major advantages of this technique include a ster­ilization time as short as 55 minut~s and the pro­duction of no toxic residuals requiring aeration to comply with Occupational Safety and Health Administration (OSHA) safety regulations.

Cold (chemical) sterilization, using a product such as gluta raldehyde, provides a high level of disinfection but does not achieve sterili zation. Minimum immersion time for disinfection with glutaraldehyde is approximately 45 minutes. Cold sterilization is commonly used by the large animal surgeon for a second or third surgery of the day when other methods of sterilization are not avail ­able. Solutions used for cold steril ization can be very irritating to tissues. Therefore, care should be taken to thoroughly rinse or immerse the instru­ments in sterile saline before use to avoid potential ti ssue damage. Specific sterilization protocols can be developed fo r you r practice by consulting further references and manufacturers' recommendations.1.2

REFERENCES

l. Freeman DE: Ster ili zation and antiseptics. In Auer JA, Stick lA, ed itors: Equine surgery, ed 2, Philadel­phia, 1999, WB Saunders.

2. Southwood LL, Baxter GM: Instrument steril ization, skin prepa ration, and wound management, Vet Ciill N Am Equine Pract 12: 173, 1996.

CHAPTER 3

Wound Closure David A. Wilson

The principles of wound closure are similar whether closing a surgical incision or a laceration. Primary closure relies on a clean field, with clean and viable wound margins and skin edges for closure. When presented with a naturally occur­ring wound, there are many factors to consid~r, but the primary objectives are to preserve the life of the patient, to determine the extent of the wound, and to prevent or minimize infection.

A minor wound should not divert attention from more serious problems, such as hemorrhagic shock, exhaustion, or cerebral contusion associ­ated with head injuries. Thus, a quick assessment of the wound should be followed by a thorough physical examination and acquisi tion of pertinent vital signs. After initial stabilization and control of bleeding, attention should be directed at deter­mining the extent of the wound and returning the patient to a normal functional and cosmetic status with the shortest delay possible.

Wounds should be thoroughly evaluated to determine their extent. Wounds over synovial st ructures such as joints or tendon sheaths are common in horses, and the involvement of these structures is often unrecognized. Tendons and lig­aments, vessels and nerves, and the eyes, sinuses, thorax, and abdomen are other structures com­monly involved in equine wounds. Thinking in three dimensions and understanding the three­dimensional anatomy of the involved structures will help the practitioner to recognize the poten­t ial extent of the injuries and to better prepare the owner for the potential problems associated with the wound.

11

WOUND PREPARATION

The objective in wound preparation is to reduce the contamination of a wound and to obtain a "clean" field. Infection is the most important factor in delaying wound healing. Infections are classified as primary, in which the contamination occurs at the time of injury, or secondary, in which the contamination occurs through the suture line or through other portals (i.e. , drai.ns, fistulas).

Before wound preparation, the wou nd should be protected by placing sterile, water-sol uble lubricating jelly or sterile moist gauze sponges into the wound. A wide area of hair around the wound shou ld be clipped. To prevent hair from falling into the wound, the hair may be dampened with water or lightly coated with a sterile, water­soluble lubricating jelly. Sponges used to pack the wound should be discarded and replaced by new ones after each stage of preparation. The wound bed itself should be gently cleansed with antisep­tic soap and sterile gauze sponges, followed by copious lavage to neutralize the detergent base of the antiseptic. The clipped area should be scrubbed at least three times with antiseptic soap and rinsed between scrubs with sterile 0.9% saline solution.

Antiseptics for Skin Preparation

The two most commonly used surgical scrubs for skin preparation are povidone-iodine and

12 PRESURGICAL PREPARATION AND ASSESSMENT

chlorhexidine. Although uncommon, one disad­vantage of povidone-iodine is a skin reaction, which seems to be more frequent after clipping, scrubbing, rinsing with 70% alcohol, spraying with povidone-iodine solution, and bandaging. Detergent forms of chlorhexidine should not be used around the eye) because exposure may lead to corneal edema and bulbous keratopathy.l-J

The mechanical effect of scrubbing the wound with these antiseptic soaps is helpful in removing debris and reducing bacterial concentration at the wound surface. A marked delay in wound healing occurs if the soap is not thoroughly rinsed from the wound. Additionally, even though these anti­septics are effective, much of the bacterial popu­lation in the skin resides in protected hair follicles) sebaceous glands) and crevices in the lipid coat of the superficial epithelium.

WOUND LAVAGE

Bacteria adhere to the wound surface by an elec­trostatic charge. Lavage cleans the wound of debris and reduces the bacterial numbers, inflam­matory mediators, and substances that potentiate infection . In addition, lavage stimulates periph­eral microcirculation through its gentle massag­ing action, which may favor the formation of granulation tissue. Lavage is easy to perform, requires no special equipment, is cost effective, and is well tolerated by most patients.

Lavage solutions are most effective when deliv­ered by a fluid jet of at least S psi: Pressures of 10 to IS psi are approximately SO% effective in removing substances that potentiate infection and adherent bacteria from a wound.s Although this pressure cannot be achieved by gravity flow or lavage with a bulb syringe, adequate pulsatile pressure can be attained by forcefully expressing lavage solutions from a 35- or 60-mL syringe through an IS-gauge needle or by using a spray bottle or a WaterPik. The WaterPik delivers 40 to 50mL/min at 10 to 15 psi at the low-intermediate setting and is effective for heavily contaminated wounds. Care must be taken not to drive conta­minants deeper into the wound or inadvertently separate loose fascial planes.

The ideal lavage solution should be sterile, iso­tonic, normothermic, nontoxic, and compatible with antibiotic or disinfectant medications that may be added. Isotonic crystalloids, such as

-

normal saline or lactated Ringer's solution, meet these criteria and are the most commonly used solutions. Tap water is often used initially to reduce gross contamination in heavily contami­nated wounds. In these cases, subsequent lavage with sterile isotonic fluid may help restore tissue normotonicity and reduce edema.

Wound lavage should also be considered for closed wounds. The advantages of flushing a closed wound include the dilution and mobiliza­tion of exudates and the delivery of medication. The disadvantages are that bacteria can be readily introduced into the wound and dead space may be created or expanded.

WOUND DEBRIDEMENT

The goal of debridement is to obtain fresh, clean wound margins and skin edges for primary closure and to remove contaminated tissues and foreign material so that wound healing can progress effi­ciently during second-intention healing.

Debridement involves the removal of dead or damaged tissue, foreign bodies, and bacteria that compromise local defense mechanisms. Liberal removal of contaminated fascia, fat, and muscle and careful retention of bone, tendons, nerves, and major vessels are important. Fascia, fat, and muscle all have excellent blood supply and provide excellent media for the growth of conta­minating organisms. Although skeletal muscle is not replaced, there are usually sufficient remain­ing muscle fibers or alternative muscle groups available to make up for the loss. Small pieces of bone that have lost their blood supply should be removed.

Surgical Debridement

Surgical debridement may be accomplished in a variety of ways (en bloc, layered, or staged). En bloc resection is probably the most effective method of surgical debridement but may result in the loss of some viable tissue. With this technique, the entire wound is excised at its niargins such that all wounded and contaminated tissue is removed. This method is primarily reserved for draining tracts and areas where significant tissue loss can occur without consequence. With layered debridement, tissue removal is started at the most superficial tissue layer and is continued into the

depths of the wound. This systematic approach helps to prevent contamination of deeper tissues with debris from more superficial layers as debridement progresses and preserves viable tissue. Staged debridement is a method of layered debridement that minimizes tissue loss. In most equine distal limb wounds, where tissue is at a premium, staged debridement is used over a number of days to avoid inadvertent removal of viable tissue. When performing staged debride­ment, the two governing criteria are color and attachment. White, tan, black, and green tissues, as well as those that are poorly attached, should be debrided. Tissues that are pink to dark pur­ple and well attached should be left in place. Non-surgical methods of wound debridement include chemical or enzymatic debridement, laser debridement, bandaging techniques, or biosur­gical therapy. These techniques are discussed elsewhere.6

WOUND CLOSURE

Priorities during wound closure are to limit in­fection or contamination, minimize skin loss, and exert the least amount of tension possible on the suture line. Ideally, wounds are managed by primary closure. Wounds most amenable to primary closure include those of the head and upper body, flap wounds with a good blood supply, and recent minimally contaminated wounds of the extremities. Wounds with considerable skin loss, or severe contamination or infection, should not be closed initially. These may be closed later using delayed primary or secondary closure techniques or allowed to heal by second intention.

Primary closure, leading to first-intention healing, is performed after surgery or soon after injury. Ideally, primary closure is performed during the golden period. The golden period relates to the time required for multiplying bacte­ria to reach an infective level, considered to be 106

organisms per gram of tissue. Theoretically, this time period is 6 hours. In actuality, this may be longer in clean wounds and considerably shorter in severely contaminated wounds. Primary clo­sure is best used for fresh, minimally contam­inated wounds with a good blood supply without involvement of vital structures.

Delayed primary closure is performed 3 to 5 days <lfter iniurv when h r of 'nfi ia

Wound Closure 13

controUed by the inflammatory and debridement phases of healing but prior to granulation tissue formation. Delayed primary closure is best used for contaminated, contused, or swollen wounds and for those involving a synovial structure. It is particularly useful in distal limb wounds, where contamination is a frequent problem.

Delayed secondary closure is performed more than 5 days after injury, once granulation tissue has begun to form . As with delayed primary closure, delayed secondary closure is used after several days of therapeutic care for contaminated wounds with compromised blood supply. At the time of closure, the granulation tissue is removed to allow apposition of skin edges. This may result in sign ificant dead space o r oozing of blood and serum. Drains may be necessary to minimize the accumulation of serum within the wound.

Second-intention healing consists of fibropla­sia followed by wound contraction and epithel ial­ization. Indications for second-intention healing include severe contamination or infection, con­siderable skin loss, excessive skin tension that pre­cludes primary closure, and unavoidable motion like that occurring in the pectoral and gluteal regions. Second-intention healing is best used for wounds not over a joint surface, those with an adequate vascular supply to the underlying soft tissues, and those with sufficient mobile skin to allow wound contraction.

SUTURE MATERIAL

Suture material selection should be based on the biologic and physical properties of the suture, the wound environment, and the tissue response to the suture (Table 3-1). The characteristics of the ideal suture include good handling quality; good knot security; adequate tensile strength; lack of allergenic, electrolytic, capillary, or carcinogenic properties; minimal tissue reaction; no adverse effects on a wound in the presence of infection; easily sterili zed; economical; and absorption soon after the suture has served its purpose.

The suture material with the best handling characteristics is silk, which, with respect to handling, sets the standard by which all other suture materials a re compared. Generally, the braided, multifilament synthetic sutures have

• • 1 r ) n m -

TABLE 3-1

Characteristics of Commonly Used Suture Materials

TRADE

GENERIC NAME NAME FILAMENT SOURCE

Absorbable Polyglactin 910 Vicrylt Multi Glycolic-lactic acid

polymer

Polyglycolic acid Dexonf Multi Glycolic acid

Polydioxanone PDS li t Mono Polydioxanone polymer

Polyglyconate Maxon t Mono Glycolic acid-polytrimethylene carbonate

Poliglecaprone 25 Monocrylt Mono Copolymers of epsilon-caprolactone and glycolide

Chromic catgut Multi Submucosa of ovine intestine or serosa of bovine intestine

PERCENT LOSS OF TENSILE STRENGTH

14 DAYS

35-50

35-60

15-25

30

70

21

DAYS

60-80

65-90

30-40

45

100

Variable

COMPLETE FOREIGN

ABSORPTION MODE OF BODY

( DAYS) DEGRADATION RESPONSE

60-70 Hydrolysis Slight

120 Hydrolysis Slight

180 Hydrolysis Slight

180 Hydrolysis Slight

110 Hydrolysis Slight

90+ Enzymatic Inflammatory

No. OF

THROWS

FOR GOOD

KNOT

SECURITY*

3

3

4

4

5

3

SIZE-

STRENGTH RATIO

Good to excellent

Good to excellent

Excellent

Excellent

Excellent

Poor

-...

"0

" m ~

C

" " -() > r "0

" m ~

" ~ -o z > z o > ~ ~ rn ~ ~ • m Z -;

•

Nonabsorbable Silk Multi Raw silk spun by

silk worm

Polymerized Supramid or Multi Polyamide strands caprolactum Braunamid enclosed in a

polyamide sheath

Stainless steel Mono Chromium nickel molybdenum

Polyester Mersilene' Multi Synthetic resin polymers (extruded)

Nylon Ethi lon' Mono Polyamide filament (extruded)

Polypropylene Prolene' Mono Polymerized polyolefin hydrocarbons (extruded)

,. An additional throw is recommended for con tinuous patterns.

tEthicon, Inc, Somerville. N.J. :j:Davis & Geck, Inc, American Cyanamid Co, Manati, Puerto Rico. NA, not applicable.

>80% in Variable Proteolysis 8 days

NA NA NA

NA NA NA

NA NA NA

30% in NA Chemical 2 years degradation

NA NA NA

Moderate 3

Moderate 5

Inert 2

Moderate 5

Minimal 4

Minimal 3

•

Poor

Good

Excellent

Excellent

Good

Fair to good

~ ~ ~ 0.

n :. ~

;;;

-'"

16 PRESURGICAL PREPARATION AND A SSESSMENT

ment sutures. Stainless steel has the worst han­dling properties.

The number of throws necessary to secure a square knot varies with the size and type of suture material. In general, multifilament sutures have better knot security than do monofilament sutures. Stainless steel has the best knot securi ty. Also, the smaller the suture, the more secure is the knot. For example, No. 2-0 polyglycolic acid suture material has better knot security than does No. 2 polyglycolic acid suture material.

The suture material should be as strong as the tissue in which it is placed. Skin and fascia are rel­atively strong, whereas fat and muscle are rela­tively weak. In traumatic wounds, the tissue immediately surrounding the wound may be compromised. Therefore, the wound margins should be debrided, if possible, to clean healthy tissue and the sutures should be placed back from the wound margins to ensure that the sutures are placed in the healthiest tissue. The strength of a sutured wound is usually dependent on both the tissue's ability to hold suture and the tensile strength of the suture material. With healthy tissue, the initial strength of the sutured wound is dependent on the strength of the suture; however, by 3 to 4 days, the repaired tissue starts to increase in strength.

All suture materials potentiate infection by acting as foreign bodies when placed in contami­nated wounds. Monofilament sutures are the least reactive and can withstand wound contamination better than can multifilament sutures of the same material. Multifilament sutures exhibit capillarity, a wicklike action that allows bacteria to move along the suture strand. Natural materials (e.g., catgut, silk, cotton, linen, collagen) are generally considered the most reactive, are weaker, and have a variable rate of absorption.

Synthetic absorbable sutures, such as polygly­colic acid, polyglactin 910, polydioxanone, poly­glyconate, and polyglecaprone, have the distinct advantage of being absorbed at a constant rate by hydrolysis. Additionally, monofilament sutures are less reactive than twisted or braided materials. Synthetic nonabsorbable sutures, such as nylon, polypropylene, and polyfilament polyamide, are generally less reactive than absorbable sutures. Polyfilament polyamide has characteristics that make it the least desirable synthetic no nab­sorbable suture, such as losing 15% to 20% of its strength when wet and being associated

with an increased incidence of suture sinus tract formation. 1

SUTURE PLACEMENT AND PATTERNS

The placement of sutures affects wound healing. Sutures should be placed such that they just appose the wound edges. Loosely approximated wounds are st ronger at 7, 10, and 21 days after surgery than are wounds tightly secured with sutures,S possibly because overtightening disrupts the microvascuJar circulation to the wound edges. Wound edges weaken over time because of colla­gen lysis; therefore, sutures should be placed at least 0.5 em from the margins. Additionally, al­though more sutures improve initial strength, the increased number of sutures compromises blood supply to the wound edges and stimulates an excessive tissue reaction and subsequently increases infection rate. Deep sutures should be placed only in fascial planes, tendons, and liga­ments, because additional deep sutures are gener­ally ineffective and cause excessive tissue reaction.

The suture pattern also can affect wound healing. Although the simple continuous pattern is the easiest to apply and provides the most uniform support, its design leads to reduced microcirculation to the wound margins and a single break resuJts in failure of the entire line. Comparatively, a simple interrupted pattern leads to less edema, does not exert a negative impact on the microcirculation, and encourages greater wound tensile strength after 5 and 10 days,' although these positive effects are attenuated at later times. 9

'13 The disadvantages of interrupted

patterns compared with continuous patterns include the use of more suture material and increased placement time. Interrupted suture pat­terns should be used when impaired healing is anticipated and excessive tension is present. Simple interrupted suture patterns cause less inflammation than vertical mattress and far-near­near-far patterns because of relatively less suture material in the incision line and fewer skin penetrations.

Suture patterns may be divided based on whether they are appositional or serve as tension suture patterns. Simple interrupted, simple con­tinuous, Ford interlocking, cruciate, and subcuta­neous or subcuticular patterns are classified as appositional suture patterns (Figures 3-1 to 3-5).

~t;.t~ Figure 3-1 Simple interrupted pattern.

Figure 3-3 A and B, Ford interlock­ing pattern.

~(k,t;..t·<Mo .

A

Figure 3-4 Interrupted cruciate pattern.

Wound Closure 17

~t;..;t __

Figure 3-2 Simple continuous pattern.

B

The ver tical and horizontal mattress patterns and the near-far-far-near or far-near-near-far or other combination suture patterns are classified as tension suture patterns (Figures 3-6 to 3-10). They are often used in conjunction with apposi­tional suture patterns to combine the benefits of both (see Figure 3-9) .

Simple Interrupted and Continuous Patterns

The simple interrupted suture pattern provides secure, anatomic closure with precise suture tension (see Figure 3-1).lt is easy to apply and the skin retains the ability to expand between the sutures. The simple continuous suture pattern is used in tissues that are elastic and are not subject

18 PRESURGICAL PREPARATION AND ASSESSMENT

~er.v..41,--Figure 3-5 Subcutaneous pattern illustrating the direction of suture placement in both the beginning and end of the pattern.

A B ~t;;,1>M.­

Figure 3-6 A, Interrupted horizontal mattress pattern. B. Horizontal mattress suture pattern wi th bol­sters used as a tension suture pattern.

to significant tension (see Figure 3-2). It provides good apposition and an airtight or watertight seal. Bites in the wound edges are made at right angles to the edges of the wound. Excess tension causes puckering and strangulation of the skin.

Horizontal Mattress Pattern

The interrupted horizontal mattress pattern can be everting or appositional depending on the depth of suture placement and dista nce from the wound edges (see Figure 3-6) . The pattern is good for large skin wounds, for wounds with increased tension, and in conjunction with pieces of rubber

I I

Figure 3-7 Continuous hor izontal mattress suture pattern. Used as a tension suture, slight everting pattern.

A

B

, ,

-- -- -

Figure 3-8 A and B, Interrupted verti cal mattress pattern.

tubing or buttons to act as a tension suture. Because of the placement of this pattern, the sutures have a tendency to reduce the blood supply to the wound edges. The continuous hor­izontal mattress pattern provides necessary tension for wound edge approximation without applying tension to the wound edge itself (see Figure 3-7) . It is often used as a tension-relieving suture for the wound edge.

Vertical Mattress Pattern

The interrupted vertical mattress pattern can also be everting or appositional depending on the depth of suture placement and distance from the wound edges (see Figure 3-8). It is stronger in tissues under tension and less compromising to

I

Figure 3~9 A and B, Com­bined vert ica l mattress tens ion suture and simple interrupted appositional suture patterns. C, Combina tion of ve rtical mat-tress sutures with bolsters and A simple interru pted apposit ional sutures to close incisions under tens ion.

,

Figure 3~ lOA and B, Near-far-far-near tension suture pattern. C and 0 , Far-near­near-fa r tension suture pattern .

"

A

B

blood supply to the wound margins than inter­rupted horizontal mattress sutures. The vertical mattress suture pattern can be used for concu r­rent closure of skin and subcutis to eliminate dead space.

Wound Closure 19

,.

,,,-:

v ' c

--B

c

D

Other Tension Patterns

The nea r-far-far-near, fa r-near-near-far, and other va riations are tension suture patterns occasionally used in equine surgery (see Figure 3- 10). They

20 PRESURG ICAL PREPARATION AND ASSESSMENT

have been shown to be excellent tension sutures; however they are time consuming to insert. In one retrospective study, an increased incisional infec­tion rate was associated with closure of the linea alba using a near-far-far-near suture pattern.14

Subcutaneous or Subcuticular Patterns

Subcutaneous or subcuticular suture patterns are used to close the subcutaneous or subcuticular tissue prior to skin closure. Subcuticular patterns can also be used in place of a typical skin closure pattern (see Figure 3-5). The first part of the suture pattern is placed by starting approximately 8 to 10mm from the apex of the incision in the subcutaneous tissue, d irecting the needle toward the apex of the incision, and emerging in either the subcutis or subcutaneous tissue depending on the pattern desired. The second bite of the suture starts at the apex and emerges approximately 8 to 10mm from the apex in the subcutaneous tissue. The knot is then tied and thus is "buried." The third bite of the suture is superficial to the knot and closer to the apex of the incision to effectively reinforce burying the knot. The remainder of the suture pattern is placed somewhat similar to a continuous horizontal mattress pattern, with the needle crossing the incision at right angles or slightly "behind" where the previous suture emerged. A knot similar to the start is placed at the end of the incision. The last two bites start in the subcutaneous tissue and the needle is directed toward the apex and somewhat more superficial. The last bite starts with the needle reversed at the same level of emergence as the previous bite, directing the needle toward the subcutaneous tissue about 8 to 10 mm from the apex. The knot is tied and the free end of the suture is cut. The needle is passed in to the subcutaneous tissue at the level of the knot, emerging through the skin about 10 to 15 mm perpendicular to the incision line. The needle and suture are then pulled tight to help bury the knot, and the suture is cut at the skin level.

Securing sutures is most commonly performed using instrument ties. However, every surgeon should be able to use one- and two-hand tie tech­niques to secure sutures. The ability to use these techniques gives the surgeon significant flexibility to apply secure ligatu res and sutures in various situations where the use of instrument ties is problematic. Ideally, the surgeon should be able to

use either right or left one-hand ties to take full advantage of their utility.

TISSUE ADHESIVES

Various tissue adhesives, such as cyanoacrylates, collagen gelatin, and fibrin glue, are used for primary wound closure.15,16 Advantages include rapid and painless application, hemostatic and bacteriostatic properties, the provision of a water-resistant protective coating, no need for suture rem oval, and an acceptable cosmetic result. " It is generally thought that tissue adhe­sives may have some benefits in small incisions or wounds in which primary suture closure is indi­cated, whereas larger wounds are unlikely to benefit from tissue adhesives. Wounds healing by second intention may benefit from tissue adhesive sprays after a healthy granulation tissue bed has formed. 16

DEAD SPACE

Dead space allows the seepage and accumulation of blood and serum in a warm and moist envi­ronment that is ideal for bacterial proliferation, thus encouraging infect ion. Dead space may be dealt with by layered wound closure when ade­quate tissue is available, by compression bandages, by drainage, or by suture obliteration,17 although the latter may promote wound infection in con­taminated wounds. Walking sutures can be used to advan ce a skin flap over the wound bed at the same time the dead space is eliminated (Figure 3- 11). A stent or tie-over bandage can be used to help obliterate dead space in wounds in which cir­cumferential bandaging is not possible. This type of bandage protects the wound and may provide relief to the primary suture line as well as direct pressure over areas of dead space (see Figure 25-12).

DRAINS

Drains are used when a la rge dead space remains after suture closure or there is sufficient tissue damage so that continued seepage of fluids is expected. Drains can be therapeutic to remove existing fluid accumulation or prophylactic to

--, • ,

• -A

,--' "

-

,

Wound Closure 21

B

4Ie~,'P<""''' ~>

C 0 Figure 3-11 A-D, Use of walking sutures placed in the subcutaneous tissue to close large defects in skin.

Figure 3-12 A, Insertion of the Jackson-Pratt negative suction drain using a trocar at a site ventral to the incision line. B, Jackson-Pratt negative suction drain in place to provide con­tinuous suction to remove exudate and fluid from the incis ion or wound site. Note use of three-way stopcock. 60-mL syringe. and needle placed through plunger to maintain suction.

A

ensu re against fluid accumulation. Drains must be maintained in a sterile environment to decrease the chance of secondary infection. They should traverse the wound from a proximal to distal ori­entat ion, adjacent to but not directly underlying the suture line, and should exit from a sepa rate incision adjacent to the wound edges to minimize

B

41 e "?/<At;, ,"f;,."'" ...... _>

the chances of retrograde infection. Drains should be sutured proximally and at the exit point.

Drains are classified as active or passive. Active drains are closed suction drains that function by negative pressure to suction out excess fluid or air (Figure 3- 12). Passive drains, including Penrose drains or other forms of rubber or polyethylene

22 PRESURGICAL PREPARATION AND ASSESSMENT

,

Figure 3-13 Partial closure of subcutaneous tissue over Penrose drain . Drain sutured in place (arrow) and exits the site distal to the incision or wound site to avoid the primary incision line.

tubing, funct ion by gravity or pressure differen­tials (Figure 3-13). The ideal drain is inert, soft, smooth, nonreactive, and radiopaque. The disad­vantages of drains include the potential introduc­tion of bacteria or foreign bodies into the wound, the care involved to maintain patency, and the potential irritation and resultant scar tissue and adhesion formation that may occur as the result of a foreign body reaction. Drains should be removed after 2 to 3 days, when infection is con­trolled, or if they are not functioning effectively. Ideally, wound drainage is expected to change from an exudate to a transudate, and the quantity is expected to graduaUy diminish to negligible levels during the 2- to 3-day period.

MANAGEMENT OF SKIN TENSION

Excess tension on a primary suture line is l.ikely to complicate healing via local ischemia, cutting out of sutures, and wound disruption. Methods to decrease tension on the primary suture line include undermining the surrounding skin, pro­viding relief incisions, and the use of tension suture patterns. Although excessive undermining is deleterious, undermining up to 4 cm from the wound edge on distal limb wounds has not been

Figure 3-14 Previously repaired pastern laceration showing evidence of skin necrosis secondary to ban ~

dages applied over tens ion suture supports. Three hor izontal mattress sutures had been placed with polyethylene supports 2 weeks previously.

associated with complications.!8 Rel ief incisions away fr0111 the wound margins can sometimes decrease tension. The relief incisions may be closed after the primary incision is closed or left to heal by second intention.

Tension suture patterns used to reduce the tension on the primary suture line are placed well back from the wound margins so that the blood supply is not compromised. Once the tension sutures are in place, the primary incision line is sutured to appose the wound edges. Widely placed vertical mattress sutures, with or without support using buttons, gauze, or rubber or polyethylene tubing, are effective in reducing tension on the primary suture line. Other tension suture patterns incl ude horizontal mattress, far-near-near-far, and far-far-near-near patterns. Tension sutures with supports are used in regions that cannot be effectively bandaged (e.g., upper body, neck), whereas no supports are used under bandages or casts, because pressure on the supports may cause tissue necrosis (Figure 3-14) . Tension sutures are removed in 4 to 10 days, depending on the appearance of the wound. Staggered removal is preferred, removing half of the sutures initially and the remaining half later.

REFERENCES

I. Hamill MB, Osato MS, Wilhelmus KR: Experimen­tal evaluation of chlorhexidine gl uconate for ocular antisepsis, Antimicrobial Agef/ts Chemother 26:793, 1984.

2. Phinney RD, Mondino BJ, Hofbauer JD, et al: Corneal edema related to accidenta1 Hibiclens

exposure, Alii J Ophtha/mol 106:210, 1988. 3. Nasser RE: The ocular danger of H ibiclens (chlor­

hexidine), Pfost Recomtr Surg 89:164, 1992. 4. Baxte r GM: Wou nds and wound healing. In

Colahan PT, Mayhew IG, Merritt AM, Moore lN, edito rs: Equine medicine alld slIrgery, ed 5, St Louis, 1999, Mosby.

5. Stashak TS: Selected factors that affect wound healing. In Stashak TS, editor: Eqlline IVOUlld mall­agement, Philadelphia, 1991, Lea & Febiger.

6. Wilson DA: Principles of early wound manage­ment, Vet elill N Alii Equine Pmct 21:45, 2005.

7. Stashak TS: Selection of suture materials and suture patterns fo r wou nd closure. In Stashak TS, editor: Equine wound management, Philadelphia, 1991, Lea & Febiger.

8. Brunius U, Ahren C: Healing of skin incisions during reduced tension of the wound area. A ten­siometric and histologic study in the rat, Acta Chir Scalld 135:383, 1969.

9. Fingland RB. Layton Cl, Kennedy GA, et al: A com­parison of simple con tin uous versus simple in ter­rupted suture pattern for tracheal anastomosis after large-segment tracheal resection in dogs, Vet SlIrg 24:320, 1995.

10. Kirpensteijn 1. Maarschalkerweerd RJ. van der Gaag I, et al: Comparison of three closure methods and

Wound Closure 23

two absorbable suture materials for closure of jejunal enterotomy incisions in healthy dogs, Vet Q 23:67, 2001.

II. Magee AA. Galuppo LD: Comparison of incisional bursting strength of simple continuous and inver­ted cruciate su ture patterns in the equine linea alba, Vet Su'g 28:442, 1999.

12. Van Hoogmoed L, Snyder JR, Stover SM, et a1: In vitro biomechanical comparison of the strength of the linea alba of the llama, using two suture patterns, Am J Vet Res 57:938, 1996.

13. We isman DL, Smeak DD, Birchard SJ, et al: Com­parison of a continuo us suture pattern with a simple interrupted pattern for enteric closure in dogs and cats: 83 cases (1991-1997), ] Alii Vet Med Assoc 21 4:1 507,1999.

14. Kobluk eN, Ducharm NC, Lumsden JH, et a1: Factors affecting incisional complication rates asso­ciated with colic surgery in horses: 78 cases ( 1983-1985 ). ] Alii Vet Med Assoc 195:639, 1989.

15. Blackford J. Shires M, Goble D, et al: The use of N-butyl cyanoacrylate in the treatment of open leg wounds in the horse, Proc Am Assoc Equille Pract 32:349, 1986.

16. Bello TR: Practical t reatment of body and open leg wou nds of horses with bovine collagen, biosyn­thetic wound d ressing and cyanoacrylate, J Eqllille Vet Sci 22: 157, 2002.

17. Trotter GW: Techniques of wound closure, Vet Clil1 N AII1 Equine Pmct 5:499, 1989.

18. Bailey lV, Jacobs KA: The mesh expansion method of suturing wounds on the legs of horses, Vet Slirg 12:78,1983.

-

CHAPTER 4

Emergency Management of the Fracture Patient Gal Kelmer

INDICATIONS

Unstable appendicular skeleton fractures.

EQUIPMENT

Bandaging material includes uniform layered cotton padding, elastic gauze, elastic adhesive, inelastic tape, and wound dressing materials. Splints can be made from any lightweight rigid material. PVC (polyvinyl chloride) pipe, 8 to 10 cm in diameter and of 4- to 8-mm wall thick­ness, sectioned longitudinally into thirds makes an excellent, inexpensive, readily available splint­ing material. The sharp edges of the splint may be rounded and should be wrapped with tightly taped padding. Other acceptable splinting mate­rials include wooden splints,S to 20 cm wide and 10 to 20mm thick, and aluminum or concrete reinforcement rods, 12 to 16 mm in diameter, cut to length (Figure 4-1).

POSITIONING AND PREPARATION

All emergency fracture stabilization should be done with the horse in a standing position while providing analgesia and mild to moderate seda­tion. Recovery from general anesthesia can chal­lenge even an ideal fracture repair by the ap­plication of extreme forces to the horse's limb. Thus, general anesthesia should be avoided unless absolutely necessary. !

24

INITIAL EVALUATION AND TREATMENT

Prompt and proper fracture stabilization in the horse can make the difference between death and an athletic future. A horse with a fractured, unsta­ble limb can rapidly induce further trauma that will markedly decrease the chance fo r successful repair and survival. The goal of the initial treat­ment and stabil ization is to prevent further trauma. Such trauma may result in eburnation of fracture ends, further fragmentation and fracture displacement, damage to neurovascular struc­tures, skin penetration leading to an open frac­ture, and additional soft tissue damage. 1·6

Initial assessment of the injured horse inclu­des evaluating the systemic condition, specifically hydration status and cardiovascular function, the bone involved, and the stabil ity of the bony column, and determining whether the fracture is open or closed. Typically, the horse will be sys­temically stable and will benefit from immediate stabilization of the injured limb. Analgesia and sedation of the fractured horse are important in order to relieve anxiety and alleviate pain, thereby minimizing further self-inflicted damage to the injured limb. Phenylbutazone (4.4 mg/kg N ) is beneficial for both its analgesic and anti-inflam­matory properties. Additional analgesia and seda­tion can be achieved using detomidine (0.01 to 0.02 mg/kg NIIM) with or without butorphanol (0.01 to 0.04 mg/kg IM). Use caution when administering these sedatives and analgesic agents, so as not to render the horse ataxic. Horses with these fractures may be dehydrated and hypo-

volemic and thus can be profoundly affected by these agents. If there is skin penetration of the injured limb, even if distant from the apparent fractu re. broad-spectrum antibiotics (e.g., gen­tamicin 6.6 mg/kg IV and potassium penicillin 22,000 Ju/kg IV, or gentamicin and procaine penicillin 22,000 IV/kg 1M, or cefazolin II mglkg IV) should be administered. In a markedly dehy­drated horse, administration of aminoglycosides (e.g., gentamicin) and nonsteroidal antiinflamma­tory drugs (NSAIDs) (Le., phenylbutazone) should be postponed until adequate hydration is achieved via intravenous fluid administration. The horse should be current on tetanus vaccination.

Limb Stabilization

Immediately after initial assessment of the patient and the affected limb, external coaptation should

- - \

Figure 4-1 Bandaging and splinting equipment.

Emergency Management of the Fracture Patient 25

be applied. Splinting can be done well with simple equipment in field situations when attention is given ~o proper technique.7

,B

Radiographs can be taken either following stabilization or later at the referral facility. The basic method of stabilization is a splint applied over a bandage to decrease interfragmentary movement and to significantly alleviate anxiety. The specific mode of immobilization differs along the limb according to the locally predominant biomechanical forces. Both forelimbs and hind limbs can be divided into the following four func­tional sections. l

.s Section 1 is the most distal fore­

limb or hind limb segment between the coronary band and the distal quarter of the metacarpus or metatarsus. Section 2 in the forelimb extends from distal metacarpus to distal radius, while in the hind limb it includes middle and proximal metatarsal fractures. Section 3 in the forelimb comprises diaphyseal and proximal radial frac­tures, while in the hind limb it includes tarsal and tibial fractures. Section 4 in the forelimb consists of fractures of the ulna, humerus, and scapula, while in the hind limb it includes proxi­mal tibial physis and femur fractures . Appropriate stabilization techniques for the previously des­cribed sections of both forelimbs and hind limbs are described next.

Section 1 The most distal forelimb or hind limb segment is between the coronary band and the distal quar­ter of the metacarpus or metatarsus ( Figure 4-2). Dorsopalmar or dorsoplantar bending is the prin-

Section 4

3

Figure 4-2 Dividing the limbs into four functional sections. Each section is stabilized in a different technique according to the local gov­erning biomechanical forces.

Section 3 ---

Section 2 - -- f- Section 2

Section 1 ---- Section 1

26 PRESURGI CAL PREPARATION AND ASSESSMENT

dpal force and is best counteracted by applying a dorsal splint-cast combination over a light band­age extending from the ground to just below the carpus. The bandage is applied with the distal limb straight and the splint applied to align the dorsal cortices. The splint is taped tightly with the carpus held in flexion. The tape material should be nonelastic, such as duct tape or white tape to prevent unwanted motion between the splint and the limb (Figure 4-3). Fiberglass cast material may be applied over the taped splint to increase rigidity. In the hind limb, the same principles hold but the splint is applied to the plantar aspect with ti,e metatarsophalangeal (fetlock) joint in slight flexion (Figure 4-4).

Figure 4-3 Section 1 forelimb fracture, distal third metacarpus to distal interphalangeal joint region, sta­bilized using a dorsal splint-cast combination over a light bandage.

Figure 4-4 Section 1 hind limb fracture, distal third metatarsus to distal interphalangeal joint region, stabi­lized using a plantar splint-cast combination over a light bandage.

Section 2 Forelimb fractures, from distal third metacarpus to distal radius, should be stabil ized with a Robert Jones bandage applied from the ground to the humeroradial joint (elbow) (see Figure 4-2). The bandage should include multiple layers of padd­ing and each padding layer is tightened with elastic gauze. Padding can be made with rolled or layered cotton. Each padding layer should be about 2 to 3 em thick with the total bandaged diameter approximately three times the limb's diameter. It is crucial that the bandage is uniform in shape and tight enough to achieve maximum stability and rigidity of the splinted limb while avoiding excessive focal skin pressure. Palmar and lateral splints that extend from the ground to the elbow should be applied. Splints should be taped as tight as possible over the bandage, using a gen­erous amount of nonelastic adhesive material such as duct tape (Figure 4-5).

Middle and proximal third metatarsal fractures (see Figure 4-2) should be bandaged from the ground to the level of the stifle. In the hind limb, the bandage should be less extensive to facilitate splint application. Plantar and lateral splints should be applied from the ground to the level of the calcaneal tuber. The lateral splint may extend to the level of the stifle for more proximal frac­tures. Splinting material and application manner are similar to those previously described (Figure 4-6) .

Figure 4-5 Sect ion 2 forelimb fracture, distal radius to distal metacarpal region, stabilized using paJmar and lateral splints over a heavy Robert Jones bandage.

Figure 4-6 Section 2 hind limb fracture, third metatarsal bone, stabi lized using plantar and lateral splints over a moderate Robert Jones bandage.

Section 3 Diaphyseal and proximal radial fractures should be stabilized with a Robert Jones bandage aug­mented with caudal and lateral splints applied as for section 2 with the exception that the lateral splin t extends proximally to lie against the lateral aspect of the shoulder (see Figure 4-2). The prox­imal extension of the splint is essential because of minimal soft tissue protection over the medial aspect of the radius. The splint prevents abduc­tion of the distal limb and penetration of the skin by the fractured bone ends at the medial aspect of the fracture line (Figure 4-7). Tarsal and tibial fractures are especially difficult to immobilize because of the reciprocal apparatus (see Figure 4-2). A Robert Jones bandage is applied as for section 2) but in this case the bandage should extend to the level of the patella with the splint preventing slippage. The splint should extend proximally to lie against the lateral thigh and hip and prevent skin penetration by fracture bone ends from limb abduction. Ideally, a lightweight metal splint or steel concrete reinforcement rod shaped to the hock and stifle angulations and bent back upon itself is used as the lateral portion of a Schroeder-Thomas splint. Cast material can be wrapped around the bent rod fo r additional strength (Figure 4-8). Alternatively, the splint can be made of a wide (20 em) wooden board (Figure 4-9). In all options, the splint is incorporated into

Emergency Management of the Fracture Patient 27

Figure 4-7 Section 3 forelimb, diaphyseal and prox­imal radial fractu res, stabilized using similar bandage and palmar splin t as for section 2 fractures. Here the lateral splint is extended to lie against the lateral aspect of the shoulder and prevent limb abd uction.

Figure 4·8 Section 3 hind limb, tibia, and tarsal frac­tures, stabilized using lateral splint over a moderate Robert Jones bandage. The splint is made of a speci fi­cally bent aluminum rod enforced with synthetic cast mater ial and extending proximally to lie against the thigh and hip to prevent limb abd uction.

I 28 PRESURGICAL PREPARATION AND ASSESSMENT

Figure 4-9 Section 3 hind limb, tibia, and tarsal frac­tures, stabilized using a lateral splint over a moderate Robert Jones bandage. The spl int is made of a broad wooden board extended proximally to lie against the thigh to prevent limb abduction.

the coaptation as tightly as possible with liberal use of inelast ic tape.

Section 4 Fractures of the ulna. humerus, and scapula are unstable as a result of loss of the triceps function , which precludes use of the limb (see Figure 4-2). A light bandage from the ground to the elbow combined with a caudal spl int spanning the carpus to lock the carpus in extension will enable weight bearing on a limb affected with an ulnar fracture (Figure 4-10). Splinting cannot aid prox­imal tibial physeal and femur fractures (see Figure 4-2). Heavy coaptation may actually cause further damage by increasing the fulcrum to distract the fragment and potentiaUy open a closed proximal tibial fracture.

PREPARATION FOR REFERRAL

In most cases, it is advisable to discuss referral and surgical options with the client only after the patient is relatively calm and the limb is properly stabilized. The nearest surgical facility should be contacted and consulted prior to transporting the horse. Euthanasia is definitely indicated in certain situations such as an open comminuted tibial fracture in an adult size horse.5 However, in most

Figure 4-10 Section 4 forelimb fractures disabling the triceps apparatus such as olecranon fractures. A caudal splint over a light bandage is applied in order to lock the ca rpus in extens ion and by that aid in control and use of the limb.

cases, initial stabilization of the limb and the patient and consultation with the nearest surgical facility will provide the best service to the horse and the client. The horse should be transported in a confined area with minimal space for body movement and adequate room for head motion and foot placement to aid in balance. A horse with an injured forelimb should face backward and a horse with a hind limb injury should face forward so as to prevent additional stress on the injured limb during emergency stops. Providing dist rac­tion for the ride in the form of a small amount of hay is recommended.2

COMPLICATIONS

Improper splinting such as using one thick padding layer without intermittent tightening with elastic gauze or a very heavy splint improp­erly secured to the limb can actually increase the amount of damage to the fractured limb.4

•s

EXPECTED OUTCOME

The prognosis depends on the horse's weight and temperament, the specific bone involved and the location of the fractu re within the bone, the frac-

I

ture configuration, and the availability of a well­equipped surgical facil ity. The goal of initial sta­bilization is to ensure that the horse reaches the referral center in the best possible condition, while minimizing additional injuries to soft tissue and fractured bones during transportation.I

,2,s

ALTERNATIVE PROCEDURES

A commercially available manufactured metal splint, "Kimzey Leg Saver" (Kimzey Welding Works, Woodland, Calif.), provides adequate sta­bilization for section 1 fractures in both forelimbs and hind limbs. Care should be taken to ade­quately cushion the most proximal aspect of the

Figure 4·11 An alternative way to stabili ze section 1 fractures and luxations is by use of a commercially available manufactured metal splint. the "Leg Saver" by Kimzey. (Courtesy Kimzey Welding Works. Woodland, Calif.)

Emergency Management of the Fracture Patient 29

splint (Figure 4- 11 ). The splint provides a quick and easily applied support; however, it may provide less rigid support than a tightly placed splint-cast combination,l ,2

COMMENTS

Joint luxations present similar to traumatic unsta­ble fractures and warrant immediate stabilization following the same described principles.

REFERENCES

I. Bramlage LR: Current concepts of emergency first aid treatment and transportation of equine fracture patients, Camp Cant Educ 5:S564, 1983.

2. Bramlage LR: First aid and transportation of frac­ture patients. In Nixon AJ, editor: Equine fracture repair, Philadelphia, 1996, WB Saunders.

3. Young DR, Kobluk CN: Diseases of bone. In Kobluk CN, Ames TR, Geor R], editors: The horse: diseases and clinical management, Philadelphia, 1995, WB Saunders.

4. Auer JA, Bramlage LR: Emergency care and trans­portation of the fracture patient. In Colahan PT, Mayhew IG, Merritt AM, Moore lN, editors: Equine medicine and SlIrgery, ed 5, St Louis, 1999, Mosby.

5. Bramlage LR: Emergency first aid treatment and transportation of equine fracture patients. In Auer lA, Stick JA, editors: Equine surgery, ed 2, Philadelphia, 1999, WB Saunders.

6. McIlwraith CW, Orsini ]A: Musculoskeletal system. In Orsini JA, Divers T], editors: MalUml of equine emergencies: treatment and procedllres, ed 2, Phil­adelphia, 2003, WB Saunders.

7. Walmsley J: Emergency management of fractures in horses, In Practice 21:122, 1999.

8. Whitton RC: Temporary splinting of fractures. In Rose RJ, Hodgson DR, editors: Manual of equille practice, ed 2, Philadelphia, 2000, WB Saunders.

CHAPTER 5

Field Anesthesia Keith R. Branson

Equine field surgery requires portable anesthesia. This factor makes it difficult to use inhalation anesthesia. Fortunately) most of the patients un­dergoing surgical procedures in the field are rela­tively healthy and require minimal supportive care while under anesthesia. Adequate) safe anes­thesia is still required) however) because regard­less of your surgical skills) a successful outcome also requires successful anesthesia. This chapter includes a discussion of the physiologic effects of the drugs commonly used for injectable anesthe­sia) how these drugs are used, and a brief discus­sion of supportive care measures and induction methods. In addition, a brief discussion of caudal epidural anesthesia and epidural catheter place­ment is included.

TRANQUILIZERS AND a,-AGONISTS

None of the injectable general anesthetics possess all the properties needed to produce good anes­thesia when used alone. For that reason other drugs are administered in conjunction with the general anesthetics. Tranquilizers and a 2-agonists are commonly used for their sedative, analgesic, and muscle relaxan t properties.

Acepromazine

Acepromazine is the most commonly used mem­ber of the phenothiazine family of tranquilizers. Members of this group of drugs are known for their sedative effects) but they also possess

30

antiemetic and antihistaminic effects. The central sedation seen with the phenothiazine tranquiliz­ers is due to their antagonism of dopamine at cen­trally located receptors. In general) increasing the dose above tha t needed for sedation will only result in an increase in duration of tranquilization and increased undesirable side effects. I Further increases in dose may even result in excitement.

Acepromazine produces a decrease in arterial blood pressure caused by a peripheral al-adreno­receptor antagonism. 2 Because of this a l antago­nism) a mixed adrenoreceptor agonist) such as epinephrine) can have a more dramatic hypoten­sive effect since its vasodilatory ~ effects will be more pronounced. In addition) acepromazine has an antiarrhythmic effect on the heart, most likely from an a-adrenoreceptor antagonism in the heart.3

,4 Minimal respiratory depression) other than a slight decrease in the respiratory rate) is associated with the use of acepromazine alone) and it does decrease the animal's ability to thermoregu­late. '" Early reports of priapism and flaccid penile paralysis in stallions and geldings given acepro­mazine have led to hesitance to use this drug in stal­lions and geldings.8

-lo Some practitioners think

that acepromazine is still a useful sedative for use in male horses) and if used) it should be adminis­tered intramuscularly (1M) and at the lowest effec­tive dose.1l There is a dose-dependent decrease in the hematocrit attributed to sequestration of ery­throcytes in the spleen. lo.n Acepromazin e is highly protein bound and has an elimination half-life of longer than 3 hours. 10 It undergoes hepatic metabo­lism to form inactive metabolites.

When used alone, the dose for acepromazine ranges from 0.02 to 0.09 mg/kg administered intravenously (IV) and 0.03 to 0.05 mg/kg 1M. Acepromazine is rarely used alone when sedation and chemical restraint for standing surgical proce­dures are desired, since it has no analgesic proper­ties. In addition, time to onset can be highly variable and the overall degree of sedation is hard to predict.

a,-Agonists

Xylazine is one of the most widely used sedative­

analgesics in veterinary medicine. Unfortunately, it also has significant undesirable cardiovascular effects since it is a nonspecific a-adrenoreceptor

agon ist. It was thought that if agents that were more specific for the centrally located <X2-

adrenoreceptol's could be developed, the periph­eral effects would be minimized. Detomidine is more specific for o r adrenoreceptors but its car­diovascular effects are very similar to those of

xylazine when equipotent doses are compared. The initial response of the peripheral vasculature

is vasoconstriction. Although there may be differ­el1Ces in the venous and arterial responses, an obvious increase in peripheral vascular resistance

and an accompanying increase in arterial blood pressure occur. l3

·15 This is especially evident if the

drug is given intravenously. These agents also have significant central sympatholytic and parasympa­thomimetic effects, which result in a decrease in

cardiac output. A decrease in heart rate occurs

both as a result of the central effects and as a response to the initial vasoconstriction-induced hypertension. l3

·l s In addition to bradycardia, atri ­

oventricula r conduction disturbances increase following (X2-agonist administration.14.16 This group

of drugs routinely causes some decrease in the res­piratory rate with little effect on PaC02; however, a

decrease in Pa02 is routinely observed at the doses needed to produce sedation. 15,16

A transient increase in UriJle output is seen after the administration of u 2-agOnlsts.1 7.18 Concern

exists that ~-agonists, especially xylazine, may

cause abortion in pregnant mares, but there is little evidence of this effect. However, intrauterine pressure is increased after the administration of

most uz-agonists. 19 Both xylazine and detomidine undergo hepatic metabolism with rapid excretion of the metabolites in the urine.20-B

When used alone, the usual dose for xylazine is 0.3 to 1 mg/kg IV and 1 to 2 mg/kg 1M.

Field Anesthesia 31

Lower doses are often used as an analgesic in colic patients. The detomidine dose is 0.01 to 0.04 mg/kg IV 01' I M when used alone, and, as with xylazine, lower doses of detomidine can be used as an analgesic. Detomidine has a longer duration of sedation than xylazine (approxi­mately 45 and 30 minutes, respectivelyL and the sedation produced lasts longer than the analgesia. When these agents are used with opioids, the Ur

agonist dose is reduced. These combinations are

discussed in a later section of this chapter. Two other selective u 2-adrenoreceptor agonists

are used in horses-romifidine and medeto­midine. Both have physiologic effects similar to xylazine a nd detomidine. 15,24 A dose of romm­

dine 0.08 mg/kg IV is equivalent to approximately 1 mg/kg of xylazine or 0.02 mg/kg of detomidine. Detomidine, at least at higher doses, produces sedation of longer duration than romifid ine

but romifidine appears to produce slightly less ataxia.25,26 Medetomidine is an u 2-agonist ap­

proved for use in dogs. Its use in horses has

been limited, but it appears a dose of 0.0075 mg/kg will produce adequate sedation of a duration longer than that normally seen with

xylazine but shorter than that seen with detomi­dine.15,27

One advantage of the uragonists is the avail­

ability of specific antagonists to reverse their effects. The most commonly used antagonists are tolazoline, yohimbine, and atipamezole, with tola­zoIine being the least specific antagonist for the

uradrenoreceptor and atipamezole being the most specific. 28 Because of tolazoline's relative

lack of (X2 specificity, its use is sometimes associ­ated with significant clinical signs as a result of the antagonism of endogenous adrenergic substances. These signs can include diarrhea, abdominal pain,

and hypotension caused by vasodHation.28 The use of the agonist atipamezole has been evaluated

as part of a lameness examination after light sedation with detomidine (0.01 mg/kg). 29 Admin­istration of atipamezole reversed most of the sedation-related stride changes, but some differ­

ences were still evident. In general, the dose of antagonist is determined by the agonist dose and

the specific agonist used. This relationship is a reflection of the relative affinity the agonist and

antagonist have for the receptors. In general, 4 mg of tolazoline is needed to adequately reverse 1 mg of xylazine, and 10 mg of atipamezole is needed to reverse 1 mg of detomidine.28.3o The time inter­val since administration of the agonist should also

I

32 PRESURGICAL PREPARATION AND ASSESSMENT

be considered when determining the dose of antagonist to administer. If in doubt, it is certainly appropriate to titrate the antagonist dose to produce the desired degree of reversal.

Benzodiazepines

The benzodiazepines are used primarily for their muscle relaxant effects. In add ition, they provide some sedation, although their sedative effects are minimal in horses. They are also used to treat seizures. The benzodiazepines function by enhancing the effect of y-aminobutyric acid (GABA), an inhibitory neurotransmitter. This results in sedation by depression of the limbic system and in muscle relaxation by inhibition of internuncial neurons within the spinal cord. 11

Limited data are available on the physiologic effects of the benzodiazepines in horses, but the cardio­vascular effects are minimal in most species. ll

•ll

•n

Three benzodiazepines are currently in use in equine anesthesia diazepam, midazolam, and zolazepam. Zolazepam is part of a fixed drug product, Telazol (Fort Dodge Animal Health ), which is a combination of zolazepam and tileta­mine, a dissociative anesthetic that is discussed further in the dissociative anesthetic section later in this chapter. Diazepam is supplied in a propy­lene glycol vehicle that makes intramuscular injection painful and the rate of absorption from the injection si te variable. Midazolam is water soluble and well absorbed after intramuscular injection.32 All of the benzodiazepines appear to undergo hepatic metabolism with the metabolites excreted in the urine. Some of the metabolites of diazepam appear to have a significant pharmaco­logic effect. 32,33 Because these drugs are rarely used alone, the commonly used doses are included in the later section on anesthetic combinations.

Guaifenesin

Guaifenesin, also known as glyceryl guaiacolate (GG), is used for its muscle relaxant properties at the internuncial neurons in the spinal cord. The cardiovascular and respiratory effects of guaifen­esin are minimal when the commonJy recom­mended clinical doses are used. It is usually supplied as a sterile powder that is dissolved to form a 5% or 10% solution of guaifenesin. A 5% solution is commonly dissolved in a 5% glucose solution to minimize hemolysis after administra-

tion.34 A 10% solution of guaifenesin in sterile water also produces minimal hemolysis.35 Less concentrated solutions are less likely to cause phlebitis or thrombus formation. 36 Perivascular administration of guaifenesin can result in severe tissue damage. If the solution is allowed to cool substantially below room temperature, the guaife­nesin will precipitate out of the solution. It can be redissolved by warming the solution. Guaifenesin undergoes hepatic metabolism and the metabo­lites are excreted in the urine. 37 Accumulation of metabolites, such as catechol, can lead to signs of toxicity, including muscle stiffness, tremors, and dyspnea. Guaifenesin is rarely used alone but is usually combined with an injectable anesthetic agent such as a barbiturate or a dissociative anes­thetic such as ketamine.

OPIOIDS

Opioids are potent analgesics; unfortunately, they often produce excitement when administered by themselves to horses. This is especially true of the full opioid agonists. The development of opioids that are agonists at only some opioid receptors has made the use of opioids in the horse easier and more effect ive. Opioid receptors are commonly classified as mu ( ~), kappa (K), and delta (0) receptors. Mu receptor activation is generally associated with profound analgesia as well as with some of the undesirable opioid effects such as bradycardia. hypoventilation. and excitement. Kappa receptor activation produces analgesia that is not as intense as that associated with mu recep­tor act ivation but is also associated with fewer undesirable effects. Delta receptors are primarily thought to modulate mu receptor activity and produce analgesia. In general, the opioids have minimal cardiovascular and respiratory effects. Small increases in heart rate, blood pressure, and cardiac output were observed after full agonists were admi nistered, probably from the excitatory effects of these drugs in the horses studied. 38 The nonselective full agonists such as morphine and fentanyl have a very narrow margin between the analgesic and the excitato ry dose, especially in pain-free animals. 39 It is important to differenti­ate the behavioral effects of opioids in pain-free horses, such as those often used in research studies, and their effects in clinically painful horses. In a study of the peri operative use of 1110r-

phine in painful horses, minimal behavioral ef­fects were seen. 40 Kappa agonists such as butor­phanol also produce some excitement but the effect is somewhat less than that seen when mu agonists such as morphine are administered.4 1

,42

Butorphanol has been administered as a continu­ous infusion to maintain analgesia at a loading dose of 0.018 mglkg IV and then a continuous infusion at 0.0237 mglkglhr'3 Another opioid that has seen limited use in horses, but has many desirable characteristks, is buprenorphine. When combined with detomidine, buprenorphine has provided good analgesia and sedation for stand­ing procedures.44 Transdermal delivery systems have provided an additional route of admin­istration for opioids. Fentanyl is commonly administered in this manner (Duragesic; Janssen Pharmaceutical Products) to a variety of species. This delivery route has been studied in horses, and it was determined that two 10-mg (100 ~glhr)

patches provided plasma levels of fentanyl that should provide analgesia. Eight to IS hours was required to reach peak plasma levels and patches needed to be replaced at 48-hour intervals to maintain the desired plasma concentrations.45 No significant undesirable effects were noted in this study.

INJECTABLE ANESTHETICS

None of the available injectable general anesthet­ics provide all of the actions of an ideal anesthetic. Therefore, when used clinically they are almost always combined with other drugs.

Ketamine

Ketamine is a dissociative anesthetic. Patients receiving ketamine appear to be in a cataleptic state while still maintaining many reflexes. The higher centers, the cerebral cortex, are dissociated from somatic input. The site of action of keta­mine is centrally located N-methyl-D-aspartate (NMDA) receptors. In addition, some of the analgesia produced by ketamine may be due to interaction with opioid receptors.46 Ketamine undergoes hepatic metabolism with urinary ex­cretion of the metabolites. Some of the metabo­lites have pharmacologic activity.47 The analgesic properties of ketamine are somewhat controver­sia l; however, many stucUes show a significant

Field Anesthesia 33

analgesic effect.48.s1 Some evidence exists that sub­anesthetic doses produce minimal analgesia. 52

•s4

The cardiovascular effects of ketamine must be separated into its indirect central effect and its direct peripheral effect. The central effect is an overall increase in sympathetic tone resulting in mild increases in heart rate, arterial blood pres­sure, and cardiac output. It does, however, have a mild direct depressant effect on myocardial con­tractiIity.46.55 Little respiratory depression is seen at cl inical doses although a slight increase in res­piratory rate and decrease in tidal volume are sometimes observed. Ketamine produces minimal muscle relaxation. Because of its poor muscle relaxant effects and tonic-clonic limb spasms, it is not used alone in veterinary anesthesia.

Tiletamine

Telazol is a proprietary mixture with equal con­centrations of zolazepam, a benzodiazepam, and tiletamine, a dissociative anesthetic. It is distrib­uted as a dry powder that is reconstituted prior to use. Tiletamine is somewhat more potent than ketamine and has a slightly longer duration of action. Its cardiovascular, respiratory, and anes­thetic effects are similar to those of ketamine.S6

Even though Telazol contains a tranquilizer as well as a dissociative anesthetic, it is not commonly used alone in equine anesthesia.

Thiopental

Thiopental is an ultra-short-acting thiobarbitu­rate. It produces rapid unconsciousness after intravenous injection. Recovery is a result of redistribution of the drug from the brain to other ti ssues in the body. Initially, the drug is redistrib­uted to muscle and other nonfatty tissues with moderate blood flow. The ultimate site of redis­tribution is poorly perfused adipose tissue but, at the time of recovery from anesthesia, the major­ity of the drug resides in moderately perfused tissues. Ultimately, it undergoes hepatic metabo­lism. If thiopental is administered for prolonged periods and then discontinued, the primary factors associated with the termination of anes­thesia are both redistribution into fat and hepatic metabolism. These are slower than redistribution into moderately perfused tissues. The site of action for barbiturates has been shown to be on the GABA receptor.46 Barbiturates enhance

34 PRESURG ICAL PREPARAT ION AND ASSESSMENT

the inhibitory effect of this neurotransmitter by decreasing the rate of its dissociation from its receptor and directly increasing the duration of GABA-associated chloride channel opening. It has no analgesic effects at subanesthetic doses. Its car­diovascular effects are a mild peripheral vasodila­tion (primarily venous) and a decrease in cardiac contractility.46 A concurrent increase in heart rate often occurs. Although thiopental can be used alone to produce equine anesthesia, the quality of recovery is poor.57 For this reason, it is commonly used with other agents.

Propofol

Propofol is a phenolic compound that is chemi­cally unrelated to thiopental , but the clinical and physiologic effects are very similar. One signifi­cant difference is the rapid hepatic metabolism of propofol. 58 This combination of redistribution and rapid metabolism results in rapid recovery even after long periods of administration. Cur­rently its cost precludes frequent use as an equine anesthetic agent, although use may increase in the future. It is used after premedication with a tran­quilizer.

STANDING SEDATION AND RESTRAINT COMBINATIONS

Many minor surgical and diagnostic procedures are done without general anesthesia. In some cases, a tranquilizer or ~-agon i st alone is ade­quate. In most cases, however, the combination of a tranquilizer o r cx2-agonist with an opioid pro­vides superior sedation, analgesia, and restraint. Many combinations are used, and the doses within t11ese combinations are variable. The attending veterinarian should use his or her judg­ment as to the precise dose to use. O ne rule to remember is that you can always give more drug if needed but it is difficult to remove a d rug from the animal once it has been administered. Table 5- 1 lists the commonly used drugs and their doses, as welJ as some specific comments.

It is important to remember that no matter which drugs are selected to sedate a horse, several other factors are important for successful sedation.

I. The horse should be caLn when the drugs are ad min istered.

2. After the drugs a re administered, they should be allowed to have an effect. It is important to wait 5 to 15 minutes after IV administration and 15 to 30 minutes after 1M administration for the drugs to have their fu ll effect.

3. If a tranquilizer or <Xragent alone is not effec­tive, it is usually best to add an opioid rather than to give more of the initial drug.

For long procedures, it is sometimes easier to administer a continuous infusion of detomidine rather than to administer additional doses during the procedure. This is especially useful during Japaroscopic procedures. After initial sedation with detomidine and butorphanol or detomidine and buprenorphine, an infusion of detomidine is administered at the rate ofO.IIlg/kg/min (0.0001 mg/kg/min ) ..... A 450-kg horse would therefore require 27 mg of detomidine/hr. Alternatively, an initial detomidine infusion rate of 0.6 J.lglkglmin can be used. The detomidine infusion rate is then decreased by half every 15 minutes. 59 Xylazine can also be given by infusion at the rate of 0.55 mg/kg/hr.60 Tn addition to the infusion, local anesthetics should be used at the surgery site. Con­stant infusions are often superior to intermittent administration in that the quality of sedation is more uniform and there is usually less ataxia since the peaks in plasma drug levels are eliminated.

INJECTABLE GENERAL ANESTHESIA

There is no ideal general anesthetic; therefore, combinations of drugs are used to produce general anesthesia. When combining drugs, it is important to select drugs that have complemen­tary effects. In addition, the duration of action of the drugs must be considered as welJ as their undesirable side effects. When the combination of xylazine and ketamine is analyzed, it is evident that ketamine provides the anesthesia as well as some analgesia but is lacking in muscle relax­ation and would cause rough inductions if used alone. The addition of xylazine adds muscle relax­ation as well as more analgesia and sedation to smooth the induction. Thei r durations of action are complementary as well. Xylazme produces approximately 30 minutes of sedation so the recovery from ketamine is generally smooth but the sedation after anesthesia is not prolonged. The addition of butorphanol or a benzodiazepine adds more analgesia-sedation or muscle relaxation-

Field Anesthesia 35 •

TABLE 5-1

Drugs Commonly Used for Standing Sedation in Horses

DRUG(S)

Single Drugs Acepromazine

Xylaline

Detomidine

Romifidine

DOSE ( IN MG/KG) (ALL CAN

BE GIVEN IV OR 1M)

0.04-0.08

0.3-1

0.Ql-0.04

0.04-0.12

Drug Combinations'" Acepromaline 0.05 Morphine 0.1-0.2

Acepromazine 0.05 Butorphanol 0.025-0.05

Xylaline 0.25-1 Butorphanol 0.01-0.05

Detomidine 0005-0.Q2 Butorphanol 0.01-0.05

Detomidine 0.01 Buprenorphine 0.006

Romifidine 0.04-0.08 Butorphanol 0.01-0.05

COMMENTS

1. May cause penile paralysis 2. Variable time to onset

1. Higher doses may cause ataxia 2. Sedation lasts longer than analgesia 3. Approximately 30-minute duration

1. Higher doses may cause ataxia 2. 60- to 90-minute duration

1. May cause less ataxia than xylazine or detomidine 2. 60- to 90-minute duration

1. May cause penile paralysis 2. Variable time to onset

1. May cause penile paralysis 2. Variable time to onset

"Note: Use of the higher doses of both drugs often results in ataxia.

sedation, respectively. Tn addition, if a local an­esthetic can be used to desensitize the surgical site, the general anesthetic requirements are often decreased.

a,-Agonist-Dissociative Combinations

Xylazine and ketamine are commonly used together for short general anesthesia. Xylazine (l.l mg/kg IV) is administered, and then after the horse is sedate (usually about 5 minutes) keta­mine is administered (2.2 to 2.75 mg/kg IV).6l·'" This will usually provide approximately I 0 minutes of light general anesthesia. Mules and donkeys do not respond adequately to this combination and may not even become recumbent if the lower ket­amine dose is used."·66 Butorphanol (0.02 mg/kg) can be administered with xylazine to enhance

analgesia and sedation, and will slightly prolong the anesthesia. A benzodiazepine can also be administered IV prior to ketamine to enhance muscle relaxation . Diazepam or midazolam can be used at the dose of 0.06 mg/kg. In draft horses, the doses of the drugs are decreased by 10% to 20%? If the duration of anesthesia needs to be extended) one half of the original dose of xylazine and ketamine can be administered together IV. Detomidine or romifidine can also be used as a preanesthetic prior to ketamine anesthesia.68

.70

The doses used are detomidine (0.02 mg/kg IV), or romifidine (0.08 to 0.12 mg/kg IV), followed by ketamine (2 to 2.2 mg/kg IV). Because of the longer duration of action of these drugs, if addi­tional time is needed, a half dose of ketamine only should be administered. Butorphanol or a benzodiazepine could also be used with these combinations.

) , 36 PRESURGICAL PREPARATION AND ASSESSMENT

a ,-Agonists can be combined with Telazol. The a,-agonist should be administered first and Telazol is administered only after the horse is sedate. Xylazine (1.1 mg/kg IV) can be combined with Telazol (1.65 mg/kg IV) to produce general anesthesia of approximately 20 to 30 minutes.62

,71

Alternatively, detomidine can be used. Detomi­dine at doses of 0.02 mg/kg or 0.04 mg/kg IV followed by Telazol (2 mg/kg IV) produced ap­proximately 25 and 30 minutes of anesthesia, respectively." Xylazine (0.44 mg/kg IV) can be followed by a mixture ofTelazol dissolved in deto­midine and ketamine to produce recumbency of approximately 40 minutes" A 500-mg bottle of Telazol is dissolved in 4 mL of 100 mg/mL keta­mine and 1 mL of 10 mg/mL detomidine. Three milliliters of the mixture per 450 kg of body weight is the recommended dose.

a,-Agonist-Dissociative-Guaifenesin Combinations

The combination of guaifenesin, ketamine, and xylazine (GKX), or "triple drip:' has been used for many years in equine anesthesia. This combina­tion was first described as an induction comb ina­tion73 and later as a maintenance anesthetic.?4 When used as a maintenance anesthetic, 0.5 mg/mL of xylazine and 1 or 2 mg/mL of ketamine are added to a 5% solution of. guaifenesin in dextrose. One liter of 5% guaifenesin would have 5 mL of 100 mg/mL xylazine and 10 or 20 mL of 100 mg/mL ketamine added. It should always be administered through a catheter because extravas­cular guaifenesin can cause severe tissue damage. In addition, the vein used for administering the anesthetic should not be occluded so blood can flow freely to allow distribution of the drug and prevent thrombophlebitis. Triple drip can be used as an induction agent in horses sedated with xylaxine.74 More commonly, however, it is used as a maintenance anesthetic following induction with xylazine and ketamine as described earlier in this section. It is infused at a rate that produces the desired level of anesthesia, but the mainte­nance infusion rate is usually 2.2 to 2.75 mLlkg/hr (approximately 1 mLllb/hr)."'·"·" The higher con­centration of ketamine allows slightly slower infusion rates for longer procedures. This is an appropriate anesthetic technique for up to 90 minutes in healthy horses. If the recovery is pro­longed, tolazoline can be used to antagonize the sedative effects of xylazine. 75 If the recovery is pro-

longed and the horse is unable to get up but does not appear sedate, fluids should be administered in an attempt to improve excretion of the drugs and their metabolites.

Detomidine can be used with guaifenesin and ketamine after induction with detomidine and ketamine.76

,77 The preparation used contains ket­amine (2 mg/mL) and detomidine (0.02 mg/mL) in 10% guaifenesin administered at approxi­mately 1 mLlkg/hr. If 5% guaifenesin is used, the ketarnine and detomidine concentrations should each be reduced by one half (l mg/mL and 0.01 mg/mL, respectively). The infusion rate for the less concentrated mixture is 2 mLlkg/hr.

Romifidine with guaifenesin and ketamine has been used as a maintenance anesthetic following induction with romifidine and ketamine. 78 The induction dose is 0.1 mg/kg of romifidine IV fol­lowed by 2.2 mg/kg of ketamine IV. The mainte­nance infusion consists of an initial bolus of 50 mg/kg of guaifenesin followed by IV infusion of romifidine (0.0825 mg/kg/hr), ketamine (6.6 mg/ kg/hr ), and guaifenesin (l00 mg/kg/hr). After 30 minutes, the guaifenesin infusion rate is decreased 50%.

Thiopental-Guaifenesin Combinations

The use of guaifenesin with thiopental allows the use of a lower dose of thiopental and usually pro­duces better recovery than the use of thiopental alone. Induction is usually preceded by the administration of an ~-agonist such as xylazine or detomidine. Both thiopental and guaifenes in will cause tissue damage. Therefore, it is essential this mixture be administered via an indwelling IV catheter located in a vessel with good blood flow. A 14-gauge or larger catheter is recommended to allow the rapid administration of the thiopental­guaifenesin mixture. To administer this mixture, 2g of thiopental is added to 1 L of 5% guaifen­esin.64 This mixture is then administered IV as rapidly as possible until the horse is recumbent. To speed induction, 1 additional gram of thiopen­tal can be administered IV as the horse begins to relax. If drug administration is stopped after the horse is recumbent, the duration of anesthesia will be 10 to 20 minutes. Additional anesthesia time can be produced by continuing the infusion to effect. The typical infusion rate will be approx­imately 1.5 mLlkg/min." If more than 1 L of the mixture is to be used, the second liter should only contain 1 g of thiopental (l mg/mL). Total anes-

thesia time with this mixture should be limited to 30 minutes or less. After short anesthetic periods, recovery from this mixture is usually quiet and uneventful.

MONITORING HORSES WHILE UNDER INJECTABLE GENERAL ANESTHESIA

In general, sophisticated monitoring equipment is not used during field anesthesia. Efforts should be made to ensure adequate circulatory and respira­tory function. 79 This can be as simple as palpating the pulse, observing chest wall movement, and observing mucous membrane color. Normal horses will have a pulse rate between 25 and 50 beats per minute and a respiratory rate of 6 to 12 breaths per minute.

Anesthetic depth is determined by assessing the palpebral and corneal reflexes and watching for the presence of nystagmus. Horses under injectable general anesthesia will appear to be at a lighter plane of anesthesia than those under inhalation anesthesia. The corneal and palpebral reflexes should be present. Also, the character of breathing will often change as the depth of anes­thes ia decreases. Commonly, deep "sighs" and intermittent breath holding will occur at a light level of anesthesia. Usually, if nystagmus is present, the depth of anesthesia is inadequate unless the procedure is almost complete. If anes­thesia is being maintained by an infusion, the rate of the infusion can be increased if deeper anes­thesia is needed. When the horse is very light, a small bolus (0. 1 to 0.5 mLlkg) of the infusion can be rapidly administered. During anesthesia with an (X2-agonist-ci issociative combination, an addi­tional dose of (X2-agonist -dissociative or dissocia­tive alone can be administered. The usual dose is half of the induction dose.

SUPPORTIVE CARE FOR HORSES WHILE UNDER INJECTABLE GENERAL ANESTHESIA

Because patients undergoing surgical procedures in the field are usually relatively healthy and support facilities are limited, intensive supportive care is usually not administered. An ocular lubri­cant or ocular antibiotic ointment (without steroids) should be placed in both eyes to prevent corneal drying and there should be nothing near the eye that could rub on the cornea. Covering the

Field Anesthesia 37

eyes with a towel will protect the eyes somewhat and eliminate visual stimulation of the patient. The surface the horse is placed on should be smooth and can be padded if padding is available. It is important to minimize the time spent positioning the patient for short procedures since limiting anesthesia time usually results in better recovery. Proper positioning of the patient will limit the potential for myopathies and neuropathies.

When in lateral recumbency, the lower front leg should be pulled as far rostral as possible to eliminate pressure on the brachial plexus and associated blood vessels. The halter should also be removed to prevent facial nerve damage on the down side. Positioning of the lower hind limb is not as critical , but it is commonly puUed forward as well to decrease pressure on the medial mus­culature. Both the front and hind upper limbs should be supported in a position parallel with the ground. Horses positioned in dorsal recum­bency should have their head and neck positioned in a natural position to ensure a patent airway. The legs should be allowed to assume a natural , semi-flexed position. Unless necessary for the pro­cedure, the hind limbs should not be kept in an extended position.

Fluid therapy is not commonly administered to equine patients undergoing short field proce­dures but is appropriate if indicated. Ally balanced crystalloid solution such as 0.9% saline or lactated Ringer's solution can be administered at a rate of 5 mL/kglhr to maintain vascular volume and promote tissue perfusion. Any significant blood loss can be treated by administering 3 mL of crys­talloid fluid for each milliliter of estimated blood loss. In healthy animals, this is usually adequate therapy for blood losses of up to 10% of the blood volume. Ideally any preexisting dehydration should be corrected prior to anesthesia. If this is not possible, the fluid deficit can be replaced while under anesthesia. The fluid deficit is commonly estimated by multiplying the perceived amount of dehydration (in percent) and the animal's weight (in kilograms) to determine the deficit (in liters). A 450-kg animal that is 5% dehydrated would need 22.5 L to replace its deficit (0 .. 05 x 450 kg = 22.5 L).

Under field conditions, intubation is not essen­tial for the equine patient. It does protect the airway from occlusion and allow mechanical ven­tilation if needed. It would certainly be beneficial to at least have an endotracheal tube available.

I I

, I

38 PRESURGICAL PREPARATION AND A SSESSMENT

Oxygen supplementation can easily be done in the field using a portable E oxygen tank, regula­tor, and flowmeter. A full E tank will hold approx­imately 650 L of oxygen. The oxygen can be administered via a nasal insufflation line at a flow rate of 5 to 10LImin. Oxygen can also be supple­mented using an E tank and a demand valve. The demand valve is attached to an endotracheal tube and can be used in two ways. If the horse is breath­ing spontaneously, the demand valve is auto­matically triggered during inspiration and the inspired air is supplemented with oxygen. Alter­natively, if the horse is not breathing well sponta­neously, the demand valve can be manually triggered to start the oxygen flow. Once an ade­quate volume has been delivered, which is deter­mined by watching the chest excursion, the trigger is released and the horse passively exhales. The demand valve must have a high maximum flow and have an adaptor to allow it to be attached to an equine endotracheal tube. Some demand valves designed for human use do not have an adequate peak flow rate. The flow rate should be in excess of 150 Llmin. At least one demand valve has both the required flow rate and necessary adaptors for equine use (Equine Demand Valve; JD Medical, Phoenix Ariz.).

INDUCTION AND RECOVERY FOR INJECTABLE FIELD ANESTHESIA

Induction

Before administering any anesthetic drugs, a quick physical examination should be performed. Any obvious health problems or injuries should be brought to the attention of the owner or agent and their effect on anesthesia discussed. The risk of anesthetic and surgical complications should be discussed and made clear to the owner as well. In a comprehensive survey of almost 42,000 equine anesthetic cases, the overall death rate (excl uding colic surgeries) was 2.4%.80 This included horses that died or were euthanized. If only the horses undergoing injectable anesthesia were evaluated, the death rate dropped to 0.3%. Although this may seem to be a big positive for injectable anesthesia, one must realize these were generally healthy horses undergoing short proce­dures with anticipated high success rates.

A level area free of obstacles should be selected for the procedure. An open grass-covered area is

ideal. The horse should be fitted with the correct size nylon halter and a sturdy lead rope should be available. If an a z-agonist-dissociative combina­tion is used, the horse can easily be induced by one person. After administration of the dissociative agent, the handler maintains control of the head. Generally, the horse will lean back and the handler may have to hold the head down to keep the horse from going over backward. Alternatively, the handler can stand at the shoulder of the horse and move the horse in a circle around him. One hand should be on the horse's shoulder and the other holding the lead rope close to the horse's head. As the dissociative agent takes effect, the rear end of the horse will usually swing away from the handler. He or she should be on the side of the patient that is to be up once the horse is anes­thetized if it is to be positioned in lateral recum­bency. As the horse goes down, the handler can step toward the head and control its fall by holding onto the lead rope. If a guaifenesin mixture is used for induction, it is difficult to hold the horse and the drug container. A second person is needed to manage the drug bottle as the horse is going down. If several assistants are available, an alternative method can be used. One person should be at the head holding the lead rope and a second person should hold the tail. If the horse is nervous, the person holding the tail should wait until the horse is almost ready to go down before grabbing it, recognizing that the horse may still kick. Two additional assistants are at the horse's shoulders. As the horse begins to relax, the assis­tants on the head and tail pull in opposite direc­tions and down. The assistants on the shoulders attempt to keep the horse from falling sideways. This should allow the horse to go down into a sternal position, and it can then be rolled onto either side.

Recovery

Recovery after short injectable anesthesia is usu­ally relatively smooth. If the horse was nervous and excited during induction, the recovery may be less than optimal. IdeaLly during recovery, the horse will move into a sternal position, wait a few minutes, and then stand uneventfully. Covering the horse's eyes with a towel often will help keep the horse from trying to get up before it is ready. In addition, it is important to keep the surround­ings as quiet as possible during recovery. A sudden loud noise may arouse the horse before it is able

to stand. If the horse is trying to get up but is unable to remain standing, a small dose of xylazine (0.2 to 0.4 mglkg IV) may calm the ani­mal and provide a quieter recovery. Some practi­tioners advocate holding the horse down until it is able to get up, and this may be of benefit. It is best done by kneeling on the horse's neck at the dorsal aspect and holding the head to keep the horse from swinging it up. Once the horse's attempts to get up have become more vigorous, the head can be released and the horse allowed to stand. After it is standing, it is important to try and steady the horse to keep it from stumbling around and injuring itself. If it is stand ing but very Wlstable, a second person holding the tail may be of benefit.

EPIDURAL ANESTHESIA AND ANALGESIA

Epidural anesthesia is an excellent method of pro­viding desensitization to the tail and perineal region of the standing horse. Local anesthetics traditionally have been used, but more recently other drugs such as opioids and ur agonists have been used separately or with local anesthetics to improve the desensitization provided by local an­esthetics or provide long-term pain control.

Anatomy

The spinal cord and meninges usually end in the sacrum. Epidural injections are usually performed at the sacrococcygeal or first intercoccygeal joint. Either location is acceptable, and the injection site can generally be determined by moving the tail up and down and palpating for the most proximal movable joint. The depth of the soft tissue over the first intercoccygeal space is 3.5 to 8 cm.Bl The nerves desensitized by the injection of a local anesthetic in this area include the caudal and 52 to S5 sacral spinal nerves. These provide nerve fibers making up the pudendal, middle rectal , and cau-dal rectal nerves. The S2 nerve also con­tributes motor innervation to most of the hind limb, and blockade of this nerve may cause hind limb ataxia. For this reason, it is important to limit the volume oflocal anesthetic injected because the volume injected will determine the rostral extent of the blockade.

Technique

After the hair is clipped, suitably cleaned, and dis­infected, the sacrococcygeal or first intercoccygeal

Field Anesthesia 39

joint is located by moving the ta il up and down and palpating for flexion. Once the joint has been located, 2 mL of a local anesthetic such as 2% li­docaine can be injected into the superficial tissues over the joint. An 18- or 20-gauge 2.5- inch (6.4-em) spinal needle is used to access the epidural space. In large or heavily muscled horses, a 3.5-inch (8.9-cm) needle may be needed, and in many horses, a standard 1.5-inch (3.75-cm) hypodermic needle will be adequate (Figure 5-1). The needle is introduced perpendicular to the skin directly over the center of the space on the midline. As the needle is advanced and the epidural space is entered, a loss of resistance will be felt. If the tip of the needle strikes the floor of the canal, it should be withdrawn slightly. There should be no resistance to the injection of fluid or air at this point. An alternative method of determining when the epidural space is entered is called the "hanging drop" technique. After the needle has been advanced through the skin and into the soft tissue overlying the intervertebral foramen, the stylet is removed (if present) and a small amount of saline or local anesthetic is instilled into the hub of the needle. As the tip of the needle pene­trates the ligamentum flavum. the fluid runs down the needle into the epidural space and the fluid in the hub disappears.

If repeated epidural injections are to be made, an epidural catheter can be placed to make this more convenient. Several commercial epidural catheter kits that are suitable for equine use are available. The needle insertion technique is the same as described above but a different needle is

Figure 5-1 A sagittal section through the sacrococ­cygeal region of an equ ine cadaver showing the needle placement for a caudal epidural injection. The upright needle is 2.5 inches long and the more caudally inserted needle is 3.5 inches in length. The horse we ighed approximately 500 kg when alive.

I

40 PRESURGICAL PREPARATION AND ASSESSMENT

used. A Touhy needle with a slightly curved tip allows easier placement of the catheter. After the needle is in place, the catheter is advanced through the needle and cranially into the epidural space. The opening on the needle should be ori­ented cranially. and this can be checked while the needle is in the animal by observing the notch on the hub of the needle. This notch will be over the opening at the distal end of the needle. The catheter should be advanced 5 to 10 cm cranially. If local anesthetics are to be injected, this d istance should be shorter, only 2 to 4 cm, to prevent an impairment of motor innervation to the hind limbs. Once the catheter is in place, the needle is withdrawn and the injection hub is attached to the catheter per the manufacturer's instructions. The catheter is then secured to the horse, and the injection hub and site of entry of the catheter through the skin are covered. It is important to secure the catheter in such a way that prevents kinking or accidental removal. The catheter should be flushed daily if no therapeutic injec­tions are performed.

Epidural Drugs

Classically, local anesthetics have been used for epidural anesthesia. They provide complete de­sensitization and can affect motor innervation as well. The dose of local anesthetic is based to a large extent on volume. The greater the volume of drug injected into the epidural space. the farther rostral the drug will have an effect. More recently, uragonists and opioids have been used alone or in conjunction with local anesthetics to prolong anesthetic effects and provide long-term analgesia without the loss of motor function . Additionally. the analgesic effects of opioids extend farther ros­trally than the sacrococcygeal region and can provide analgesia for hind limb and even abdom­inal pain.82

•83 A volume of 5 to 7 mL of local anes­

thetic is commonly used for a 4S0-kg horse. The local anesthetics most commonly used in the United States are 2% lidocaine, 2% mepivacaine, and 0.5% bupivacaine. The duration of effect can be variable. but lidocaine will typically provide 30 to 60 minutes of desensitization. Mepivacaine can provide 90 to 120 minutes of desensitization, and bupivacaine can produce up to 4 hours of desensitization. The addition of epinephrine (\ :1 00.000) will prolong the duration. The onset of blockade after local anesthetic injection may

take up to 20 minutes. The opioid most com­monly used for epidural injection is morphine; the dose usually used is 0.1 mglkg." This dose can provide analgesia without any motor effects for up to 18 hours. Commercial preservative-free mor­phine preparations are available that should be used if possible. especially if multiple injections are to be performed. Unfortunately. the currently available preservative-free preparations are so dilute, the volume required is too large to be prac­tical. When the more concentrated morphine preparations are used, they should be diluted to a total volume of 10 mL with 0.9% sterile saline. Xylazine can be administered epidurally by itself or with other drugs. It appears to have some weak local anesthetic effects that are not reversed by Cl2-

antagonists as well as analgesic effects produced by adrenergic receptors in the spinal cord. The usual dose is 0.17 mglkg" The author often adds I mL of 100 mglmL xylazine to 4 mL of 2% lido­caine to be used for caudal epidural injection in a 4S0-kg horse.

REFERENCES

I. Tobin T, Ballard S: Pharmacological review-the phenothiazine tranquilizers, J Equine Med Surg 3:460. 1979.

2. Walker M, Geiser 0: Effects of acetylpromazine on the hemodynamics of the equine metatarsal artery, as determined by two-dimensional real-time and pulsed Doppler ultrasonography, Am J Vet Res 47:1075.1986.

3. Muir WW, Werner LL, Hamlin RL: Effects of xylazine and acetyl promazine upon induced ven­tricular fibrillation in dogs anesthetized with thi­amylal and halothane. Alii J Vet Res 36: 1299. 1975.

4. Maze M. Hayward E. Gaba DM: Alpha I-ad­renergic blockade raises epinephrine-arrhythmia threshold in halothane-anesthetized dogs in a dose-dependent fashion, Anesthesiology 63:611, 2004.

5. Geiser DR: Chemical restraint and analges ia in the horse, Vet Clin N Am Equine Pmct 6:495, 1990.

6. Marroum Pl. Webb AI. Aeschbacher G, et 31: Phar­macokinetics and pharmacodynamics of acepro­mazine in horses, Am J Vet Res 55:1428,1994.

7. Parry BW. Anderson GA, Gay CC: Hypotension in the horse induced by acepromazine m31eate, AI/st Vet J 59:148.1982.

8. Jones RS: Penile paralysis in stallions. J Am Vet Med Assoc 149:124. 1966.

9. Lucke IN, Sansom J: Penile erection in the horse after acepromazine, Vet Rec 104:2 1, 1979.

10. Ballard S, Shults T. Kownacki AA, et al: The phar­macokinetics. pharmacological responses and behavioral effects of acepromazine in the horse, J Vet Phannacol Tiler 5:21, 1982.

11. Principles of sedation, analgesia and premedica­tion. In Hall LW, Clarke KW. Trim eM, editors: Veterinary Ql1aesthesia, ed 10, St Louis, 200 I, WB Saunders.

12. Gillespie JR, Schalm CW, Tyler WS: Hematologic response of the horse to general anesthesia: a review and new data. Proceed ings of the First International Sym posium on Equine Hematology Mich igan State Un ive rsity, East Lans ing. Mich., 490, 1975.

13. Bloor BC, Schmeling WT: Cardiovascular effects of alpha2-adrenoreceptors. Allaest" Pharmacal Rev 1:246, 1993.

14. Sarazan RD, Starke WA. Krause GF. et al: Cardio­vascular effects of detomid ine, a new alpha 2-adrenoceptor agonist, in the conscious pony, ] Vet Pharmacol Ther 12:378, 1989.

15. Yamashita K, Tsubakishita S, Futaok S, et al: Car­diovascular effects of m edetomidine, detomidine and xylazine in horses,] Vet Med Sci 62:1025, 2000.

16. Wagner AE, Muir WW III , Hinchcliff K\V: Cardio­vascular effects of xylazine and detomidine in horses, Am ] Vet Res 52:651, 1991.

17. Nunez E, Steffey EP, Ocampo L, et al: Effects of alpha2-adrene rgic receptor agonists on urine pro­duction in horses deprived of food and wate r, Am J Vet Res 65: 1342, 2004.

18. Thurmon ]C, Steffey EP, Zink1 ]G, et al: Xylazine

causes transient dose-related hyperglycemia and increased urine volumes in mares, Am ] Vet Res 45:224, 1984.

19. Schatzmann U, Jossfck H , Stauffer IL, et al: Effects of alpha 2-agonists o n intraute rine p ressure and sedation in horses: comparison between detomi­dine, romifi dine and xylazine. Zentralbl Veter;l1 -armed A 41:523, 1994.

20. Spyridaki MH, Lyris E, Georgoulakis I, et al: Deter­mination of xylazine and its metabolites by GC-MS in equine urine for dopi ng analysis, ] Pharm Biollled A,wl 35: 107, 2004.

21. Sa lonen }S, Suoli n na EM: Metabolism of deto mi­dine in the rat. I. Compar ison of 3H-labell ed metabo lites formed in vitro and in vivo, Eur ] Drug Metab Pharmacokiflet 13:53, 1988.

22. Salonen JS, Vaha-Vahe T, Vainio 0, et al: Single­dose pharmacokinetics of detomidine in the ho rse and cow,] Vet PllQrmacol Ther 12:65, 1989.

23. Mudib AE, Chui YC, Young LM, et al: Characteri­zation of metabolites of xylazi ne produced in vivo and in vitro by LC/MS/MS and by GC/MS, Drug Metab Dispos 20:840, 1992.

24. Freeman SL, Bowen 1M, Bettschar t-Wolfensberger R, et al: Cardiovascular effects of romifidine in the standing horse, Res Vet Sci 72: 123, 2002.

Field Anesthesia 41

25. England GC, Clarke K\V, Goossens L: A comparison of the sedative effects of three alpha 2-adrenoceptor agonists (rom ifidine, detomidine and xylazine) in the horse,] Vet PllQrmacol Ther 15:194, 1992.

26. Hamm D, Turchi P, }ochle W: Sedative and an­algesic effects of detomidine and rom ifidine in horses, Vet Rec 136:324, 1995.

27. Hobo 5, Aida H , Yoshida K: Assessment of the seda­tive effect of medetomidine and determ ination of its optimal dose in thoroughbred horses,] Vet Med Sci 57:507, 1995.

28. Tranquilli WJ, Maze M: Clinical pha rmacology an d use of alpha2-adrenergic ago nists in veterinary anaesthesia, Allaesth Pharmacol Rei' 1:297, 1993.

29. Buchner HH, Kubber P, Zohmann E, et aJ: Sedation and antisedation as tools in equine lameness exam­ination, Equine Vet] SuppI30:227, 1999.

30. Kollias-Baker CA, Court MH, Williams LL: Influ­ence of yohimbine and to lazoline on the cardiovas­cula r, resp iratory, and sedative effects of xylazine in the ho rse,] Vet Pharmacol Titer 16:350, 1993.

31. Corn ick-Seahorn JL, Seahorn TL: Card iopul­monary and behavioral effects of midazolam Hel and reversal with flum azenil in pony foals, Proceedings of the 22nd Annual Meeting of the American College of Veterinary Anesthesiologists, Phoenix, Ariz., 17,2004.

32. Stoelting RK: Benzodiazepines. In Stoelting RK, ed itor: Pharmacology and physiology i/1 anesthetic practice, ed 3, Ph iladelphia, 1999, Lippincott Raven.

33. Marland A, Sarkar P, Leavitt R: The uri nary elimi­nation profiles of diazepam and its metabolites, nordiazepam, temazepam, and oxazepam, in the equine after a 10-mg intramuscular dose, ] Anal ToxicoI23:29, 1999.

34. Wall R, Muir WW III: Hemolytic potential of gua ifenesin in cattle. Comell Vet 80:209, 1990.

35. Grandy }L, McDonell WN: Evaluation of concen­trated solutions of guaifenesin for equine anesthe~ sia,] Am Vet Med Assoc 176:6 19, 1980.

36. Herschl MA, Tr im CM, Mahaffey EA: Effects of 5% and 10% gua ifenesin infusion on equine vascu lar endothelium, Vet SlIrg 21 :494, 1992.

37. Davis LE, WolffWA: Pharmacokinetics and metab­olism of glyceryl guaiacolate in ponies, Alii ] Vet Res 31:469, 1970.

38. Muir WW, Skarda RT, Sheehan WC: Cardiopul­monary effects of narcotic agonists and a partial agonist in ho rses, Am / Vet Res 39: 1632, 1978.

39. Amadon RS, Cra ig AH: The actions of morphine on the horse. Preliminary studies: diacetylmor­phine (heroin), dihydrodesoxymo rphine-D (deso­mo rphine) and dihydroterocod ine,] Am Vet Med Assoc91:674,1937.

40. Mircica E, Clutton RE, Kyles KW, et a1: Problems associated with perioperative morphine in horses: a retrospective case analysis, Vet AnaestIT Allalg 30: 147,2003.

1

II

42 PRESU RGICAL PR EPARATION AND ASSESSMENT

41. Kamerling $, Weckman T, Donahoe J. et al: Dose related effects of the kappa agonist U-50, 488H on behaviour, nociception and autonomic response in the horse, Eqlline Vet J 20: 114, 1988.

42. No lan AM, Besley W, Reid ]. et al: The effects of butorphanol on locomotor activity in ponies: a prelimina ry study, J Vet Pllarmacol Ther 17:323 , 1994.

43. Sellon DC, Monroe VL. Roberts Me, et al: Phar­macokinetics and adverse effects of butorphanol administered by single intravenous injection or continuous intravenous infusion in horses, Am J Vet Res 62: 183, 200 I.

44. van Dijk P, Lankveld DP, Rijkenhuizen AB, et a1: Hormonal, metabolic and physiological effects of laparoscopic surgery using a detomidine­buprenorphine combination in standing horses, Vet Allaestll Allnlg 30:72, 2003.

45. Maxwell LK, Thomasy SM, 510vis N, et al: Phar­macokinetics of fentanyl fo llowing intravenous and transdermal administration in horses, Equine Vet' 35:484, 2003.

46. Reves ]G, Glass PSA, Lubarsky DA, et al: Intra­veno us nonopio id anesthetics. In Miller RD, ed itor: Miller's anesthesia, ed 6, Philadelphia, 2005, Church ill Liv ingstone.

47. Chang T, Glazko AJ: Bio transformation and dispo­sition of ketamine, int Anesthesiol eli" 12:157. 1974.

48. Rogers R, Wise RG, Painter OJ, et al: An investiga­tion to dissociate the analgesic and anesthetic properties o f ketamine using functional magne­tic resonance imaging, Allest/lesiology 100:292, 2004.

49. Kapfer S, Alfonsi p, Gu igna rd B. et a l: Nefopam and ketamine comparably enhance postoperative anal­gesia. Anesth Allnlg toO: 169, 2005.

50. Ed rich T, Friedrich AD, Eltzsch ig HK, et al: Keta­mine for long-term sedat io n and analges ia of a burn patient, Allestlt Analg 99:893, 2004.

51. Ozyalcin NS, Yuce! A, Camlica H, et al: Effect of pre-emptive ketamine on sensory changes and postoperative pain after thoracotomy: comparison of epidural and intramuscular routes, Br , Annesth

•

93:356, 2004. 52. Katz J, Schmid R, Snijde!aar OG, et al: Pre-emptive

analgesia using intravenous fenta nyl plus low-dose ketamine for radical prostatectomy under general anesthesia does not produce short-term or long­term reduct ions in pain or analgesic use, Pa in 110:707,2004 .

53. Van Elst raete AC, Lebrun T, Sandefo I, et al: Keta­mine does not decrease postoperative pain after remifentanil-based anaesthesia for tonsillectomy in adults, Acta AI/aesth esiol Scn lld 48:756, 2004.

54. Hocking G, Cousins MJ: Ketamine in chronic pain ma nagement: an evidence-based review, Allesth AI/alg 97: 1730, 2003.

55. General pharmacology of the injectable agents used in anaesthesia. In Hall LW, Clarke KW, Trim CM, ed itors: Veterinary anaesthesia, ed to, St Louis, 2001, WS Saunders.

56. Wilson RP, Zagon IS, Larach DR, et al: Card iovas­cular and respi rato ry effects of tiletaminezola­zepam, Pharmacol Biochem Belwv 44: I , 1993.

57. Taylor PM: The stress response to anaesthes ia in ponies: barbiturate anaesthesia, Equine Vet} 22:307, 1990.

58. Simons Pj, Cockshott !D, Douglas Ej, et al: Species differences in blood profiles, metabolism and excretion of C l4-propofol after intravenous dos ing to rat, dog and rabb it, Xenobiotica 2 1: 1243, 1991.

59. W ilson DV, Bohart GV, Evans AT, et al: Retrospec­t ive analysis of detomidine infusion for standing chemical restraint in 5 I horses, Vet Anaesth Analg 29:54, 2002.

60. Anaesthesia of the horse. In Hall LW, Clarke KW, Trim CM, editors: Veterinary anaesthesia, ed 10, St Lo u is, 2001 , WB Saunders.

61. Hall LW, Taylor PM: Clinical trial of xylazine with ketamine in equine anaesthesia, Vet Rec 108:489, 1981.

62. Lin HC, Branson KR, Thurmon JC, et al: Ketamine, Te!azol, xylazine and detomidine. A comparative anesthetic drug combinatio ns study in ponies, Acta Vet Sca lld 33: 109, 1992.

63. Muir WW, Skarda RT, Milne OW: Evaluation of xylazine and ketamine hydrochloride for anesthe­sia in horses, Am J Vet Res 38:195, 1977.

64. Muir WW III , Lerche P, Robertson JT, et al: Com­parison of four drug combinations for total intra­venous anesthesia of horses undergoing surgical removal of an abdominal testis, J Am Vet Med Assoc 217:869, 2000.

65. Matthews NS, Taylor T5, Skrobarcek C L, et al: A comparison o f injectable anaesthetic reg imens in mules, Eqllille Vet' SlIppl 34, 1992.

66. Matthews NS, Taylor TS: Anesthetic management of donkeys and mules. In Steffey EP, editor: Recellt advances in allesthetic mallagement of large domes­tic animals, Ithaca, N.Y., 2000, International Veteri­na ry Information Service (www.ivis.org).

67. Olson KN: Anesthesia for laryngoplasty with or without sacculectomy in 85 draft horses: compari ­son with 322 Thoroughbreds, Vet Arwestl, Analg 29:97, 2002.

68. Freeman SL, Bowen 1M, Bettscha rt-Wolfensberger R, et al: Cardiopulmo nary effects of romifidine and detomidine used as premedicants fo r ketaminel halothane anaesthesia in ponies, Vet Rec 147:535, 2000.

69. Kerr CL, McDonell WN, Young SS: Card iopul­monary effects of romifidine/ketamine o r xylazinel ketami ne when used for short duration anesthesia in the horse, Call' Vet Res 68:274, 2004.

70. Taylo r PM, Bennett Re, Brearley Je, et al: Com ­parison of deto midine and romifidine as premed­icants before ketam ine and halothane anesthes ia in ho rses undergoing elective surgery, Am J Vet Res 62:359,200!.

71. Hubbell JA, Bednarski RM. Muir WW: Xylazine and tiletamine-zolazepam anesthesia in horses, Am J Vet Res 50:737, 1989.

72. Muir WW III , Gadawski JE, Grosenbaugh DA: Car­diorespiratory effects of a tiletamine/zolazepam­ketamine-detomidine combination in horses, Am J Vet Res 60:770, 1999.

73. Muir WW, Skarda RT, Sheehan W: Evaluation of xyiazine, guaifenes in, and ketamine hydrochloride for restraint in horses, Alii J Vet Res 39:1274, 1978.

74. Greene SA, Thurmon le, Tranqu illi WJ. et al: Car­diopuJmonary effects of continuous in travenous infus ion of guai fenes in , ketamine, and xylazine in ponies, Am J Vet Res 47:2364, 1986.

75. Lin HC, Wallace SS, Robbins RL, et a1: A case report on the use of gua ifenesin-ketam ine-xylazine anesthesia for equine dystocia, Cornell Vet 84:6 1, 1994.

76. Taylor PM, Luna SP, Sear JW, et al: Total intra ­venous anaesthesia in ponies using detomidine, keta mine and guaiphenesin: pharmacokinetics, ca rdiopulmonary and endocrine effects, Res Vet Sci 59: 17, 1995.

77. van Dijk P: Intraveno us anaesthesia in horses by gua iphenesin-ketamine-detomidine infusion: some effects, Vet Q 16(suppI 2):SI22, 1994.

Field Anesthesia 43

78. McMurphy RM, Young LE, Marlin Dj, et a1: Comparison of the cardiopulmonary effects of anesthesia maintained by continuous infusion of romifidi ne, guaifenes in , and ketamine with anes­thesia maintained by inhalation of halothane in horses, Am J Vet Res 63: 1655, 2002.

79. Am erican College of Veterinary Anesthesio logy: Suggestions fo r monitoring anestheti zed veterinary patien ts, J Am Vet Med Assoc 206:936, 1995.

80. Johnston GM, Eastment JK, Wood JLN, et al: The Confide ntial Enqui ry into Perioperative Equine Fatalities (CEPEF): mortality resu lts of Phases I and 2, Vet Afwesth A I/alg 29:159,2002.

81. Hall LW: Spinal analgesia. In Hall LW, editor: Wright's veterillary aI/aesthesia alld allalgesia, London, 197 1, Balliere and Tindall.

82. Robinson EP: Preferential derma to mal analgesic effects of epidurally-administered morphine in horses. In Bryden 0 1, editor: Animal paill alld its control, Sydney, 1994, University of Sydney.

83. Natalini CC, Robinson EP: Evaluation of the anal­gesia effects of epidurally administered morphone, alfentinil. butorphanol, tramadol, and U50488H in horses. Am J Vet Res 61:1579, 2000.

84. Grubb TL, Riebold TW, Huber MJ: Com parison of lidocaine, xylazine and xylazinellidocaine for caudal epidural analgesia in ho rses, J Am Vet Med Assoc201:1 187, 1992.

1MB URGERIES

45

Chapter 6

Periosteal Transection and Elevation Rick D. Howard

INDICATIONS

Performed alone for the treatment of angular limb deformities in foals with mild to moderate deformity or in combination with transphyseal bridging for foals with more severe deformities. Most commonly used for treatment of carpal valgus and tarsal valgus but also for varus or valgus deformities of the metacarpophalangeal or metatarsophalangeal joints.

EQUIPMENT

A hooked surgical blade and periosteal elevator.

POSITIONING

Dorsal recumbency is preferred for bilateral procedures or when performed concurrent with transphyseal bridging. Lateral recumbency is pre­ferred for unilateral cases or for bilateral cases (with rolling) not requiring concurrent trallsphy­seal bridging.

ANATOMY

The surgical approach for treatment of carpal valgus is over the distolateral aspect of the radius just proximal to the distal radial physis (Figure 6-1). The vertical skin incision is positioned

46

between the common and lateral digital extensor tendons, a site with minimal soft tissue overlying the radius. The surgical approach for treatment of tarsal valgus is over the lateral malleolus of the tib ia just proximal to the distal tibial physis (Figure 6-2). The vertical skin incision is posi­tioned either just cranial or caudal to the lateral digital extensor tendon. The surgical approach for treatment of metatarsophalangeal or metacar­pophalangeal angular limb deformities is on the concave side of the limb using an approach just proximal to the distal physis of the 3rd metacar­pal bone or the 3rd metatarsal bone. Periosteal transection and elevation to augment growth at the proximal physis of the first phalanx through an approach just distal to the proximal physis of the 1st phalanx may be indicated in certain cases.

PROCEDURE

Periosteal transection and elevation is performed on the lateral aspect of the limb for treatment of valgus deformities and on the medial aspect of the limb for the treatment of varus deformities. A 3-to 4-cm vertical incision is made in the skin and subcutaneous tissues parallel to the long axis of the bone beginning I to 2 cm proximal to the physis and extending proximally. The incision is carried to the level of the periosteum. Curved hemostatic forceps are used to bluntly dissect between the periosteum and overlying soft tissues extending from the distal aspect of the incision in

•

1-

Site of surgical ___ -1',

approach

Figure 6-1 Incision site for periosteal transection on the lateral aspect of the left forelimb between the common (1) and lateral (2) digital extensor tendons sta rting at the level of the distal radial physis and extending proximal 3 to 4 em.

I

Figure 6-2 Incision site for periosteal transection on the lateral aspect of the left tibia on either side (dotted lines) of the lateral digital extensor tendon (1) starting at the level of the dista l tibial physis and extend­ing proximal 3 to 4 em.

the cranial and caudal planes. The subcutaneous tissues and tendons are elevated with curved hemostatic forceps. A No. 12 hooked scalpel blade is used to transect the periosteum along the lateral hemicircumference of the bone. When performed for treatment of carpal valgus, the rudimentary cartilaginous ulna should also be transected using a No. 10 scalpel blade. When ossified, as is typical

Periosteal Transection and Elevation 47

Figure 6-3 Occasionally, a rudimentary cartilagi­nous ulna is noted, which should be transected using a No. 10 scalpel blade. When ossified, as is typical in older foals. a segmental ulnar ostectomy should be performed

• uSing rongeurs.

Figure 6-4 The periosteum is initially transected along the lateral hemicircumference of the bone. The periosteum is then incised longitudinally extending proximally 3 to 4 em from and connecting with the hor­izontal periosteal transection. The resulting paired tri­angular shaped flaps of periosteum are elevated with a periosteal elevator.

in older foals, a segmental ulnar ostectomy should be performed using rongeurs (Figure 6-3) . The periosteum is then incised longitudinally extend­ing proximally 3 to 4 em from and connecting with the horizontal periosteal transection. The resulting paired triangular shaped flaps of per­iosteum are elevated with a periosteal elevator (Figure 6-4). The subcutaneous tissues are sutured with absorbable material in a simple continuous pattern, and the skin is sutured closed with intra­dermal sutures or with simple interrupted sutures of No. 3-0 nonabsorbable monofilament suture material. The wound is bandaged routinely .

•

48 LIMB SURGERIES

POSTOPERATIVE CARE

Postoperative Care

Bandaging: Postoperatively, the surgical site is maintained under a bandage for 10 to 14 days. Suture Removal: If skin sutures are placed, they should be removed after 10 to 14 days. Exercise: The foal is strictly confined to a stall for 10 to 14 days. Exercise restriction is instituted postoperatively to reduce trauma to the asym­metrically loaded physis and cuboidal bones and is considered an essential component of the ther­apeutic plan during postoperative convalescence. The duration and degree of exercise restriction are dependent on the age of the foal and the severity of the angular limb deformity; however, strenuous exercise should not be allowed until the angular limb deformity has been corrected. Other: The hooves should be trimmed to achieve balance and the foal maintained on a nutritionally balanced diet.

EXPECTED OUTCOME

The expected degree of correction is proportional to the amount of growth expected to occur at the affected physis during the 6 to 8 weeks following surgery. It is considered that after this amount of time no further benefit is derived from periosteal transection and elevation. In cases where partial but inadequate correction is achieved, repeated surgery may be warranted provided adequate growth potential remains. In contrast to the transphyseal bridge procedure, overcorrection of the angular limb deformity is not a complication of periosteal transection and elevation.

COMPLICATIONS

Complications include incomplete correction of the angular limb deformity, incisional dehiscence, and development of arthropathy as sequelae to the damage induced by asymmetric loading of the cuboidal bones during weight bearing.

ALTERNATIVE PROCEDURES

An alternative technique to the open technique as described involves performing periosteal transec-

tion and elevation using a blind approach through a I-em-length skin incision. Using the blind tech­nique, the surgical wounds are allowed to heal by second intention under a bandage. The primary advantages of the technique are the decreased sur­gical time and decreased incisional complications. Postoperative care is essentially as described for the open technique for periosteal transection and elevation.

COMMENTS

The differential diagnoses for angular limb defor­mities in foals include intercarpal or intertarsal ligament laxity, crushed carpal or tarsal bones, distal radial or tibial physeal dysplasia, and physeal trauma resulting in premature closure of the physis. Preoperative radiographs are important to confirm the source of the angular limb deformity and to determine if surgical manipulation of the growth plate is indicated for treatment of the defor­mity. Dorsopalmar (plantar) and lateral medial radiographic views of the affected area will gener­ally confirm the source of the angular deformity.

Periosteal transection and elevation is best indicated for deformities associated with physeal dysplasia. Periosteal transection and elevation requires a functioning physis to be effective. If the physis is crushed, as occurs with Salter-Harris type V or VI fractures, the procedure will not be effective because the physis is unable to respond.

Angular limb deformities may also be associ­ated with the metaphysis or diaphysis of long bones; typically the third metacarpal or metatarsal bones. These deformities are usually congenital and their repair is beyond the scope of this book.

Since its introduction into equine surgery in 1980, periosteal transection and elevation has been widely accepted as an effective method for augmentation of axial limb growth in the treat­ment of angular limb deformities. 1.2 The effec­tiveness of the procedure has been questioned. The results of a study on the efficacy of periosteal transection and elevation for the treatment of experimentally induced carpal valgus indicated foals treated with stall confinement and hoof trimming alone or with the addition of periosteal transection and elevation demonstrated a similar correction in angular limb deformity.3 Although the results were significant, it is important to note that the transphyseal bridge model for carpal valgus used in that study may be an inadequate

•

ld approach through Jsing the blind tech­:e allowed to heal by ndage. The primary re the decreased SUf­

lonal complications. Ily as described for teal transection and

limb defor­or intertarsal tarsal bones.

pP"tSla, and physeal closure of the

are important to limb deformity

ianipullati', In of the of the defor­

lateral medial area will gener­

deformi ty. elevat,,' 'n is best

with physeal and elevation effective. If the

Salter-Harris will not be

to respond. also be associ­

of long or metatarsal

indicated and hoof

In'''' ,n'to note for carpaJ

an inadequate

model for naturally occurring carpaJ valgus and that extrapolation of the results to naturally occurring disease may be inappropriate.

REFERENCES

1. Auer JA, Martens RJ: Angular limb deformities in young foals, Proc Am Assoc Equine Pract 26:81, 1980.

Periosteal Transection and Elevation 49

2. Auer JA, Martens RJ. Williams EH: Periosteal tran­section for correction of angular limb deformities in foals. J Am Vet Med Assoc 181 :459. 1982.

3. Read EK, Read MR, Townsend HG, et al: Effect of hemi -circumferential periosteal transection and ele­vation in foals with experimentally induced angular limb deformities. ] Am Vet Med Assoc 221 :536,2002.

CHAPTER 7

Transphyseal Bridging Rick D. Howard

INDICATIONS

Transphyseal bridging is performed alone or in combination w ith periosteal transection and elevation for the treatment of angular limb de· formities associated with the carpus, tarsus, meta­carpophalangeal, or metatarsophalangeal joints in young foals «3 months of age) with severe angular limb deformity or in foals with clinically significant deformity after the potential for rapid growth has passed: 2 months for the distal 3rd metacarpal) 3rd metatarsal, and proximal 1st phalangeal physes; 4 months for the distal tibial physis; and 6 months for the distal radial physis.' ·2

EQUIPMENT

An AO-ASIF 4.5-mm or 5.5-mm screw set, instru­mentation for placement and removal of screws, and orthopedic wire are required. Alternatively, self-tapping screws may be used, reducing the required orthopedic equipment to a drill, an appropriate-size drill bit, screwdriver, self-tapping screws, and orthopedic wire. Equipment for ob­taining intraoperative radiographs is also neces­sary.

POSITIONING

Dorsal recumbency is preferred for bilateral pro­cedures or when performed concurrently with

50

periostea l transection and elevation. Lateral re­cumbency is used for unilateral cases not requir­ing periosteal transection and elevation.

ANATOMY

Regardless of the technique used, transphyseal bridging requires the placement of an orthopedic implant in the epiphysis of the operated bone. The surgeon should become famili ar with the size and contour of the epiphyses of commonly operated bones to avoid inadvertent damage to the articu­lar surfaces of the adjacent joint. Because of the irregular shape and narrow proximal-to-distal dimension of the distal tibial epiphysis, radi­ographic guidance is essential to avoid the risk of errant placement of the implant into the tibio­tarsal joint. Radiographic confirmation of correct screw placement is recommended for transphy­seal bridging at all locations.

PROCEDURE

Transphyseal bridging is performed on the medial aspect of the limb for the treatment of valgus deformities and on the lateral aspect of the limb for the treatment of varus deformities. Periopera­tive antibiotics are administered, the foal is anes­thetized and positioned, and the surgical site is prepared aseptically fo r surgery. A curvilinear incision is made in the skin and subcutaneous tissues oriented along the long axis of the radius

•

':,L '---- Epiphysis

Figure 7-1 A curvilinear incision (dotted lille) is made over the medial aspect of the left distal radial physis or iented along the long axis of the radius, begin­ning at the level of the radiocarpal joint and extending toward the diaphysis of the bone for exposure of the epiphysis, the physis, and 2 to 3 em of the metaphysis .

beginning at the level of the radiocarpal joint and extending toward the diaphysis of the bone for exposure of the epiphysis, the physis , and 2 to 3 cm of the metaphysis (Figure 7-1). The soft tissues are bluntly dissected and retracted. Then 22-gauge I.S-inch needles are placed into the radiocarpal joint space and the physis. A I-em incision is made with a scalpel through the collateral liga­ment midway between the needles for placement of the epiphyseal screw (Figure 7-2). Using radi­ographic guidance for screw placement and ori­entation, a 3.2-mm pilot hole is drilled, measured, and tapped for placement of a 4.5-mm screw. As a general rule, the epiphyseal screw is placed roughly parallel to the physis, except in the distal tibial physis, where a shorter screw is used and the screw mllst be angled from distal to proximal to avoid entering the tibiotarsal joint. A 40-mm­length cortical screw is inserted into the epiphysis and incompletely tightened. A I-em incision is made in the periosteum over the metaphysis at a site approximately 2 to 3 cm from the physis. The periosteum is elevated, and a 4.5-mm 40-mm­length cortical screw is similarly placed in the

Transphyseal Bridging 51

.,,:[~t;..t'«... .

Figure 7-2 Hypodermic needle in position to iden­tify the distal radial physis . Two screws are placed per­pendicular to the long axis of the bone approximately I to 2 em proximal and distal to the physis.

Figure 7-1 A figure of eight wire (IS-gauge ortho­pedic wire) is placed around the heads of the screws and tightened using a wire hvister or pliers.

~(}.v.,c.,;t~ Figure 7-4 A second figure of eight wire is placed and tightened as described and the wire twists are bent against the bone toward the adjacent joint.

metaphysis and tightened incompletely. A figure of eight wi re (lS-gauge orthopedic wire) is placed around the heads of the screws and tightened using a wire twister or pliers (Figure 7-3). A second figure of eight wire is placed and tightened as described, and the wire twists are bent against the bone toward the adjacent joint (Figure 7-4).

•

,

52 LIMB SURGERIES

The screws are tightened with a screwdriver until the heads are flush with the soft tissues, taking care not to tighten the screws excessively as this will cause the wires to become dislodged over the screw heads. Tightening the screws places addi­tional tension on the figure of eight wires as the bevel of the screw head engages the wires. The subcutaneous tissues are sutured with absorbable material in a simple continuous pattern, taking care to cover as much of the implant as possible. The skin is sutured with simple interrupted sutures of No. 3-0 nonabsorbable monofilament suture material. The wound is bandaged routinely, and a thin cotton padded outer wrap is placed to reduce external trauma to the surgical sites.

POSTOPERATIVE CARE

An essential component of the postoperative care is the timely removal of the transphyseal bridge implants. Client education is a key component of successful case management. Clients should be instructed that the implants must be removed when the deformity has corrected or just prior to complete correction. In contrast to periosteal transection and elevation, overcorrection of the angular limb deformity occurs if timely removal of implants is neglected. In cases where bilateral transphyseal bridging is performed, the removal of implants may need to be performed on sepa­rate occasions to allow adequate correction for each limb. Although implant removal may be achieved in some foals using sedation and local anesthesia, general anesthesia greatly facilitates the procedure and is indicated for most cases. Following routine aseptic preparation, the position of the screw heads is identified by probing with a hypodermic needle and a stab inci­sion is made down to each screw head. A mos­quito hemostatic forceps is used to retract the soft tissues while a screwdriver is manipulated and firmly seated into the screw head and used to remove each screw. A sturdy curved hemostatic forceps placed through the stab incision over the metaphyseal screw is used to hook the loops of the figure of eight wires for extraction by firm trac­tion. The skin incisions are sutured and the sur­gical site bandaged for 10 to 14 days until the sutures are removed.

Postoperative Care

Bandaging: The surgical site is maintained un­der a bandage until skin sutures are removed at 10 to 14 days. Exercise Restrictions: Postoperatively, the foal should be strictly confined to a stall. Exercise restriction is instituted postoperatively to reduce trauma to the asymmetrically loaded physis and cuboidal bones and is considered an essential component of the therapeutic plan during post­operative convalescence. The duration and degree of exercise restriction are dependent on the age of the foal and the severity of the angular limb deformity; however, strenuous exercise should not be allowed until the angular limb deformity has been corrected. Suture Removal: Skin sutures are removed at 10 to 14 days. other: The hooves should be trimmed to achieve balance and the foal maintained on a nutritionally balanced diet.

EXPECTED OUTCOME

The expected amount and rate of axial correction are proportional to the growth potential of the affected physis and are dependent on the age of the patient and the physis affected. Typically, rapid correction of the angular limb deformity occurs in young foals) while slower, but steady, correction is anticipated fo r the older patient.

Swelling, inflammation, and scar tissue formation at the surgical site of the implants are common but typically become less apparent once the limb has straightened and resolve once the implants have been removed. The development of infection may result in subcutaneous abscess or skin inci ­sion dehiscence and in some cases necessitates premature removal of the surgical implants. The most serious potential complication is overcor­rection of the angular limb deformity. The gravity of this complication should not be underempha­sized; for example, a mild carpal valgus is typically only a cosmetic impairment compared with the

•

I

potentially severe performance-limiting conse­quences of a carpal varus deformity that may result from delayed removal of transphyseal bridge implants. Timely removal of implants is essential to reduce the frequency of this compli­cation.

ALTERNATIVE PROCEDURES

An alternative to the open technique as described involves performing the surgery through stab incisions made over the location of each screw site. 2 The soft tissues between the screw holes are bluntly undermined with mosquito hemostatic forceps forming a tunnel for passage of the figure of eight wires. Postoperative care is as described for the open technique for transphyseal bridging.

An alternative to screws and wires for transphyseal bridging is the use of orthopedic staples, initially described in 1963.3 Staples have the advantage of being easier and quicker to place and have a low complication rate.4 Two sizes of staples are commercially available: 22 x 22 mm (Zimaloy Epiphyseal Staple; Zimmer, Inc., Warsaw, Ind.) and 29 x 22 mm (Blount E.S.; Stryker, Kalamazoo, Mich.). Disadvantages of sta­ples include the lack of compression across the growth plate in the early postoperative period and the limited flexibility in placement caused by the fixed leg length of the staple.

Another alternative is the recently described technique for the placement of a single transphy­seal screw for transphyseal bridging.s The de­scribed technique involves the placement of a single fully threaded screw at an oblique angle in lag fashion from the medial malleolus, across the physis and into the metaphysis of the tibia. The approach to the medial malleolus is via a stab inci­sion and is associated with minimal soft tissue dissection. Advantages cited for this technique include reduced need for soft tissue dissection, improved cosmetic result, and reduced risk of infection. Although the authors indicate they had used th is procedure in the treatment of carpal valgus, the current report was limited to treat­ment of tarsal valgus in 4- to 12-month-old horses. In this report of 11 cases, the tarsal valgus resolved and the cosmetic result was considered excellent. 5 We have used this method for correc­.tion of carpal valgus in foals. In the carpus, the

Transphyseal Bridging 53

Figure 7-5 Dorsopalmar radiograph of the carpus with a single 4.S-mm cortical bone screw placed across the distal radial physis as an alternative for transphyseal bridging.

screw can be placed distal to proximal or proxi­mal to distal as shown in Figure 7-5.

COMMENTS

The primary advantage of transphyseal bridging compared with periosteal transection and eleva­tion is the more consistent response achieved even in severely deformed or older patients. Unless the physis is damaged on the side opposite the side bridged or the physis is too mature to respond, correction will occur. The disadvantages of the procedure include increased time and cost of the procedure, the increased risk of infection, the increased likelihood of a less-than-satisfactory cosmetic appearance, the requirement for more special equipment, the possibility of overcorrec­tion, and the need for a second surgery to remove the implants to avoid overcorrection. . The differential diagnoses for angular limb

deformities in foals include intercarpal or inter­tarsal ligament laxity, crushed carpal or tarsal bones, distal radial or tibial physeal dysplasia, and physeal trauma resulting in premature closure of the physis. In addition, angular limb deformities may also be associated with the metaphysis or dia­physis of long bones, typically the third metacarpal

•

I

54 L I MB SU RG ERIES

or metatarsal bones. These metaphyseal or dia­physeal deformities are usually congenital, and their repair is beyond the scope of this book.

Preoperative radiographs are important to confi rm the source of the angular limb deformity and to determi ne if su rgical manipulation of the growth plate is indicated for treatment of the deformity. Dorsopalmar (plantar) and lateral medial radiographic views of the affected area will generally confi rm the source of the angular deformity.

Transphyseal br idging requires a functioning physis to be effective and is best indicated for deformities associated with physeal dysplasia. If the physis is crushed, as occurs in Salter-Harris type V or VI fractures, transphyseal bridging will not be effect ive because of the inability of the con­tralateral side of the physis to respond. If the origin of the deformity is associated with the joint (e.g., crushed carpal bones), transphyseal bridging can cosmetically straighten the external appearance of the limb, but the internal misalign­ment may result in degenerative joint disease and lameness.

Transphyseal bridging may also be used in concert with periosteal transection and elevation in foals with severe deformities, as the two proce­dures are performed on opposite sides of the limb. There is no objective evidence indicating the com­bination results in better or faster correction of the deformity.

REFERENCES

I. Fretz PB, Cyubaluk NF, Pharr jW: Quant itative anal­ysis of long bone growth in the horse, Am f Vet Res 45: 1602, 1984.

2. Auer JA: AnguJar limb deformities. In Auer lA, Stick lA, editors: Equine surgery, ed 2, Philadelph ia, 1999, WB Saunders.

3. Heinze CD: Epiphyseal stapling, Proc Am Assoc Equine Pmct 9:203, 1963.

4. Hunt Rl: Management of angular deformities, Proc Am Assoc Equine Pmct 46: 128, 2000.

5. Witte S, Thorpe PE, Hunt RJ, et al: A lag-screw tech­nique fo r bridging of the medial aspect of the distal tibial physis in horses. f Am Vet Med Assoc 225: 158 1, 2004.

•

CHAPTER 8

Distal Limb Perfusion Joanne Kramer

INDICATIONS

Infection of bone and soft tissues in the distal limb (Figure 8- 1).

EQUIPMENT

A cannulated screw with an appropriately sized drill bit and tap or commercially ava ilable intraosseous infusion needles are needed for intraosseous perfusion (Figu re 8-2) . A 20- to 26-gauge I -inch catheter is necessary fo r intra­venous perfusion. For both techn iques, an Esmarch bandage or pneumatic tourniquet and the selected antibiotic diluted in 60 mL of normal saline are necessary.

POSITIONING AND PREPARATION

The limb should be clipped and prepared for aseptic surgery. Care should be taken to isolate open, infected sites from the perfusion entry site. Depending on the nature of the horse, the proce­dure can be performed with the horse standing or under general anesthesia. For intraosseous perfu­sion, the initial procedure is often performed under general anesthes ia and follow-up proce­dures are performed standin g. Standing proce­dures require sedation and regional anesthesia above the area to be perfused.

55

ANATOMY

Regional perfusion delivers antibiotic into the venous system by intraosseous or intravenous infusion. With pressure, the perfusate distends the venous vasculature, allowing the perfusate to enter tissue wi th intact venous vasculatu re. Antibiotics then enter ischemic tissue and exu­dates via increased hydrostatic pressure in cap­il lar ies and diffusion across a concentra tio n gradient. ' ,2 During regional perfusion, the timing of antibiotic del ivery to the tissues is expected to follow a similar pattern to that observed follow­ing contrast medium. Shortly after intravenous injection, contrast is in both the venous and arter­ial system s; 15 m inutes after injection. contrast has started to d iffuse into adjacent soft ti ssues; and 30 minutes after injection, contrast is pri­marily in the adjacent soft tissues' (Figure 8-3).

PROCEDURE

Selected Antibiotics

Antibiotics must be approved for intravenous administration. Concentration-dependent antib i­o tics such as gentam icin and amikacin are com­monly used, but other antibiotics may be used as well. Ideally, antibiotic choice is guided by culture and sensi tivity results. Because such high tissue concentratio ns ca n be achieved locally with small doses of antibiotic, antibiotics that are cost­prohibitive to use systemically can be used. In

56 LIMB SURGERIES

Figure 8-1 A horse with a chronic distal limb infec­tion.

Figure 8-2 Cannulated 4-mm scre"1 with a nut and adapter welded to the head.

Figure 8-3 Contrast distribution 5 minutes after injection into the palmar digital vein in the distal pastern region.

reports, 125 to 1000 mg of amikacin or gentam­icin per perfusion has been used.3

-6 For other

antibiotics, the systemic dose o r less is used.

Exsanguination

Exsanguination of blood from the distal limb is recommended before perfusion of the tissues. Placement of the intravenous catheter is easier before exsanguination. Placement of the bone screw can be done eas ily before o r after ex­sanguination. For exsanguination, an Esmarch bandage is applied to the limb from the hoof to the distal cannon bone and secured tightly at the proximal end to prevent loss o f the perfusate into the systemic circulation. A pneumatic tourniquet can also be applied at the proximal end of the Esmarch bandage to prevent loss of the perfusate. After applying the tourniquet or securing the Esmarch bandage at the proximal end, the distal portion o f the bandage is unwrapped (Figure 8-4). In cases with extensive cellulitis, application of an Esmarch bandage is not recommended because of the risk of forcing bacteria from the

B

A Figure 8-4 A. A pneumatic tourniquet is applied at the proximal end of the Esmarch bandage to prevent loss of the perfusate. B. The distal portion of the bandage is then unwrapped.

interstitial flu id into the lymphatic system.? In these cases, a tourniquet is applied to the distal metacarpus without prior Esmarch bandage ap­plication.

Intravenous Perfusion

A 20- to 26-gauge I-inch catheter is placed in the palmar vei n at the level of or just distal to the sesamoid bones. The catheter and extension set

Figure 8-5 A 20- to 26-gauge i-inch catheter is placed in the palmar digital vein at the level of or just distal to the sesamoid bones. The catheter and exten­sion set are then glued and taped into place. The selected antib iotic diluted in 60 mL of saline is injected slowly using a sma ll syringe. Because of the pressure needed to deliver the antibiotic, a three-way stop-cock is used to allow the diluted antibiotic to be delivered with a small syringe.

Distal Limb Perfusion 57

are then glued and taped into place. The selected antibiotic diluted in 60mL of saline is injected slowly using a small syringe. Because of the pres­SUfe needed to deliver the antibiotic, we com­monly use a three-way stop-cock to allow the diluted antib iotic to be conveniently delivered with a smail syringe (Figure 8-5). The tourniquet is left in place for 30 minutes. After release of the tourniquet, the catheter is removed and pressure is applied to the puncture site for several minutes.

Intraosseous Perfusion

A stab incision is made in the proximal portio n o f the pastern midway between the lateral and dorsal aspect. An appropriately sized drill bit is used to create a pilot hole for the cannuJated screw (Figure 8-6). The hole is tapped and the cannu­lated screw is placed (Figure 8-7). The selected antibiotic diluted in 60 mL of normal sal ine is then slowly injected using a three-way stop-cock and small syringe. The tourniquet is left in place fo r 30 minutes. After release of the tourniquet, the screw is removed and the skin is closed with an interrupted suture.

POSTOPERATIVE CARE

Postoperative Care

Bandaging: A sterile dressing is placed over the incision or catheter site and a half limb bandage is applied. Exercise Restrictions: Stall rest with limited activity is advised until the sepsis is resolved. Medications: Systemic antibiotic therapy is con­tinued as indicated by the underlying condition. When the same antibiotic is given systemically as is used in the perfusion, we omit one systemic dose of the antibiotic on the day the perfusion is performed. Tetanus prophylaxis is provided if nec­essary. Suture Removal: Skin sutures are removed 12 days postoperatively.

EXPECTED OUTCOME

Synovial structure and bone infections are diffi­cult to treat and can have a poor outcome despite aggressive treatment. Regional antibiotic perfu­sion is an adjunctive therapy in the treatment of

I' I

58 LIMB SURGERIES

Drill bit

Cannulated screw

Tap ~P"" ,t.:1.,., .

•

Figure 8-6 A stab incision is made in the proximal portion of the pastern midway between the lateral and dorsal aspect. An appropriately sized drill bit is used to create a pilot hole fo r the cannu lated screw.

Figure 8-7 lntraosseous screw placement for perfu­sion of the pastern and coffin joint region.

sepsis and does not replace systemic antibiotic therapy, appropriate debridement, lavage, and drainage. Because regional antibiotic perfusion can achieve high tissue levels of antibiotics in affected sites, it can improve the outcome. In one stud y, the overall survival rate was 86% when distal limb perfusion was used in conjunction with aggressive systemic and local therapy.8

COMPLICATIONS

Severe tissue irritation from the antibiotic perfu­sion may occur but is rare. Partial thrombosis of the vein used for perfusion may occur, especially if used repeatedly. Complete thrombosis is un­common.

ALTERNATIVE PROCEDURES

Regional perfusion can be performed in many areas of the limb and has been described in the tarsus, radius, and carpus.9,]O lntraosseous perfu­sion can also be performed with a 14-gauge needle placed through a 2-mm drill hole or the male end of a Luer tip extension set placed through a 4-mm hole, but slight inaccuracies in fit can result in leakage of the perfusion solution. ]]

COMMENTS

In some studies, intravenous perfusion techniques have resulted in higher tissue levels of antibiotics than intraosseous techniques.4,12 Both methods produce much higher tissue levels than the recommended peak serum concentrations. Intra-

venous perfusion requi res less equipment than intraosseous perfusion but can be difficult to perform in limbs with significant swell ing or in veins that have had multiple perfusions. Sites for intraosseolls perfusion can be used multiple times after the original hole is drilled.

Additionally, a study comparing intraarticular injection of gentamicin with regional intraven ~

ous perfusion of gentamici n in normal horses found the techniques produced similar bone concentratio ns and that intraa rticular injection produced greater synovial fluid concentrations than regional intravenous perfusion. 13 In clinically affected horses, the increased hydrostatic pressure achieved in regional perfusion techniques may result in better perfusion of capillaries obstructed by debris or fibrin , but this has not been objec­tivelyevaluated.

REFERENCES

1. Finste rbush A. Argaman M. Sacks T: Bone and join t perfusion of antib iotics in the treatment of exper­imental staphylococcal infection in rabbits, I Balle loint SlIrg 52: 1424, 1970.

2. Finsterbush A, Weinburg H: Venous perfusion of the limb with antibiotics for osteomyel itis and other ch ronic infections, I Balle loint SlIrg Alii 54: 1227,1972.

3. Palm er SE, Hogan PM: How to perform regional li mb perfusion in the standing horse, Proc Am Assoc Eqllille Pmct 45: 124, 1999.

Distal limb Perfusion 59

4. Butt TD, Bailey lV, Dowling PM, et al: Comparison of 2 tech niques for regional anti biotic delivery to the equine forelimb: intraosseous perfusion vs. intravenous perfusion, Call Vet I 42:617, 200 I.

5. Mattson 5, Boure L, Pearce 5: Intraosseous gen­ta micin perfusion of the distal metacarpus in standing horses, Vet Slirg 33(2): 180, 2004.

6. Werner LA, Hardy ], Bertone AL: Bone gentamicin concentratio n after in tra-articuJa r injection or regional intravenous perfusion in the ho rse, Vet Stlrg 32(6):559, 2003.

7. O rsini JA, Elce Y, Kraus B: Management of severely infected wounds in the equine pati ent, Clill Tech Eq Pmct 3(2):225,2004.

8. Santschi EM, Adams SB. Murphey ED: How to perform equi ne intraveno us digital perfusion, Proc Am Assoc Equine Pract 44: 198, 1998.

9. Kettner NU, Parker lE, Watro us B1: lntraosseous regional perfus ion for treatmen t of septic physiti s in a t\'10 week old foal, J Am Vet Med Assoc 222(3):346,2003.

10. Whitehair KJ. Blevins WE, Fessler JF. et al: Regiona l perfusion of the carpus for antibiotic delive ry, Vet SlIrg21 (4):279, 1992.

II. Richardson OW: Local an ti m icrobial delivery in equine orthopedics, Proc Am CoIl Vet SlIrgeollS Vet Symp 13: 162,2003.

12. Scheuch BC, Va n Hoogmoed WD. Wilson JR, et al: Comparison of intraosseous or intravenous infu­sion fo r del ive ry of amikacin sulfate to the tibio­tarsal joint of horses, Am J Vet Res 63(3):374, 2002.

13. Werner LA. Hardy J. Bertone AL: Bone gentamicin concentration after intra-articula r or regional in tra­venous perfusion in the horse, Vet SlIrg 32(6}:559, 2003.

CHAPTER 9

Mid Metacarpal-Metatarsal Tendon Laceration Repair Joanne Kramer

INDICATIONS

Treatment of flexor and extensor tendon lacera­tions in the metacarpal or metatarsal region that do not involve the digital sheath (Figure 9-1 ). Care of lacerations involving the digital sheath requires intensive management to treat synovial structure sepsis and is discussed elsewhere l

-3 (Figure 9-2).

EQUIPMENT

Cast material and associated supplies are essentia1. Recommended suture materials for tendon repair include nylon, polydiaxone, and coated Kevlar (FiberWire, Arthex, Naples, Fla.). Size No.2 or larger suture material is used.

POSITIONING AND PREPARATION

The horse is positioned in lateral recumbency with the affected limb positioned for access to the laceration. The circumference of the limb should be clipped and prepared aseptically from at least the fetlock to the mid carpal/tarsal region.

ANATOMY

The proximal extent of the digital tendon sheath is in the distal th ird of the metacarpal-metatarsal region. The distal end of the sheath lies just prox-

60

imal to the navicular bursa within the hoof capsule. The distal end of the sheath and naviClI­lar bursa are separated by the transverse lamina. In the mid metacarpal-metatarsal region) the cross section of the flexor and extensor tendons varies from flat to circular (Figure 9-3).

ASSESSMENT AND SURGICAL PROCEDURES

Stabilization

A brief observation of the laceration and limb position is made and the need for immediate stabilization is determined. Elevation of the toe indicates complete deep digital flexor tendon laceration (Figure 9-4), and mild to moderate dropping (hyperextension) of the fetlock suggests superficial digital flexor tendon laceration or partial disruption of the suspensory apparatus (Figure 9-5). Severe hyperextension of the fetlock suggests transection or complete disruption of the suspensory apparatus (Figure 9-6). Buckling forward at the fetlock or difficulty extending the distal limb suggests common or long digital extensor tendon rupture (Figure 9-7).

The need for stabil ization must be balanced agai nst the need to determine the extent of the wound and to offer owners who have economic concerns a general prognosis before proceeding with potentially costly procedures. Examination of the injury can be performed with the limb held up before stabilization is applied, but often a detailed examination is not possible until the

Mid Metacarpal-Metatarsal Tendon laceration Repair 61

Figure 9·1 Flexor tendon laceration in the mid metacarpal region proximal to the flexor tendon sheath.

Figure 9·2 Flexor tendon laceration in the palmar pastern region involving the flexor tendon sheath.

Common digital extensor tendon =-___ ......, .....

" i· .. >, . ." .. '

horse has been placed under anesthesia. Stabiliza­tion should be applied before induction of anes­thesia or transport. Flexor tendon lacerations, whether complete or partial, require Kimzey splint (Kimzey Welding Works, Woodland, Calif.)

• application or similar support to reduce the tension on the flexor tendons (Figure 9-8). Exten­sor tendon lacerations can be stabilized in a weight-bearing position by incorporating a PVC or wood splint into the bandage along the dorsal or palmar-plantar surface of the limb (Figure 9-9).

Synovial Structure Involvement

If the wound is near the digital sheath, involve­ment of the sheath can be determined byasepti­cally inserting a needle into the sheath at a site distal from the wound and distending the sheath with sterile saline. Involvement of the sheath is confirmed if fluid is observed at the wound site.

Vascular Status

Laceration of the digital vein and artery may accompany flexor tendon lacerations. In general, despite significant laceration of the vasculature, it is rare to have ischemic complications if only one side of the vasculature is transected. Lacerations involving both the lateral and medial vasculature

Long digital extensor tendon--

MT III

~;;::=:::==::::~~e"l- Me II II

A

Digital check

Interosseous mel "" __ (suspensory lig.)

B

Figure 9·3 A, Transverse section through the middle metacarpal region. B, Transverse section through the middle metatarsal region.

62 LIMB SURGERIES

Figure 9-4 Horse with a complete laceration of the deep digital flexor tendon. The toe is elevated from the ground, indicating hyperextension of the coffin joint.

Figure 9-5 Horse with a partial laceration of the superficial digital flexor tendon showing mild fetlock hyperextension.

risk ischemic compromise to the distal limb but can also heal adequately. Unfortunately, a practi­

cal way of assessing the ab ility of collateral circu­lation to provide adequate blood supply in the future healing period is not available.

Wound Debridement and Repair

Removal of contaminated and devitalized tissue is performed with layered debridement. In relatively

Figure 9-6 Horse recovering from suspensory liga­ment disruption. Note the fetlock hyperextension.

Figure 9-7 Buckling forward of the fetlock seen with long digital extensor tendon transection.

clean transections with potential for primary closure, debridement should be as conservative

as possible. The wound should be lavaged ex­tensively before, during, and after debridement (Figure 9-10) . If closure is performed, gloves and instruments are changed after debridement and

before closure. If the free cut ends of the flexor tendon are

cleanly transected and appear healthy, primary repair should be performed to improve alignment

Mid Metacarpal-Metatarsal Tendon Laceration Repair 63

Figure 9-8 Kimzey splint support for a deep d igital flexor tendon laceration. An extended elevated heel shoe has also been placed on the limb for support during bandage changes.

Figure 9-9 PVC splint support for an extensor tendon laceration.

and ea rly strength of the repair.'" If the ends of the fl exor tendon are extensively retracted) swollen, or discolored or the wound appears to be significantly infected, the area should be debrided and allowed to heal by second intention. In select cases, delayed primary closure can be performed with or without tendon suturing. All situations require a minimum of 6 weeks of cast or splint support. Partial flexor tendon lacerations can be managed with wound closure and limb immobi-

Figure 9-10 Extensive lavage during the initial stages of laceration repair.

lization without tendon suturing. If the laceration involves greater than 75% of the cross-sectional area of the tendon, tendon suturing may offer similar benefits to repair of complete transec­tions.6

Many extensor tendon lacerations have a sig­nificant degloving component and extensive soft tissue trauma, which precludes reconstruction. With appropriate wound care, these lacerations can heal by second intention and often have minimal functional impairment. Fibrosis between the tendon ends eventually results in a mechani­cal link between the tendon ends and, in many cases, return of extensor function of the digit.6

However, if the wound is amenable to primary closure and the tendon ends are transected cleanly, primary tendon repair is preferable.

Suture Patterns for Tendon Laceration Repair

Modified Far-Near-Near-Far Pattern This pattern is the simplest pattern to perform, and is best used in flat tendons. The needle is placed perpendicular to and approximately 1.5 em from the proximal tendon end for the initial far bite. The needle then enters the distal tendon end 0.5 to 1 em from the end for a near bite in a posi­tion slightly axial to the far bite. It is then looped back to the proximal end of the tendoll) and a near bite is taken 0.5 to 1 em from the end in the same plane as the previous near bite. The suture is then brought to the distal end, and a far bite is taken in the same plane as the initial far bite 1 to 1.5 em from the end. The two far ends are then tied (Figure 9-1 I).

64 LIMB SURGERIES

\

Figure 9-11 Modified far-near-near-far pattern.

Figure 9-12 Modified compound locking loop.

Modified Compound Locking Loop This pattern is strong and works best in flat tendons or ligaments. but it can also be used in round tendons. A superficial transverse bite locks around small groups of fibers to decrease pull­through of larger vertical bites approximately 2 em from the tendon end. The pattern starts with a superficial transverse bite about 1 em wide. A vertical bite is then placed through both tendon ends, and a similar transverse bite is taken in the opposite tendon end. A vertical bite is then taken from the distal tendon end to the proximal tendon end and tied to the start of the first transverse bite. A similar but wider locking loop is next placed slightly closer to the tendon ends' (Figure 9-12). Alternatively, both locking loops can be placed as a continuous pattern.4

Three-Loop Pulley This pattern is strong and has less gap formation than other repair patterns.8

,9 It works best on round tendons such as the deep digital flexor tendon in the metacarpal region. The end result is three loops equally dividing the cross-sectional area of the tendon and intersecting at 60-degree

Figure 9-13 Three-loop pulley.

angles. The initial loop is placed perpendicular to the long axis of the tendon in a near-far pattern. The second loop is placed in a plane 60 degrees relative to the initial loop with bites taken similar distances apart from each tendon end. The final loop is placed in a far-near pattern 60 degrees from the second loop (Figure 9-13).

POSTOPERATIVE CARE

Flexor Tendon Lacerations

No suture pattern or material provides the strength required for flexor tendon function after repair. 4

,9,10 Therefore, during the early stages of tendon healing, the repair must be protected from weight-bearing forces with cast application or other external support. External support should be provided for a minimum of 6 to 8 weeks fol­lowing repair. After this period, support should be gradually reduced. An elevated extended heel shoe andlor splint should be provided for the follow­ing 4 to 6 weeks. The optimal extent of heel ele­vation required has not been determined, but the initial hoof angle achieved is typically between 65 and 75 degrees. Heel elevation and extension are then gradually reduced over the next 12 weeks to adapt the tendon to increasing tension . Som e horses require long-term heel extension after flexor tendon transection.

Repair of superficial digital flexor tendons in the hind limb may benefit from Kimzey splint application rather than half limb cast application. Because hock flexion is normally accompanied by fetlock flexion, tension in the superficial digital flexor tendon is increased when a horse flexes its hock but is constrained from fetlock flexion by a half limb cast. The Kimzey splint supports the

Mid Metacarpal-Metatarsal Tendon Laceration Repair 65

limb in fetlock flexion. Disadvantages of the Kimzey splint include prolonged immobilization with the distal limb in flexion and the need to keep the limb from bearing weight during bandage changes. A full limb cast extending to the proximal tibia will decrease strain on the superfi­cial digital flexor tendon during repair by pre­venting hock flexion , but generally, the risk of complications with a full limb cast is not worth the benefit when repairing superficial digital flexor tendon lacerations in the metatarsal region.

Extensor Tendon Lacerations

In the early phases of extensor tendon healing, a distal limb splint is recommended to support the digit in extension. Often, the support of a bandage is sufficient to prevent flexion, as some digital extension is due to momentum as the limb swings forward. If primary repair is performed, cast or splint support should be provided for a minimum of 4 weeks.

Contralateral Limb Support

Support should be provided for the opposite limb to dec rease the risk of contralateral limb lameness, reduce edema, and elevate the contralateral limb to a similar height as the casted limb. A support bandage and foot elevation are often applied to the contralateral limb, II In cases of severe injury, support to the contralateral limb is essential to decrease the chances of contralateral limb lamini­tis. This can be provided in the form of frog and caudal support, heel elevation, and decreased breakover. Commercial shoes are available and work well for this purpose (Redden Modified Ultimate, Nanric Inc. , Versailles, Ky.).

EXPECTED OUTCOME

With optimal treatment, riding soundness occurs in approximately 75% of extensor tendon lacera­tions and 50% of flexor tendon lacerations. '2-'4

Return to significant athletic activity has been reported in 23% to 50% of flexor tendon lacera­tions12

·'4 and 71 % of extensor tendon lacerations. '2

COMPLICATIONS

Complications of extensor tendon lacerations include wound infection, dehiscence, bone seques-

tra, excessive granulation tissue, stringhalt gait, and fetlock contracture if the limb is chronically flexed because of pain or inadequate extensor tendon function. Wound infection, dehiscence, sequestrum formation, and excessive granulation tissue can be managed by local debridement and wound therapy. Stringhalt development is uncommo nly seen after wounds in the proximal dorsal metatarsal region and may require surgery for treatment. l s Distal limb contracture can be prevented by monitoring for adequate use of the lower limb and splinting as needed.

Complications of flexor tendon lacerations include dehiscence, wound infection, tendon degeneration secondary to infection, inadequate repair strength, vascular compromise to the lower limb, cast complications, adhesions, contracture, and contralateral limb laminitis. Dehiscence and wound complications are managed by debride­ment and second intention healing. Inadequate repa ir strength is best prevented and managed by adequate limb immobilization and a gradual decrease in limb support. No direct treatment is available for vascular compromise. Cast compli­cations are common but can be minimized by careful daily monitoring of the cast and cast changes as indicated. Contracture is a complex problem resulting from prolonged immobiliza­tion or pain and healing with excessive surround­ing scar tissue. Flexor tendon lacerations in nonsheathed areas are less likely to have this complication, and a gradually increasing exercise program improves most cases. Contralateral limb laminitis is a severe complication. Appropriate support of the contralateral limb and early aggres­sive treatment for the primary problem can min­imize its occurrence. Appropriate treatment for contralateral limb laminitis includes corrective shoeing, deep bedding, stall rest, analgesics and, ideally, resolution of the primary problem.

ALTERNATIVE PROCEDURES

Annular ligament desmotomy may be indjcated in some cases if superficial or deep digital flexor tendon swell ing is impeded by the annular ligament. Typically, this is performed several weeks or even months after the tendon injury. A limited case report suggests that annular ligament desmotomy within 1 to 3 days after acute super­ficial tendon rupture in racehorses may be beneficial. '6

66 LIMB SURGERIES

COMMENTS

Although the modified fa r-near-near-far suture pattern is not as strong as the compound locking loop or three- loop pulley patterns. it is simple to perform and does not requ ire extensive exposure to perform. Placement of the near bites axial to the far bites may decrease sutu re pull-out. It is most usefuJ for superficial digital flexor tendon and extensor tendon repair.

REFERENCES

I. Bertone AL: Infectious tenosynovitis. Vet Cli,l N Am Equille Pmcl 11:163, 1995.

2. Gaughn EM: Orthopedic wounds tendon and tendon sheath, Proc Am Coil Vet Surgeolls Vet Symp 13: 167,2003.

3. Honnas eM, Schumacher J, Watkins JP, et aJ: Diag­nosis and treatment of septic tenosynovitis in horses, Comp COllt Educ 13:301, 199 1.

4. Bertone AL, Stashak TS, Sm ith FW, et al: A com­parison of repair methods for gap healing in equine flexor tendon, Vet SlIrg 19:254, 1990.

5. Jann HW, Good JK, Morgan SJ. et al: Healing of t ransected equ ine superfic ial digital flexor tendo ns with and without tenorrhaphy, Vet SUtg 21:40, 1992.

6. Bertone AL: Tendon lacerations. Vet Clill N Am Equille Pmct 11 :293,1995.

7. Watkins JP: Treatment principles of tendon disor­ders. In Auer lA. Stick lA, edito rs: Equine surgery, Philadelph ia, 1999, WB Saunders.

8. Adair HS, Gobel DO, Rohrback BW: In vitro com­pa rison of the locking loop and the three loop pulley suture techniques in the repair of equ ine flexor tendons, } Equille Vet Sci 9: 186, 1989.

9. Jann HW, Stein LE, Good JK: St rengt h characteris­tics and failure modes of locking-loop and three­loop pulley suture patterns in equine tendo ns, Vet 511rg 19: 18, 1990.

10. Lochner FK, Milne OW. Mills EJ, et al: In vivo and in vitro measurement of tendon strain in the horse. Alii VetJ Res 41:1929, 1980.

11. Hendrickson DA, Stokes M, Wittern C: Use of an elevated boo t to reduce contralateral support limb complications secondary to cast appl ication, Proc Am Assoc Equi1le Pmc 43: 149, 1997.

12. Belknap JK, Baxter GM, Nickels FA: Extensor tendon laceration in horses: 50 cases (1982- 1988), J Alii Vet Med Assoc 203:428, 1993.

13. Foland JW, Trotter GW, Stashak C, et al: Traumatic injuries involving tendons of the dista l limbs in ho rses: a retrospective study of 55 cases, Equine Vet J 23:422, 1991.

14. Taylo r DS, Pascoe JR, Meagher OM. et al : Digital flexor tendon lacerations in horses: 50 cases. (1975-1990), J Am Vet Med Assoc 206:342, 1995.

15. Crabill MR, Honnas eM, Taylor DS. et al : String­halt secondary to trauma to the do rsoproximal region of the metatarsus in ho rses 10 cases (1986-1991 ), J Am Vet Med Assoc 205:867,1994.

16. Mackay-Smith MP: How to surgically treat and post-operatively rehabilitate acute athletic rupture of superficial d igital flexor tendon, Proc Am Assoc Equine Pract 47:279.2001.

CHAPTER 10

Annular Ligament Desmotomy Joanne Kramer

INDICATIONS

Annular ligament constriction caused by primary annular ligament desmitis (Figure 10-1) and annular ligament constriction secondary to ten­donitis or septic tenosynovitis.

EQUIPMENT

Closed techniques are performed with a Mayo scissors, bistoury knife, or groove director.

ANATOMY

The palmar-plantar annular ligament attaches on the abaxial surfaces of the proximal sesamoid bones and partially surrounds the tendon sheath blending with its palmar-plantar wall and making up the palmar-plantar wall of the fetlock canal (Figure 10-2). The proximal and distal extent of the palmar-plantar annular ligament can be esti­mated by palpating the apex and base of the sesamoid bones.

POSITIONING AND PREPARATION

The horse is positioned in lateral recumbency. The circumference of the limb should be clipped and prepared aseptically from the mid metacarpus-metatarsus region distally.

67

PROCEDURE

Open Te(hnique

A 6- to 8-em skin incision is made over the lateral aspect of the superficial digital flexor tendon (SDFT) at the level of the palmar annular liga­ment. The incision is made palmar to the neu­rovascular bundle and should be just axial to the palmar edge of the sesamoid bone' (see Figure 10-2). A small incision is made in the proximal border of the digital sheath or annular ligament, and a groove director or forceps is passed under the annular ligament to act as a guide for further transection. The incision is continued through the entire proximal annular ligament, being careful not to damage the underlying tendons (Figure 10-3). The flexor tendons and exposed sheath are examined for adhesions. If present, they are resected. The tendon sheath is lavaged as required by the primary problem.

Subcutaneous tissues are closed with No. 2-0 absorbable suture in a continuous o r interrupted pattern. The skin is closed with an interrupted pattern.

Closed Te(hnique

This is the preferred method if the tendons within the fetlock ca nal do not need to be exposed. A 2-cm incision is made through the skin just proxi­mal to the palmar annular ligament. The sheath is entered through a similar or smaller incision, and the distal extent of the annular ligament is defined

68 LIMB SURGERIES

Figure 10-1 Appearance of a limb with const riction of the palmar annular ligament.

by passing a groove director or forceps under the annular ligament and palpating the distal end of the ligament (Figure 10-4). Care should be taken to exclude the proximal digital annular lig­ament. The annular ligament is then transected by passing a bistoury knife underneath the ligament and transecting the ligament (Figure 10-5, A, B) or by passing the groove director underneath the ligament to guide a scalpel blade' (Figure 10-5, C). Care must be taken to not incise the skin if the bistoury knife is used. Alternatively, the annular ligament can be transected with scissors. A small subcutaneous plane is created for I blade of the scissors, and the annular ligament is transected by closing the blades of a scissors passed so that one blade of the scissors is deep to the annular liga­ment and the other blade superficial to the liga­ment in the subcutaneous plane created2 (Figure 10-6) . The tendon sheath can then be lavaged as requited by the primary problem.

If the incision in the proximal tendon sheath is large, it can be closed with No. 2-0 absorbable suture. Subcutaneous tissues are closed with No. 2-0 absorbable suture. The skin is closed in an interrupted pattern.

A

neurovascular bundle

(the circle)

Site of approach

•

• J. . -" .. i , . • •

• .. • •

• ,

B

- DDF tendon

Tendon sheath

annular lig.

--.., SDF tendon

~t;.t:~

Figure 10-2 The palmar-plantar annular ligament attaches on the abaxial surfaces of the proximal sesamoid bones and partially surrounds the tendon sheath blending with its palmar-plantar wall and making up the palmar-plantar wall of the fetlock canal. A. Lateral view. B, Cross section.

•

~e...,.,.t;;..ta... .

Figure 10-3 Transection of the annular ligament using the open technique.

A

'1 \ \ \

B

Annular Ligament Desmotomy 69

Figure 10-4 Entrance into the digital sheath through a small skin incision proximal to the palmar annular ligament in a closed annular ligament resection. ArrolVs show the approximate proximal and distal borders of the palmar an nular ligament.

c

Figure 10-5 The 3n l1 uJar ligament is transected by A, passing a bistoury kni fe underneath the ligament, B, ro tat­ing the bistoury kn ife 90° so that the cutting edge is toward the ligament, and transecting the ligament, or C, passing the groove director underneath the ligament to guide a scalpel blade.

70 LIMB SURGERIES

Figure 10-6 The annular ligament can also be transected with scissors. A. A small subcutaneous plane is created for one blade of the scissors, and B, the annular ligament is transected by closing the blades of a scissors passed so that one blade of the scissors is deep to the annular ligament and the other blade is superficial to the ligament in the subcutaneous plane created.

POSTOPERATIVE CARE

Postoperative (are

A

Bandaging: A sterile dressing is placed over the incision and a half limb bandage is applied. The initial bandage is changed 24 hours after surgery. Subsequent bandage changes are performed at 4-to S-day intervals or more frequently if indicated. Bandaging is applied for a minimum of 4 weeks regardless of whether the open or closed technique is performed. Exercise Restridions: Stall rest is provided for 10 days, after which a gradual increase in daily hand­walking is important to minimize adhesion forma­tion. In cases without underlying tendon pathology, light daily lunging at a trot or limited small paddock turnout may be performed 3 weeks postoperatively. Gradual return to work may begin in 6 weeks or as indicated by the healing of any underlying tendon • • InJury. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and at 2.2 mg/kg BID for an additional 5 days. Further

EXPECTED OUTCOME

After desmotomy, the lower limb profile has mild to moderate symmetrical enlargement resulting from release of the constricting liga­ment. This decreases over time, but it is rare fo r a completely normal cosmetic appearance to return. The prognosis for soundness is good for cases with primary constriction or thickening of the annular ligament. Cases with minor tendon

I ) \ \

.11 '

B

phenylbutazone therapy is dictated by underlying tendon damage and the level of lameness present. Antibiotic therapy is continued in cases with preex­isting infection and in select cases where delayed incisional healing is anticipated. Suture Removal: Skin sutures are removed 12 days postoperatively. Intrasynovial Medications: Intrasynovial so­dium hyaluronate is a useful adjunctive therapy in cases where adhesions have been transected or a high level of inflarnmation is present within the sheath. Although sodium hyaluronate has been shown in an experimental adhesion model to decrease adhesion formation and increase hyaluronic acid content within the digital sheath,' no products are specifically labeled for digital sheath use. The author has used 20 to 40 mg of sodium hyaluronate labeled for intraarticular use at the time of surgery and 10 to 14 days postoperatively.

lesions can also have a good prognosis, but exten­sive tendon lesions or significant sheath adhesions limit future soundness. The prognosis is guarded for cases with septic tenosynovitis.

COMPLICATIONS

Complications include wound dehiscence, septic tenosynovitis, synovial fistula formation, and adhesions. Complications are rare following the

closed technique. The use of the open technique increases the risk of complications, but with appropriate postoperative care and monito ring, complications are not common.

ALTERNATIVE PROCEDURES

Extrasynovial Transection

Performance of an annular ligament desmotomy without entering the tendon sheath has been described.4 The technique relies on the presence of a small extrasynovial space between the SDFT and the palmar annular ligament_ A 2-cm skin incision is centered between the proximal border of the annular ligament and the ergot on palmar or plantar midline. Sharp dissection is continued through the subcutaneous tissues until the trans­verse fibers of the annular ligament are identified. Careful sharp dissection is continued through the annular ligament until the division between the annular ligament and longitudinal fibers of the SDFT is identified through a 5-mm incision in the annular ligament. Curved Kelly forceps are directed through the incision in the annular liga­ment to identify the dissection plane. The Kelly forceps are opened several millimeters and a No. 15 blade is used to incise the ligament. The forceps are advanced distally and then turned and advanced proximally to allow complete incision of the ligament. In most cases, the palmar axial attachment of the flexor sheath to the SDFT on either side of midline can be seen in the surgical field.

Desmoplasty

Desmoplasty of the annular ljgament has been described in four horses with primary annular lig­ament desmitis.s The procedure involves identify­ing hypo echoic lesions in the annular ligament

Annular Ligament Desmotomy 71

and under ultrasound guidance, creating partial­thickness incisions in the hypoechoic regions with a No. II blade.

Endoscopic Transection

Endoscopy of the digital sheath with guided transection of the annular ligament has also been described6

-s and offers an improved prognosis for

horses with digital sheath pathology.

REFERENCES

1. Adams SB, Fessler JF: Palmar-plantar an nular liga­ment division. In Adams SB, Fessle r JF, editors: Atlas of equifle Sl/rger)', Philadelphia, 2000, WB Saunders.

2. Turner AS, Mcllwraith CW: Sectioni ng of the palmar or plantar annular ligament of the fetlock. In Turner AS, Mcllwraith CW, editors: Techniques ill large allimll( sllrgery, Philadelphia, 1989, Lea &

Febiger. 3. Gaughan EM, Nixon AJ, Krook LP, et al: Effects of

sodium hyaluronate on tendon healing and adhe­sion formation in horses, Am J Vet Res 52:764, 1991.

4. Hawkins DL, Churchill EA: Extrasynovial palmar/plantar an nular ligament desmotomy, Proc Am Assoc Eqlline Pmc 44:210, 1998.

5. McGhee JD, White NA, Goodrich LR: Primary desmitis of the palmar and plantar annular liga­ments in horses: 25 cases ( 1990-2003), } Am Vet Med Assoc 226:83, 2005.

6. Fortier LA, Nixon AJ, Ducharme NC, et al: Teno­scopic examination and proximal annular ligament desmotomy for treatment of equi ne complex digital sheath tenosynovitis, Vet Surg 28:429, 1999.

7. Nixon AJ, Same AE, Ducharme NG: Endoscopic assisted annular ligament release in horses, Vet Surg 22:501, 1993.

8. Wilderjans H, Boussauw S, Madder K, et al: Tenosynovitis of the digital flexor tendon sheath and annular ligament constriction syndrome caused by longitudinal tears in the deep digital flexor tendon: a clinical and surgical report of 17 cases in Warm­blood horses, Equine Vet} 35:270, 2003.

CHAPTER 11

Lateral Digital Extensor Tenectomy Joanne Kramer

INDICATION

Treatment of conventional stringhalt (Figure 11-1 ).

EQUIPMENT

Large Carmalt forceps are used for removing the muscJe tendon un it from the proximal incision.

ANATOMY

The lateral digital extensor muscle of the hind limb o riginates from the lateral collateral ligament of the stifle and the adjacent region of the tib ia and fibu la. It proceeds lateral to the long digital extensor muscle and enters its tendon sheath in the groove of the lateral malleolus of the tibia. In th is region, the tendon and sheath are covered by extensive crural fascia and the distal extensor reti­naculum of the tarsus. Just distal to the tarsus, the lateral digital extensor tendon joins the long digi tal extensor tendon (Figure 11-2).

POSITIONING AND PREPARATION

The procedure is performed with the horse under general anesthesia in lateral recumbency with the affected limb up or standing with sedation and local anesthesia. When the procedure is

72

performed standing, local anesthetic is infiltrated directly over and deep to the distal and proximal skin incision sites. The lateral aspect of the mid to distal tibia and the proximal metatarsal region are clipped and prepared aseptically.

PROCEDURE

A 3~cm incision is made directly over the palpa­ble lateral digital extensor tendon just proximal to its junction with the long digital extensor tendon. The tendo n is elevated to the level of the incision. A second lO-cm vertical skin incision is made directly over the lateral digital extensor starting at the muscle tendon junction and extending proxi­mally (Figure 11-3, A). Pulling on the isolated lateral digital extensor tendon in the distal inci­sion can be used to guide the exact location of the proximal incision. The subcutaneous tissue and fasciae are incised to expose the lateral digital extensor muscle belly. Blunt dissection and large Carmalt forceps are used to elevate the muscle to the level of the incision. A small amount of sharp and blunt dissection is also used to free restrict­ing tissue from the muscle tendon unit. The latera l digital extensor tendon is then excised in the distal incision (Figure 11 -3, B). The entire tendon is then pulled through the proximal incision (Figure 11-3, C). This is the most difficult aspect of the procedure and is best accomplished by placing large forceps underneath the tendon of the lateral digital extensor muscle and pulling proximally and laterally. The muscle is then severed in the

I

Figure 11-1 Marked hyperflexion of the hock in a horse with a stringhalt gait.

Tendon of long digital extensor m.----l,

Digital retinaculum

A

Tendon of lateral digital extensor m.

lateral Digital Extensor Tenectomy 73

proximal portion of the incision so that at least 2 cm of muscle is removed (Figure 11-3, DJ. [f nec­essary, the remaining muscle stump is cauterized or Qversewn with absorbable suture material in a Halstead or Cushing pattern. Some surgeons believe the success rate of the surgery increases with removal of more muscle, and in some cases recurrence of stringhalt has been treated with resection of an additional 3 to 4 inches of lateral digital extensor muscle. 1,2 The crural fasciae are then closed with a simple interrupted or simple continuous pattern with No. 0 synthetic absorbable suture material. Closure of the subcu­taneous tissue is optional. The skin is closed with No. 0 suture material in an interrupted or contin­uous pattern of the surgeon's choice. The distal incision requires closure of the skin only.

Long digital­extensor m.

Lateral digital extensor

Long digital

Lateral digital extensor tendon

• .-:;.. . . . ~ :" . . .~­• • · . -. , '. ~

• • • . -- --~ -{.

•

B

-

c

Figure 11~2 A, Location of the lateral digital extensor muscle and tendon with cross sections near B. the muscle­tendon junctions and C. distal incision site.

74 LIMB SURGERIES

b

a

A c

B o

~_~.1!. ,

Figure 11-3 A, A 3-cm incision is made directly over the palpable lateral digital extensor tendon just proximal to its junction with the long digital extensor tendon (aJ . A second lO-cm ver ti cal skin incision is made directly over the lateral digital extensor starting at the muscle-tendon junction and extending proximally (b). B, The lateral digital extensor tendon is excised in the distal incision. C. The entire tendon is pulled through the proximal incision. D, The muscle is severed in the proximal portion of the incision so that at least 2 em of muscle is removed.

POSTOPERATIVE CARE

Postoperative Care

Bandaging: A sterile dressing is placed over the incisions and a full limb bandage is placed from the proximal tibia distally. The bandage is changed as needed every 2 to 4 days and maintained until the incisions have healed. Exercise Restridions: Stall rest is required for 2 weeks and followed by small area turnout for 2 weeks. Meditations: Phenylbutazone is administered at 4.4 mg/kg BID for 24 hours. Suture Removal: Skin sutures are removed 12 days postoperatively.

EXPECTED OUTCOME

Although positive results from the surgery are often dramatic and very rewarding) owners should be forewarned that the results of the

surgery are variable and cannot be predicted. Improvement, when present, may occur in the immediate postoperative period or days to months after the surgery.2

COMPLICATIONS

Dehiscence of the incision may occur) especially if a stringhalt gait persists in the early postoperative period. Seroma or hematoma formation associ­ated with the stump of the lateral digital extensor muscle may also occur.

COMMENTS

Stringhalt is a gait abnormality characterized by exaggerated hyperfl exion of one or both hind limbs. Several forms have been described. The Australian, or outbreak, form of stringhalt is bilat­eral, occurs in groups of horses on pasture, and is

thought to be caused by a plant toxin. It has been identified in Australia, New Zealand, and Califor­nia. 3

,4 The Australian form and possibly other forms of st ringhalt have been shown to have an underlying neuTopathy.4,S

Conventional, or class ic) stringhalt occurs in individual horses and is typically unilateral. The majority of conventional stringhalt cases have no known initiating factors. Some cases are as­sociated with trauma to the dorsal proximal metatarsal region, with the suspected etiologies being adhesion formation involving the lateral digital extensor tendon and altered myotactic response due to injury,6 Other causes of stringhalt may be peripheral neuropathy associated with neurologic disease such as equine protozoal myelitis. 5

In one report, a stringhalt-like gait improved after local anesthesia of the tarsometatarsal and distal intertarsal joints and resolved after intraar­ticular corticosteroid trea tment. 7 The authors have also observed stringhalt- like gaits in horses with thin soles after trimming and horses with hind limb laminitis. These horses have a normal or significantly inlproved gait on soft footing or after abaxial anesthesia.

When a horse is presented with a stringhalt­like gait, a dietary history, neurologic exam, and search for identifiable sources of pain should be undertaken and treatment is based on these results if indicated. Surgical treatment is generally indicated for cases of stringhalt associated with dorsal metatarsal trauma or horses with stringhalt of unknown etiology. One author recommends surgical treatment if th~ gait improves after local anesthetic solution is injected into the lateral digital extensor muscle.s

With the exception of the stringhalt gait, many cases will have an unremarkable history and din­ical examination. The improvement in gait after surgery is difficult to predict for individual cases,

,

lateral Digital Extensor Tenedo y 7S

but the authors have not seen 'diopathic cases improve without surgery. In horses with stringhalt secondary to dorsal metatarsal trauma, response to treatment was reported in nine horses.6 Of the four horses treated with exercise, one resolved, two improved, and one had no change in gait. Of the five horses trea ted surgically, two resolved, two had gait improvement, and one had no change in gait.

REFERENCES

I. Turner AS, McJlwraith CW: Lateral digital extensor tenotomy. In Turner AS, McIlwraith CW, editors: Techl1iques ill large allima{ surgery, Philadelphia, 1989, Lea & Febiger.

2. Sullins KE: Lameness. Part X. The tarsus. In Stashak TS, editor: Adam's lame/less in horses, Philadelphia, 2002, Lippincott, Will iams and Wilkins.

3. Adams SB, Fessler IF: Lateral digital extensor myotenectomy for stringhalt. In Adams SB, Fessler J F, ed itors: Atlas oj equine surgery, Philadelphia, 2000, WB Saunders.

4. Siocombe RF, Huntington PI, Fr iend SCE, et al: Pathological aspects of Australian stringhalt, Eqllille Vet/24:174,1992.

5. Va lentine B: Mechanical lameness in the hindlimb. In Ross MW, Dyson 5J, edito rs: Diag1l0sis a1ld man­agement oj lame1less i1l the horse, St Louis, 2003, WB Saunders.

6. Crabill MR, Honnas eM, Taylor OS, et al: Stringhalt secondary to trauma to the dorsoproximal region of the metatarsus in horses: 10 cases (1986- 1991), J Am Vet Med Assoc 205:87,1994.

7. Hebert C, Jahl1 HW: Intra-articular corticosteroid treatment for stringhalt in a Quarter horse a case report, J EquinE Vet Sci 14:53, 1994.

8. Bennet SD: Lameness in the American Saddlebred and other trotting breeds with collection. In Ross MW, Dyson SJ, editors: Diagnosis and mallage­ment of lameness ill the horse, St Louis, 2003, WB Saunders.

CHAPTER 12

Medial Patellar Desmotomy Joanne Kramer

INDICATIONS

Horses with persistent upward patellar fixation or horses with continued intermittent upward patel­lar fixation after appropriate conditioning and maturation have been achieved (Figure 12-1).

EQUIPMENT

A blunt- tipped bistoury knife is used to transect the medial patellar ligament.

POSITIONING AND PREPARATION

Surgery is performed with the horse standing. The limb should be fully weight bearing with the stifle extended. The tail should be wrapped and tied out of the surgical field. The medial aspect of the stifle region is clipped and prepared aseptically. Local anesthetic is injected subcutaneously cranial and deep to the medial patellar ligament.

ANATOMY

The medial patellar ligament inserts distally in a groove o n the proximal medial aspect of the tibial tuberosity and proximally on the medial aspect of the patella through the para patellar fibrocartilage. Upward fixation of the patella occurs if during

76

maximal stifle extension the fibrocartilage is ele­vated and rotated over the medial troch lear ridge of the femur' (Figure 12-2). The patella is released when the patella is rotated laterally and elevated slightly by the quadriceps to clear the medial trochlear ridge. The locked and unlocked posi­tions of the patella are shown in Figures 12-1 through 12-4.

PROCEDURE

With the limb fully weight bearing and the stifle extended. a 2-cm vertica l skin incision is made just cranial to the distal part of the medial patellar ligament (Figure 12-5) . Curved Kelly forceps are advanced under the medial patellar ligament to create a plane of dissection deep to the medial patellar ligament. Keeping close to the medial patellar ligament and on its distal aspect, a bistoury knife or Bard Parker handle with a new No. 10 blade is advanced under the medial patel­lar ligament with the cutting side facing distal. When the tip of the blade or bistoury knife is pal­pable on the caudal side of the medial patellar lig­ament, the instrument is rotated 90 degrees and the medial patellar ligament is severed (Figure 12-6). When the ligament is transected, the stifle will flex slightly. After transection. the aponeurotic insertion of the sarto rius muscle is palpable just caudal to location of the patellar ligament.2

-4 The

skin is closed with interrupted sutures.

.. - -- ---.. - .;"1 ' T

Figure 12-1 A horse with upward fixation of the patella. Note the extended stifl e and hock and flexed distal limb.

Cartilaginous process (parapatellar fibrocartilage)

Medial patellar

Figure 12-2 The locking mechanism.

Patellar ligaments:

medial---:c-:-

Cartilaginous process (parapatellar fibrocartilage) ..__--..

middle==J~tT lateral-

Incision site ~--

Medial Patellar Desmotomy 77

--. -• - . - --

Figure 12-3 Exaggerated flexion of the limb after release of the patella.

--- • -.. r -

Figure 12-4 Normal limb position at the start of the next stance phase.

Figure 12-5 Location of the skin incision for medial patellar desmotomy.

78 LIMB SURGERIES

Figure 12~6 Transection of the medial patellar liga­ment with a bistoury knife.

Postoperative Care

Bandaging: None is practical or required in this •

region. Exercise Restridions: Stall rest with handwalk­ing for 2 weeks followed by small paddock turnout for a minimum of 90 days after the surgery. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for 24 hours. Suture removal: Skin sutures are removed 12 days postoperatively.

EXPECTED OUTCOME

If rested extensively after surgery, most horses have an uneventful recovery and return to their intended use. A retrospective study supports a high return to athletic activity with appropriate

case selection. 5 Fragmentation of the patella or middle patellar ligament desmitis may occur in some horses. If associated with lameness, frag­mentation of the patella may require arthroscopic treatment. 6,7

COMPLICATIONS

Surgical errors are rare but include entrance into the femoropatellar joint capsule, severance of the medial femorotibial or middle patellar ligament, and incomplete transection of the medial patellar ligament. If a blade is used for transection and is not securely attached to the handle, it may detach when being turned 90 degrees against the liga­ment. Medial patellar ligament desmotomy may predispose horses to distal fragmentation of the patella from increased stress on the middle patel­lar ligament. 6

,7 A case of apical fracture has also been reported.s Extensive fibrosis or surgical site swelling may also develop and usually resolves with extended rest but rarely results in lameness or recurrent upward patellar fixation.9

ALTERNATIVE PROCEDURES

A modification of the procedure performed under general anesthesia that involves transection of the aponeurosis of the gracilis and sartorius in addi­tion to the medial patellar ligament transection has been described. 1O This procedure may mini­mize the risk of recurrent fixa tion.

Medial patellar ligament splitting has been described as an alternative to medial patellar lig­ament desmotomy.ll The procedure induces a localized desmitis and thickening of the ligament that theoretically makes locking the patella more difficult. Using ultrasound guidance, percuta­neous splitting of the proximal third of the medial patellar ligament is performed. Advantages of the procedure include a reported high success rate with early return to work after surgery, and reduced incidence of fragmentation of the patella and middle patellar ligament desmitis.ll

Injections of counterirritants into the medial and middle patellar ligaments have been used as a treatment for intermittent upward patellar fixation and may work by creating fibrous tissue that restricts stretching of the medial patellar ligament. 12,13

COMMENTS

In a horse with upward patellar fixation, the limb

is positioned with the stifle and hock held in extension with the distal limb held in partial fl exion (see Figure 12-1). Release of the limb often occurs with a quick and exaggerated flexion (see Figure 12-3) . Three situations have been described.2 Persistent fixat ion occurs when the

patella remains fixed for a prolonged period of time, o ften requiring assistance or multiple

attempts by the horse to release the patella. Inter­mittent fixa tion occurs when the patella remains fixed with the limb held in extension behind the horse for several seconds and then is released during a normal step. Momentary fixat io n occurs when the patella temporarily fixes, causing a slight delay in the start of protraction and a slightly exaggerated flexion when the limb is released.

Conservative therapy should always be attempted before su rgical correction of upward patellar fixation. Most cases of intermittent up­

ward patellar fixatio n occur in young horses with poor quadriceps condition or in horses that have had a period of extended stall rest. These horses o ften respond to an exercise program that increases the strength of the quadriceps and su r­

rounding musculature. Cases that a re cand idates for surgery have intermittent upward patellar fix­ation despite adequate condi tioning programs or

have persistent locking that cannot be manually released or recurs after release.2.4·6, '4

Although most cases of upward patellar fixation are primary, u pward pateUar fixation can occur secondary to neurologic disease and to stifle pathology and in horses with coxofemoral joint luxation.4,'4.'7 If necessary, these conditions

should be ruled out before performing surgery. Because of possible fragmentation of the distal

patella and middle patellar ligament desmitis after desmotom y, the amount of postoperative rest has been increased. The optimum rest period for healing is not know n. C urrent reco mmendations va ry and include 4 to 6 weeks if no signs of lame­ness are present,S 2 to 3 months,9.'8 2 to 5 months,4

and 4 to 5 months.6

REFERENCES

I. Dyce KM, Sack WO, Wensing CJG: The h indlimb of the horse. In Dyce KM, Sack WO, Wensing CJG, editors: Textbook of veterillary anatomy, Philadel­phia, 1987, WB Saunders.

Medial Patellar Desmotomy 79

2. Adams S8, Fessler IF: Medial patellar desmotomy. In Adams S8, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders.

3. Jansson N: Treatment fo r upward fixat ion of the patella in the horse by medial patella r des motomy in dications and complications. Equine Pract 18:24, 1996.

4. Walmsley JP: The sti fle. In Ross MW, Dyson 51, editors: Diagllosis and mallagemem of lame1less in the horse, Philadelphia, 2003, WB Saunders.

5. Bathe AP, O'Hara LK: A retrospective study of the outcome of medial patella r ligament desmotomy in 49 horses, Proc Am Assoc Equine Pract 50:476, 2004.

6. Gibson K, Mcl lwraith CW, Parks RD, et al: Production of patellar lesions by medial patellar desmotomy in normal horses, Vet Surg 18:466,

1989. 7. Mcllwraith CW: Osteochondral fragmentation of

the distal aspect of the patella in horses, Equine Vet ]22:157,1990.

8. Riley CB, Yovich JV: Fracture of the apex of the patella after med ia l patellar desmotomy in a horse, Aust Vet J 68:37, 1991.

9. Dyson 51: Patellar injuries. In White NA, Moore TN editors: Curreflt techniques ill equine surgery and lameness, Philadelph ia, 1998, WB Saunders.

10. Wright I: Ligaments associated wi th joints, Vet Ciin N Am Equille Pract II :249, 1995.

11. Tribnar MA: Medial patellar ligament sp litting for the treatment of upward fixation of the patella in 7 equids, Vet Surg 3 1 :462, 2002.

12. Brown M: The effects of an injection of counterir­ritant into the patellar ligament of ponies: applica­tion to st ifle lameness, J Equine Vet Sci 3: 149, 1983.

13. van Hoogmoed LM, Agnew DW, Whitcomb MB, et al: Ultrasonographic and histologic evaluation of medial and middle patellar ligaments in exercised horses followi ng injections with ethanolamine oleate and 2% iodine in almond oil, Am J Vet Res 63:738, 2002.

14. Sullins KE: Lameness. Part XII. The stifle. In Stashak TS, editor: Adam's lameness ill horses. Philadelphia. 2002, Lippincott Williams and Wilkins.

15. Black 18: The Western performance horse. In Ross MW, Dyson SJ, editors: Diagllosis and management of lameness ill the horse, Philadelphia, 2003, WB Saunders.

16. Walmsley 1P: Medial desmotomy for upward fixa­tion of the patella, Equine Vet Educ 6: 148, 1994.

17. Clegg PO, Butson RJ: Treatment of coxofemoral joint luxation secondary to upward fixa tion of the patella in a Shetland pony, Vet Rec 138: 134,

1996. 18. Latimer FG: Tarsus and stifle. In Hinchcliff KW.

Kaneps AI, Geor RJ, editors: Equille sports medicine and surgery, New York, 2004, WB Saunders.

1 __________________________________________________________________ __

CHAPTER 13

Distal Check Ligament Desmotomy Joanne Kramer

INDICATIONS

The primary indication for distal check liga­ment desmotomy is deep digital flexor tendon (DDFT) contracture with coffin joint contrac­ture (Figure 13- 1). It is also occasionally used in the treatment of metacarpophalangeal fl exural deformities and in the treatment of caudal foot lameness with upright hoof wall or pastern con­formation.

EQUIPMENT

Specialized instruments are not required for this surgery. The foot should be trimmed and examined for subsolar abscesses. Toe exten­sions are applied in some cases to protect the toe and to provide a lever arm during breakover to gradually stretch the DDFT (Figures 13-2 and 13-3).

ANATOMY

The distal check ligament wraps around the DDFT on the dorsal and lateral surface of the DDFT and often forms a slight C shape aro und the DDFT (Figure 13-4). The palmar vei n, artery, and nerve lie close to the DDFT and distal check ligament (see Figure 13-4). Care should be taken to not exteriorize or transect these with the check ligament.

80

POSITIONING AND PREPARATION

The horse is positioned in lateral recumbency with the affected limb up. When both limbs are affected, the distal check ligament on the down side can be approached medially. Alternatively, the horse may be positioned in dorsal recumbency when the condition is bilateral. The circumference of the limb should be clipped and prepared asep­tically fro m the fetlock to the mid carpal region.

PROCEDURE

A 6-cm skin incision is made near the distal end of the proximal third of the metacarpus over the DDFT (Figure 13-5). The approach can be per­formed on the lateral or medial aspect of the limb. The lateral approach is generally simpler and is fa rther from the neurovascular bundle. The sub­cutaneous tissues and palmar fascia are incised, and the intersection between the distal check lig­ament and DDFT is palpated or visualized (Figure 13-6). The intersection between the DDFT and distal check ligament is usually found best by pal­pation with fingers or the tip of an instrument. Occasionally, it can be visualized. Because of the C shape of the distal check ligament) it o ften wraps around the DDFT such that the DDFT is deep to the intersection of the superficial digital flexor tendon and distal check ligament.

Blunt dissection between the distal check liga­ment and DDFT with a curved Kelly forceps or

Figure 13-1 Deep digital flexor tendon contracture in the left forelimb.

Figure 13-2 A toe extension created by setti ng a larger size shoe forward after trimming.

Figure 13-3 A toe extension created with acryli c hoof material.

Distal Check ligament Desmotomy

.-•

. ~ " - ' . •

-

" • -

•

,. .

-

81

•

•

82

•

I

L IMB S URGER IES

Common tendon sheath of SDF and DDF

Communicating branch

,--- Interosseous -­medius

(suspensory lig.)

Lateral palmar v.a. (palmar common

digital v. III)

Lateral palmar n'

palmar v.a.

palmar n.

SDF tendon

Communicating branch

Figure 13~4 Anatomy of the distal check ligament and palmar metacarpus.

\ / Site of approach

I

Figure 13-5 Location of the ski n incision for distal check ligament desmotomy,

~ DDFtendon ~ ''<-'- - Distal

check lig.

~s.....,t;.:l,u.....-

Figure 13-6 Ident ificatio n of the intersection be­tween the distal check ligament and DDFT.

Figure 13-7 Intraoperative view of the exteriorized check ligament.

-;lG>c.ot;..t(... .

Figure 13-8 Exteriorizat ion of the check ligament with curved forceps.

Metzenbaum scissors is used to separate the struc­tures and exteriorize the check ligament (Figure 13-7), To enable exterioriza tion of the entire check ligament, it is helpful to dissect bluntly to the far side of the tendon bundle with the curved tips facing palmar and then rotate the ti p dorsally when exteriorizing the check ligament (Figure 13-8).

Distal Check Ligament Desmotomy 83

DDF tendon,~ Distal check j

Figure 13-9 Transection of the distal check liga­ment.

Figure 13-10 Gap form ation between the ends of the check ligament after transection.

After confirming that the check ligament has been exteriorized, the check ligament is transected with a scalpel blade (Figure 13-9). Complete tran­section is assessed by careful exami nation of the transected ends and the gap between the ends of the ligament when the foot is extended. A gap of at least 1 em should be present. and the ends of the check ligament should be visualized (Figure 13-10). If intact fibers of the check ligament remain, these should be transected.

The palmar fascia and subcutaneous tissues are closed with a simple continuous pattern using No. 2-0 absorbable suture material. The skin is closed with a continuous or simple interrupted pattern using No. 2-0 or No. 3-0 suture material.

84 LIMB SURGERIES

POSTOPERATIVE CARE

Postoperative Care

Bandaging: A sterile dressing is placed over the incision and a half limb bandage is applied. The bandage is changed every 3 to 4 days and the limb is maintained in a bandage for 3 weeks. Exercise Restrictions: Handwalking should be introduced 5 days postoperatively and the time period of handwalking gradually increased over the following 3 weeks up to 30 to 45 minutes twice daily. When controlled exercise is not possi­ble, turnout in a small area is provided. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and 2.2 mg/kg BID for an additional 3 days. Continued phenylbutazone administration at lower doses or less frequent intervals may be necessary for pain management. Suture removal: Skin sutures are removed 12 days postoperatively.

Corrective Trimming

If not done preoperatively. the heels should be trimmed or rasped to lower the hoof angle. In some cases, toe extensions are used in the post­operative period to increase tension on the DDFT during breakover and to protect the toe from

• excessive wear. A large change in hoof angle subsequent to

surgery and corrective trimming may cause sig­nificant postoperative pain and subsequent con­tractural reflex. In these cases, the foot can be trimmed and a temporary heel elevation can be placed on the foot (Figure 13-1 I) . The elevation

Figure 13-11 Temporary heel elevation using acrylic.

is then gradually lowered over the first postoper­ative week to allow for an adaptation period.

Dietary Modification

Rapid growth should be controlled to the extent possible. Early weaning may be indicated in foals of heavy lactating mares. High-energy diets should be avoided. and there may be some benefit to limiting feed intake to grass hay only for 30 days. I More commonly, growing weanlings are fed a grass hay or grass-alfalfa mix hay-based diet with concentrate rations of 0.5% body weight for a 60-day period.

EXPECTED OUTCOME

Most horses with DDFT contracture improve dra­matically with distal check ligament desmotomy, corrective trimm ing or shoeing, and management of controllable underlying factors. Younger horses and those with deformities of less than 90 degrees have the best prognosis.2

-s The results for treat­

ment of metacarpophalangeal deformity vary.2.3,6 In a single report of selected cases of caudal foot lameness, results were good.7

COMPLICATIONS

Complications include excessive scar tissue for­mation and recurreflt contracture. The amount of

-Figure 13-12 No ground contact at the heel in a horse with deep digita l flexor tendon contracture.

scar tissue formed may be partly related to the size of gap between the ends of the check ligament after transection. Excessive scar tissue formation can be minimized by adequate hemostasis, careful and minimal dissection during surgery, and appropriate bandaging after surgery. Recurrent contracture is usually due to inadequate hand­walking during the recovery period, or persistent pain from uncorrected underlying problems (e.g., severe developmental orthopedic disease, reCUf­

fent toe abscesses).

ALTERNATIVE PROCEDURES

Ultrasound Guided Transection

Ultrasound guided transection of the distal check ligament has been described." The technique is technically more difficult than the traditional technique but can be performed with the horse standing.

Corrective Trimming and Shoeing

Mild cases of DDFT contracture often respond to lowering the heels. The toe then acts as a fulcrum

and the weight of the foal forces the coffin joint to extend. 9 In some cases treated conservatively, lowering the heel alone results in continued pro­gression of contracture. This is presumably due to

pain or damage in the dorsal lamina and third phalanx secondary to abnormal weight-bearing forces. This is particularly true when after trim­ming, the heels do not contact the ground during normal weight bearing (Figure 13-12). Select cases of this type have been treated without surgery by lowering the heel and applying a shoe with a raised heel. The rationale behind this approach is that it allows for decreased tension on the DDFT while allowing the entire foot to be trimmed and bear weight normally. to

COMMENTS

With DDFT contracture, excessive stress on the toe causes widening of the white line, excessive wear of the toe, and in some cases remodeling of

the tip of the third phalanx. Before surgery, the foot should be checked carefully for subsolar abscesses near the toe. If abscesses are present,

treatment is preferred before distal check ligament

Distal Check ligament Desmotomy 8S

desmotomy. II Radiographs are useful for evaluat­ing the position and architecture of the third phalanx.

Before proceeding with surgery, the horse should be examined for sources of pain that are contributing to the contracture through a pain withdrawal reflex. In most cases, sources of pain

are related to physitis or foot pathology and are treated in conjunction with distal check ligament

desmotomy. Rarely, other sources of pain such as shoulder osteochondrosis are present and affect the prognosis.

REFERENCES

1. Owens JM: Abnormal flerion of the corono-pedal joint or "contracted tendons" in unweaned foals, Equine Vet J 7:40, 1975.

2. Adams SB, Santschi EM: Management of congeni­tal and acquired flexural deformities, Proc Am Assoc Equille Pract 46: 117,2000.

3. Mc1lwraith CW, Fessler IF: Evaluation of inferior check ligament desmotomy for treatment of acquired flexor tendon contracture in the horse, J Am Vet Med Assoc 172:293, 1978.

4. Stick lA, Nickels FA, Williams MA: Long-term effects of desmotomy of the accessory ligament of the deep digital flexor muscle in Standardbreds: 23 cases (1979-1989), J Am Vet Med Assac 200:1131, 1992.

5. Wagner PC, Grant BD, Kaneps AJ, et al: Long term results of desmotomy of the accessory ligament of the deep digital flexor tendon (distal check liga­ment) in horses, J Am Vet Med Assoc 187:1351, 1985.

6. Blackwell RB: Response of acquired flexural defor­mity of the metacarpophalangeal joint to desmo­tomy of the inferior check ligament, Proc Am Assoc Equine Pract 28:107,1982.

7. Turner TA, Rosenstein OS: Inferior check desmo­tomy as a treatment for caudal hoof lameness, Proc Am Assac Equine Pract 38: 157, 1992.

8. White NA: Ultrasound guided transection of the accessory ligament of the deep digital flexor muscle (distal check ligament desmotomy) in horses, Vet Surg 24:373,1995.

9. Curtis SJ: Farriery in treatment of acquired flexural deformities and a discussion on apply­ing shoes to young horses, Equine Vet Ed 4: 193, 1992.

10. Redden RF: A method for treating club feet, Proc Am Assoc Equine Pract 34:321, 1988.

11. Adams SB, Fessler JF: Distal check desmotomy. In Adams SB, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders.

••

CHAPTER 14

Proximal Check Ligament Desmotomy Joanne Kramer

INDICATIONS

Proximal check ligament desmotomy is used in the management of metacarpophalangeal flexural deformities (Figures 14-1 and 14-2) and in the management of superficial digital flexor ten­donitis (Figure 14-3) .

EQUIPMENT

Gelpi or Weitlaner retractors, electrocautery, and suction should be available for this procedure.

POSITIONING AND PREPARATION

The horse is positioned in lateral recumbency with the affected side down. Bilateral cases are repositioned after one limb is complete. Alterna­tively, dorsal recumbency can be used when the condition is bilateral. Dorsal recumbency has the advantage of natural hemostasis, but access to the surgical site is awkward. The circumference of the limb should be clipped and prepared asepti­cally fro m the carpus to the mid radial region.

ANATOMY

The proximal check ligament originates on the caudomedial aspect of the radius, courses obliquely, and inserts broadly on the medial

86

and cranial aspect of the superficial digital flexor tendon at the musculotendinous junction (Figures 14-4 and 14-5). From the lateral aspect, the ligament lies adjacent to the proximal and medial aspects of the carpal tendon sheath. From the medial aspect, the ligament lies adjacent to, and is fused with, the deep sheet of the flexor reti­naculum. To gain access to the proximal check lig­ament from the medial aspect, the antebrachial fascia must be incised where it is extended as the superficial sheet of the flexor retinaculum. This exposes the tendon of the flexor carpi radialis muscle, which is retracted caudally to expose the ligament.

The fibers of the proximal check ligament are in two layers~superficial and deep.

The palmar carpal branch of the proximal radial artery is the nutrient artery for the superfi ­cial digital flexor tendon (SDFT). It is exposed at the proximal aspect of the ligament and runs in a distolateral di.rection between the superficial and deep layers of the proximal check ligament.

PROCEDURE

An 8- to l O-cm incision is made on the medial aspect of the limb 1 cm caudal to the radius and cranial to the cephalic vein. The incision starts 1 em proximal to the level of the distal physis and extends proximally (see Figure 14-4). The subcu­taneous tissues are incised and electrocautery is used as needed to achieve hemostasis. The com­municating branch of the proximal rad ial vein

Figure 14-1 Moderate superficial digital flexor ten­don contracture in both forelimbs.

Figure 14-2 Superficial digital flexor tendon con­tracture with fetlock contracture in the left forelimb.

that perforates the antebrachial fascia and joins the cephalic vein is ligated and transected. The cephalic vei n is then retracted caudally (Figure 14-6). The superficial sheet of flexor retinaculum and the antebrachial fascia are incised to expose the tendon and distal muscle belly of the flexor carpi radialis. Gelpi or Weitlaner retractors are used to retract the flexor carpi radialis caudally (Figure

Proximal Check Ligament Desmotomy 87

Figure 14-3 Superficial digital flexor tendonitis in the left forelimb.

Site of approach

~~t;.r;~~VI(_

Figure 14-4 Location of the incision for proximal check ligament desmotomy.

14-7). The proximal check ligament is fused with the deep sheet of flexor retinaculum. The fibers of the ligament are generally oriented obliquely and can be traced to the distal radius. Palpation and blunt dissect ion are used to define the limits of the proximal check ligament.

88 LIMB S URG ERIES

The palmar carpal branch of the proximal radial artery courses through the proximal margin of the check ligament, and other small but deep vessels can be found throughout the ligament. When isolated and visualized, the proximal check

Figure 14-5 Intraoperative view of the proximal check ligament (arrow),

Superficial of flexor retinaculum

ligament is carefully transected a small amount at a time, taking care to avoid vessels coursing through the ligament (Figure 14-8). Visualizing the distal extent of the check ligament may require transecting a small amount of the deep sheet of the flexor retinaculum. When the excision is complete, the muscle belly of the radial head of the deep digital flexor tendon (DDFT) is visible (Figure 14-9) . The carpal sheath may also be visible in the distal portion of the incision (Figure 14-10). If the carpal sheath has been incised, the area should be lavaged liberally. The area is checked for bleeding before closure.

The incision in the superficial sheet of the flexor retinaculum is closed with No. 2-0 or No. o absorbable suture material in a continuous pat­tern. The subcutaneous tissues are closed with No. 2-0 absorbable suture material. The skin is closed with an interrupted pattern using No. 2-0 suture material (Figure 14-11).

fascia (a)

Deep communicating branch to the proximal radial v. (b)

Cephalic v. (c)

Tendon sheath of flexor carpi (cut) radialis m.

Tendon flexor carpi radialis m.

Figure 14-6 Ligation and transection of the communicating branch that perforates the antebrachial fascia. and incision of the superfi cial sheet of retinaculum and tendon sheath of the fl exor carpi radialis.

Proximal Check Ligament Desmotomy 89

b (cut)

c

~~t;..tc,~ . Figure 14-7 Retraction of the flexor carpi radialis caudally to expose the proximal check ligament fused with the deep sheet of flexor retinaculum. a, Antebrachial fascia; b, cut end of the deep communicating branch to the proxi­mal radial vein; c, proximal check ligament; d, tendon of fl exor ca rpi radialis muscle; e, tendon sheath of flexor carpi radialis muscle;f, deep sheet of flexor retinaculum; g, superficial sheet of flexor retinaculum.

," (cut)

I > Layers of proximal check lig.

~t;..t (, ..

Figure 14-8 Transection of the proximal check ligament. a, Deep communicating branch to the proximal radial vein; b, proximal radial artery (palmar carpal branch); c, deep sheet of flexor retinaculum; d, superficial sheet of flexor retinaculum.

Figure 14-9 Visualization of the muscle belly of the radial head of the deep digital flexor tendon (arrow)

after transection of the proximal check ligament.

, •

SuperfiCial> L f ayers 0 proximal check lig.

c Carpal

~t;,,£'~

Figure 14-10 The carpal sheath exposed after tran­section of the proximal check ligament. a, Superficia l sheet of fl exor retinaculwn; b, deep sheet of flexor reti­naculum; c. proximal radial artery (palmar carpal branch).

90 LIMB SURGER I ES

POSTOPERATIVE CARE

Postoperative care Bandaging: A sterile dressing is placed over the incision, and a pressure bandage is applied over the incision site. The limb is then bandaged from the incision site distally. The limb is kept bandaged for 3 weeks and the bandage is changed every 3 to 4 days. For flexural deformities, polyvinyl chlo­ride (PVC) splints may be necessary to prevent the fetlock from buckling forward and to maintain load on the flexor tendons. Exercise Restrictions: The horse is stall rested for 2 weeks without handwalking and then stall rested with handwalking for the following 2 weeks. Exercise is then gradually increased as indicated by the primary problem. Medications: Phenylbutazone is administered at 4.4 mglkg BID for the initial 24 hours and 2.2 mglkg BID for an additional 3 days. Con­tinued phenylbutazone administration at lower doses or less frequent intervals may be necessary for pain management in flexural limb deformities. Antibiotics are used preoperatively but generally not continued in the postoperative period. Suture Removal: Skin sutures are removed 12 days postoperatively. Other: When contractural deformity is present, the foot should be trimmed to as normal an angle as possible. In mild cases, an elevated heel may be beneficial to allow lengthening by a gradual increase in load on the tendon. In severe cases, a vertical bar shoe may be indicated.'

Figure 14-11 Closure of the superficial retinaculum, subcutaneous tissue, and skin.

EXPECTED OUTCOME

The prognosis is guarded for mild to moderate metacarpophalangeal flexural deformities and poor for severe deformities.2.3 When performed for superficial digital flexor tendonitis, the prog­nosis for a return to racing appears to be improved for racehorses, with Standardbreds showing greater improvement.4.6

COMPLICATIONS

Seroma formation is the most common compli­cation. Seromas should be left to resorb sponta­neously. Seromas that continue to increase in size can be aseptically aspirated or, rarely, treated by drainage after postoperative days 12 through 14.7 Incisional or carpal sheath infections are possible but not common. Increased strain on the sus­pensory ligament after proximal check ligament desmotomy may predispose to suspensory liga­ment desmititis.8

,9 Horses treated for metacar­pophalangeal flexural deformities may not have significant improvement with proximal check lig­ament desmotomy alone and may require addi­tional procedures.

ALTERNATIVE PROCEDURES

In horses with superficial flexor tendon core le­sions, percutaneous tendon splitting may improve

healing by draining hematomas or seromas asso­ciated with the core lesion and creating a com­munication between the tendon core and the peritenon that promotes healing. The procedure is often performed in conjunction with proximal check ligament desmotomy.7,10

Tenoscopically assisted superior check liga­ment desmotomy has also been described and may offer the advantages of decreased incisional complications and operative time,l1 ,12

Flexural limb deformities of the metacar­pophalangeal joint will sometimes respond to inferior check ligament desmotomy alone or in combination with proximal check ligament desmotomy. 2,1l Fetlock flexural deformities have also been treated with superficial digital flexor tenotomy.2

COMMENTS

Proximal check ligament desmotomy is more dif­

ficult than distal check ligament desmotomy. A thorough understanding of the anatomy, careful attention to hemostasis, and strict asepsis are

important for consistently good results.

Determining the most appropriate surgical

treatment for fetlock flexural deformities can be

difficult. For mild cases where the fetlock angle is less than 180 degrees, the limb can be forced into extension and the superficial and deep digital fl exor tendons palpated. If the tautest structure is

the DDFT, distal check ligament desmotomy may be beneficial. If the tautest structure is the SDFT or the superficial and deep feel equally taut, prox­ima l check ligament desmotomy is then per­

formed. In moderate or severe cases where the

fetlock angle is greater than 180 degrees, both pro­cedures are performed.2 If response is not ade­

quate after transection of both check ligaments,

tenotomy of the SDFT is performed. As discussed previously, severe cases have a poor prognosis for

correction because of joint capsule and suspen­

sory ligament contracture. These cases are candi­

dates for fetlock arthrodesis. Several, but not ail, studies suggest that proxi­

mal check ligament desmotomy increases the like­

lihood of return to racing after superficial digital flexor tendonitis.4

-6

,9 The reason for improvement

is not clearly understood but is likely related to the functional lengthening of the superficial digital flexor musculotendinous unit that occurs after

desmotomy. When the proximal check ligament is

Proximal Check ligament Desmotomy 91

intact, the majority of the load during weight bearing is sustained by the tendon from the prox­imal check ligament distally. Desmotomy is thought to allow the muscle to assume a greater portion of the load and contribute to the elastic­ity of the entire unit. 14 The actual strain in vitro on the SDFT after proximal check ligament desmotomy increases, but the elongation of the musculotendinous unit also increases during load application. 15 This elongation and recruitment of muscle fibers may allow for increased elasticity in the musculotendon unit compared with those that heal without desmotomy. 14

REFERENCES

1. Auer ]A: Flexural deformities . In Aller JA, Stick lA, editors: Equine surgery, ed 2, Philadelphia, 1999, WB Saunders.

2. Adams S8, Santsch i EM: Management of congeni­tal and acquired flexural deformities, Proc Am Assoc Equine Pract 46: 117. 2000.

3. Kidd lA, Barr ARS: Flexural deformities in foals, Equine Vet Edu, 14(6):311,2002.

4. Fulton Ie, Maclean AA, O'Reilly JL, et al: Superior check ligament desmotomy fo r treatment of super­ficial digital flexor tendonitis in Thoroughbred or Standardbred horses, At/st Vet J 71:233, 1994.

5. Hawkins JF, Ross MW: Transection of the accessory ligament of the superficial digital flexor muscle for the treatment of superficial digital flexor tendonitis in Standardbreds: 40 cases (1988- 1992), J Am Vet Med Assoc 206(5):674, 1995.

6. Hogan PM, Bramlage LR: Transection of the acces­sory ligam ent of the superficial digital flexor tendon for treatment of tendonitis: long term results in 61 standardbred racehorses horses ( 1985-1992 ), Equine Vet J 27(3):22 1, 1995.

7. Adams SB, Fessler JF: Proximal check desmo­tomy/Percutaneous tendon splitting. In Adams SB, Fessler JF, editors: Atlas of equine surgery, Philadel­phia, 2000, WB Saunders.

8. Alexander GR, Gibson KT, Day RE: Effects of supe­rior check desmotomy on flexor tendon and sus­pensory ligament strain in equine cadavers, Vet Surg 30:522, 200 I.

9. Gibson KT, Burbd ige HM, Pfeiffer DU: Super­ficial digital flexor tendonitis in thoroughbred race horses: outcome following non-surgical treatment and superior check desmotomy, Aust Vet J 75:631,

1997. 10. Henninger R, Bramlage L, Schneider R: Shor t term

effect of superior check ligament desmotomy and percutaneous tendon splitting as treatment for acute tendonitis, Proc Am Assoc Equine Pract 36:539, 1990.

92 LI MB SURGERIES

11. Kretzschmar BH, Desjardins MR: Clinical evalua­tion of 49 tenoscopically assisted superior check ligament desmotomies in 27 horses, Proc Am Assoc Equine Pract 47:484, 2001.

12. Southwood LL, Stashak TS, Kainer RA: Desmo­tomy of the accessory ligament of the superficial digital flexor tendon in the horse with use of a tenoscopic approach to the carpal sheath, Vet 5urg 28:99, 1999.

13. Blackwell RB: Response of acquired flexural defor­mity of the metacarpophalangeal joint to desmo­tomy of the inferior check ligament, Proc Am Assoc Equine Pract 28:107,1982.

14. Bramlage LR: Superior check desmotomy as a treatment for superficial digital flexor tendonitis: Initial report, Proc Am Assoc Equine Pract 32:365, 1986.

15. Shoemaker RS, Bertone AL, Mohammad LN, et al: Desmotomy of the accessory ligament of the super­ficial digital flexor muscle in equine cadaver limbs, Vet SlIrg 20:245, 199L

CHAPTER 15

Distal Splint Bone Resection Joanne Kramer

INDICATIONS

Fractures in the middle or distal third of the splint bones with nonunion, excessive callus, sequestra, or septic osteitis (Figure 15- 1).

Figure 15-1 Mid metatarsal splint bone fracture.

93

EQUIPMENT

A chisel or osteotome, bone rasp. and tourniquet are used for this procedure.

ANATOMY

The distal aspect of the splint bone has rudimen­tary attachments to the palmar/plantar fascia and proximal ligament of the ergot (Figure 15-2). The interosseous ligament attaches the splint bones to the third metacarpal-metatarsal bone. In the hind limb, the dorsal metatarsal artery lies between metatarsal bones III and IV. The dorsal branch of the ulnar nerve (la teral) and the palmar meta­carpal or plantar metatarsal nerves (lateral and medial) run in the area of the distal end of the splint bone (see Figure 15-2).

POSITIONING AND PREPARATION

The horse should be placed in lateral recumbency with the affected splint bone up or in dorsal recumbency with the affected limb suspended. The limb should be prepared and draped for full circumferential access to the entire metacarpal! metatarsal region.

PROCEDURE

A vertical incision is made directly over the affected splint bone starting 4 em proximal to the

94 LIMB SURGER I ES

Interosseous Ii

Distal end of lateral splint bone

Palmar n. IV

•

Jig. 01 the

Lateral extensor

Dorsal br. of ulnar n.

ergot Lateral palmar a.v.

Interosseous digital a.v. III) medius (suspensory lig.) Lateral palmar n.

'-,''--- Distallig. of the ergot

~t;.e". _ ..

Common digital '",o~ tendon

• . .,

, •••• -

Figure 15-2 Anatomy of the distal splint bone.

Interosseous medius m . (suspensory lig.)

01 the ergot

Medial palmar a.v. (palmar common

digital a.v. II)

Medial palmar n.

Within the digital

tendon sheath

Figure 15-3 Freeing the spl int bone from its distal attachments.

fracture site and ending 2 cm distal to the distal aspect of the splint bone. The distal end of the splint bone is slightly rounded and can usually be palpated directly. If the region is significantly swollen, the opposite splint bone can often be pal­pated and used as a rough estimate of the distal landmark. The incision is then deepened to the level of, but not through. the periosteum. In severe cases, extensive scar tissue is present surrounding the splint bone. The distal end of the splint bone is identified and sharp dissection used to free it from its distal attachment to the palmar fascia and proximal ligament of the ergot (Figure 15-3). The end is then grasped with a towel clamp or forceps, and a curved osteotome or chisel is used to sever the attachments to the third metacarpal or metatarsal bone (Figure 15-4). Care should be taken to avoid damaging the dorsal metatarsal artery in the pelvic limb, which may be difficult to identify in cases with extensive fibrous tissue.

In some cases, the distal splint bone and frac­tured portion can be freed past the fracture site

Figure 15-4 Severing the interosseous ligament attaching the splint bone to the cannon bone.

~t;..t'~

Figure 15-5 Amputation of the splint bone proxi­mal to the fracture site with an osteotome.

for removal in one unit. The osteotome is used 2 em proximal to the affected area to create the proximal amputation site (Figure 15-5) . The splint bone and affected portion with its perios­teum can then be removed as one unit (Figure 15-6), Other cases may have extensive callus for­mation, making removal in one unit from the distal end difficult. These require removal of the portion distal to the affected site , creation of the proximal amputation site, and further dissection to remove the remaining portion of affected bone. All sequestra, surrounding mineralized tissue, and

Distal Splint Bone Resection 95

Figure 15-6 Removing the affected portion of splint bone.

Figure 15-7 Using a bone rasp to smooth the edge of the remaining proxi mal splint bone after excision of the distal portion.

discolored tissue should be removed. The area is then lavaged. The proximal aspect of the remain­ing splint bone is tapered or smoothed with a bone rasp to avoid leaving any sharp edges (Figure 15-7) .

Bleeding from the region can be controlled as needed through the use of cautery, hemostat application, and occasionally ligation. Although the region is generally very vascular, most bleed­ing can be controlled by postoperative pressure bandaging. Tourniquet application facilitates the procedure.

The subcutaneous tissues are closed with a syn­thetic absorbable suture material. If the amount of dead space is extensive, a Penrose drain can be placed before closure of the subcutaneous tissues. Most cases can be managed without a drain. The skin is closed with an interrupted pattern.

96 LI MB SURGERIES

POSTOPERATIVE CARE

Postoperative Care

Bandaging: A sterile dressing is placed over the incision and a half limb bandage is placed and changed the day following surgery. An inner pres­sure bandage can be placed over the incision site to control postoperative hemorrhage and swelling. If placed, this should be removed the day follow­ing surgery. The bandage is changed every 2 to 4 days for 3 weeks. If a drain has been placed, it should be removed within 3 days or sooner if drainage is minimal. Exertise Restridions: Strict stall rest is advised for the first 10 days followed by stall rest with handwalking for the following 2 weeks. Return to activity is then dependent on healing of the site and the degree of any concurrent suspensory lig­ament damage. In general, exercise is limited to small-area turnout for at least 2 months postop­eratively. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and 2.2 mg/kg BID for an additional 3 days. Further anti­inflammatory use is dependent on concurrent problems such as suspensory desmitis. Antibiotic use and duration are dependent on the presence of infection and ideally guided by culture results. If a drain is placed, antibiotic therapy should be continued 24 hours past removal of the drain. Generally, if debridement is thorough, the need for antibiotic therapy is minimal. Suture Removal: Skin sutures are removed 12 days postoperatively.

EXPECTED OUTCOME

The prognosis for middle and distal splint bone fractures is exceUent. The prognosis for proximal splint bone fractures is variable.

COMPLICATIONS

Seroma formation may occur especially if a large amount of dead space was present during closure. This is generally treated by continued bandaging or, if persistent, by opening the distal end of the incision. Dehiscence of the incision is possible, especially if a seroma develops. Generally, this is only partial dehiscence and can be allowed to heal by second intention. Excessive bone reaction near

the amputated portion of the splint bone is unlikely but may require additional rest, antiin­flammatory therapy, and possibly fur ther surgical removal.

ALTERNATIVE PROCEDURES

Segmental ostectomy of the affected portion of the splint bone leaving the proximal and distal segments intact has been described as an alterna­tive to resection of the entire splint bone distal to the fracture. Results were good in the 17 cases described. l

COMMENTS

Minimally displaced fractures will often heal ade­quately with conservative management.2

-4 Frac­

tures in the proximal third of the splint bone may require internal fixation or complete removal of metatarsal bone IV.,·6 Amputation of the splint bone in the proximal one fou rth of the splint bone potentially destabilizes the remaining portion of the splint bone and is not recommended without consideration of internal fixation of the remain­ing proximal fragment. If the proximal fragment is stable) some open proximal fractures may be managed by debridement without disturbing the proximal or distal segment attachments. 2

•4

,7

Distal splint bone fractures are often associated with hyperextension injuries or suspensory liga­ment desmitis. 8

.9 These conditions should be as­

sessed preoperatively and may dictate postopera­tive therapy. Fractures in the middle third of the splint bone are generally a result of trauma and are more likely to be associated with infection or sequestrum formation.

REFERENCES

1. Jenson PW, Gaughan EM, Lillich JD, et al: Segmen­tal ostectomy of the second and fourth metacarpal and metatarsa l bones in horses: 17 cases (1993-2002),1 AII1 Vet Med Assoc 224(2):271, 2004.

2. Adams SB, Fessler JF: Excision of distal splint bone fractures. In Adams SB, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders.

3. Dyson SJ; The metacarpal region. In Ross MW, Dyson SJ, editors; Diagllosis and management of lamelless in the horse, St Louis, 2003, WB Saunders.

4. Jenson PW, Gaughn EM, Lillich JO, et a1: Spl int bone disorders in horses, Camp COlIl Educfor the Pract Vet 25(5):383,2003.

5. Baxter GM, Doran RE. Allen 0: Complete excision of a fractured fourth metatarsal bone in eight horses, Vet SLlrg 2 1(4):273, 1992.

6. Peterson PR, Pascoe JR, Wheat JD: Surgical man­agement of proximal splint bone fractures in the horse, Vet SlIrg 16( 1): 13, 1987.

Distal Splint Bone Resection 97

7. Kidd 1: Management of splint bone fractures in the horse, In Practice 25(7):388, 2003.

8. Bukowiecki CF, Bramlage LR, Gabel AA: In vitro strength of the suspensory apparatus in training and resting horses, Vet SlIrg 16(2): 126, 1987.

9. Verschooten F, Gasthuys F, De Moor A: Distal spl int bone fractures in the horse: an experimental and clinical study, Eqllille Vet] 16:532, 1984.

CHAPTER 16

Deep Digital Flexor Tenotomy Joanne Kramer

INDICATIONS

Severe distal interphalangeal joint contracture or severe laminitis with rotation of the third phalanx (P3) (Figures 16-] and 16-2).

EQUIPMENT

A heel wedge is used during standing procedures. Modified table knives or malleable retractors are useful when isolating the tendon during transec­tion ' (Figure 16-3).

Figure 16-1 Severe deep digital flexor tendon contracture.

98

POSITIONING AND PREPARATION

The procedure is most often performed with the horse standing in adult horses with laminitis and recumbent in foals with severe deep digital flexor tendon (DDFT) contracture. When performed with the horse standing, heel wedges are tem­porarily placed on the horse to take tension off the DDFT during the procedure. A high palmar­palmar metacarpal nerve block or inverted-U block is performed in the proximal metacarpal region. The limb is clipped circumferentially and prepared for aseptic surgery in the mid metacarpal region. A sterile adhesive drape or short drapes proximal and distal to the site are used.

Figure 16-2 Laminitis with rotation of the third phalanx.

ANATOMY

The heads of the DDFT originate from the medial epicondyle of the humerus, olecranon, and caudal radius and insert as a single tendon on the palmar surface of the third phalanx. Transecting the DDFT eliminates the pull of the deep digital flexor muscle on the coffin bone, reducing shearing forces between the dorsal coffin bone and hoof wall and essentially eliminating coffin joint

Figure 16-3 Bent table knives are useful during iso­lation and transection of the deep digital flexor tendon. The curvature of the top instrument is greater than that of the bottom instrument.

Common digital extensor tendon

Lateral digital extensor tendon

MC IV

Dorsal br. ofulnarn.

Lateral palmar a.v. (palmar common

digital a.v. III)

Lateral palmar n.

~ .

•

Deep Digital Flexor Tenotomy 99

flexion. The incision for mid metacarpal deep digital flexor tenotomy is located above the prox­imal extent of the digital flexor tendon sheath and is typically below the distal check ligament inser­tion. At this level. the neurovascular bundles lie directly over and slightly dorsal to the DDFT. Care must be taken to not exteriorize or transect these with the tendon (Figure 16-4).

PROCEDURE

A 3-cm incision is made over the DDFT in the middle third of the metacarpus, avoiding the flexor tendon sheath, which extends proximally to the level of the second and fourth metacarpal bones (Figure 16-5). The palmar fascia is incised, and blunt dissection is used to create a space between the superficial digital flexor tendon and the DDFT. A space is then created between the DDFT and the suspensory ligament (interosseous medius tendon). The bent knife with the larger curvature is slid on the palmar surface of the DDFT, and the bent knife with the smaller curva­ture is slid on the dorsal surface of the DDFT until the instruments overlap (Figure 16-6). Slight

. • I,. . • ", ' .... • • ... . " ...... - -• • • - '.

- --•

.'

MC II

Interosseous medial m. (suspensory lig.)

Medial palmar a.v. (palmar common digital a.v. II)

Medial palmar n.

SDFT

Figure 16-4 Cross sectional anatomy of the deep digital flexor tendon and mid metacarpal region.

2

100 LIMB SURGERIES

i of 't-a :pproach

Figure 16-5 lncision location for deep digital flexor tenotomy.

Figure 16-6 Isolation of the deep digital flexor tendon.

overlapping of and tension on the instruments bring the DDFT to, but not out of, the incision. The DDFT is then transected with a No. JO blade (Figure 16-7). I f the distal check ligament is present at the level of the incision, it is isolated and transected with the DDFT. After transection, the heel elevation can be removed to check for adequate gap formation between the tendon ends. Closure of the subcutaneous tissue is optional. Closure of the skin is performed with an inter­rupted apposing or everting pattern using No. 2-0 monofilam ent suture material.

POSTOPERATIVE CARE

Postoperative Care

Bandaging: A sterile dressing is placed over the incision and a half limb bandage is applied. The limb should remain bandaged for 30 days, and the bandage is changed every 5 to 7 days or more frequently if needed. Exerc:ise Restrictions: Horses with laminitis should be rested as their condition indicates and are not allowed significant turnout for a minimum of 6 months. Foals with contracture can be allowed turnout in a small area after I week, and the amount of exercise allowed is gradually increased over the next 60 days. Free choice turnout should not be allowed for up to 6 rnonths.' Medications: Phenylbutazone should be admin­istered for a rninirnum of 5 days. Suture Removal: Skin sutures are removed 12 days postoperatively. Other: Continued corrective shoeing is an essen­tial component of treatment. Surgery should not be performed without considerations for postop­erative corredive trimming and shoeing. Prin­ciples of shoeing to reestablish the normal relationship between the solar surface of P3 and the sole following deep digital flexor tenotomy have been described',' and are essential when tenotomy is performed as a component of lamini­tis treatment. Foals with severe fiexural deformi­ties should be trimmed in a normal fashion. The need for corrective shoeing in these cases depends on the amount of release achieved after tenotomy.

~e..v, t;;..tl< '1 _

Figure 16~ 7 Transection of the deep digital flexor tendon.

EXPECTED OUTCOME

Deep digital flexor tenotomy is a salvage proce­dure, although some horses may become sound for athletic activity. The intended goal should be limited to an improvement in comfort level and pasture soundness. Severe chronic cases of coffin joint contracture may have such severe joint capsule and surrounding tissue contracture that limb position may not improve significantly after tenotomy.5,6

The prognosis for horses with laminitis likely depends on the condition of P3 and blood supply. An improvement in pain, but not survival rate, has been reported in horses with acute refractory laminitis,7 In selected cases of chronic laminitis, an improved prognosis for survival has been reported.s

COMPLICATIONS

Incisional dehiscence or drainage is rare. Sever­ance of the palmar artery, vein, or nerve is possi­ble and care must be taken that these structures are not isolated with the DDFT. Pain following tenotomy in foals with contracture may be signif­icant because of stretching of the joint capsule and soft tissue and can be managed with nonsteroidal antiinflammatory medication. Occasionally, tem­porary heel elevation is used to allow for a more gradual change in foot conformation. Hyper­extension of the coffin joint may occur and is managed with heel extension and elevation. Superficial digital flexor tendonitis may result from the increased strain on the superficial digital flexor tendon. Recurrent infection, abscessation, and sequestration of P3 are associated with chronic pain. If chronic pain persists, flexural deformity of the metacarpophalangeal joint may occur.

Deep Digital Flexor Tenotomy 101

ALTERNATIVE PROCEDURES

Tenotomy at the level of the mid pastern has been described.9 The procedure is performed under general anesthesia. A vertical 3-cm midline in­cision is made on the palmar aspect of the mid pastern. The incision is continued through the subcutaneous tissue and digital flexor tendon sheath. Curved forceps are placed under the tendon, and it is transected with a scalpel. The incision in the tendon sheath is closed with No. 2-0 absorbable suture. The subcutaneous tissues are closed with 2-0 absorbable suture and the skin is closed in an interrupted pattern.

The DDFT can be isolated and elevated outside the incision with curved forceps as has been tra­ditionally described. to During standing surgery, we prefer to use the modified table knives described by Redden because the neurovascular structures are easily protected from transection without having to exteriorize the tendon. Because of the anatomic location and peri tendinous attachments, tenotomy at the level of the pastern may provide greater release than tenotomy at the mid metacarpal level. I I No difference in outcome has been demonstrated between tlle two tech­niques, and we prefer mid metacarpal tenotomy because of the lack of tendon sheath in the mid metacarpal region and the more proximal loca­tion for standing surgery.

REFERENCES

I. Redden RF: Shoeing the laminitic horse. In Redden RF, editor: Understanding laminitis, Lexington, 1998, The Blood Horse Inc.

2. Sullins KE: Standing musculoskeletal surgery. In Bertone A, editor: Standing surgery in the horse, Vet Clin N Am Equine Pract 7:687, 199 1.

3. Nickels FA: Laminitis. In Ross MW, Dyson S1. editors: Diagnosis mId management of lamelless in the horse, Philadelphia, 2003, WB Saunders.

4. Redden RF: Shoeing the laminitic horse, Proc Am Assoc Equine Pract 43:356, 1997.

5. Adams SB, Santschi EM: Management of congeni­tal and acquired flexural deformities, Proc-Am Assoc Equine Pract 46: 117, 2000.

\ •

I

102 LIMB SURGER IES

6. Mcllwraith CW, Fessler IF: Evaluation of inferior check ligament desmotomy for treatment of acquired flexor te ndon contracture in the horse, J Am Vet Med Assoc 172:293, 1978.

7. Hunt RJ, Allen DA, Baxter GM, et a1: Mid metacarpal deep digital flexor tenotomy in the management of refractory laminitis in horses, Vet 5urg 20:15,1991.

8. Eastman TG, Honnas eM, Hague BA: Deep digital flexor tenotomy as treatment for chronic laminitis in horses: 37 cases, Proe Am Assoc Eqllille Pmct 44:265, 1998.

9. Allen 0, White NA, Foerner 1F, et al: Surgical management of chronic laminitis in horses: 13 cases (1983-1985), ] Am Vet Med Assoc 189:1604, 1986.

10. Adams S8, Fessler JF: Deep digital flexor tenotomy. In Adams 5B, Fessler JF, editors: Atlas of eqllille surgery. Philadelphia, 2000, WB Saunders.

11. Hunt Rl: Laminitis. In Ross MW, Dyson 5J, editors: Diagllosis and management of lameness ;n tlte horse, Philadelphia, 2003, WB Saunders.

CHAPTER 17

Semitendinosus Tenotomy and Myotomy Joanne Kramer

INDICATIONS

Treatment of gait abnormalities secondary to fibrosis or ossificat ion of the semitendinosus muscle (fibrotic myopathy).

EQUIPMENT

No special equipment is required for tenotomy. A blunt-tipped bistoury is useful for the myotomy procedure.

ANATOMY

The semitendinosus muscle originates from the transverse processes of the first and second caudal vertebrae, the sacrosciatic ligament, and the ventral surface of the ischiatic tuberosity. It inserts on the tibial crest, crural fascia proper, and cal­caneal tuberosity. The tendon of insertion on the medial aspect of the proximal tibia is transected in the tenotomy procedure. The myotomy proce­dure involves transecting muscle fibers at the distal extent of the fibrotic region and is typically performed on the caudal aspect of the limb just proximal to the musculotendinous junction.

POSITIONING AND PREPARATION

The semitendinosus tenotomy procedure is per­formed with the horse in lateral recumbency with

103

the affected limb positioned down. The myotomy procedure is performed with the horse standing with local anesthesia and sedation.

PROCEDURE

Semitendinosus Tenotomy

Palpation of the proximal medial tibial region usually reveals the location of the horizontally ori­ented tendon of insertion. Generally, the tendon is about four fingers' width distal to the proximal tibia. The distal end of the tibial crest can also be used as a proximal to distal guide. An 8-cl11 verti­cal incision is made over the tendon caudal to the medial saphenous vein. The incision is extended through the subcutaneous tissues and the dense crural fascia to expose the tendon. Curved forceps are passed underneath the tendon, and the tendon is transected (Figure 17-1). The fascial layer is closed with an interrupted or continuous pattern using synthetic absorbable suture material. The subcutaneous tissue is closed with a continu­ous pattern using synthetic absorbable suture material. The skin is closed in an interrupted pattern.

Semitendinosus Myotomy

Infiltration of local anesthetic is performed in an inverted-U pattern surrounding and distal to the most taut palpable area of fibrosis . A 6-cm vertical incision is made over the caudal aspect

104 LIMB SURGERIES

A

Tendon of semitendinosus m.

I

Saphenous a. and n. and medial saphenous v.

___ Incision line

Figure 17-1 Location (A) and incis ion (B) of the semitendinosus tendon of insertion on the proximal tibia

of the semitendinosus muscle beginning at the distal extent of the fibrosis and extending distally. Blunt dissection is used to deepen the incision to the level of palpable fibrosis. A blllnt­tipped bistoury is used to transect the muscle or tendon attachments at the distal extent of the fibrotic area (Figure 17-2). Taut vertical fibrotic bands that appear to limit cranial movement when the limb is pulled forward by an assistant are transected.! The horse is then walked several steps to judge the effect of the release. If necessary, the procedure is repeated until the gait improves or until the entire area distal to the fibrosis has been transected. The incision is lavaged copiously with sterile saline and packed with sterile roll gauze. Partial closure of the skin is performed and the remainder of the incision is left to heal by second intention. Alternatively, a Penrose drain can be placed and the incision closed primarily. When other muscles such as the semimembra­nosus or biceps femoris are involved, a similar myotomy procedure can be performed.

POSTOPERATIVE CARE

Postoperative Care

Bandaging: If myotomy is performed, the gauze packing is changed the following day and removed in 2 days. Exercise Restrictions: Stall rest with light hand­walking is advised for the first 2 weeks, followed by gradually increasing exercise. Full turnout is allowed 6 weeks following surgery. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and 2.2 mg/kg BID for an additional 5 days. Antibiotic therapy is continued until 24 hours after drain or packing removal. Horses should receive a tetanus toxoid booster if it has been longer than 6 months since the previous vaccination. Suture Removal: Skin sutures are removed 12 days postoperatively.

B

----- Bistoury knife

Semitendinosus Tenotomy and Myotomy 105

~ 09 ......... ,,~..:t:u...-

Fibrotic region

Fibrous bands

Figure 17-2 The use of a bistoury knife to transect restr ictive scar tissue on the distal aspect of the affected • region.

EXPECTED OUTCOME

Reported cases treated with tenotomy have had good results, but only a small number of cases have been reported.2

,3 Horses with mild scarring often improve considerably with tenotomy, and the procedure has minimal complications. In the author's opinion, horses with more severe fibrosis genera lly require myotomy fo r improvement and have a higher likel ihood of recurrence. In one report, 75% of horses treated with myotomy had 75% or greater improvement in gait. At approxi­mately 2-year follow- up, one th ird of these horses had some recurrence of gait restriction. Some horses with some recurrence of restriction were able to perform at their intended level. 4 Horses with fibrosis confined to the semitendinosus muscle have a better outcome than those with additional fibrosis in the biceps femoris or semi­membranosus muscles.s In cases where muscles other than the semitendinosus are involved, tran­section of fibrosis in the involved muscle may be beneficial. 1.6

COMPLICATIONS

Dehiscence, seroma formation, and infection are possible but not common if the tenotomy only is performed. If myotomy is performed, the likel i­hood of these complications increases. Extensive postoperative fibrosis may result in recurrence of the gait abnormal ity.

ALTERNATIVE PROCEDURES

Transect io n of the semitendinosus muscle's in­sertion on the calcaneal tuber has also been described for cases where a taut band is palpable. The limb is protracted during surgery after tenotomy of the tibial insertion. If a taut band is palpable over the calcaneal tuber insertion, it is transected through an incision caudal and distal to the first incision. 2

•7

Complete removal of the area of fibrosis and a 4-cm portion of tendon has also been described.8

,9

The procedure can be effective, but a high inci-

106 LIMB SURGERIES

dence of complications probably caused by the extensive dissection required and large remaining dead space has been reported. Additionally, recur­rence in gait restriction secondary to fibrotic healing is likely. I,1O

COMMENTS

Fibrotic myopathy is commonly a result of trauma to the semitendinosus muscle with subsequent inflammation, hematoma formation, and fibrosis or ossification. Involvement of the semimembra­nosus, biceps femoris, and gracil is muscles is also possible. In cases where the inciting injury was observed, the hind limb has been caught cranially and underneath the horse or slipped forward excessively during sLiding stops. It has been reported after in tramuscular injections. 2

.s,1O Two congenital cases and three cases associated with peripheral neuropathy have been reported.2ol1

The gait associated with fibrotic myopathy is likely caused by an effective shortening of the semitendinosus muscle and adhesions between the semitendinosus muscle and biceps femoris or semimembranosus muscles. This functional shortening limits protraction of the hindlimb and results in the limb being retracted just before ground contact and contacting the ground in a pronounced vertical slapping motion. The abnor­mality is most easily observed at a walk. The gait restriction appears to be primarily mechanical and not directly associated with pain.

REFERENCES

I. Irwin DHG, Howell DW: Fibrotic myopathy, hematomas and scar tissue in the gaskin area of the thoroughbred, J South African Vet Assoc 52:65, 1981.

2. Bramlage LR, Reed SM, Embertson RM: Semi­tendinosus tenotomy for treatment of fibrotic myopathy in the horse, } Am Vet Med Assoc 186:565, 1985.

3. Pickersgill CH, Kriz N, Malikides N: Surgical t reat­ment of semitendinosus fibrotic myopathy in an endurance horse management, complications and outcome, Equine Vet Educ 12:242, 2000.

4. Magee AA, Vatistas NJ: Standing semitendinosus myotomy for the t reatment of fibrotic myopathy in 39 horses, Proc Am Assoc Equine Pract 44:263, 1998.

5. Villamandos RG, Santisteban JR, Avila I: Tenotomy of the tibial insertion of the semitendinosus muscle of two horses with fibrotic myopathy, Vet Rec 126:67,1995.

6. Dabare iner RM, Schmitz DG, Honnas eM, et al: Gracilis muscle injury as a cause of lameness in two horses, ] Am Vet Med Assoc 224:1630, 2004.

7. Adams SB, Fessler JF: Semitendinosus tenotomy for fibrotic myopathy. In Adams SB, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders.

8. Adams OR: Fibrotic myopathy in the hindlegs of horses, J Am Vet Med Assoc 139: 1 089, 1961.

9. Sullins KE: Lameness. Part XlII: the femur. In Stashak TS, editor: Adam's lameness in horses, Philadelphia, 2002, Lippincott, Williams & Wilkins.

10. Turner AS, Trotter GW: Fibrotic myopathy in the horse, } Am Vet Med Assoc 184:335, 1984.

II. Valentine BA, Rouselle SD, Sams AE, et al: Dener­vation atrophy in three horses with fibrotic myopa­thy, J Am Vet Med Assoc 205:332, 1994.

CHAPTER 18 •

Palmar-Plantar Digital Neurectomy Joanne Kramer

INDICATIONS

Chronic lameness that improves significantly after palmar/plantar digital anesthesia and has not improved with alternative treatment options. Typical indications include selected cases of nav­icular disease, navicular bone fractures, wing frac­tures of the third phalanx, idiopathic heel pain, and palmar-plantar foot injuries (Figure 18-1).

EQUIPMENT

Specialized instruments are not required for the guillotine or Black's method of neurectomy. Perineural capping requires Gerald or similar smooth-tipped forceps (Figure 18-2) .

POSITIONING AND PREPARATION

This surgery can be performed with the horse standing or under general anesthesia. Maintaining sterile and atraumatic technique is more difficult during standing surgery because of the proximity of the ground and inadvertent limb movement. Standing surgery is performed with the horse under sedation with local anesthetic over the palmar digital nerves at the level of the sesamoid bones. Peripheral anesthesia is also beneficial when the surgery is performed under general anesthesia.

Horses under general anesthesia are placed in lateral or dorsal recumbency. When bilateral

107

surgery is performed, the lateral side of the upper forelimb and the medial side of the lower forelimb are operated on initially. The horse is then rolled onto the opposite side and the procedures are repeated. Alternatively, the horse can be placed in dorsal recumbency with the limbs extended or flexed on the sternum.

When possible, surgery time is decreased by having two surgeons operate simultaneously. The circumference of the limb should be clipped and prepared aseptically from the fetlock distally.

ANATOMY

The palmar-plantar branch of the palmar-plantar digital neurovascular bundle lies in the space between the palmar/plantar border of the pastern and the abaxial border of the deep digital flexor tendon (DDFT). The nerve is just palmar/plantar to the artery and is found just deep to the liga­ment of the ergot. The presence of small accessory nerve branches varies; when present, they often lie palmar/plantar and deep to the ligament of the ergot.

PROCEDURE

A 3-cm skin incision is made over the abaxial border of the DDFT in the mid to distal pastern region (Figure 18-3, A) . The incision is extended carefully through the subcutaneous tissue. Blunt dissection is used to isolate the palmar digital

•

Figure 18-1 Preoperative image of a horse with nav­icular d isease. Note the typical pointing stance of the left forelimb.

A

o

Site of approach

1

Figure 18-2 Gerald forceps used when performing perineural capping.

of digital cush ion

B

c

.-.--1

E

~Pp- t;;.l,-~ .. _, __

Figure 18-1 A, Incision location for palmar digital neurectomy. B, Location of the palmar digital nerve in relation to surrounding structures. C, Palpation of longitudinal fibers when the nerve is stretched over a smooth instrument. OJ Crimped appearance of the nerve after it has been released. E, Transection of the palmar digital nerve. 1, Palmar d igital ne rve; 2, palmar digital vein; 3, palmar digital artery; 4, ligament of the ergot.

nerve (Figure 18-3, B) . Identification of the nerve is confirmed by its appearance (smooth, white, and glistening), by the crimped appearance of the nerve after it has been stretched and released, and by palpating longitudinal fibers when the nerve is stretched over the smooth portion of an instru­ment (Figures 18-3, C and D). When isolation of the nerve is confirmed, a 2- to 3-cm section of the nerve is freed from the surrounding tissues. The nerve is stretched, and the proximal end is tran­sected sharply with a new blade as proximal as possible. The distal portion is then transected sharply (Figure 18-3, E). The surgical site is eval­uated for accessory nerve branches. If identified, they are transected in a similar manner. Subcuta­neous closure is optional. The skin is closed with a continuous or interrupted pattern using No. 2-0 suture material.

POSTOPERATIVE CARE

Postoperative Care

Bandaging: A sterile dressing is placed over the incisions, and a limited-pressure bandage is applied over the incision sites using folded gauze sponges and 3-inch Elasticon. A half limb bandage is then applied. The initial bandage is changed 24 hours after surgery and replaced without the pres­sure bandage. Subsequent bandage changes are performed at 4- to 5-day intervals or more fre­quently if indicated. Bandaging is applied for a minimum of 3 weeks. Exercise Restridions: Stall rest is provided for 4 weeks. After 10 days, handwalking is al­lowed. After 4 weeks, the horse may resume normal activity. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the first 24 hours and 2.2 mg/kg BID for an additional 5 days. Suture Removal: Skin sutures are removed 12 days postoperatively. Other: When performed for navicular disease, corrective shoeing to decrease the biomechanical forces on the navicular bone should be continued. The bottom of the foot should be checked daily for puncture wounds, or the horse should be shod with pads.

EXPECTED OUTCOME

Reported soundness rates 1 year after palmar digital neurectomy are 74%1 and 77%.2 After 2

Palmar-Plantar Digital Neurectomy 109

years, the reported soundness rate is 63%. I Reasons for lameness vary and may be directly related to surgical complications, reinnervation, or secondary lameness in the limb.

COMPLICATIONS

Progression of the underlying problem may occur. In severe cases of navicular disease, progression can result in DDFT rupture or navicular bone fracture. To decrease the incidence of these com­plications, we generally avoid performing neurec­tomy in horses with erosion of the flexor cortex of the navicular bone or extremely large medullary cavity cysts (Figure 18-4). If neurectomy is per­formed in horses with flexor cortex lesions, the horse should be shod with moderate to significant heel elevation and activity should be limited. In all cases of navicular disease, corrective shoeing for navicular disease should be continued postop­eratively.

Undetected foot abscesses may occur from lack of sensation, and the foot should be examined daily for evidence of puncture. Reinnervation can occur within months of the surgery, and treat­ment options are limited to repeat neurectomy at a more proximal location. Neurectomy above the dorsal branch of the palmar digital nerve is not recommended. Painful neuroma formation is somewhat unpredictable. 3 Its occurrence is thought to increase when excessive inflammation

Figure 18-4 Horse with large medullary cavity cyst. This horse is at increased risk for deep navicular bone fracture following neurectomy.

110 LI MB SU RG ERIES

occurs. This may be related to performing surgery too soon after diagnostic anesthesia, traumatic surgical technique, excessive postoperative move­ment, or incisional site problems. Ideall y, surgery should not be perfo rmed for a minimum of 2 weeks after diagnostic anesthesia of the palmar digital nerve. Surgical technique and handling of the nerve should be as atraumatic as possible, and excessive dissection minimized. Adequate postoperative rest and proper bandaging tech­niques should be emphasized to the owner. Loss of the hoof wall as a result of ischemia is a ra re but possible complication. Reasons for its occur­rence are not well understood.4

ALTERNATIVE PROCEDURES

Black's Technique

This method of neurectomy allows for removal of a longer section of nerve, decreasing the cha nces of accessory nerve branch innervation to the region. The proximal nerve endin g may also lie deeper in the incision, potentially decreasing the incidence of neuroma formation. 5

A 2-cm skin incision is made over the abaxial border of the DDFT just above the medial or lateral cartilage of the third phalanx in the distal pastern region. The incision is extended carefully through the subcutaneous tissue. Blunt dissection is used to isolate the palmar digital nerve. Identi­fi cation of the nerve is confirmed by crimping of the nerve after it has been stretched and released and palpating longitudinal fibers when the nerve is stretched over the smooth portion of an instru­ment. Closed Kelly forceps are placed below the nerve, and traction is appl ied to identify the loca­tion of the nerve in the proximal pastern region. A 2-cm incision is made in the proximal pastern region distal to the base of the proximal sesamoid bone directly over the nerve being held in trac­tion. The nerve is isolated in th is region, and trac­tion is applied to the proximal and distal ends to ensure the same nerve is exposed through both incisions (Figure 18-5). A new scalpel blade is then used to transect the nerve as proximal as pos­sible through the upper incision. Traction is applied to the distal end of the nerve in the distal incision, and a 6- to 8-cm portion of nerve is stripped through the incision (Figure 18-6) . The exposed nerve is then severed as distally as possi­ble, and the skin is closed routinely (Figure 18-7).

Figure 18-5 Exposure of the palmar digital nerve in the proximal and distal incisions used in Black's method of neurectomy.

Figure 18-6 The nerve has been transected proxi­mally and pulled through the distal incision in Black's method of neurectomy.

Figure 18-7 Two-day postoperative view of the inci­sions used in Black's method of neurectomy.

Perineural Capping

Perineural capping of the proximal nerve end may be performed in an attempt to decrease painful neuroma formation.} Controlled studies with high case numbers are lacking, but if the tech­nique can be performed atraumatically it is likely beneficial. The palmar digital nerve is isolated and exposed as for the guillotine technique. The distal end of the nerve is severed. The end of the prox­imal nerve is grasped with hemostats, and Gerald or similar dressing forceps are used to free the combined epineurium and perineurium (per­ineural sleeve) from the nerve (Figure 18-8, A and B). After freeing of the perineural sleeve, the proximal end of the nerve is sharply transected. If sufficient nerve length is available, two partial incisions in the nerve can be made before tran­seeting the nerve. The purpose of these incisions is to slow axon regeneration and allow increased time for the perineural capping seal.3 After nerve transection) the edge of the perineural sleeve is grasped and pulled over the nerve (Figure 18-8, e) . The perineural sleeve is closed with one or two interrupted sutures using 4-0 absorbable suture. Subcutaneous and skin closures are routine.

Other techniques for neurectomy have been described, including a method of tunneling the proximal nerve end into bone and the use of a carbon dioxide laser to perform neurectomy) and they appear to have good success rates.6

,7

COMMENTS

Careful selection of cases should be performed. Significant improvement in lameness after palmar digital anesthesia is important, as well as an owner who understands potential complications and will provide excellent short- and long-term postoper­ative management. A variety of techniques for neurectomy are available, but no single technique has proven to be superior. Atraumatic technique and adequate postoperative rest are the essential components of all techniques. Although potential complications of neurectomy dictate limited use of the procedure) palmar digital neurectomy can offer significant pain relief and return to athletic function in horses that have not responded to other treatment options.

Palmar-Plantar Digital Neurectomy III

A

B

C Figure 18-8 Perineural capping on a cadaver limb. A. The nerve ending is grasped with hemostats, and smooth-tipped forceps are used to strip the perineural sleeve proximally. B, The perineural sleeve has been stripped proximally, and the nerve is exposed. C, After severing the exposed nerve, the nerve ending retracts proximally within the perineural sleeve. The perineural sleeve is then closed with No. 4-0 suture material.

112 LIMB SURGER I ES

REFERENCES

I. Jackman BR, Baxter GM, Doran RE. et al: Palmar digital neurectomy in horses: 57 cases (1984-1990). Vet Su'g 22:285, 1993.

2. Matthews S, Dart A, Dowling B: Palmar digital neurectomy in 24 horses using the guillotine tech­nique, Aust Vet} 81 :402, 2003.

3. Evans LH: Procedures used to prevent pa inful neu­romas, Proc Am Assoc Equine Pmct 16: 103. 1970.

4. Taylor TS, Vaughan IT: Effects of denervation of the digit of the horse,} Am Vet Med Assoc 177: 1 033, 1980.

5. Black J8: Palmar digital neurectomy: an alternative surgical approach, Proc Am Assoc Equine Pmct 38:429, 1992.

6. Harris JM, Kermedy MA: Modified posterio r digital neurectomy for management of chronic heel pain in horses, Proc Am Assoc Equine Pract 45:99, 1999.

7. Haugland LM, Collier MA. Panciera RJ. et al: Effect of C02 lase r neurectomy on neuroma formation and axonal regeneration. Proc Am Assoc Eqllille Pmct 39:229, 1993.

•

CHAPTER 19

Cast Application Joanne Kramer

INDICATIONS

Casts provide mechanical support and physical protection for fractures, luxations, and tendon and ligament injuries. Casts also provide physical protection and soft tissue immobilization for wounds and are commonly used to facilitate wound healing.

EQUIPMENT

Fiberglass casting material, cast padding, syn­thetic stockinette, orthopedic felt, and acrylic are used (Figure 19-1). A variety of fiberglass casting material is available. J,2 We commonly use Delta Lite "S."*

POSITIONING AND PREPARATION

Most casts are applied under general anesthesia with the affected limb uppermost. Standing application is possible but increases the risk of a poorly fitting cast due to movement. Half limb and distal limb casts are put on with the horse under general anesthesia. Foot casts and some forelimb distal limb casts are put on with the horse standing with the affected limb held up by an assistant.

"Delta-Lite "$"; Johnson & Johnson, Raynham, Mass.

113

CAST APPLICATION

Preparation

The limb should be clean and the foot trimmed normally. A sterile dressing is applied over inci­sions or wounds. A double layer of stockinette is applied to the region of limb to be cast (Figure 19-2). The stockinette should conform to the limb and not be allowed to wrinkle. Orthopedic felt is applied at the proximal limit of the cast (Figure 19-3).

Limb Positioning and Handling

The limb is generally cast in a weight-bearing position. Exceptions include flexor tendon lacera­tions, where the limb may be cast in a slightly flexed position. The hind limb is often cast in slight flexion to decrease tension on the superfi- . cial digital flexor tendon from the reciprocal apparatus when the stifle and hock flex. If traction is required, wires may be placed through the hoof wall and used with a steel bar to apply traction. Wires may also be useful to maintain foot posi­tion while casting. When handling the limb during cast application, the limb should be held only at the foot and above the cast. Pressure on the cast m aterial during the curing process can create focal pressure points that lead to cast sores or areas of stress concentration.

-

114 LIMB SURGERIES

Figure 19-1 Supplies used in cast application. From left to right, stockinette, orthopedic felt, foam cast padding, and fiberglass casting material.

Figure 19-2 Applying a double layer of stockinette.

Figure 19-3 Orthopedic felt applied at the antici~ pated proximal limit of the cast.

Handling of Cast Material

The strength of a cast depends on the thickness of the cast and the bonding between the individual layers of cast tape. The polyurethane resin i.n the casting tape starts to cure when immersed in

" , , '>

$ ; II!

'" ..

Figure 19-4 A cast where all layers have cured simultaneously.

Figure 19-5 A cast where individual layers of cast material have cured separately. The result is a weak cast prone to break.

water. Specific directions for handling vary with each manufacturer. Generally, the cast material is immersed in water at room temperature (68° to 77° F, 20° to 25° C) and squeezed four to five times while immersed, before application. Cast material curing time can be slowed slightly by exposing the material to cooler water for a shorter time period. As cast material cures, it stiffens to provide rigid support. AlI layers of the cast should cure simul­taneously to provide adequate strength. Once cast application is begun, subsequent layers of cast tape must be applied rapidly to avoid individual layers of cast material stiffening before becoming bonded to the surrounding layers (Figures 19-4 and 19-5).

Application of Cast Material

A layer of cast padding is applied before the cast material is applied to ensure even contact between

Figure 19-6 Foam padding applied before fiberglass casting tape is applied.

the cast and the limb and to protect the skin from the fiberglass material. A variety of materials are available for cast padding.1 A water-curable foam padding>!- is commonly used and appears to de­crease cast sores' (Figure 19-6). The foam padding should be set on the limb with only minimal tension. The cast material should be applied with only enough tension to avoid wrinkling. Each turn should be overlapped by half a tape width. The tension used when applying the cast material can be increased gradually as the number oflayers in the cast increases. For most fiberglass cast materials, the horse should be maintained in recumbency for 20 minutes after cast application to allow for curing.

Half Limb Cast

A double layer of stockinette is rolled from the foot to above the carpus or tarsus and held in place with towel clamps. The stockinette should fit snugly and be stretched to avoid wrinkles. A 2-inch-wide felt strip is then placed over the metacarpal-metatarsal bones at the proximal limit of the cast, which should be 2 em distal to the ca rpal or tarsal joint. Custom support foam or other cast padding material is applied starting proximally and working distally, with special attention paid to adequately cover the coronary band. This is immediately followed by a layer of 2- to 3-inch-wide casting material. The initial 2- to 3-inch layer allows better contouring of the cast material to the limb but has decreased

"Custom Support Foam; 3M Animal Health Care Prod­ucts, St. Paul, Minn.

Cast Application 115

Figure 19-7 Applying fiberglass casting material.

Figure 19-8 Incorporation of a heel wedge into the bottom of the cast. A partial roll of casting tape has been incorporated into the heel (left) and acrylic applied to provide an even weight bearing surface (right).

strength compared with wider casting tape. Four­inch-wide cast tape should be used for subsequent layers (Figure 19-7). Cast material should be applied with only enough tension to avoid wrin­kling and with each turn overlapped by half a tape width. Before the last layer of cast material is applied, the stockinette is folded down and held in place by the last cast layer. Adhesive tape is used to seal the proximal end of the cast. The entire length of cast should be covered in five to eight layers of tape.' Generally, five or six rolls of casting tape are used in a half limb cast. Casts providing mechanical support for severe orthopedic injuries require more layers than do casts providing soft tissue support for wound healing. A heel wedge should be placed so that the toe and heel of the cast are level when the limb is directly under the horse (Figure 19-8). Acrylic or other durable material is applied to the bottom of the cast to prevent wear (Figure 19-9).

116 LI MB SURGERIES

Figure 19-9 Applying acrylic to protect the bottom of the cast from excess ive wear.

Figure 19-10 Applying a dist.l limb cast.

Distal Limb Cast

This cast terminates at the proximal pastern, allowing fet lock flexion and extension (Figure 19-10). Distal limb casts are most commonly used in the treatment of heel bulb and distal pastern and coronary band lacerations.5,6 The palmar-plantar aspect of the cast is slightly shorter than the dorsal aspect of the cast to allow for fetlock exten­sion. Stockinette is applied and felt padding is placed around the proximal aspect of the first phalanx. The limb is cast in a weight-bearing posi­tion. Cast padding and 2- or 3-inch cast material is used to allow for adequate contouring. Acrylic is placed on the bottom of the foot to decrease wear. The heel is not typically elevated. Deter­mining the optimal weight-bearing position of the fetlock is difficult and is best assessed when the cast has cured and the limb is bearing weight. In some cases, the cast may have to be trimmed back slightly if it appears to impinge on the fetlock

Figure 19-11 A foot cast used to protect hoof wall injuries or aid in third phalanx fracture stab ilization.

joint dorsally or the proximal sesamoid bones palmarly or plantarly.'

Foot Cast

Foot casts terminate just below the coronary band on the hoof wall (Figure 19-11 ). They can be used in the management of hoof wall injuries or coffin bone fractures. ' Felt padding should be applied to the heel bulb region. Two-inch casting material is used to allow for adequate contouring. Acrylic is placed on the bottom of the cast to decrease wear.

Bandage Cast

Bandage casts are used when frequent access to the limb is desired or as reduced support in the transition from a traditional half limb cast to ban­daging. Two or three pieces of th in sheet cotton are rolled around the limb and secured with brown roll gauze. Vetrap* is then applied. The foot is included in the wrap for increased immo­bilization. Orthopedic felt is applied at the proxi­mal limit of the cast. Application of custom foam support is recommended but optional. The cast is then constructed with the desired amount of casting tape (generally five or six rolls of 4-inch casting tape). Acrylic is applied to protect the foot. At the first required bandage change, the cast is cut with an oscillating saw along the medial and lateral or dorsal and palmar aspects. The bandage is then changed, and the two halves are reapplied and secured with duct tape.s

*Vetrap; Animal Care Products, 3M Health Care, SI. Paul, Minn.

A modification of this procedure is performed when less immobilization is required or the ban­dage cast is used as a transition to bandaging alone after a half limb cast has been removed. The initial layer of bandage material described earl ier is placed without Vetrap, and a second identical layer is placed over the initial layer and secured with an elastic wrap. The cast is then constructed without inclusion of the bottom of the foot and bivalved at the first bandage change (Figure 19-12, A to C).

POSTOPERATIVE CARE

Posto erative care

Bandaging: A support bandage and foot eleva­tion are often applied to the contralateral limb' (Figure 19-13). In cases of severe injury, support to the contralateral limb is essential to decrease the risks of contralateral limb laminitis. This can be provided in the form of frog and caudal support, heel elevation, and decreased breakover. Com­mercial shoes are available and work well for this purpose~

Exercise Restridions: Horses with casts should be confined to a stall. After cast removal, exercise must be gradually increased to avoid overloading articular cartilage, bone, and soft tissues. The longer the period of immobilization, the more important and gradual is this reintroduction period.

*Redden Modified Ultimate; Nanric Inc., Versailles, Ky.

A B

Cast Application 117

cast Removal

In adult horses, casts are generally removed or replaced within 4 to 6 weeks. With very careful monitoring, an adult horse showing no problems may wear a cast up to 6 to 8 weeks. In young foals, casts should be removed in 10 to 12 days. For older foals, casts can be left in place for up to 3 weeks.

For orthopedic support, cast application is often necessary for 8 weeks. For wound support, cast application is required for 2 to 3 weeks.

Casts are removed with an oscillating cast cutter and cast spreaders. The medial and lateral sides of the entire length of the cast are cut full thickness with an oscillating saw (Figure 19-1 4). The cast spreaders are then inserted in the cut line and the cast pried open (Figure 19-15). The underlying stockinette is then cut, and the cast is removed from the limb. When the osc illating saw has penetrated the depth of the cast, a character­istic "give" is felt. The cast cutters should not be

dragged back and forth along an area to be cut. Even pressure should be applied without moving the saw until the cast has penetrated the depth of the cast. The cast cutters are then removed and reinserted so that the previously cut area is over­lapping halfway with the next area to be cut. Cast spreaders should not be inserted until the entire length of cast is cut. If the thickness of the cast is symmetrical and the layers of casting tape have cured in a one-layer cast, removal is straightfor-

C Figure 19-12 A bandage cast used for transition to bandaging after traditional half limb casting. A, The casting material is placed over a double layer of bandage material. B, At the first desired bandage change, the bandage cast is split into two halves. C, After the bandage is changed, the halves are supported with duct tape, allowing subsequent bandage changes to be performed as needed.

118 LIMB SURGERI ES

ward. Special care should be taken over bony prominences, joints, and the coronary band, as these are the areas most likely to be injured with the cast cutter.

Bandaging or splint application is indicated after cast removal to prevent edema and to ease

Figure 19-13 Bandaging and elevation of the con­tralateral limb.

Figure 19-14 Cast removal using an oscillating saw.

Figure 19-15 After the entire cast has been split with an oscillating saw. Cast spreaders are inserted to sepa­rate the two halves of the cast.

the transition between cast support and normal weight bearing. Foals often require temporary heel extension after cast application because of flexor tendon laxity (Figure 19-16).

Cast Monitoring

Casts must be monitored daily for the presence of heat, discharge, pressure sores, and cracking. Horses wearing casts should be monitored closely for changes in the level of lameness present. Early cast removal and replacement or reassessment are indicated immediately if the cast has broken or the horse has had a significant change in lameness level.

COMPLICATIONS

Cast sores, disuse osteopenia, articular cartilage softening, joint stiffness, tendon or ligament laxity, or breakage of the cast may occur.2

•4

•1O

,11

Pressure or fr ictio n sores generally occur at the proximodorsal aspect of the thi rd metacarpal bone, the proximoplantar aspect of the superficial digital flexor tendon, and the palmar/plantar aspect of the sesamoid bones in half limb casts (Figures 19-17 and 19-18). In distal limb casts, pressure or friction sores are most common at the proximopalmar aspect of the pastern. Foals and thin-skinned horses are particularly susceptible to cast sores. The degree of articular cartilage atrophy and disuse osteopenia and laxity is likely related to the length of cast immobilization and to the use or lack of use of the limb during the casting period. In foals, marked flexor tendon

Figure 19-16 Application of a heel extension to provide flexor tendon support in a foa l with tendon laxity secondary to cast application.

A B

Figure 19-17 Areas prone to cast sore development when a half limb cast is worn.

Figure 19-18 Cast sores on the palmar aspect of the fetlock.

laxity occurs within a short period of time. Prox­imal sesamoid bone fracture secondary to disuse osteopenia after hind limb cast application has been reported in two horses.12 Half-limb casts ending too low can create stress concentration on the metacarpal bone and risk fracture, especially during recovery from anesthesia.

Breaking of the cast usually occurs at the level of a moveable joint. Breakage is a result of inade­quate cast material strength due to inadequate thickness or inadequate curing (curing of two or more individual layers). Broken casts need to be removed immediately and replaced entirely.

Cast Application 119

Figure 19-19 Incorporation of a dorsal-palmar splint to increase bending strength in a half limb cast.

ALTERNATIVE PROCEDURES

Splints

During cast application, longitudinal splints of cast material can be applied on the dorsal and palmar aspect of the cast for additional strength. The splints are applied after several layers of cast material have been applied, and the final layers of cast material are used to incorporate the splints into the cast (Figure 19-19).

Preplaced Fetotomy Wires

Plastic-covered fetotomy wires can be prep laced on the medial and lateral aspects of the limb superficial to the cast padding but deep to the casting tape. The cast is then removed by placing handles on the wire and using the wire to saw the cast open on each side?

COMMENTS

Casts are only rarely used as the primary stabi­lization method for fractures or luxations. More often, casting is used as initial first aid stabiliza­tion for the transport of horses with severe orthopedic injuries. For more information on the appropriate form of stabilization for specific injuries, Chapter 4 on emergency stabilization of orthopedic injuries should be consulted.

The benefits of cast application in wound healing are often overlooked because of a per­ceived increase in cost. We have found that the

120 LIMB SURGER IES

cost of frequent bandage changes is often similar

to the cost of initial casting and have had good success with cast application as an aid to wound

h eal ing. To minimize complications, the period of

cast application should be as short as possible. and removal, reassessment, and replacement should

be performed if there is any question as to the

status of the underlying limb. Foals can develop cast complications quickly because of their thin

skin, high activity level, and tendency toward

severe ligament laxity.

REFERENCES

1. Booth TM, Dart AJ. Watkins JP: Equine limb casts: materials and methods, Comp Cant Educ Prac Vet 25:701.2003.

2. Murray RC, Oebowes RM: Casting techniques. In Nixon AI, editor: Equine fracture repair, Philadel­phia, 1996, WB Saunders.

3. Bramlage LR, Embertson RM, Libbey CJ: Resin impregnated foam as a cast liner on the distal limb, Proc Am Assoc Vet Pract 37:481,1991.

4. Riggs CM: Indications for and application of limb casts in the mature horse, Equine Vet Educ 9:190, 1997.

5. Blackford JT, Latimer FG, Wan PY, et al: Treating pastern and foot lacerations with a phalangeal cast, Proc Am Assoc Equille Pmct 40:97.1994.

6. Booth TM, Knottenbelt DC: Distal limb casts in equine wound management. Equine Vet Educ 11:273.1999.

7. Booth TM, Dart AI. Watkins JP: Equine limb casts: materials and methods, Camp Can t Educ Pmct Vet 25:708.2003 .

8. Hogan PM: How to make a bandage cast and indi­cations for its use, Proc Am Assac Equine Pract 46: I SO. 2000.

9. Hendrickson DA, Stokes M, Wittern C: Use of an elevated boot to reduce contralateral limb support complications secondary to cast application, Proc Am Assoc Equine Pmct 43: 149. 1997.

10. Richardson OW, Clark CC: Effects of shor t- term cast immobilization on equine articular ca rtilage, Am I Vet Res 54:449. 1993.

11. vanHarreveld PO, Lillich JD, Kawcak CE: Effects of immobilization followed by remobilization on mineral density, histomorphometric features and formation of the bones of the metacar­pophalangeal joint in horses, Am / Vet Res 63:276, 2002.

12. Malone ED, Anderson BH, Turner TA: Proximal sesamoid bone fracture following cast removal in two horses, Equine Vet EdriC 9:185,1997.

EAD AND ECK URGERIES

121

CHAPTER 20

Intraoral Wire Fixation of Rostral Mandibular and Maxillary Fractures

David A. Wilson

INDICATIONS

Fractures of the rostral mandible, maxi lla, and incisive bones that can be repaired with wire and! or acrylic. Only fractures that can be readily repaired with stainless steel wires are discussed.

EQUIPMENT

Stainless steel wire (16 or 18 gauge), needle holders or pliers, wire cutters, acrylic, and drill. A spool speculum or section of PVC tubing placed between the cheek teeth improves access to the oral cavity. Ideally, a nasotracheal tube is also placed during the surgery to facilitate breathing.

POSITIONING AND PREPARATION

Simple fractures involving one to three incisors can be repaired in the standing, sedated horse with local anesthesia. Mental and infraorbital nerve blocks provide effective regional anesthesia in these cases. Alternatively, local anesthesia can be used. Fractures involving the interdental space are more commonly repaired under general anes­thesia in either lateral or dorsal recumbency depending on fracture configuration. Antibiotics and nonsteroidal antiinflammatory agents are administered prior to surgery. Ideally, a nasotra­cheal tube is placed to protect the airway. The mouth is rinsed with water to remove accumu-

122

lated feed material, and the area surrounding the fracture site is scrubbed with povidone-iodine soap and rinsed again. If a wire will be passed around the premolars, stab incision sites are clipped and prepared aseptically.

ANATOMY

The primary structures potentially involved in the repair of these fractures are the maxilla, incisive bone, incisive part of the mandible, incisors, canine teeth, mental and infraorbital nerves, intermandibular synchondrosis, and permanent tooth roots. The permanent incisors, canines, and premolars are formed from separate enamel organs that are derived from lingual (med ial) extensions of the dental laminae of the deciduous teeth. 1 The permanent incisors erupt on the lingual aspect of the deciduous incisors.

The mental nerve emerges from the mental foramen on the rostrolateral aspect of the hori­zontal ramus, approximately midway between the second premolar and the third incisor. A smaller portion of the mental nerve continues rostral in a smaller canal along with the vasculature of the lower incisors.1

PROCEDURE

Various methods have been described to repair fractures of the rostral mandible and incisive bone.'· " The first step of the surgery is thorough

•

Intraoral Wire Fixation of Rostral Mandibular and Maxillary Fractures 123

debridement of the fracture site. Remaining food material, clotted blood, and bone fragments are removed. A bone curette may be used to freshen the edges of exposed bone, being careful to not manipulate or damage exposed, unerupted per­manent teeth. Completely detached or broken teeth should be removed. However, loose decidu­ous teeth are maintained if possible. These teeth often survive better than expected and provide stability, structure, and positioning for future permanent tooth eruption. Fractures involving alveoli can result in infectious periodontitis and puipitis, necessitating removal of the tooth.9

However, removal of the tooth should be delayed until the fracture heals.

Fractures that involve four or fewer incisors can be repaired with cerclage wire fixation tech­niques. As a rule of thumb, wires should engage a minimum of two teeth as the teeth immediately adjacent to the fracture will not be very stable. A minimum of two loops should be used to secure a fracture fragment . Ideally, there should be overlap of the wire loops to improve stabilization (Figure 20-1). A 14-gauge hypodermic needle with or without a 2-mm drill hole can be used to guide the stainless steel wire (16 to 18 gauge [I­to l.2-mm diameter]) through the interalveolar spaces. In young horses, the 14-guage needle may be used without prior drilling. The 14-guage needle may also be used as a cannula after drilling

A B

to facilitate wire passage between the incisors. The wires should be applied tightly by hand and twisted one or two turns followed by additional twisting using fencing pliers, needle drivers, or the equivalent, being careful not to overtighten the wires and cause wire breakage. When necessary, additional stabilization can be achieved by secur­ing the corner incisor(s) to the exposed canine if erupted or second or third premolar (Figures 20-2 and 20-4).

Incorporating the second premolar into the fixation involves placing a tension band wire from the incisors to the second premolar (Figure 20-3). A stab incision is made through the cheek directly over the space between the second and third premolars. Hemorrhage is minimized by incising through the skin and using blunt dissection to separate underlying soft tissues. The buccal mucosa is penetrated, and the drill bit with a pro­tective drill guide is positioned between the second and third premolars just ventral to the gin­gival margin. The drill guide is left in place after drilling between the teeth is completed to help thread the wire through the drilled hole. The wire is then pulled through the cheek and directed rostral to be laced through the holes previously made between the incisors. The wires spanning the interdental space are twisted together to increase compression at the fracture line. After tightening, the ends of the wi res are bent flat and may be

c

"7J.p"...,,! ~ .. ( .,.

Figure 20~ 1 A. Using a hypodermic needle as a wire guide to help pass the wire between teeth. B. Second passage of the wire using the hypodermic needle to help pass the wire. C, Wires in position to repair a rostral mandibular fracture involving the first and second right incisors in a young horse without canine teeth. Note overlap of wire loops, which reinforces the fixation.

....

124 HEAD AND NECK SURGERI ES

B

A ~e",._t:...~ <.L. '" Figure 20·2 A. Rostral mandibular fracture involv­ing the first left incisor and all three right incisors. In older ho rses, the canines can be used to anchor the stabilizing sutures. B. Note the "notch" in the canine to help hold the wires in position (arrow).

A

B

covered with a small amount of acryl ic. In young, rapidly growing horses, both sides of the mandible should be included in the fixa tion to the premo­lars to minimize the risk of developing disparate mandibular growth or placing undue stress on the symphysis.

Bilateral fractures in the interdental space with displacement are often unstable and require more than wire fixation. In comminuted fractures of the interdental space, the mandible tends to collapse when the wires are tightened. A buttress is needed to maintain the mandible in position. Acryl ic reinforcement of intraoral wiring can be used in some of these fractures, resulting in a relatively stable fixation. 12 Ideally, cold curing acrylic should be used or the acrylic should be lavaged with saline as the acrylic is curing.

A tension band wire is placed from the incisors to the first or second cheek tooth as previously described. After the wires are placed, an intraoral splint is made by molding acrylic around the wires and contouring it to fit the mouth from the incisors to the second cheek tooth. The wires run

c Figure 20-3 A. Positioning of drill th rough cheek between first and second cheek teeth fo r insertion of tension band wi re for repair of rostral mandibular frac ture. B. Initial wire insertion to repair rostral mandibular fracture

• involving the right incisors. In young horses. a 14- or 16-guage needle can be used to insert the wires between teeth. In older ani mals, a small drill (about 2 mm) can be used to provide a path for the wire. C. Wires in place fo r repa ir of a rostral mandibular fracture involving the right incisors in the absence of canine teeth. After the wires are tight­ened, the ti ed ends should be folded over aga inst the gum to minimize soft tissue irritation. A small amount of acryl ic may be applied over the wire ties to minimize irritation .

Intraoral Wire Fixation of Rostral Mandibular and Maxillary Fractures 125

~e __ -;t;~' ...............

Figure 20-4 Comparison of techn ique to repair the same fracture as Figure 20-3 showing how the fra cture would be repaired if the canines were present.

through the acrylic and hold it into place. Addi­tional strength can be gained by wiring the acrylic to the mandible, incisors, or premolars. In frac­tures that have minimal displacement or maintain reduction easily, the acrylic may be formed to the mouth first, allowed to harden, and then removed prior to the insertion of wires. This allows removal of sharp edges or excessive material with a rasp or Dremel tool. Holes are then drilled into the acrylic splint. and the splint is wired to the mandible, premolars, and incisors.

POSTOPERATIVE CARE

Postoperative Care

Medications: Because these fractures are often open, with significant contamination, broad-spec­trum antibiotic therapy should be considered, but it generally is not necessary beyond the first 3 to 5 postoperative days. Nonsteroidal antiinflamma­tory drugs are typically administered for 1 to 3 days. Tetanus prophylaxis should be current. Other: Horses generally return to a norrnal diet immediately after surgery, but in some cases a pelleted feed or gruel may be of benefit. The mouth may be rinsed out at least twice daily for the first week. Additionally, the horses should not be allowed to graze for 2 to 4 weeks, and the wires should be checked daily for breakage.

EXPECTED OUTCOME

Rostral fractures usually heal without complica~ tion in 4 to 6 weeks, provided there is adequate stabilization and permanent tooth buds are not involved. Fractures involving the interdental space may require a longer healing period. typically 8 weeks. In most cases, the wires can be removed in the standing horse with minimal sedation.

COMPLICATIONS

Purulent drainage, bone sequestration. septic osteitis, difficult mastication, unusual incisor eruption, wire loosening. and fixation failure are potential complications. Brachygnathism has also been reported in three foals following repair of bilateral fractures of the mandible.' In one study, 27% of horses experienced short-term complica­tions. 5 Fortunately, although short-term compli­cations may be common, the long-term prognosis for functional and cosmetic outcome is favorable.

COMMENTS

Young, curious horses typically incur these frac­tures when they try to free themselves after getting their head or teeth caught. Delay or failure to repair these fractures may result in malocclusion, tooth loss, osteomyelitis, loss of function, and less than optimal cosmesis.5 Because the oral side of the mandible and maxilla is the tension surface, intraoral wire fixation provides strong, effective fixation in many fracture configurations.

REFERENCES

1. Dixon PM: Dental anatomy. In Baker GJ, Easley J, editors: Equ ille dell tis try, London, 1999, WB Saunders.

2. Murch KM: Repair of bovine and equine mandibu­lar fractures, Can Vet J 21:69, 1980.

3. Staton AL: Simplified wiring procedure for frac­tured jaw, Pulse 2:9, 1988.

4. DeBowes RM: Fractures of the mandible and maxilla. In Nixon AJ. editor: Equine fracture repair, Philadelphia, 1996, \rVB Saunders.

5. Henninger RW, Beard WL: Rostral mandibular and maxillary fractures: repair by interdental wiring, Proc Am Assoc Equine Pract 43: 136, 1997.

126 HEAD AND NECK SURGER IE S

6. Steenhaut M: Surgical-treatment of dental prob­lems and mandibuJar fractures in the horse, Vlaams Diergeneeskundig TijdschriJt 67:23, 1998.

7. Martens A, Steenhaul M, Boel K. et al: Conserva­tive and surgical treatment of mandibular and maxillary fractures in 54 horses. Vlaams Dierge­neeskundig Tijdschrift 68: 16. 1999.

8. Beard WL: The skull. maxilla. and mandible. In Auer JA. Stick lA . editors: Equine surgery, ed 2, Philadelphia, 1999, WB Saunders.

9. Crabill MR. Honn<1s CM: Mandibular and maxil ­lary fracture osteosynthesis. In Baker G], Easley J. editors: Eqllille dentistry. London. 1999, WB Saunders.

10. Henninger RW, Beard WL, Schneide r RK, et al: Fractures of the rostral portion of the mandible and maxilla in horses: 89 cases (1979-1997), J Am Vet Med Assoc 214:1648,1999.

11. Adams S8, Fessler JF: Repair of mandibular and maxillary fractures In Adams S8 , Fessler]F editors: Atlas oj equine surgery, Philadelphia. 2000. WB Saunders.

12. Peavey CL. Edwards RB, Escarcega A], el al: Fixa­tion technique influences the monotonic properties of equine mandibular fracture constructs, Vet Surg 32:350, 2003.

•

CHAPTER 21

Sinus Trephination David A. Wilson

INDICATIONS

Sinus trephination can be performed for both diagnostic and therapeutic purposes to confirm the presence of purulent exudate; to obtain sirtus contents for cytology, biopsy, or culture; and to provide a portal for sinus irrigation or tooth repulsion. I

-3

EQUIPMENT

A Steinmann intramedullary pin of 3/ W or 1/4- inch diameter or a trephine instrument is used for this procedure.

POSITIONING AND PREPARATION

The procedure is performed in the standing, sedate horse with local anesthesia. 3

-s The trephine

site is clipped and prepared for surgery. Instilla­tion of local anesthesia should create a skin bleb and infiltrate the underlying periosteum.

ANATOMY

Important landmarks for defining the boundaries of the sinuses and determining entrance portals include the infraorbital canal, the facial crest, the facial tubercle, the orbit, and the nasolacrimal duct. The course of the nasolacrimal duct can be

127

approximated by a line from the medial canthus of the eye to the infraorbital canal. This line should be avoided when creating entrance portals to the sinuses. The location of the sinuses are illus­trated in Figures 21-1 through 21-3 and the approximate boundaries of the sinuses are described below.'

Maxillary Sinuses

The dorsal boundary corresponds to a line drawn caudad from the infraorbital foramen parallel to the facial-crest . The ventral boundary varies with the age of the horse. The last three or four cheek tooth roots project into the ventral aspect of the maxillary sinus to an extent that var ies with age. The rostral boundary is at the level of the infraor­bital foramen, and the caudal border is at the level of the ventral port ion of the orbit. The maxillary sinus is divided into rostral and caudal portions by an oblique septum, whose lateral margin is com­monly about 5 cm caudal to the facial tubercle, but can be quite variable (see Figure 21-1). The infra­orbital canal separates the maxillary sinus into a lateral bony compartment occupied by the roots of the cheek teeth and a medial compartment within the ventral concha! sinus.

Frontal Sinus

The frontal sinus is roughly triangular-shaped with the base on midline. The right frontal sinus is separated from the left sinus by a complete septum. The rostral limit of the frontal sinus is at

~""-......................... ~- ..... ~---

128 HEAD AND NECK SURGER IES

Infraorbital canal

Nasolacrimal

Rostral maxillary sinus Caudal maxillary sinus

~t;.1. ___ Figure 21-1 Lateral view of skull with bone removed over the frontal and maxillary sinuses. Note position of in fra­orbital canal and nasolacrimal duct (dotted lilies).

\

-+ Conchofrontal Sinus Infraorbital canal

Caudal maxillary

Rostral maxillary sinus

Facial tubercle

'-- Nasolacrimal duct

~ Q.,...,t;;;J.;.,..,......, Figure 21-2 Overview of skull with bone removed over the frontal and maxillary sinuses. Note relative posi tions of infraorbital canal and nasolacrimal duct (dotted lilles).

a point halfway between the infraorbital foramen and the orbit at the approximate level of the fifth cheek tooth. The caudal limit is at the level of the caudal border of the orbit. The lateral extent is near the level of the medial canthus. The medial extent is on midline. In the horse, the dorsal conchal sinus has an extensive communication with the frontal sinus. and together they are com­monly referred to as the conchofrontal sinus. The rostral extent ofthe concha! sinus is at the level of the facial tubercle.

The caudal maxillary and fro ntal sinuses communicate through a large frontal maxillary opening and drain into the nasal cavity through the nasomaxillary opening in the middle meatus. The rostral maxillary sinus drains into the nasal cavity through a separate opening in the middle meatus.

PROCEDURE AND PREPARATION

Several sites are recommended for sinus trephina­tion in the horse. The trephine portal for the frontal sinus is 3 to 4 cm caudal to the most rostral aspect of the frontal sinus and 3 to 4 cm lateral to midline. The trephine portal for the caudal max­illary sinus is 1 to 2 cm dorsal to the facial crest and 7 to 8 cm caudal to the most rostral aspect of the facial crest. The trephine portal for the cranial maxillary sinus is J to 2 cm dorsal to the facial crest and 3 to 4 em caudal to the facial tubercle. As the septum dividing the maxiUary sinuses is variable, these locations are guidelines only.

The infraorbital foramen and the levator nasolabialis and levator labii maxillaris muscles

Dorsal conchal

Dorsal nasal concha

Ventral nasal

Rostral maxillary

Sinus Trephination 129

-0,-- Nasolacrimal duct

Infraorbital canal

Dorsal, middle, and ventral nasal meatus

---'; '+----'t Palatine artery

~~d;.vL , "

Figure 21-3 Transverse section through the skull at level of M2 (between the medial canthus and the facial tubercle).

Concho­frontal siinu'i~

Caudal maxillary

Sinus Rostral ~-:

i I

tubercle

Site of penetration of intramedullary pin

Facial crest

Figure 21~4 Identification of the limits of potential trephine sites in the maxillary and frontal sinuses. The diagonal dotted line is the approximate site of the septum between the rostral and caudal maxillary

• sinuses.

are palpable and should be avoided when creating portals for the maxiJJary sinuses.

For diagnostic trephination, a I-em stab incision is made through the skin and periosteum. A Steinmann intramedullary pin is used to pene­trate the bone. The pin should be positioned in the chuck such that a maximum of 1/ 2 inch of the pin length is protruding (Figure 21-4). The goal is to penetrate the bone without damaging deeper structures. Excess pin length protruding from the handle of the pin chuck should be guarded to protect the surgeon . This size portal provides access for aspiration or for placement of a lavage catheter, biopsy instruments, or a 4-111111 arthro­scope for inspection of the sinuses.

Occasionally) there is a need for a larger portal into the sinuses. Commercial trephine instru­ments are available up to 2.5 cm in diameter) which is large enough to allow digital palpation of the sinuses if necessary. A circular incision) slightly larger than the size of the trephine. is made and the skin is discarded. Alternatively) a cross-incision can be made through skin and periosteum. The four resultant flaps are elevated

,

130 H EAD AND NECK SURG ERIES

from the underlying bone to provide access for the trephine instrument. The skin edges are elevated from the trephine site to avoid binding the soft tissues in the instrument as it is turned. The trocar point of the trephine should be extended to prop­erly seat the saw blade. Once the saw blade is seated, the trocar point should be retracted to minimize the risk of penetrating any underlying structures. Oscillating rotations are used to cut and ream o ut a circular plug of bone, with care taken to control the instrument as the cut is nearing completion to avoid damaging st ructures within the sinus.

POSTOPERATIVE CARE

Postoperative therapy depends on the primary problem. Sinus trephination is principally used for diagnostic purposes and sinus irrigation. With the except io n of primary sinusitis, most condi­tions will require further surgical therapy once the primary problem is determined. Portals can remain open for 10 to 12 days to allow repeated irrigation or entrance. Mild cellulitis surrounding the portal site often develops, which can be managed by cleaning the site at Jeast daiJy with moistened gauze sponges.

EXPECTED OUTCOME

Even large trephine holes typically heal without complicat ion in 3 to 4 weeks. Replacement bone or fibrous tissue fills the defect. A small depression is often palpable, but not visible, once the hair grows out. The long-term prognosis depends on the primary problem.

COMPLICATIONS

The most common complication is hem orrhage. The sinus mucosa is extremely vascular, and this vascularity is increased in inflammatory condi­tions. Generally, direct pressure will control the bleeding. Inadvertent penetration of structures within the sinus can result in additional compli ­cations such as oronasal fistula formation, bone sequestration, hemorrhage, and death depending on the structure penetrated. These severe compli ­cations can be virtually eliminated by controlling

the depth of penetration during the trephination procedure.

ALTERNATIVE PROCEDURES

Endoscopic examination using arthroscopic equipment allows visualizatio n of the caudal maxillary and frontal sinuses through a frontal sinus portal and of the sphenopalatine sinus thro ugh a caudal maxillary sinus portaI. 7

- \O The potential advantages of endoscopic examination include the ab ility to obtain a more diagnostic biopsy, the potential to treat minor problems, and the abi lity to visualize a greater portion of the respective sinuses. AJthough many disorders of the sinuses can be addressed by sinus trephinatio n with or without sinus endoscopy, several disor­ders, such as resectio n or treatment of neoplastic and nonneoplastic growths, may require a sinus bone flap surgery to properly address the disorder. 11

COMMENTS

Specific diseases of the sinuses include empyema, sinusitis, tumors, and alveola r periostitis. Chronic, un ilateral purulent nasal discharge is the primary sign associated with paranasal sinus empyema in horses. Other clinical signs associated with disor­ders of the sinuses include facial swelling and d is­tortion and ocular discharge.

REFERENCES

I. Merriam ]G: Field sinusotomy in the management of chronic sinusitis and alveolitis, Proc Am Assoc Equine Pmct 39:235, 1993.

2. Worster AA, Hackett RP: Equine sinus endoscopy using a fl exible endoscope: diagnos is and treatment of sinus disease in the standing sedated horse, Proc Alii Assoc Equille Pmct 45:1 28 1999.

3. Adams SB, Fessler JF: Sinus trephination. In Adams SB, Fessler JF, editors: Atlas of equil1e surgery. Philadelphia, 2000, WB Saunders.

4. Ford TS: Standing surgery and procedures of the head, Vet Ciin N Am Equ ille Pmct 7:583, 1991.

5. Schumacher J: Standing sinus surgery of the horse. Proe ACVS Vet Sylltp 132,2004.

6. Gerard MP: Applied paranasal sinus anatomy. Proc, ACVS Vet Sylllp 128, 2004.

7. Ohnesorge B, Stadler P: Minimal invasive and conventional surgery of progressive ethmoidal haematomas in horses, Tiemrztliche Praxis Ausgabe Grosstiere Nlltztiere 29:219, 200 I .

8. Ohnesorge B, vonBorstei M, vonOppen T: Endo­scopic therapy of progressive ethmoidal haematomas in horses via sinus maxillary trepanation: case reports, Pferdeheilkunde 20:316, 2004.

Sinus Trephination 131

9. Ruggles AJ. Ross MW, Freeman DE: Endoscopic examination of normal paranasaJ sinuses in horses, Vet SlIrg 20:418, 1991-

10. Ruggles A]. Ross MW, Freeman DE: Endoscopic examination and treatment of paranasal sinus disease in 16 horses, Vet Surg 22:508, 1993.

11. Hilbert B}, Little CB. Klein K. Thomas 18: Tumours of the paranasal sinuses in 16 horses, AI/st Vet J 65:86, 1988.

CHAPTER 22

Tooth Repulsion David A. Wilson

INDICATIONS

Repulsion is indicated for cheek teeth that cannot be removed orally, teeth with broken crowns, or fragmented teeth. '·' Although the techniques described in this chapter are applicable to the first five cheek teeth, repulsion in field or suboptimal conditions is most practical for the rostral cheek teeth. Improved extraction techniques and anes­thetic protocols have expanded the capabil ity of oral extraction of affected teeth. Oral extraction is the preferred method of removal when possible and practical.J,5-7

Specific indications for tooth removal include retained deciduous teeth, interventional ortho­dontics, severe periodontal disease, loose teeth, supernumerary teeth, dental impactions, end­odontic disease with secondary osteomyelitis, severe disease or injury to the dental crown or root, malocclusions, occlusal trauma, neoplasia, biting discomfort, and sinus disease secondary to dental disease.s

The clinical signs associated with dental disease are broad and typically include quidding, the presence of a head tilt while eating, nasal dis­charge, sinusitis, the presence of a chronic drain­ing tract, headshaking, facial pain, excessive sal ivation (ptyalism), anorexia or pica, and the presence of long forage stems or whole grain in the feces. Additional but less common clinical signs include facial swelling or distortion, weight loss, diarrhea, colic, reluctance to start eating, slow or intermittent eating, difficulty in prehension, choke, and epistaxis.s A thorough oral exam ina-

132

tion, including the use of a full-mouth speculum with appropriate illumination, and a radiographic examination are recommended if dental disorders are suspected. Additionally, ultrasou nd, nuclear scintigraphy, and computed tomography may be useful to evaluate certain dental disorders.9

EQUIPMENT

A dental punch and mallet are used for tooth repulsion. A trephine or large bone rongeurs, or a high-speed burr can be used to remove overlying bone to access the tooth roots. Ideally, pre­operative, intraoperative, and postoperative radi­ographs should be taken to ensure identification of the correct tooth, to assess the approach, to evaluate the positioning of the dental punch, and to check the tooth root socket for remaining frag­ments after repulsion.

POSITIONING AND PREPARATION

The horse should be placed under general anes­thesia in lateral recumbency with the affected tooth up. If a mandibular tooth is affected, the horse may be placed in lateral recumbency with the affected tooth up or in dorsal recumbency.

ANATOMY

Pertinent structures to be aware of when consid­ering tooth repulsion include the facial muscles,

facial crest, orbit, infraorbital canal, nasolacrimal duct, frontal and cranial and caudal maxillary sinuses, facial artery and venous plexus, parotid salivary duct. and branches of the facial nerve (Figure 22-1). The alveoli of the second and third premolars (teeth numbered six and seven in the Triadan system) and often the rostral aspect of the fourth premolar (tooth 108 or 208 in the Triadan system) are embedded in the maxillary bone.1O The three molar tooth roots (9 through 11 in the Triadan system) and part of the fourth premolar in younger horses extend to a variable degree into the maxillary sinus depending on the age of the horse. In young horses, the large reserve crowns virtually fill the sinus, whereas in the old horse with shorter roots, the sinus becomes fairly large (Figures 22-2 and 22-3). The caudal aspects of the fourth premolar and the first molar lie in the rostral maxillary sinus, and the second and third molars lie in the caudal maxillary sinus. (See Chapter 21 for a discussion on sinus trephination and for a more detailed description of the rostral

levator anguli ",<U Malaris ", ..

Angularis oculi a.v. , Zygomatic

Dorsal part of lateral nasal m.

Dorsalis nasi levator nasolabialis m.

Nasal diverticulum

levator labii

i m. Depressor labii

inferioris m.

Tooth Repulsion 133

and caudal maxillary sinuses and their relation­ship to the cheek teeth. ).

The upper cheek teeth usually have three roots-two small lateral roots) and a larger medial root (Figure 22-4). Occasionally four roots are present. The lower cheek teeth have two roots (with the exception ofM3, which has three roots), one caudal and one rostral. The reserve crown and roots of the rostral cheek teeth are roughly per­pendicular. The reserve crown and roots of the caudal three cheek teeth are curved caudally.

PROCEDURE

Selection of the surgery site is critical to success­ful tooth repulsion. The surgery site is based on the location of the tooth or teeth involved and their curvature. The first two or three (depending on the age of the horse) maxillary cheek teeth and all of the mandibular teeth are directly accessible, but tlle caudal three o r four maxillary cheek teeth

-"set,,, Dorsal and vee,": '" m. buccal brs. of

Parotid gland

Parotidoauricularis m.

Ventral masseteric v.

~_- and masseteric br. a.

Parotid duct

jugUlar v.

Depressor anguli oris m. from cutaneous faciei m.

labial a.

Buccinator . Parotid duct a.v.

Figure 22·1 Lateral view of head with skin removed showing superficial structures.

I

-

134 H EAD AND N ECK SURGERIES

Figure 22-2 Radiograph of 8-year-old horse.

Figure 22-3 Radiograph of 12-year-old horse.

need to be accessed through the maxillary sinus. The third upper molar is better accessed through a frontal sinus trephination site to allow position­ing of a dental punch through the frontomaxiilary opening into the caudal-maxillary sinus II or a combination of frontal and maxillary trephina­tion sites. 12 Occasionally, a bone flap may be used to provide greater exposure to the tooth roots. iJ

\

~"_ ... .:J. .. __

A B Figure 22-4 Lateral and ventral views of mandibu­lar and maxillary cheek teeth showing differences in root structure. A. maxillary tooth with three roots (some have four roots); B. mandibular tooth with two roots.

Ideally, radiographs are taken at various inter­vals throughout the procedure to ensure accurate placement of the surgical site, removal of a minimal amount of bone over the affected tooth, and accurate placement of the punch. Radi ­ographs provide an accurate method of placing the punch along the sagittal plane but not in the frontal plane. The teeth accessible through the sinuses are usually more toward midline than anticipated (see Figure 21-3). In young horses with long tooth roots that virtually fili the sinuses, a trephine site that is very close to the infraorbital ca nal will be necessary.

After the appropriate surgery site has been selected, a 5-cm skin incision is made. The bone overlying the tooth roots is removed with either rongeurs or a trephine (Figure 22-5). The punch is seated with the mallet, and a hand is positio ned in the mouth over the affected tooth to detect vibrations fro m the punch. Radiographs can be taken at this point to verify accurate placement and orientation of the punch. Once it is verified that the tooth being punched is the affected tooth, several hard hits are generally required with the mallet to loosen the tooth (Figure 22-6). The

Figure 22-5 Horse in lateral recumbency showing trephination of the caudal maxillary sinus.

~e.. .... .:t-,.. .

Figure 22-6 Dental punch in position to repulse the left second maxillary molar.

rostral cheek teeth can often be removed intact. Because of the limited space in the oral cavity, the caudal cheek teeth may be too long to remove intact. If this is the case, molar cutters or Gigli wire can be used to decrease their length in order to remove them completely.

Once removed, the tooth is examined carefully for missing roots or fragments. The tooth root socket is thoroughly explored to remove any residual fragments oftooth or bone. This is a crit­ical point of the surgery as many of the compli­cations associated with this procedure are due to bone or tooth sequestra.

In most cases, the tooth socket is filled with a plug to prevent packing of feed material in the tooth socket. Plugs can be made of a variety of materials such as 4 x 4 gauze sponges, acrylic, dental wax, or other material. 14 Acrylic plugs should be inserted such that they do not extend too deep into the socket, to facilitate ease of removaL Generally, the socket should remain packed for 2 to 3 weeks to allow formation of a good granulation tissue bed in the tooth socket

Tooth Repulsion 135

that will be resistant to future infection. If t~e plug does not come out on its own, the horse should be sedated or anesthetized and the plug removed. If gauze sponges are used for packing, the sponges should be replaced every 2 to 3 days.

POSTOPERATIVE CARE

Postoperative Care

Exercise Restridions: The horse should be stall rested for at least 2 weeks with controlled hand walking only. Medications: Broad-spectrum antibiotics are recommended for 3 to 5 days. Further antibiotic therapy may be indicated if infection of the tissues surrounding the affected tooth is extensive. Non­steroidal antiinflammatory drugs are recommen­ded for 1 to 2 days. Other: The mouth should be lavaged and the surgery site cleaned daily. If an acrylic plug or dental wax was placed at the time of surgery, it should either be expelled on its own or removed within 30 days of surgery. Following plug removal, the surgery site is cleaned at least daily until the wound is completely filled with granulation tissue.

EXPECTED OUTCOME

Owners should be forewarned that although post­operative care is not technically difficult, it is involved and may be necessary for extended periods. Short-term complications are likely, but the long-term prognosis for healing is good.

COMPLICATIONS

Complications from this procedure can be divided into categories that include problems associated with restraint or general anesthesia, the extraction itself, wound healing, and long­term complications. 5

,15, 16 Complications associated with the extraction itself include hemorrhage, removal of the wrong tooth, and damage to struc­tures adjacent to the tooth being removed (i.e., palatine artery. sinuses, alveolar bone, jaw, adja­cent teeth, nasolacrimal duct, parotid salivary duct, and facial nerve).

Complications associated with wound healing include wound dehiscence or persistent drainage

:

136 HEAD AND NECK SURGERIES

resulting from fistula formation, incomplete tooth removal, bone sequestrum, infected tooth root socket, packing breakdown, mucous membrane healing prior to wound granulation, or the pres­ence of a foreign body in the wound. Long-term complications can be associated with an incorrect initial diagnosis resulting in persistence of the primary problem, removal of the wrong tooth, or leaving behind a diseased tooth or tumor.

Therapy starts with exploration of the tooth root socket under general anesthesia. Generally, a bone or tooth root fragment is identified, and removal typically results in rapid heal ing of the surgery site. If bone or root fragments are not identified, alveolar bone damage may be present. Because the alveolar bone between cheek teeth is relatively thin, damage to the alveolar bone may expose the root of the adjacent tooth, which may result in periodontal disease in the adjacent tooth.

Inadvertent removal or loss of the alveolar plate can occur as a result of the original inflam­matory process or during surgery. Removal of the alveolar plate such that the cement surface of the reserve crown of the adjacent tooth is exposed will result in incomplete healing as granulation tissue will not adhere to exposed cementum. Similarly, aggressive curettage of the socket can result in destruction of mesenchymal cells that would have contributed to healing of the socket. Generally, these errors will result in the development of chronic draining tracts and periodontal disease with the potential future need for removal of the affected adjacent tooth.

Repulsion of a mandibular tooth may result in a fractured mandible if the dental punch is posi­tioned on the mandible rather than on the tooth root or if the punch slides off the tooth root and this redirection is not recognized by the surgeon. This is a surprisingly easy complication if care is not taken to correctly position the punch and continually monitor its orientation. Fortunately, unless the mucous membranes have been pene­trated, these fractures can heal well following removal of any small bone fragments.

Because of the orientation of the cheek teeth, gaps created by tooth removal are gradually closed by movement of the cheek teeth to fill the gap. This movement creates another problem that will require continued tooth care for the rest of the horse's life. Tooth overgrowth can occur at either the site of tooth removal or the first or last cheek tooth of the opposing arcade.

ALTERNATIVE PROCEDURES

Several options exist for treatment of periapical infections in horses. Medical therapy is limited to the systemic administration of antibiotics and is often ineffective. Ideally, the antibiotic therapy is guided by bacterial culture and sensitivity results. In the absence of bacterial culture results, we gen­erally recommend long-term therapy (30 to 60 days) of a potentiated sulfonamide. Typically, the drainage stops or at least diminishes during the course of therapy, only to return shortly after the antibiotics are discontinued. One publication reported successful medical therapy in three of five horses treated medically. 17

Occasionally lateral buccotomy and alveolar plate removal are indicated for removal of teeth with damaged crowns or teeth surrounded by sclerotic bone that would make removal by con­ventional oral extraction or repulsion difficult.!! Additionally, the caudal mandibular cheek teeth may be removed with this technique.18 Lateral buccotomy and alveolar bone plate removal are more tedious and time consuming than oral extraction or repulsion and therefore are not practical in field situations. A thorough descrip­tion of the technique is available elsewhere.SJ

1

Ideally, endodontic therapy for periapical infections in horses would allow for the tooth to remain in place, thus avoiding many of the complications associated with their removal. Endodontic therapy requires special surgical skills, knowledge, and equipment and is generally a long general anesthetic procedure. The reported long-term success rates have ranged frol11 44% to 81 %.1.19,20

An alternative procedure for periapical infec­tions of the mandibular teeth has been re­ported.9

,21 Periapical curettage involves identifying the affected area, removing the overlying cortical and cancellous bone, and identifying the affected alveolus. Using curettage and irrigation. infected material is removed, with care taken to not disturb the healthy root. The wounds are then left to heal via second intention. Postoperative therapy con­sists of removing the external serum crusting on a daily basis and applying petrolatum to the skin around the wound to prevent serum scalding. The wounds are not flushed, and postoperative antibi­otics and analgesics are recommended but not required. The success rate has been reported to be

over 75%, but a large number of cases have not been reported.21 Those deemed unsuccessful were subsequently treated successfully with tooth repulsion. Periapical curettage appears to be a reasonable option for resolving the periapical infection and maintaining the mandibular tooth.

COMMENTS

The difficulty of and time required for dental repulsion vary considerably. Repulsion of the more caudal upper teeth because of their curved roots and sinus involvement is technically more difficult and requires additional surgical time and intraoperative monitoring and more postopera­tive care. Repulsion of teeth from older horses with shorter reserve crowns is less difficult than repulsion of teeth from young horses with exten-

• Slve reserve crowns. Simultaneous or preoperative loosening of the

affected tooth with molar spreaders and extrac­tion forceps is beneficial and results in a shorter and less traumatic repulsion.

Each tooth is independently and firmly attached to the bony structure (alveolus) by the periodontal ligament and gingiva. The periodon­tal ligament consists of bundles of connective tissue fibers that run in various directions from the bone of the socket wall to the cement cover­ing the reserve crowns and the tooth roots. The gingiva has a mucous membrane surface with a dense internal fibrous attachment to the perios­teum and the peripheral cement of the tooth. Even in cases with extensive periodontal disease, there may be significant remaining gingival or peri­odontal ligament attachments to make tooth removal difficult, particularly in young horses where the reserve crown may be as long as 8cm.

REFERENCES

1. Prichard MA. Hackett RP, Erb HN: Long term outcome of tooth repulsion in horses. A retrospec­tive study of 61 cases, Vet 5urg 21: 145,1992.

2. Schumacher J. Honnas eM: Dental surgery, Vet Clill N Am Equine Pract 9:133,1993.

3. Dixon PM: Dental extraction and endodontic tech­niques in horses, Comp COrl t Edltc Pmct Vet 19:628,

1997.

Tooth Repulsion 137

4. Gaughan EM: Denta l surgery in horses, Vet Clill N Am Equille Pract 14:381, 1998.

5. Easley J: Equine tooth removal (exodontia). In Baker GJ, Easley J, editors: Equine dentistry, London, 1999, WB Saunders.

6. Tremaine WH: Oral extraction of equine cheek teeth, Equine Vet Educ 16:151, 2004.

7. Lowder MQ: O ral extraction of equine teeth, Camp Cant Educ Pmct Vet 2 1:11 50,1999.

8. Knottenbelt DC: The systemic effects of dental disease. In Baker GJ, Easley J, editors: Equine den­tistry, London, 1999, WB Saunders.

9. Gibbs C. Dental imag ing. In Baker GJ, Easley J, editors: Equine dentistry, London, 1999, WB Saunders Co.

10. Dixon PM: Dental anatomy. In Baker GJ, Easley J, editors: Equine Dentistry, London, 1999, WB Saunders.

11. Lowder MQ: Tooth removal, reduction, and preser­vation. In VVhite NA, Moore JM, editors: Currellt techniques in equine surgery and lameness, Philadel­phia, 1998, WB Saunders.

12. Boutros CP, Koenig JB: A combined frontal and maxillary sinus approach for repulsion of the third maxillary molar in a horse, Catl Vet J 42:286, 2001.

13. Hahn K, Kohler L: Removal of upper cheek teeth of the horse using bone flap technique, muscle trans­position and alveolar closure, Tierarztliche Praxis Allsgabe Grosstiere N'ltztiere 30:50, 2002.

14. Trostle 55, Juzwiak J5, 5antschi EM: How to use antib iotic impregnated plaster of paris for alveolar packing after tooth removal, Proc Am Assoc Equine Pract 46: 180, 2000.

15. Lillich JD: Complications of denta l surgery, Vet Clin N Am Equ ine Pmct 14:399, 1998.

16. Pascoe JR: Complications of dental surgery, Proc Am Assoc Equine Prnct 37:14 1, 1991.

17. Dixon PM, Tremaine WH, Pickles K, et al: Equine dental disease. Part 4: a long-term study of 400 cases: apical infections of cheek teeth, Equine Vet J 32: 182, 2000.

18. Lane Gl: Equine dental extraction--repulsion vs buccotomy: techniques and results. Proceedings of the 5th Wo rld Veterinary Dental Congress, Birmingham, 1997.

19. Lowder MQ: Diseases of the teeth. In Colahan PT, Mayhew IG, Merritt AM, Moore IN, ed itors: Equine medicine and surgery, ed 5, Philadelphia , 1999. Mosby.

20. Baker GJ: Endodontic therapy. In Baker GI, Easley J. editors: Equine dentistry. London, 1999, WB Saunders.

21. Carmalt JL, Barber SM: Periapical curettage: an alternative su rgical approach to infected mandibu­lar cheek teeth in horses, Vet Surg 33:267, 2004.

CHAPTER 23

Tracheotomy David A. Wilson

INDICATIONS

Indications for tracheotomy are to establish an emergency airway because of an upper airway obstruction, or to relieve nasal or laryngeal inflammation. Tracheotomy is a life-saving proce­dure in the face of an upper respiratory obstruc­tion. Tracheotomy is also used to "rest" an inflamed upper respiratory tract. Tracheotomy can also be used as a route for endotracheal intu­bation for general anesthesia when nasotracheal or orotracheal intubation limits access to the sur­gical field.

EQUIPMENT

Tracheotomy tube and scalpel blade.

POSITIONING AND PREPARATION

Ideally, a wide area is clipped and routinely pre­pared for aseptic surgery; however, in emergency situations little preparation is dOf\e. The proce­dure is ideally performed standing with the head extended using local anesthesia. In an emergency situation, a variety of positions are used. When llsed as a route for endotracheal intubation, the procedure is often performed in lateral recum­bency after induction of anesthesia. Light seda­tion may be necessary for fractious patients. Draping is not necessary, but sterile instruments and gloves are desirable.

138

ANATOMY

The paired muscle bellies of the sternomandib­ularis, sternothyroideus. and sternohyoideus mus­cles lie on the ventral aspect of the trachea and are separated during the approach. The tracheal rings are spaced closely together, but incision of the annular ligament allows enough separation to insert the tracheotomy tube without removal of portions of the tracheal ring (Figures 23-1 through 23-5).

PROCEDURE

A 6- to 8-cm ventral midline incision is made between the upper and middle thirds of the neck in a region where the trachea is easily palpable. In cases where a permanent tracheostomy is antici­pated or even a possibility, the tracheotomy site should be caudal enough to allow space in the cranial third of the neck for the subsequent tra­cheostomy (Figure 23-6). Long incisions should be avoided to improve the "fit" of the tracheotomy tube.

The subcutaneous tissues are incised, and the paired sternothyrohyoideus muscles are separated on midline. Blunt dissection should be minimized to decrease subcutaneous emphysema and seroma formation. Two tracheal rings in the center of the incision are identified, and a transverse stab inci­sion is made between the two rings. The stab inci­sion should completely penetrate the tracheal

,----- -----------

~roo<>:t,;..!"'--

Figure 23-1 Ventral view of the neck with the skin removed showing cutaneous colli muscles.

Figure 23-3 Ventral view of the neck with skin and cutaneous coll i and sternomandibular is muscles removed.

Paired omohyoideus mm.

Sternohyoideus mm.

sternomandibularis mm.

,*~t ... .....t"(.I.<J .

Figure 23-2 Vent ral view of neck with skin and cuta­neous colli muscles removed.

Paired omohyoideus mm.

Left external jugular

Paired sternothyrohyoideus mm.

Paired sternomandibularis --\

mm. (cut)

140 HEAD AND NECK SU RGERIES

Atlas (C1

Longus capitis

Common carotid a.

Sternomandibularis

Sternothyroideus

Omohyoideus and __ sternohyoideus mm.

Cutaneous colli m. ----

Maxillary v.

-- Esophagus

--- Parotid gland

'---- Linguofacial v.

Trachea

,*-~t .... ..:t:~

Figure 23-4 Transverse section through cervical region at level of C l.

Longus capitus

Sternomandibularis m.

Common carotid

Left external jugular v.

Sternothyroideus mm. Sternohyoideus mm .. - -

Omohoideus m. - -

Cutaneous coll i

~~4-t" ..... : .

Figure 23-5 Transverse section of the neck at the level of C4.

Tracheotomy incision site + -

'e..<_.-".fC _ _

Figure 23-6 Incis ion site fo r tracheotomy.

Figure 23-7 View of the tracheotomy site just prior to inserting self-retaining tracheotomy tube.

mucosa. A stab incision that is too shallow may result in separation of the mucosa from the tra­cheal ring, which will increase bleeding and may lead to granuloma formation. The annular liga­ment is incised from midl ine ] to 2 em in both directions (about one third of the circumference of the lumen),

A tracheotomy tube is then placed (Figure 23-7) . We prefer self- retaining tracheotomy tubes,

Tracheotomy 141

but care must be taken to make sure the second flange of the tube does not dissect subcutaneously. This complication can be avoided by careful posi­tioning and palpation of the tube after placement. The self-retaining tracheotomy tubes have the advantage of not completely relying on the tra­cheotomy tube for an open airway. Therefore, if the tube becomes clogged, there remains a residual, albeit compromised, airway. Collapse or "kinking" of the tube is also avoided with the use of self-retaining tracheotomy tubes.

POSTOPERATIVE CARE

Postoperative Care

Tracheotomy Tube Management: Trache­otomy tubes require almost continuous mon­itoring and management. The tubes and the surrounding skin should be cleaned at least daily. Scrubbing of the tracheotomy site should be avoided. Exudate and blood clots should be removed with a dry, sterile sponge, and the skin surrounding the site should be cleaned. Extra tubes should be immediately available. Medications: Broad-spectrum antibiotics and nonsteroidal antiinflammatory agents are generally not necessary unless indicated for the treatment of the underlying problem. other: After removal of the tracheotomy tube, the wound is allowed to heal by second intention with daily cleaning. Cleaning of the wound during closure is performed at least once daily or as needed with moistened gauze sponges. Petrola­tum (Vaseline) is applied to the skin surrounding the surgery site to prevent scalding from the anti­cipated drainage. Healing is generally complete in 2 to 3 weeks.

COMPLICATIONS

Fortunately, in horses there are few complications associated with tracheotomy. Most complications are associated with the primary problem rather than the tracheotomy procedure. However, sub­cutaneous emphysema, hemorrhage, and inflam­mation are relatively common. t

.} Minimizing soft tissue dissect ion, avoiding separation of the tracheal mucosa from the cartilage rings, and avoiding tracheal ri ng trauma will minimize these complications. Rare complications include

-

142 H EAD AND NEC K SU RGERIES

tracheal stricture, granulomas, chondromas, and pneumothorax.I

-4

REFERENCES

I. Turner AS, Mcllwraith CW: Tracheostomy. In Turner AS, Mcl lwraith CW, editors: Techniques ill large al/ill/al sllrgery, ed 2, Philadelphia, 1989, Lea & Febiger.

•

2. Freeman DE: Standing surgery of the neck and thorax, Vet Clin N Am Equille Pract 7:603, 199 1.

3. Adams S8, Fessler JF: Tracheotomy. In Adams S8, Fessler JF, editors: Atlas of equille surgery. Philadel­phia, 2000, WB Saunders.

4. Kelly G, Prendergast M, Skelly C, et al: Pneumotho­rax in a horse as a complication of tracheotomy,lrish Vet J 56: 153. 2003.

CHAPTER 24

Tracheostomy David A. Wilson

INDICATIONS

Tracheostomy is indicated for any permanent dis­order of the larynx and upper trachea in which airflow is impaired.

EQUIPMENT

No special equipment is required. Self-retaining retractors and Rochester Carma!t forceps or similar forceps are desirable.

POSITIONING AND PREPARATION

The surgery can be performed with the horse standing with mild sedation and local anesthesia or in dorsal recumbency under general anesthe­sia. The head should be extended for either pro­cedure. If the procedure is performed in dorsal recumbency, care should be taken to position the neck, head, and body without twisting or torquing such that the skin incision is directly on midline when the horse stands. The ventral cervical region is clipped and prepared routinely for aseptic surgery.

ANATOMY

The paired sternothyrohyoideus muscles originate from manubrium sterni and extend on the ventral

143

aspect of the trachea. The smaller sternothy­roideus inserts on the caudal border and abaxial surface of the thyroid cartilage, and the larger sternohyoideus continues on to insert on the basihyoid bone. The paired omohyoideus muscles originate from the subscapular fascia close to the shoulder joint and join the sternohyoideus in the prox.imal third of the neck. The trachea primarily consists of from 48 to 60 hyaline cartilage rings. These rings are ( -shaped and open dorsally, with the ends connected by the transversely oriented tracheal muscle, l

PROCEDURE

Several similar techniques have been described.2•4

A 10- to 12-cm ventral midline incision is made in the proximal th ird of the neck in a region where the trachea is palpable (Figure 24-1). If a tra­cheotomy has been performed previously, this site should be avoided.

The cutaneous colli and subcutaneous tissues are incised, and the paired sternothyrohyoideus and omohyoideus muscles are identified. The right and left sternothyrohyoideus muscles are separated on midline and retracted laterally to expose a section of three or four tracheal rings. Sections of the paired sternothyrohyoideus muscles as well as the most axial portions of the omohyoideus muscles are clamped with an angiotribe, straight Rochester-Pean or Rochester­Carmalt forceps, transected, and excised at the proximal and distal extent of the tracheostomy

•

144 HEAD AND NECK SURGERIES

Tracheostomy incision site

Figure 24-1 Incision site for tracheostomy, just caudal to the first tracheal ring.

A

B

c

site to minimize the tension on the tracheal mucosa-skin junction during subsequent closure. Bleeding is controlled with hemostat application and or ligation if necessary. Subcutaneous tissue may be sutured to the peritracheal fascia to decrease dead space.

A midline and two paramedian incisions are made 15 mm on each side of midline in the exposed tracheal rings (Figures 24-2 and 24-3 ). Care should be taken to start on midline and to avoid incising the mucosa. The rectangular seg­ments of tracheal cartilage that are created are carefully dissected free of mucosa. The mucosa is desensitized with topical application oflocal anes­thetic solution and incised in a double-Y -pattern. Stay sutures are placed to align and prevent retrac­tion of the mucosa. The mucosa is then apposed to the skin using No. 2-0 PDS and a simple inter­rupted pattern. Care should be taken to close all gaps between mucosal edges or between mucosa and skin. The remaining skin incision, proximal

D

Figure 24-2 Ventral view of the neck illustrat­ing tracheostomy procedure. A, Dotted lines show­ing proposed incision lines th ro ugh tracheal cartilage only. S, After incising through cartilage and removal of the first fou r tracheal sections. C, After removal of all tracheal sections. Dotted line shows proposed double-Y incis ion in tracheal mucosa. D, Finished tracheostomy showing tra­cheal mucosa sutured to skin.

and distal to the created stoma, is apposed in an interrupted pattern.

POSTOPERATIVE CARE

Postoperative Care

ExeKise Restriction: The horse should be con­fined to a stall for 2 weeks with controlled hand­walking only. Medications: Broad-spectrum antibiotics and nonsteroidal antiinflammatory agents are recom­mended for 1 to 2 days. Suture Removal: The sutures are removed in 10 to 14 days. Other: The surgery site should be cleaned once or twice daily until the sutures are removed and once daily indefinitely.

EXPECTED OUTCOME

Tracheostomy sites generally heal with minimal complications, but slight dehiscence may occur and may require additional repair. Owners should be warned that in some cases it may take as long as 4 months for sufficient stoma healing to occur before the required once or twice daily cleaning is reduced to maintenance levels. The required long­term maintenance varies from cleaning once per day to less than on ce per month. Long-term outcome of tracheostomy is generally favorable. In one study, more than 90% of owners were pleased with the resul ts (Figure 24-3).'

COMPLICATIONS

The most common complications include partial dehiscence of the tracheal mucosa-skin suture line, excessive inflammation, granulation tissue formation, stricture, skin growth or apposition over the tracheostomy site, and coughing. Long­term complications include coughing during exercise, stridor, and exercise-induced dyspnea.4

Complications can be reduced if sufficient por­tions of the paired sternothyrohyoideus and por­tions of the omohyoideus muscles are removed, the mucosa-to-skin suture line is placed with little to no tension, and care is taken to place sutures sufficiently close together to eliminate all gaps between mucosal edges or between mucosa and skin. Stricture of the stoma size or insufficient

Tracheostomy 145

Figure 24-3 A, Immediate postoperative appearance of tracheostomy. B, View 3 weeks after surgery.

stoma size can be repaired by enlargement of the stoma, either by removing the ventral portion of additional tracheal rings or by removing greater portions of muscle to reduce the tension on the tracheal mucosa-skin suture line. Removal of a 3 x 6-cm portion of skin over the stoma site to decrease the chances of functional appositional closure of the stoma site has also been described.) Additionally, sm all elliptical portions of skin m ay be taken out of either side of the stoma after it is created to reduce the chances of functional appo­sition. If partial dehiscence occurs, the granula­tion tissue, if present, should be resected and sutures placed to reattach the mucosa to skin.

Tracheostomy affects pulmonary defense mechanisms by disruption of the mucociliary escalator, reduced airway temperature control, and altered humidification of inspired gases. Horses with preexisting pulmonary disease may experience an exacerbation of the existing disease resulting from this reduction in pulmonary defense mechanisms.5

A

B

146 H EAD AND NECK SURGERIES

REFERENCES

I. Hare WeD: Equine respira tory system. In Getty R, editor: Sisson alld GrossnulII's The anatomy of the domestic arlima/s, ed 5, Philadelphia, 1975, WB Saunders.

2. Shappell KK, Stick lA, Derksen FJ. et al: Permanent tracheostomy in Equidae: 47 cases (1981-1986), J Am Vet Med Assoc 192:939, 1988.

3. McClure SR, Taylor TS, Honnas eM, et al: Perma­nent tracheostomy in standing horses: technique and results, Vet Slirg 24:231. 1995.

4. Rakestraw PC, Eastman TG, Taylor TS, et al: Long term outcome of horses undergoing permanent tra­cheostomy: 42 cases, Proc Am Assoc Equine Pract 46:111,2000.

S. Murray JF: Tile normal hlllg: the basis for diagnosis and treatmellt of pulmonary disease. ed 2, Philadel­phia, 1986, WB Saunders.

CHAPTER 25

Surgical Treatment Options for Dorsal Displacement of the Soft Palate

David A. Wilson

INDICATIONS

Dorsal displacement of the soft palate (DDSP) causes temporary or intermittent exercise intoler­ance. A number of factors potentially influ ence soft palate position, and accordingly a va riety of procedures have been described for the treatment of DDSP. Altering the head position, changing tack, and using a "tongue-tie" or a figure-eight noseband are a few of the conservative treatment options that may help horses with DDSP and aid in the diagnosis and determination of the cause of the displacement. Various su rgical procedures have been described to treat DDSP, including sternothyrohyoideus myectomy, sternothyroideus tenectomy, staphylectomy, and epiglottic aug­mentation.1' 13 Var ious combinatio ns of the proce­dures have also been described ,14. !9 Also, various laser procedures to either resect or cauterize the soft palate, and a tie-forward procedure have been recently described to address DDSP, IO,!2,13,!7,20

None of these procedures are very effective for persistent DDSP because of the likely damage to innervat ion of the soft palate and pharynx in these cases.

EQUIPMENT

Rochester-Carmalt forceps, straight Rochester­Pean forceps with longitudinal serrations, an angiotribe or a similar instrument, and a Penrose drain are used for the myectomy procedures. A

147

spay hook may be useful for the sternothyroideus tenectomy procedure.9 A Gelpi or Weitlaner self- retaining retractor, Allis tissue forceps. long­handled or right-angle scissors, and curved sponge forceps are used fo r soft palate resection. An Nd:YAG, CO" or diode laser may be used to transect muscle or to perform the staphylectomy or photothermoplasty procedures. IO,12.13,17,19

PREPARATION AND POSITIONING

Most procedures are best performed with the horse under general anesthesia in dorsal recum­bency and the head extended; however, with ·expe­rience, they can be accomplished in the standing sedated horse with local anesthesia.

Staphylectomy procedures require tempora ry access to the larynx. This is typically accomplished by using intravenous anesthesia. When an endo­tracheal tube is used, it is removed for the portion of the procedure requiring access to the larynx.

ANATOMY

The sternomandibularis originates from manu­brium sterni , extends the entire length of the neck, forming the ventral border of the jugular furrow; and inserts on the caudal border of the ramus of the mandible (see Figures 23-1 through 23-5) . At approximately the mid-cervical region, the paired sternomandibularis muscle diverges from midline, exposing the underlying paired

•

148 HEAD AND NECK SURGER IES

Mandibular inn.

Unguofacial v. --+---" Parotid gland

Paired omohyoideus mm.

Paired sternohyoideus mm.

Paired sternomandibularis mm. -1-'1=

Figure 25-1 Ventral view of the head and rostral neck with the skin and cutaneous colli muscle removed.

sternothyrohyoideus muscles. The paired ster­nothyrohyoideus muscles originate from manu­brium sterni and extend on the ventral aspect of the trachea. The smalJer sternothyroideus inserts on the caudal border and abaxial surface of the thyroid cartilage. The larger sternohyoideus muscle inserts on the basihyoid bone and the lingual process of the hyoid bone (Figures 25- J and 25-2), The paired omohyoideus muscles orig­inate from the subscapular fascia close to the shoulder joint and merge with the sternohyoideus in the proximal third of the neck

Important landmarks for the laryngotomy incision include the paired sternohyoideus muscles overlying the larynx and the V-shaped cricothyroid membrane, which lies between the thyroid and cricoid cartilages.

PROCEDURE

Myectomy and Tenectomy Procedures

Sternothyrohyoideus Myectomy This procedure can be performed in the standing patient or under general anesthesia. A 6- to 8-cm-

Lingual process of ---+r' basihyoid bone

Basihyoid bone

Thyroid cartilage

Paired thyrohyoideus mm.

Cricothyroid _ membrane

Cricoid cartilage ~

Paired sternothyroideus mm.

Figure 25-2 Ventral view of the larynx.

long incision is made through the anesthetized skin on the ventral midline of the neck (Figure 25-3), The level of the caudal portion of the inci­sion is at the level where the sternomandibularis diverges from midline, exposing the paired ster­nothyrohyoideus muscles, The rostral portion of the incision is at the level of convergence of the omohyoideus and sternohyoideus muscles. At this mid-cervical region, the sternothyrohyoideus muscles are well exposed and are relatively free from other structures.

The incision is continued through the subcu­taneous tissue and the cutaneous coll i muscle. The sternohyoideus muscle is then exposed and split longitudinally on midline. The dissection contin­ues laterally along the trachea to the lateral borders of the sternothyrohyoideus muscles, The ventral surface of the muscles is then separated from the cutaneous colli and sternomandibularis muscles by scissors and blunt fin ger dissection. The dissection should continue until a 5-cm lon­gitudinal section of the paired muscle is under­mined and separated from the surrounding tissues. The combined sternothyrohyoideus mus­cles are elevated from the wound and an approx­imately 5-cm length of muscle is removed by

Incision site for

myectomy

Figure 25-3 Surgical approach for sternothyrohy­oideus myectomy.

cross-clamping the muscles with Rochester­Carmalt, straight Rochester-Pean, or similar forceps. Mayo scissors, a scalpel blade, or a laser (Nd:YAG or diode) can be used to cut the muscle and remove the 5-c01 section of muscle between the clamps. Electrocautery may also be used, but the electrical stimulation causes significant muscle contraction. The forceps are then removed from the ends of the muscles and the muscles are allowed to retract, leaving a large area of dead space next to the trachea (Figure 25-4). Hemor­rhage is usually negligible, but small bleeders may be clamped with hemostats.

A Penrose drain may be placed and tunneled through stab incisions, rostral and caudal to the surgical incision (Figure 25-5). A three-layer closure consisting of cutaneous colli muscles, sub­cutaneous tissue,. and skin is performed. The cuta­neous colli muscles and subcutaneous tissue are closed in separate layers using an absorbable monofilament suture material with a simple con­tinuous suture pattern. The skin is closed with suture and pattern of the surgeon's choice. We typically use No. 2-0 nylon in a Ford's interlock­ing pattern, or skin staples. Alternatively, the

Dorsal Displacement of the Soft Palate 149

Rostral

Omohyoideus m.

Sternohyoideus m. -+ Retracted

cut ends of the sternohyoideus and

sternothyroideus (smaller) mm.

Caudal

Figure 25-4 Intraoperative view of ste rnohyoidec­tomy and sternothyroidectomy for DDSP.

Figure 25-5 Sutured ventral neck inCISion with Penrose drain in place emerging proximal and distal (arrows) to the primary incision.

entire incision may be left to heal by second inten­tion.7 Complete healing with minimal scar for­mation will occur within 2 to 3 weeks.

Sternothyrohyoideus and Omohyoideus Myectomy A variation of this procedure involves an incision in the prox:imal third of the neck and partial myectomy of the omohyoideus muscle (Figure 25-6). This procedure involves more dissection than the sternothyrohyoideus myectomy and may be slightly more likely to develop postoperative seromas. The axial portion of the omohyoideus muscles must be transected from their attach-

150 HEAD AND NECK SURGERIES

Sternothyroideus

Sternohyoideus

Figure 25-6 Intraoperative view of sternohyoidec­tomy. sternothyroidectomy. and omohyoidectomy for DDSP.

Sternothyroideus. m.

Omohyoideus m.

Figure 25-8 Close-up view of the sternothyroideus musculotendinous section showing dotted lines where resection will occur. The omohyoideus muscle is being retracted.

Ceratohyoideus m. Cricoid cartilage

Ceratohyoid bone

Lingual process

,.,.,. ....-Cricothyroid lig. Figure 25-7 Lateral view of

the larynx illustrating the inser­tion of the sternothyroideus on the thyroid cartilage. The omohy­oideus muscle is being retracted.

of basihyoid bone c:~~

ments to the sternohyoideus muscles. This proce­dure is better performed with the patient under general anesthesia because of the more extensive dissection. although it can be accomplished in the standing patient. This procedure has the advan­tage of removing all of the caudaJ retractors of the larynx.

Sternothyroideus Tenectomy and Sternohyoideus Myectomy Another variation of this procedure involves a sternothyroideus tenectomy and sternohyoideus myectomy. A 5-cl11 ventral mid-line skin incision is made over the larynx and is extended caudally to the level of the fi rst tracheal ring. The longitu­dinal incision is extended through the paired ster­nohyoideus muscles to expose the ventral aspect of the larynx, the cricoid cartilage, and the crico­tracheal space. The musculotendinous portion of the sternothyroideus muscle is located at the level of the cricoid cartilage. about 3 to 4 cm off midline. The tendon is followed to its attachment

of i of the omohyoideus m.

sternothyroideus m.

on the caudal edge of the thyroid cartilage to ensure that the correct structure is isolated. A spay hook may be used to help isolate and exteriorize the tendon' (Figure 25-7). A small vein often lies adjacent to the tendon and should be avoided. Forceps are placed across the muscular portion of the sternothyroideus muscle. The tendon is tran­sected, and a 2-cm portion of the muscle is removed (Figure 25-8). The omohyoideus is dissected from the sternohyoideus muscle. and a 5-cm section of sternohyoideus is then removed (see Figure 25-6) .

Staphylectomy A ventral midline laryngotomy is performed at the level of the cricothyroid membrane. A to-cm incision is made star ting at the cranial border of the thyroid cartilage and extending caudal to the first tracheal ring (Figures 25-9 and 25-10). The incision is continued through the cutaneous coUi muscles and subcutaneous tissue. The paired sternohyoideus muscles are identified and sepa-

inn.

cartilage oall ventricle

'hP"..,,-/-J.:........ .

Figure 25-9 View of the ventral throat region illus­trating the relative position of the larynx in relation to the mandible and the laryngeal ventricle in relation to the cricothyroid membrane.

Incision site for

Figure 25-10 Surgical approach for laryngotomy . mClSlon.

Dorsal Displacement of the Soft Palate 151

rated longitudinally the length of the incision (see Figure 25-1). A self-retaining retractor is inserted between the muscle bellies to expose the fascia overlying the cricothyroid membrane. Sharp dis­section is continued through the fascia . A small vein is often present within the fascia that is tran­sected. Bleeding is controlled with either hemo­stats or electrocautery. The exposed cricothyroid membrane is palpated. The caudal border of the thyroid cartilage and the cranial border of the cricoid cartilage are identified. The laryngotomy is then performed by placing the back of the scalpel blade against the cricoid cartilage. An initial stab incision is made into the laryngeal lumen, and the incision is continued rostral to the center of the thyroid cartilage. The self-retaining retractors are then repositioned within the larynx. The laryngeal lumen may be swabbed with a gauze sponge that has been soaked with local anesthetic solution (2% mepivacaine).

A finger or curved sponge forceps is inserted into the larynx, over the epiglottis to displace the caudal free edge of the soft palate into the airway. If freeing the soft palate is difficult, the epiglottis should be pushed ventral while lifting the head. This action should displace the epiglottis and free the caudal edge of the soft palate (Figure 25-11). The free edge of the soft palate is then grasped on midline with Allis tissue forceps. The forceps should grasp approximately 5 to 8 mm of tissue. The tissue is retracted to provide tension on the caudal border of the palate. Long-handled or right-angle scissors are then used to start a cut to one side of the forceps and directed to the oppo­site side. The tissue removed should taper to a point and be about 2 cm in length (Figure 25-12). The procedure is repeated on the opposite side. The tissue removed should be crescent shaped: wide at the center (about 6 to 10 mm) and taper­ing to a point about 2 cm on either side of midline (Figure 25-12, D). The laryngotomy incision is left to heal by second intention.

Alternative Staphylectomy Procedures Other surgeons have recommended removal of a small notch of tissue at the caudal midline of the soft palate.6 For this procedure, Rochester or equivalent forceps are used to grasp the soft palate in the center of the caudal border) and Metzen­baum scissors are used to cut around the tips of the forceps. The size of tissue removed approxi­mates an equilateral triangle with each side mea­suring about 8 to 10 mm .

•

152 H EAD AND NECK SURGER IES

B

A

C Figure 25-11 A, Once the incision has been made through the cricothyroid membrane, self- retai ning retractors are placed to aid visual ization of the caudal aspect of the larynx. B, The soft palate is elevated from below the ep iglot­tis and becomes visible within the larynx (arrow) . C, The free edge of the soft palate is then grasped on midline with Allis tissue fo rceps.

B

A

o

Figure 25-12 A, The free edge of the soft palate is retracted caudally. B, Long-handled or r ight angle scisso rs are used to sta rt a cut on midline d irected to the opposite side. The tissue removed should taper to a point and be app roximately 2 em in length. C, The procedure is repeated on the opposite side. D, The tissue removed should be wide at the center and tapering a maximum of 10 mm to a point approximately 2 em on either side of midline.

Staphylectomy is often used in conjunction with sternothyrohyoideus myectomy. A compos­ite procedure has been described that includes a ventriculectomy in addition to myectomy and partial staphylectomy." Staphylectomy has also been used in conjunction with epiglottic aug­mentation for cases of flaccid epiglottis. 16

An alternative combination procedure has been described and reviewed that combines a sternothyroideus myectomy, small staphylectomy, and caudal soft palate photothermoplasty.19 The procedure is performed through a typicallaryn­gotomy approach. Prior to penetrating the cricothyroid membrane, both caudal margins of the thyroid cartilage are exposed and the ster­nothyroideus muscles are transected at their musculotendinous junctions. The cricothyroid membrane is then incised to expose the laryngeal lumen. The caudal free edge of the soft palate is grasped with Allis tissue forceps, and a CO, laser is used (at a power setting of 35 Wand focused spot size of 0.22 mm) to make several lines in a sweeping motion through the oral mucosa of the soft palate, parallel to and extending rostral 4 to 5 em from the caudal free margin of the palate. A small (4 mm x 8 mm), semicircular section of tissue is then sharply resected from the caudal free margin of the soft palate. The cricothyroid mem­brane is closed with polyglactin 910 in a simple continuous pattern. The remaining layers are left to heal by second intention.

Laser ablation of the caudal aspect of the soft palate can also be performed in the standing sedated horse using the Nd:YAG or diode laser or electrocautery with endoscopic visualization in an attempt to increase the rigidity of the palate. To perform the procedure effectively, the palate must be displaced during the procedure. Maintaining this position can be difficult due to swallowing, etc., in the conscious horse. 17

Tie-Forward Procedure A tie-forward procedure has also been described in which a suture is placed from the basihyoid bone to each wing of the thyroid cartilage at the insertion site of the sternothyroideus muscle.ll .

20

This suture maintains the larynx in a rostral and slightly more dorsal position. Therefore, instead of preventing caudal retraction of the larynx by means of the myotomy-tenotomy procedures, the "tie-forward" procedure maintains the larynx in a fixed cranial position.

Dorsal Displacement of the Soft Palate 153

POSTOPERATIVE CARE

•

Postoperative Care for Myectomy and Tenectomy Procedures

Exercise Restrictions: The horse should be rested in a stall for at least 1 week with controlled handwalking followed by return to normal exercise over the next 2 to 3 weeks. Medications: Perioperative therapy rnay consist of antibiotics and nonsteroidal antiinflammatory drugs. These generally do not need to be contin­ued beyond the first postoperative day unless a drain is in place. Suture Removal: The sutures are removed in 10 to 14 days. Other: A towel stent or neck bandage may be applied over the incision site and maintained for 2 to 4 days after surgery (Figure 25-(3). The stent or bandage protects the wound and provides counterpressure to the wound to reduce edema, hematoma, and seroma formation. The Penrose drain should be removed in 2 to 3 days.

o

: \ , ,

, , \ ,

J i \lj

),"'-

Figure 25-13 Towel stent sutured in position for sternohyoideus myectomy, sternothyroideus tenectomy for either DDSP or modified ForsseU's procedure. The stent is applied to protect the incision and to apply pres­sure to the incision site to minimize postoperative hematoma or seroma formation.

154 HEAD AND NECK SURGERIES

Postoperative Care for Staphylectomy Procedures

Exercise Restrictions: The horse should be rested in a stall with controlled handwalking only for 2 weeks to allow the inflammation of the soft palate to subside. The horse may then return to its normal activity. Medications: Broad-spectrum antibiotics and nonsteroidal antiinflammatory drugs are adminis­tered for 2 to 5 days depending on the amount of postoperative drainage and local inflammation. Suture Removal: Laryngotomy incisions may be left to heal by second intention. Other: The incision site is cleaned at least once daily with moistened sterile sponges. Petrolatum is applied around the incision to minimize scalding.

EXPECTED OUTCOME

The incision should heal completely within 2 to 3 weeks with minimal scarring. Previous reports have indicated a 50% to 85% chance for return to normal activity following the various versions of sternothyrohyoideus myectomy.2.4,15 The progno­sis for horses with intermittent dorsal displace­ment to return to normal activity following staphylectomy is about 60%.4.1S.16 Combinations of these procedures have been reported to improve the prognosis. 15.19 Horses with persistent DDSP or a hypoplastic epiglottis with DDSP have a poor prognosis. In cases with a hypoplastic epiglottis. a partial staphylectomy with or without epiglottic augmentation may be a better surgical option.

COMPLICATIONS

Following myectomy-tenectomy procedures. the complications are few but can include seroma or hematoma formation, incisional infections. and reWliting of the severed ends of the muscles through scar formation. Seromas and hematomas are best treated by controlling bleeding at the time of surgery, adequate counterpressure applied to the wound postsurgery, and limiting exercise in the immediate postoperative period. There may be a cosmetic defect at the site of muscle resec­tion. Staphylectomy complications include dys-

phagia if too much of the caudal palate is removed and granulation tissue at the exposed edge of the palate.

COMMENTS

DDSP is a common cause of poor performance in racehorses. but it also occurs in other types of per­formance horses. particularly those that have exaggerated flexion at the poll during work. DDSP is one of the common causes of noise at exercise and the noise is typ ically characterized as a "gur­gling" sound, generally loudest on expiration. It is often a diagnosis by exclusion of other common causes of noise at exercise or decreased perfor­mance. Horses with DDSP often have significant

Figure 25-14 A. Endoscopic view of normal equine larynx. B. Endoscopic view of equine larynx with dorsal displacement of the soft palate.

A

B

airway compromise during exercise but can recover quickly when the horse is allowed to swallow to replace the palate in the correct posi­tion. During clinical examination, the palate may not displace unless specific conditions, such as the type of tack used and the head posi tion used during performance, can be duplicated . Un less the specific condi tions are duplicated, the "noise" reported by the owner or trainer will not be noted and the airway will generally appear completely normal on endoscopic examination at rest or after exercise {Figure 25- 14}. Endoscopic examination while the horse is working on a high-speed tread­mill , ideally with the same tack and head position that exist when the DDSP typically occurs, is fre­quently the only way to directly make the diagno­SiS .

21

DDSP may occur secondary to other airway abnormalities that cause turbulent airflow, in­creased negative airway pressure, or to signifi­cant upper airway inflammat ion. These common airway abnormali ties include la ryngeal hemiple­gia, epiglottic entrapment, guttural pouch dis­orders, and pharyngeal lymphoid hyperplasia. Therapy to address these potential primary prob­lems is warranted before proceeding with any of the surgical options discussed here.

REFERENCES

1. Mcllwraith CW, Turner S: Myectomy of the ster­

nohyoid, sternothyroid, and omohyoid muscles. In Mcllwraith CW, Turner S, editors: Equine surgery advallced techniques, Philadelphia, 1987. Lea & Febiger.

2. Harrison rw, Raker CW: Sternothyrohyo ideus myectomy in ho rses: 17 cases (1984-1985), ] Am Vet Med Asso, 193: 1299, 1988.

3. Shappell KK, Caron JP, Stick JA, et al: Staphylec­tomy for treatment of dorsal displacement of the soft palate in two foals, ] Am Vet Med Assoc 195:1395,1989.

4. Ande rson ]D, Tulleners EP. Joh nston JK, et al: Ster­

nothyrohyoideus myectomy o r staphylectomy for treatment of inte rmittent dorsal displacement of

the soft palate in racehorses: 209 cases ( 1986-1991),

] Am Vet Med Assoc 206: 1909, 1995. 5. Duncan DW: Retrospective study of 50 Thorough­

bred racehorses subjected to radical myectomy surgery for trea tment of dorsa l displacement of the

soft palate, Proc Am Assoc Equil1e Pmct 43:237,

1997.

Dorsal Displacement of the Soft Palate 155

6. Llewe1.lyn H R. Petrowitz AB: Sternothyroideus myotomy for the treatment of dorsal displacement

of the soft palate, Proc Am Assoc Equine Pract 43:239,1997.

7. Robertson JT: Dorsal displacement of the soft

palate. In White NA II , Moo re IN, editors: Curre1lt teclllliqlles ;11 equine surgery and lameness. Philadel­

ph ia, 1998, WE Saunders. 8. Holcombe SJ, Ducharme NG: Pha rynx. In Aue r JA,

Stick ]A, editors: Equine surgery. ed 2, Philadelphia. 1999, WE Saunders.

9. Ada ms SB, Fessler IF: Sternothyrohyoideus

myectomy. In Adams SB, Fessler JF, ed itors : Atlas of equine sllrgery, Philadelph ia , 2000. WB

Sau nde rs. 10. JagerHauer K, Lutkefels E. Deegen E, et al: Expe ri­

men tal study on transendoscop ic laser su rge ry of dorsa l d isplacement of the soft palate in horses,

Tierarztliche Praxis Ausgabe Grosstiere Nutztiere 31:18,2003.

11. Ducharme NG: Treatment consid erations for

DDSP, Pro, ACVS Vet Symp 13:2 10, 2003. 12. Stick JA: Soft palate displacement: treatment

o ptions, Proc ACVS Vet Symp 13: 189,2003. 13. Tate LP, Sweeney C L, Bowman KF, et al: Transendo­

scopic Nd:YAG laser surgery for treatment of

ep iglottal entrapment and dorsaJ displacemen t of the soft palate in the horse. Vet Surg 19:356, 1990.

14. O'Rielly JL, Beard WL, Renn TN, et al: Effect of combined staphylectomy and laryngotomy on upper airway mechan ics in clin ically normal

horses, Am ] Vet Res 58: 10 18, 1997. 15. Bo nenClark G, Bryant ], Hernandez J, et al:

Sternothyroideus tenectomy or sternothyroideus

tenectomy with staphylectomy for the trea tment of soft palate displacement, Proc Am Assoc Equine Proct 45:85, 1999.

16. Ada ms SB, Fessler JF: Epiglottic augmentation and staphylectom y. In Adams SB, Fessler JF, editors: Atlas of equine surgery. Philadelphia, 2000, W B

Saunde rs. 17. Hogan PM, Palmer SE, Congelosi M: Transendo­

scopic laser cauterization of the soft palate as an

adjunctive treat ment for dorsal disp lacement in the racehorse, Proc Am Assoc Equine Pract 48:228,

2002. 18. Barakzai SZ. Johnson VS, Bai rd DH. et al: Assess­

men t of the efficacy of composite surgery for the

treatmen t of dorsa l displacement of the soft palate in a group of 53 racing Thoroughbreds (1990-1996),

Eqllifle Vet J 36: 175, 2004.

19. Smith 11. Embertson RM: Sternothyroideus Myotomy, staphylectomy, and oral caudal soft

palate photothermoplasty for treatmen t of dorsal displacement of the soft palate in 102 Thorough­

bred racehorses, Vet SlIrg 34:5, 2005.

•

156 HEAD AND NECK SURGERIES

20. Ducharme NG, Hackett RP, Woodie JB, et al: Investigations into the role of the thyrohyo id muscles in the pathogenesis of dorsa l displacement of the soft palate in horses, Equille Vet J 35:258, 2003 .

21. Parente El, Marti n BB, Tulleners EP. et al. Dorsal d isplacement of the soft palate in 92 horses during high-speed t readmill exam ination (I993-1998), Vet Surg 31:507. 2002.

CHAPTER 26

Modified Forssell's Operation for Cribbing David A. Wilson

INDICATIONS

The primary indication for this procedure is mod­ification of cribbing behavior when nonsurgical methods fail.

EQUIPMENT

Large Rochester-Carmalt, straight Rochester-Pean or angiotribe forceps, and a Penrose drain are used for this procedure. An Nd:YAG or diode laser may be used to transect muscle.]

ANATOMY

The ventral branch of the accessory nerve (CNXl) is located on the dorsomedial aspect of the ster­nomandibularis and enters the muscle about 5 em from the musculotendinous junction. The paired sternothyrohyoideus muscles lie on the ventral aspect of the trachea. The tendon of insertion of the sternothyroideus muscle is on the caudal border and abaxial surface of the thyroid cartilage (see Figure 25-2) . The larger stemohyoideus mus­cle continues on midline to insert on the basihy­oid bone. The paired omohyoideus muscle merges with the sternohyoideus muscle in the proximal third of the neck (see Figures 23-2 to 23-5).

157

POSITIONING AND PREPARATION

This procedure is best perfo rmed under general anesthesia with the horse in dorsal recumbency and the head extended; however, with experience, it can be accomplished in the standing sedated horse with local anesthesia. Transecting the ster­nohyoideus at the attachment to the hyoid appa­ratus is difficult in the standing horse. The ventral cervical region is clipped and prepa red for aseptic surgery.

PROCEDURE

A 3D-em ventral midline incision is made starting 2 em rostral to the la rynx at the basihyoid bone and extending caudally (Figure 26-1). The skin is retracted laterally, and hemostasis is achieved as needed in the subcutaneous tissue. A plane of dissection is established between the omohy­oideus and sternomandibularis muscles to expose the medial aspect of sternomandibularis 5 em caudal muscles to the musculotendinous junction. The sternomandibularis muscle is gently retracted and rolled slightly abaxial to expose the dorsal medial aspect. The nerve can be located by palpa­tion of a slight indentation in the musculature where the nerve enters or by identifying the nerve just caudal and ventral to a small arterial branch supplying the sternomandibularis muscle (Figures 26-2 through 26-4). In most cases, a small amount of fascia will need to be dissected from the ster-

158 HEAD AND NECK SURGERIES

Incision site for modified

Forssell's procedure

~f>..--~.:6 ____

Figure 26-1 Incision site for modified Forssell's pro­cedure. A 30-cm vent ral midline incision starts 2 em rostral to the larynx at the basihyoid bone and extends caudally.

~e ....... t;;'""J-..... ....-.

Figure 26-2 Lateral view of neck illustrating the approximate insertion site of the ventral branch of the spinal accessory nerve as it traverses the axial surface of the sternomandibularis muscles (dotted lilies) prior to entering the muscle belly approximately 5 em caudal to the musculotendinous junction.

nomandibularis muscle to expose the nerve. Contraction of the sterno mandibular is muscle and flexion of the head are observed when the nerve is pinched with hemostats. A 5- to 1O-C111

section of nerve is exposed using blunt dissection and removed (Figure 26-5) . A sternohyoideus

~e._t;C~

Figure 26-3 The sternomandibularis muscle is retracted laterally exposing the insertion of the ventral branch of the sp inal accessory nerve. In most cases, a small amount of fascia covers the nerve and wili need to be dissected off to expose the nerve.

~ e.r .... ;t;; J;g",~

Figure 26-4 The inse rtion of the spinal accessory nerve is best identified by palpation for a depression on the axial bo rder of the sternomandibulari s muscles.

myectomy and a sternothyroideus tenectomy are then performed as described in Chapter 25. Additionally, when performing myectomy for cribbing behavior, a portion of the omohyoideus is removed and the sternohyoideus and omohy­oideus are ideally transected rostral to the ventral aspect of the larynx.

Figure 26-5 Once the spinal accessory nerve is identified, it can be bluntly dissected free from the muscle to expose a 5- to lO-em section of the nerve to be removed.

Modified Forssell's Operation for Cribbing 159

Ventral

POSTOPERATIVE CARE

Postoperative Care

Exer<ise Restridions: The horse should be confined to a stall for 2 weeks with controlled handwalking only. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and 2.2 mg/kg BID for an additional 2 days. Broad-spec­trum antibiotic therapy is indicated until 24 hours after drain removal. Suture Removal: Sutures are removed 12 to 14 days after surgery. Stent Removal: The stent is typically removed 2 days after surgery. Drain Removal: The Penrose drain is removed 2 to 5 days after surgery depending on the amount of drainage. Dther: In the event that hematomas or seromas occur, they should be managed conservatively.

COMPLICATIONS

The most common complication is failure to resolve the behavioral abnormaUty.2-8 Factors that may help to minimize recurrence of the cribbing behavior include excising the muscle belly cranial enough to prevent scar tissue from facilitating retraction of the larynx and instituting environ­mental and behavioral changes. Other complica­tions include seroma or hematoma formation and incisional infections. Seromas and hematomas are best treated by controlling bleeding at the time of

•

accessory n. Sternohyoideus m.

surgery, applying adequate counterpressure to the wound postsu rgery, and limiting exercise in the immediate postoperative period. The long-term consequences of the incisional complications are minimal. These incisions can heal very well by second intention if necessary. Therefore, even with complete dehiscence, the incisions heal with very little scar formation. A cosmetic defect may be present at the site of muscle resection, partic­ularly if the muscles are resected in the mid­cervical region.

EXPECTED OUTCOME

Reported success rates using the modified Fors­sell's procedure range from 50% to 100%.1-3.6 Many horses undergoing this procedure show various levels of cribbing following surgery. For­tunately, most just apply their teeth to a flat object, such as the top of a post or fence, but do not grasp as they did prior to surgery and do not flex the neck or make gulping noises as they did prior to surgery. Success has been attributed to transecting the sternohyoideus and omohyoideus rostral to the ventral aspect of the larynx. This success may occur because the entire insertion of the omohy­oideus is removed. If a more caudal transection is performed, it is difficult to include all of the omo­hyoideus. Additionally, remaining rostral portions of the sternohyoideus muscle may establish some adherence to the surrounding tissues and regain some retraction function. Cosmesis is generally very good, particularly if the muscle transections are as far proximal and distal as recommended. Muscle resections in the mid cervical region may

160 HEAD AND NECK SURGERIES

result in visual "steps" on the ventral aspect of the neck where the muscle becomes reattached to the fascia overlying the ventral trachea.

ALTERNATIVE PROCEDURES

Nonsurgical methods to modify cribbing behav­ior include moving the horse to a pasture or increasing the frequency of turnout, applying noxious agents to the surfaces used for cribbing, providing the horse with a companion such as another horse, a goat, or a pony, the application of cribbing straps, the use of electric shock collars, acupuncture, J and the use of opioid antagonists in an attempt to block the pleasurable sensation caused by the cribbing and wind-sucking activity.?

REFERENCES

I. Delacalle J, Burba OJ, Tetens J, et a1: Nd:YAG laser­assisted modified Forssell's procedure for treatment of cribbing in horses, Vet SlIrg 31 :111, 2002.

2. Greet TR: Windsucking treated by myectomy and neurectomy, Equine Vet J 14:299, 1982.

3. Turner AS, White N, Ismay J: Modified Forssell's operation for crib-biting in the ho rse, J Am Vet Med Asso, 184:309, 1984.

4. Mcllwraith CW, Turner AS: Myectomy of the ster­nohyoid, sternothyroid, and omohyoid muscles. In Mdlwraith CW, Turner AS: Equine surgery adva1/ced tecillliqlles, Philadelphia, 1987, Lea & Febiger.

5. Fjeldborg I: Results of surgical management of crib­bing by neurectomy and myectomy, Eqllille Pract 7:34, 1993.

6. Schofield WL, MulvilJe JP: Assessment of the modi ­fied Forssell's procedure for the treatment of oral stereotypes in 10 horses. Vet Rec 142:572, 1998.

7. Adams S8: Biology and treatment of specific muscle d isorders. In Auer JA, Stick JA , editors: Equille surgery, ed 2,. Philadelphia, 1999, WB Saunders.

8. Adams SB, Fessler JF: Modified Forssell's operation for cribbing. In Adams SB, Fessler IF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders.

9. Oodam NH, Shuster L, Court MH, et al: Investiga­tio n into the use of narcotic antagonists in the treat­ment of a stereotypic behavior pattern (crib-biting) in the horse, Am J Vet Res 48:311,1987.

..... PHTHALMIC URGERIES

161

CHAPTER 27

Nasolacrimal Flush Laurence E. Galle

INDICATIONS

Catheterization and flushing of the nasolacrimal duct is indicated to confirm or rule out naso­lacrimal obstruction as a cause for epiphora, mucoid, or mucopurulent discharge. Flushing of the nasolacrimal duct may also be a therapeutic procedure in that it call dislodge sm all foreign bodies or purulent debris that obstruct the flow of tears through the duct. ! If an obstruction is diagnosed within the nasolacrimal system, dacry­ocystorhinography can be performed to deter­mine the anatomic location of the obstruction by the injection of radiopaque contrast media through the catheter.2

EQUIPMENT

A 5-Fr male urinary catheter or polyethylene tubing is needed for nasolacrimal catheterization. A 3-mL syringe, %-inch 25-gauge needle, and local anesthetic are needed if local anesthesia or akinesia is to be used to facilitate placement of the catheter. If the catheter is to be sutured into place, a No. 10 Bard-Parker blade, needle drivers, general operating scissors, and No. 2-0 or No. 3-0 mono­filament non absorbable suture are also needed.

POSITIONING AND PREPARATION

Nasolacrimal catheterization is typically per­formed with standing sedation . Local anesthesia

162

or akinesia of the eyelids and nares may facilitate insertion of the catheter.

ANATOMY

The structures of the nasolacrimal system are divided into secretory and drainage components. The tearfi lm is a trilaminar fluid secreted by the lacrimal gland, third eyelid gland, conj unctival goblet cells, and meibomian glands. The tearfilm is drained from the eye through the dorsal and ventral puncta into the dorsal and ventral canali­culi (Figure 27-1). The canaliculi merge ventro­medial to the medial canthus and form the lacrimal sac, a dilation of the proximal naso­lacrimal duct that lies with in the lacrimal fossa of the lacrimal bone. The nasolacrimal duct passes medially through the maxillary bone and contin­ues rostrally through the soft tissues of the nares to the opening or orifice of the duct. This opening is located on the floor of the nasal cavity approx­imately 5 to 7 cm from the opening of the nares near the mucocutaneous junction (Figure 27-2). The nasolacrimal duct is approximately 4 to 5 mm in diameter and is narrowed proximally as it passes through the maxillary bone. l,3·s

PROCEDURE AND PREPARATION

The opening of the nasolacri mal duct is located on the floor of the vestibulum of the nasal cavity, and a 5-Fr male urinary catheter is placed into

~--Dorsal lacrimal punctum

'-----Ventrallacrimal punctum

Nasolacrimal Flush 163

Nasolacrimal sac ----,

Nasolacrimal --'--­duct

Figure 27-1 lacrimal duct.

Schematic illustrating the anatomy of the dorsal and ventral puncta, nasolacrimal sac, and naso-

/

Figure 27-2 Nasolacrimal punctum in the vest i­bulum.

the ostium and advanced gently in a retrograde manner, I Using the index finger, gentle pressure is applied over the opening to «sea!" it around the catheter. Patency of the nasolacrimal system can be tested by injecting 15 to 20 mL of sterile saline through the catheter. Patency of the dorsal and ventral puncta at the medial canthus is individu­ally determined by alternately applying digital pressure over each canaliculus.

Alternatively, the nasolacrimal system can be catheterized in an antegrade manner from the dorsal punctum.6 The surgeon should first use appropriate local anesthesia or akinesia of the eyelids, topical anesthesia of the cornea, and seda­tion. The catheter is inserted into the dorsal punctum and is flushed with sterile saline. The ventral canaliculus should be occluded with digital pressure to ensure flushing of the naso­lacrimal duct to its opening (Figure 27-3).

The nasolacrimal catheter can also be tem­porarily sutured in place to provide patency of the nasolacrimal system while treating an obstruc­tion. If the surgeon intends to suture the naso­lacrimal catheter in place, then local anesthesia of the dorsal or lateral nasal wall adjacent to the nares should be injected prior to placing the tube. A stab incision is then made through the anes­thetized area using a No. 10 Bard-Parker scalpel. The nasolacrimal catheter is inserted retrograde as described above and is advanced to the naso­lacrimal sac. The free end of the catheter is inserted from inside the nasal cavity through the

164 OPHTHALMIC SURGERIES

Figure 27-1 Catheter placed in the dorsal punctum demonstra ti ng the use of digital pressure to obstruct

the ventral canaliculus.

stab incision and exits dorsally or dorsolaterally along the face. The catheter is sutured in place adjacent to the opening of the duct with two simple-interrupted No. 3-0 monofilament non­absorbable sutures. Additional sutures are placed along the face to secure the catheter7 (Figure 27-4).

POSTOPERATIVE CARE

Postoperative Care

Medications: If obstruction of the nasolacrimal duct is diagnosed, then flush material is submit­ted for bacterial culture and susceptibility, the results of which should direct antibiotic use. Antimicrobial therapy should be continued for at least 14 days. other: Nasolacrimal catheters that are sutured in place to maintain patency of the duct during treatment should remain in place for at least 2 to 3 weeks.' Topical antimicrobial therapy should be continued until the catheter is removed.

COMPLICATIONS

Congenital ostium malformation or scarring of the nasolacrimal duct or puncta may prevent

~-'(;."-'''-

Figure 27-4 Nasolacrimal catheter sutured in place

to treat nasolacrimal obstruction.

catheteriza tion. Catheters that exit the dorsal or ventral puncta and are sutured in place have the potential to rub the cornea and cause corneal ulceration. Care should be taken to avoid contact of the catheter or sutures/with the cornea.

REFERENCES

1. Moore C: Eyelid and nasolacrimal disease, Vet Clill N Alii Equine Pract 8:499, 1992.

2. St rubbe D, Gelatt KN: Ophthal mic examination and diagnostic procedures. In Gelatt KN, editor: Veteri­nary ophthalmology, ed 3, Philadelphia, 1999, Lip­

pincott Williams & Wilkins. 3. Cooley PL Normal equine ocular anatomy and eye

examination, Vet Clin N Alii Equine Pmct 8:427, 1992.

4. Carastro SM: Equine ocu lar anatomy and oph- . thalmic examination, Vet Clill N Am Equille Pmct 20:285, 2004.

5. Samuelson D: Ophthalmic an atom y. In Gela tt KN, editor: Veterinary ophthalmology, ed 3, Philadelphia, 1999, Lippincott Williams & Wilkins.

6. Sla tte r D: Lacrimal system. In Slatter D, editor:

Fundamel1tals of veteri1lary ophthalmology, ed 3, Philadelphia, 2001, WB Saunders.

7. Brook D: Use of an indwelling nasolacrimal cann ula for the administration of medication to the eye,

Eqlline Vet] (Suppl ) 2:135, 1983.

CHAPTER 28

Inferomedial Subpalpebral Lavage Tube Placement Laurence E. Galle

INDICATIONS

A sub palpebral lavage tube is indicated to facili­tate the administration of topical ophthalmic solutions,l .6

EQUIPMENT

Needle drivers) general operating scissors. 12-gauge trocar, and one sterile silicone sub palpebral lavage tube device approximately 90 em long with a I-em-diameter footplate are needed2

.3 (Figure

28-1). The sub palpebral lavage tube device may be purchased from commercial sources or manufac· tured by the surgeon from appropriate materials.

POSITIONING AND PREPARATION

Subpalpebral lavage tubes can be placed in sedated patients using appropriate nerve blocks to provide eyelid akinesia and sensory anesthesia including topical corneal anesthesia.

ANATOMY

Ventromedial subpalpebrallavage tube placement requires knowledge of the lower eyelid, medial canthus, third eyelid, and orbital rim. The poste· rior surface of the ventral eyelid is the palpebral

165

conjunctiva. The palpebral conjunctiva is firmly adherent to the eyelid at the eyelid margin and becomes loosely attached toward the conjunctival fornix. In the ventral aspect of the medial canthus, the conjunctiva in the fornix: reflects onto the anterior surface of the third eyelid. The conjunc­tiva of the third eyelid again reflects into a fornix on its posterior surface before becoming associ­ated with the globe as it becomes the bulbar conj unctiva' (Figure 28-2). The inferomedial sub­palpebral lavage tube will be positioned such that its footplate is in the inferomedial conjunctival fornix between the ventral eyelid and the third eyel id.'

PROCEDURE

The surgeon should ensure patency of the sub­palpebral lavage tube prior to attempting to insert it into the patient. The tip of a 12-gauge trocar is directed deep into the conjunctival fornix between the ventral eyelid and third eyelid. The index finger is used to guide the trocar and prevent injury of the globe with the trocar (Figure 28-3). The trocar is advanced through the con­junctival fornix and through the skin ventral to the medial canthus. A stainless steel thimble may be used to advance the trocar, and needle drivers may be placed adjacent to the exit site of the trocar through the skin to provide counterpressure to facilitate trocar placement. The free end of the subpalpebral lavage tube is inserted externally

[

166 OPHTHALMIC SURGERIES

Figure 28·1 Footplate of lavage tube.

Tarsal plate ---;-

Cilia

Tarsal

glands --::::::::::: Skin'

Orbicularis oculi m.

lavage tube in

conjunctiva _ev,lIor palpebrae sup~rioris m.

conjunctiva

Semilunar fold I tertia,

third eyelid)

~P-A.itO.t-" ,

Figure 28-2 Schematic of eyelid anatomy.

into the trocar from the conjunctival fornix. The tubing is advanced until it is visualized in the tip of the trocar and the trocar and tubing are then advanced through the skin, leaving the subpalpe­brallavage tube in the ventral eyelid as the trocar is removed. The surgeon advances the subpalpe­bral lavage tube until the circular footplate is secure aga inst palpebral conjunctiva. Prior to suturing the lavage tube into place, a 20-gauge Luer stub adapter with attached injection port is inserted into the free end of the lavage tube and patency is again tested by injecting saline or fluo­rescein through the lavage tube. Short strips of duct tape or porous medical grade tape are secured to the lavage tube adjacent to the exit site through the ventral eyelid, between the eyes, and

Figure 28-3 Finger guiding trOCilr.

•

Figure 28-4 Horse's head with lavage tube in place.

adjacent to the ipsi lateral ea r. These tabs of tape are then sutured in place using two No. 2-0 monofilament nylon simple interrupted sutures per tab of tape to secure the lavage tube to the patient (Figure 28-4).

POSTOPERATIVE CARE

Postoperative Care

Protection: A protective eye cup is recommended to prevent self-trauma and failure of the lavage tube. Other: The tube and footplate should be tested daily for patency; the blunt-tipped Luer adapter is a common site for failure with leaking of the tube and may need to be replaced if worn. Tubes leaking from sites rostral to the ears will need to be replaced with a new lavage tube. Tape tabs and sutures should be inspected for loosening and should be resutured if necessary.'·5 Medication: Only 0.1 mL of medication is nec­essary for injection through the lavage tube. The dose of medication is advanced through the lavage tube by slowly injecting approximately 1 mL of air through the tube using a tuberculin syringe.'

COMPLICATIONS

Ocular complications of subpalpebrallavage tube placement include displacement of the footplate from the conjunctival fornix, corneal ulceration, swelling of the ventral eyelid, and loss of the foot­plate within the eyelid. Nonocular complications include leakage or loss of the injection port, need

Inferomedial Subpalpebral Lavage Tube Placement 167

for resuturing of tape tabs, and tearing o r break­age of the lavage tube system. 3

,5 The most fre­quently reported complications of inferomedial lavage systems are displacement of the footplate from the conj unctival fornix (18%) and need for resuturing of tape tabs (14%). '

REFERENCES

1. Brooks DE: Equine ophthalmology. In Gelatt KN, editor: Veterinary ophthalmology, ed 3, Philadelphia, 1999, Lippincott, Williams & Wilkins.

2. Miller TR: Principles of therapeutics, Vet Clin N Am Equille Pract 8:479, 1992.

3. Giuliano EA, Maggs DJ, Moore CP, et al: Inferome­dial placement of a single-entry subpalpebral lavage tube for treatment of equine eye disease, Vet Opll­t/In/mo/ 3: 153, 2000.

4. Frauenfelder H, McJlwraith W: Placement of a sub­palpebral catheter in a standing horse, Vet Med Small Arl;m c/irl 74:724, 1979.

5. Sweeney CR, Russel l GE: Complications assoc iated wi th use of a one-hole subpalpebrallavage system in horses: 150 cases (1977-1996), , Am Vet Med Assoc 2 11 :127 1,1997.

6. Gelatt KN: Postoperative subpalpebral medicat ions in horses and dogs, Vet Med 62:1165,1967.

7. Samuelson D: Ophthalmic anatomy. In Gelatt KN, editor: Veterillary ophthalmology, ed 3, Philadelphia, 1999, Lippincott, Williams & Wilkins.

CHAPTER 29

Eyelid Laceration Repair Laurence E. Galle

INDICATIONS

Simple traumatic eyelid lacerations can be repaired with simple, multilayer suturing tech­niques. If, however, defects are excessively large with significant loss of eyelid tissue from devital­ization or necrosis, advanced blepharoplastic tech­niques may be required. 1

,2

EQUIPMENT

General surgical pack, Derf needle drivers, Bishop­Harmon tissue forceps, Stevens tenotomy scissors.

POSITIONING

Although some minor lacerations may be repaired with standing sedation-anesthesia and appropri­ate local anesthesia-akinesia, general anesthesia with the patient in lateral recumbency is recom­mended for most eyelid lacerations. 1.3

ANATOMY

The four major layers of the eyelid, from external to internal, are skin, orbicularis oculi muscle, fibrous tarsal plate, and conjunctiva4

•S (see Figure

28-2).

168

PROCEDURE AND PREPARATION

The surgical site is cleaned of debris with gentle lavage with saline or a 1 :50 dilution of povidone­iodine solution. Necrotic tissue is identified and debrided, leaving as much viable eyelid tissue as possible.J,6 If the laceration involves the lacrimal canaliculus near the medial canthus, then tempo­rary cannulation of the affected canaliculus prior to suturing is necessary to align the lacerated ends of the canaliculus during suturing. I.' Subconjunc­tival connective tissue is closed using No. 3-0 or No. 4-0 absorbable simple horizontal mattress sutures. The first suture should be placed adjacent to the eyelid margin to provide optimal eyelid margin apposition, and subsequent sutures are placed toward the apex of the incision. Eyelid lacerations should be repaired with a minimum of two suture layers (i.e., subconjunctival sutures and skin sutures); however, excessive tension across the laceration or significantly compro­mised eyelids may require an additional suture pattern or a temporary tarsorrhaphy.1 Skin clo­sure is performed with No. 3-0 monofilament nylon suture. The first skin suture to be placed is a figure-of-eight suture within the eyelid margin to provide optimal eyelid margin apposition2

•3

(Figure 29-1). The remainder of the skin is closed in a simple interrupted pattern.

A B

C 0 'ii"-,,, .;t~ • . _

Figure 29-1 Schematic demonstrating A, B, subcon­junctival closure and C, figure-of-eight suture at eyelid margin. D, The reminder of the skin laceration is closed in a simple interrupted pattern.

POSTOPERATIVE CARE

Postoperative Care

Medications: Systemic and topical broad-spec­trum antibiotics are used initially pending culture and susceptibility of the affected area, and tetanus prophylaxis should be given. Appropriate antibi­otics are continued for 7 days. Nonsteroidal anti­inflammatory therapy is necessary for a minimum of 3 days. other: Cold compresses should be applied post­operatively to combat inflammation and edema. Protedion: Protective eye cups are recom­mended to prevent self-trauma.2

,3

Eyelid laceration Repair 169

COMPLICATIONS

The most frequent complication of eyelid lacera­tion repair is wound dehiscence. This is most commonly a result of single-layer closure, but it may also occur as a result of devitalized wound edges or excessive tension across the surgical site. If wound dehiscence occurs, a second surgical repair with debridement and suturing is recom­mended to prevent eyelid margin defects and to reduce the potential for corneal abrasion or ulceration.

Some patients may develop a notch-like defect of the eyelid. Slich defects, if significant, can cause abnormal tearfilm distribution, and corneal irri­tation or ulceration. Minor defects of the eyel id margin may be left alone if they do not adversely affect the corneal surface; more significant defects, however, require additional blepharoplastic tech­niques to correct or remove the defect. These eyelid margin defects are most easily prevented by two-layer closure and an appropriately placed figure-of-eight suture at the eyelid margin.'

REFERENCES

1. Brooks DE, Wolf D: Ocular trauma in the horse, Equille Vet J (Su ppl ) 2:1 41,1983.

2. Millichamp NJ: Ocular trauma, Vet Clin N Am Eqllille Pract 8:521,1992.

3. Moore CP: Eyelid and nasolacrimal disease, Vet Clin N Am Equine 8:499, 1992.

4. Samuelson D: Ophthalmic anatomy. In Gelatt KN, editors: Veterinary ophthalmology, ed 3, Philadel­phia, 1999, Lippincott, Williams & Wilkins.

5. Cooley PL: Normal equine ocular anatomy and eye examination, Vet Cli ll N Am Equine Pract 8:427, 1992.

6. Moore CP, Constantinescu GM: Surgery of the adnexa, Vet c/in N Am Small Allim Pract 27: J 0 I J,

1997. 7. Miller TR: Eyelids. In Auer lA, Stick JA, editors: Equine

surgery, ed 2, Philadelphia, 1999, WB Saunders.

CHAPTER 30

Enucleation-Transconjunctival and Transpalpebral Laurence E. Galle

INDICATIONS

Enucleation is indicated when there is minilnaJ or no chance for maintenance of vision and when leaving the globe would result in continued patient discomfort or leave the patient at risk of systemic complications. Common indications for enucleation include ruptured globes, intraoc­ular neoplasia, panophthalmitis, and chronic uveitis or glaucoma. 1,2 It is imperative that the surgeon consider aU alternatives that might otherwise retain a comfortable, visual eye prior to performing an enucleation. The tran5-conjunctival approach is preferred for optimal cosmesis and minimal need for hemostasis. The transpalpebral approach, with use of a complete tarsorrhaphy prior to enucleation, is indicated for contaminated or infectious ocular disorders where reducing the potential of contaminating the orbit with conjunctival microbial flora is desired. 3

EQUIPMENT

A general surgical pack is appropriate for an enu­cleation. Additional instrumentation that may prove valuable includes suction, electrocautery, Steven's tenotomy scissors, and Bishop-Harmon tissue forceps.

170

PREPARATION AND POSITIONING

The patient should be placed in lateral recum­bency under general anesthesia with the affected eye up.

ANATOMY

Unlike carnivores, the equine globe is positioned within a completely enclosed bony orbit (Figure 30-1 ). Extraocular muscles, vascular supply, fat, fascia, and the optic nerve form the orbital cone as they converge to the posterior aspect of the orbit. The orbital cone is completely enclosed within a connective tissue fascial sheath called Tenon's fascia, which merges anteriorly with the sclera adjacent to the limbus. The conjunctiva is firmly attached to the limbus, becomes more elastic and loosely attached as it forms the con­junctival fornix, and reflects onto the posterior surface of the eyelids where it again becomes firmly attached at the eyelid margin. The fibrous tarsal plate of the eyelids is continuous with dense connective tissue called the orbital septum that inserts on the orbital rim. 4

,5

PROCEDURE

Transconjunctival Enucleation

A lateral canthotomy is performed with Metzen­baum scissors to facilitate exposure of the globe.

Enucleation-Trans(onjunctival and Transpalpebral 171

Infratrochlear notch Zygomatic process of frontal bone Zygomatic process of

temporal bone Caudal lacrimal process

Fossa of lacrimal sac

r

•

< I

I

•

Z /

.,.-

Caudal alar foramen

Temporal process of zygomatic bone

Figure 30-1 Schematic demonstrating the horse's bony orbi t.

Using delicate toothed forceps, such as Bishop­Harmon tissue forceps. the conjunctiva is gently grasped adjacent to the limbus and tented, and the conjunctiva is snipped approximately 2 mm from the limbus with Steven's tenotomy scissors to create an incision. A peritomy (360° conjunctival incision adjacent to the limbus) is performed using blunt and sharp dissection with Steven's tenotomy scissors, leaving approximately 2 mm of conjunctiva attached to the limbus for grasping with forceps for globe manipulation (Figure 30-2, A and B). The dense fibrous connective tissue attachment of Tenon's fascia is grasped and incised with tenotomy scissors. Tenon's capsule is incised near its insertion over its circumference, and the extraocular muscles and fascial attach­ments are transected at their insertions using curved Metzenbaum scissors or curved Steven's tenotomy scissors. Avoiding rostral traction of the

•

globe, the optic nerve is isolated and clamped approximately 4 to 5 mm caudal to the sclera. Using curved Metzenbaum scissors or enuclea­tion scissors, the optic nerve is transected between the sclera and the clamp to leave approx­imately 2 to 3 mill of optic nerve attached to the enucleated globe. The conjunctiva, third eyelid, and third eyelid gland are removed using Met­zenbaum scissors. The eyelid margins are excised from the eyelids approximately 4 mm from the eyelid margin using Mayo scissors. Hemostasis during removal of the conjunctiva and eyelid margins is provided with hemostatic clamps or electrocautery. The surgical site is closed in three layers. A simple continuous pattern of No. 3-0 absorbable suture is used to close the fascia and connective tissue attached to the orbital rim in a manner to create a diaphragm to minimize concavity postoperatively. A simple continuous

•

172 OPHTHA LM IC SURGERIES

A

B

c

Figure 30-2 A and B. Schematic demonstrating a peritomy. C, Schematic demonstrating Allis tissue forceps clamped to the eyelid margins and attached skin to faci litate exposure during dissection for transpalpe­bral enucleation.

pattern of No. 3-0 absorbable suture is placed in the subcutaneous tissues. The skin is closed with No. 3-0 nylon in a simple interrupted pattern.3.6

Transpalpebral Enucleation

A complete temporary tarsorrhaphy is performed using No. 2-0 monofilament nylon in a simple continuous pattern. An elliptical skin incision is made around the palpebral fissure using a scalpel, leaving approximately 5 mm of skin attached to the eyelid margin. Allis tissue forceps may be clamped to the eyelid margins and attached skin to facilitate exposure during dissection (Figure 30-2, C). Blunt dissection should be used in a pos­terior direction, being careful not to enter the con­junctival cul-de-sacs. Caudal to the conjunctival fornix, blunt dissection should be continued toward the sclera until the sclera is exposed. Extraocular muscle transection and optic nerve transection should be performed as described in the transconjunctival enucleation procedure. Once the optic nerve has been transected, the globe and attached conjunctiva, third eyelid, and its gland are removed from the orbit. The surgical site is closed in three layers as described for transconjunctival enucleation.3

,6

POSTOPERATIVE CARE

Postoperative Care

Protedion: A protective eyecup is used for 1 week postoperatively to prevent self-trauma.

Medications: Nonsteroidal antiinflammatory drugs may be used from 3 to 7 days to minimize associated discomfort and edema.'

Suture removal: Suture removal is recom~ mended in approximately 14 days.

COMPLICATIONS

Patients commonly exhibit significant periorbital swelling and discomfort for 2 to 3 days postoper­atively. This can be minimized through appropri­ate intraoperative hemostasis and postoperative antiinflammatory therapy.) Orbital cysts or mucoceles may develop several weeks to months postoperatively if the conjunctiva is not com­pletely excised. Such cases require surgical explo­ration and removal of remaining conj unctiva. Because the nasolacrimal duct is not ligated and is usually patent immediately postoperatively, it is not uncommon to observe serosanguinous dis­charge from the ipsilateral nares postoperatively. This is not usually a complication but will often worry an observant client who was not appro­priately informed of this possibility prior to discharge.

REFERENCES

I. Michau TM, Gilger BC: Cosmetic globe surgery in the horse, Vet Ciin N Am Equine Pmct 20:467, 2004.

2. Brooks DE, Wolf D: Ocular trauma in the horse, Eq"ille Vet] (Suppl ) 2:141,1983.

3. Brooks DE: Orbit. In Auer JA, Stick JA, editors: Equille surgery, ed 2, Philadelphia, 1999, WB Saunders.

4. Samuelson D: Ophthalmic anatomy. In Gelatt KN. editor: Veterinary ophthalmology, ed 3, Philadelphia, 1999, Lippincott, Williams & Wilkins.

5. Cooley PL: Normal equine ocular anatomy and eye examinatjon, Vet Ciill N Am Equine Pmc! 8:427, 1992.

6. Ramsey OT. Fox DB: Surgery of the orbit, Vet Clill N Am Small Allim Pract 27: 1215, 1997 .

CHAPTER 31

Entropion Laurence E. Galle

INDICATIONS

Equine entropion occurs most commonly in neonates secondary to dehydration, septicemia, or malnutrition. ]-4 Some breeds, however, may be predisposed to congenital entropion or primary anatomic entropion that is unrelated to systemic illness.5 Primary anatomic entropion and entro­pion that occurs as a complication of systemic illness are often exacerbated by pain and bleph­arospasm, which results in spastic entropion. Regardless of the etiology, entropion in the neonate should be initially managed with tempo­rary tacking sutures rather than a permanent sur­gical procedure. The usefulness of such everting sutures is twofold. For spastic entropion, they prevent corneal irritation and discomfort resul­tant to cilia and hair of the eyelids contacting the corneal surface, thus breaking the cycle of corneal pain and blepharospasm. For secondary entro­pion, the sutures maintain a more normal anatomic relationship of the cornea and eyelids while the underlying illnesses are resolved, If entropion persists after repeated tacking suture procedures have failed. then a permanent method of correction, the Hotz-Celsus blepharoplasty technique. may be necessary.4

EQUIPMENT

Bishop- Harmon tissue forceps, Derf needle drivers, general operating scissors. and a No. 3-0

173

or No, 4-0 monofilament nylon or braided silk suture are needed to place temporary tacking sutures . In addition to these instruments, a No. 15 Bard-Parker scalpel blade on a No, 10 scalpel handle and Steven's tenotomy scissors are needed to perform a Hotz-Celsus blepharoplasty,

PREPARATION AND POSITIONING

Tacking sutures are easily placed in sedated or anesthetized patients using appropriate local anesthesia-akinesia. Anesthesia or sedation, how­ever, is often contraindicated in patients with systemic illnesses that are frequently responsible for entropion, The eyelids of most debilitated neonates can be tacked with only local anesthesia and aki nesia, and this is often performed with the patients restrained in lateral recumbency. Hotz­Celsus blepharoplasty is also performed with the patient in lateral recumbency with the affected eye upward, but this requires general anesthesia.

ANATOMY

The major layers of the eyelids, from external to internal, are skin, orbicularis oculi muscle, fibrous tarsal plate, and conjunctiva. The eyelids are covered with hair to within 2 to 3 mm of the eyelid margin, and well-developed cilia (eye­lashes) are on the upper eyelid6

,' (see Figure 28-2),

174 OPHTH ALMIC SURGER I ES

Figure 31-1 Schematic of Lembert sutures placed in eyelid.

PROCEDURE

Temporary Eyelid Tacking

Simple interrupted Lembert sutures are placed to evert the affected eyelid margin. Lembert sutures are placed in the eyelid skin such that the most distal portion of the suture is approximately 3 mm from the eyelid margin (Figure 31-1 ). The number of Lembert sutures to be placed will vary by the extent of entropion and the degree of tension necessary to maintain eyelid eversion, but a minimum of two or three Lembert sutures should be placed.

Hotz-Celsus Blepharoplasty

The length of affected eyelid margin and amount of inward rolling are estimated before the patient is anesthetized or local anesthesia is injected. Hair should be clipped and the surgical site prepared for aseptic surgery. The surgeon removes a cres­cent-shaped strip of skin and underlying orbicu­lar is oculi muscle of the approximate shape and size of the area affected by entropion.s An incision is made through skin and underlying orbicularis oculi muscle 3 mm from, and parallel to, the affected eyelid margin, using a No. 15 scalpel blade. A curvilinear incision is made proximal to, and parallel to, the first incision, joining the ends of the two incisions to create a crescent (Figure

A

B c

D

Figure 31-2 Schematic of crescent-shaped skin being removed and "bisecting" method o f suture place­ment to close Hotz-Celsus blepharoplasty.

31-2, A). One corner of the crescent is grasped with Bishop-Harmon forceps, and the crescent of skin and orbicularis oculi is excised sharply using Steven's tenotomy scissors. Closure of the surgical site should be with No. 4-0 monofi lament nylon or braided silk in a simple interrupted pattern. To ensure appropriate alignment of the curvil inear incisions, the fi rst suture should be placed in the center of the incision, with subsequent sutures placed such that they bisect the area remaining to be sutured (Figure 31-2, B to D ).

POSTOPERATIVE CARE

Postoperative Care

Protedion: A protective eye cup is recom­mended for either surgical procedure unti l sutures are removed to prevent rubbing of the surgical site. Suture Removal: Tacking sutures should be left in place for 7 to 10 days but may "cut through" the skin prior to this time. Hotz-eelsus blepharo­plasty sutures should be removed in 14 days.

COMPLICATIONS

Care should be taken to prevent sti ff suture ends of monofilament nylon from making contact with the cornea as such contact will cause corneal

irritation and may precipitate corneal ulceration. Overcorrection of entropion by removing too much tissue may result in ectropion and exposure keratitis. Therefore, the surgeon should err on the side of removing less tissue if any doubt exists as to the amount of tissue to be removed. Client edu­cation about the potential of overcorrection or the need for a second Hotz-Celsus procedure if undercorrected is imperative.

REFERENCES

1. Latimer C, Wyman M, Hamilton J: An ophthalmic survey of the neonatal ho rse, Equine Vet J (Suppl) 2:9, 1983.

Entropion 175

2. Koch S, Cowles R, Schmidt G: Ocular disease in the newborn horse: a preliminary report. } Equine 511rg 2: 167, 1978.

3. Gelatt KN: Congenital and acquired ophthalmic disease in the foal, Anim Eye Res 1-2: 15, 1993.

4. Turner AG: Ocular conditions of neonatal foals, Vet Clill N Am Equine Pract 20:429, 2004.

5. Munroe G, Barnett K: Congenital ocu lar disease in the foal, Vet Clin N Am Large Anim Pmct 62:519, 1984.

6. Cooley PL: Normal equine ocula r anatomy and eye examination, Vet Clin N Am Equille Pmct 8:427, 1992.

7. Samuelson D: Ophthalmic anatomy. In: Ge1att KN, editor: Veterinary opllthalmology, ed 3, Philadelphia, 1999, Lippincott, Williams & Wilkins.

8. Moore CP, Constantinescu GM: Surgery of the ad­nexa, Vet Clin N Am S1IIall Anim Pmct 27:101 1,1997.

CHAPTER 32

Nerve Blocks for Ophthalmic Procedures: Lacrimal, Zygomatic, Infratrochlear, Palpebral, and Supraorbital Nerve Blocks

Laurence E. Galle

INDICATIONS

The indications for the lacrimal, zygomatic. and infratrochlear nerve blocks are to provide local anesthesia to the dorsolateral, ventrolateral, and ventromedial eyelids. These sensory nerve blocks are primarily used for minor diagnostic or thera­peutic procedures such as sub palpebral lavage tube placement, conjunctival biopsy, or eyelid lac­eration repair. These blocks do not provide aki­nesia of the eyelids. [·3

The supraorbital nerve block provides sensory anesthesia of the dorsomedial two thirds of the eyelid to facilitate examination or minor surgical procedures. This block does not provide akinesia of the eyelids.' -3

The palpebral nerve block is used to provide eyelid akinesia for ophthalmic examination and to facilitate diagnostic or minor surgical procedures. It does not, however, provide sensory anesthesia of the eyelids.1

-3

EQUIPMENT

A 5-mL syringe, 'Is-inch 25-gauge needle, and 2% lidocaine.

PREPARATION AND POSITIONING

These procedures may be performed in restrained patients but are facilitated by sedation.

176

ANATOMY

The lacrimal, zygomatic, infratrochlear, and frontal nerves provide sensory innervation to the eyelids of the horse. The lacrimal nerve innervates the dorsolateral third of the eyelid, the zygomatic nerve innervates the ventrolateral eyelid, the infratrochlear nerve innervates the medial can­thus and ventromedial aspect of the eyelids, and the frontal nerve innervates the dorsomedial two thirds of the eyelids (Figure 32- 1). The zygo­matic nerve is a branch of the maxillary branch of the trigeminal nerve (CN V), whereas the lacrimal, infra trochlear, and frontal nerves are branches of the ophthalmic branch of the trigem­inal nerve. 1

.4 The lacrimal, zygomatic, and infra trochlear nerves exit the orbit from beneath the orbital rim adjacent to the areas they inner­vate, whereas the frontal nerve exits the orbit with the frontal artery and vein through the supraor­bital foramen of the supraorbital process of the frontal bone.

The palpebral nerve is a branch of the auricu­lopalpebral branch of the fac ial nerve (CN VII) and innervates the orbicularis oculi muscle. The palpebral nerve is most easily palpated as it crosses the dorsal border of the zygomatic arch' (Figure 32-2) .

PROCEDURE

The lacrimal nerve block is performed by palpat­ing the dorsolateral orbital rim_ Using a 25-gauge

Infra­trochlear n.

n.

Figure 32-1 Schematic demonstrating innervation of the eyelids by the lacrimal, zygomatic, frontal and infratrochlear nerves.

Nerve Blocks for Ophthalmic Procedures 177

needle, inject 3 to 5 mL of 2% lidocaine along the lateral third of the orbital rim. The zygomatic nerve block is performed in the same manner, but along the ventrolateral third of the orbital rim. The infratrochlear nerve is blocked by injecting 2 to 3 mL of 2% lidocaine over a notch palpated along the ventromedial aspect of the orbital

• nm.

The supraorbital foramen is located by grasp­ing the rostral and caudal borders of the supraor­bital process of the frontal bone using the thumb and middle fingers. Moving the thumb and middle finger medially as the process widens, the index finger is used to palpate the depression of the supraorbital foramen approximately hal fway between the middle finger and thumb. A 25-gauge needle is passed subcutaneously to the opening of the supraorbital foramen or into the supraorbi-

Figure 32-2 Schematic demonstrating palpebral nerve anatomy in relationship to the zygomatic arch and orbital rim. F, Frontal; J, infra trochlear; L, lacrimal; Z, zygomatic.

=

178 OPHTHALMIC SURGERIES

tal foramen and 2 to 3 mL of 2% lidocaine are injected. l

The palpebral nerve is located by palpation along the dorsal aspect of the zygomatic arch with the index finger. A 25-gauge needle is inserted through the skin adjacent to the nerve as it crosses the zygomatic arch, and 1 to 5 mL of 2% lidocaine are injected subcutaneously. The injection si te should be gently massaged for 2 to 3 minutes. Resulting eyelid akinesia may last 45 minutes to 1 hour. I

COMPLICATIONS

Inserting the needle directly into the supraorbital foramen for frontal nerve block is preferred by some clinicians but has the potential hazards of intravascular injection and breaking off the

needle within the foramen in fractious patients. Surgical exploration to remove the needle is nec­essary if this latter complication occurs.

REFERENCES

1. Strubbe DT. Gelatt KN: Ophthalmic examination and diagnostic procedures. In Gelatt KN. editor: Vet­erinary ophthalmology, ed 3, Philadelphia, 1999, Lip­pincott, Williams & Wilkins .

2. Cooley PL: Normal equine ocular anatomy and eye examination, Vet Clill N Am Equine Pract 8:427,

1992. 3. Carastro SM: Equine ocular anatomy and oph­

thalmic examination, Vet Clill N AII1 Equine Pract 20:285, 2004.

4. Samuelson D: Ophthalmic anatomy. In Gelatt KN. editor: Veterinary ophthalmology, ed 3, Philadelphia, 1999, Lippincott, Williams & Wilkins.

• . I,~ 1

• •

CHAPTER 33

Temporary Tarsorrhaphy Laurence E. Galle

INDICATIONS

A temporary tarsorrhaphy is performed to pro­vide temporary decreased exposure of the globe, protection of the cornea, or both. ]-3 It is most often used to protect an ulcerated cornea but may also be used to maximize eyelid closure when excessive corneal exposure is likely (e.g., facial nerve [eN VII] paralysis-paresis).'"

EQUIPMENT

Derf needle drivers, Bishop-Harmon ophthalmic forceps, and general operating scissors are neces­sary for this procedure.

PREPARATION AND POSITIONING

This procedure is most easily performed using general anesthesia with the patient in lateral recumbency. It can be performed, however, in a standing patient with heavy sedation and appro­priate nerve blocks to obtain eyelid akinesia and sensory anesthesia.

ANATOMY

A thorough understanding of eyelid anatomy is imperative for appropriate suture placement in a temporary tarsorrhaphy. The major layers of the

179

eyelids are composed of skin) muscle, a fibrous tarsal plate, and conjunctiva from the external to internal surfaces. The meibomian glands are buried within the distal end of the fibrous con­nective tissue tarsal plate wi th openings in the eyelid margin. Well-developed cilia (eyelashes) are on the upper eyelid6 (see Figure 28-2).

PROCEDURE

The skin of the dorsal eyelid is grasped with forceps, and a simple horizontal mattress suture of No. 2-0 or No. 3-0 monofilament nylon is placed using a curved cutting needle. The suture pattern is started 5 mOl from the dorsal eyel id margin, and the needle shouJd be inserted down to, but not through, the fibrous tarsal plate. The needle should be advanced such that it exits the eyelid margin slightly anterior to the meibomian gland orifices. The horizontal mattress su ture crosses the palpebral fissure, is inserted into the ventral eyelid margin slightly anterior to the mei­bomian gland orifices, and should exit the eyel id skin approximately 5 mm from the eyelid. This completes half of the mattress suture. The hori­zontal mattress suture is completed by placing the suture from the ventral to dorsal eyelid using the same depth of Suture placement as in the first half of the suture placement. The number and spacing of the horizontal mattress sutures are determined by the surgeon.7

.S Stents may be used to minimize

cutting of the suture into the eyelid.8 The eyelids may be completely closed with this technique, or

180 OPHTH ALMIC SURGERIES

only a portion of the palpebral fi ssure may be dosed to cover a localized lesion. In either case, the sutures are tempora ry.

POSTOPERATIVE CARE

Postoperative Care

Protedion and Cleaning: The eye should be covered with a protective eye cup to prevent rubbing. The cup should be cleaned daily, and the tarsorrhaphy should be inspected for potential complications. Suture Removal: The palpebral fissure will begin to "gap" open to expose the sutures, usually in 7 to 10 days. This exposed suture may rub the cornea and could lead to corneal ulceration. The sutures should be removed or replaced when gapping begins to occur.

COMPLICATIONS

If the mattress sutures are placed too shallow within the eyelid or exit too far an terior to the meibomian glands, the inverting nature of the suture pattern may cause the eyelid margins to rub the cornea (i.e., entropion). If the sutures are placed too deep (e.g., through the conjunctival surface), the suture material may contact the

cornea. Either situation predisposes the patient to corneal ulceration, and such sutures should be removed or replaced immediately. As noted for postoperative care, the palpebral fissure may begin to "gap" as early as 7 days postoperatively; tarsorrhaphies that are "gapped" should be removed or replaced to prevent ulceration.

REFERENCES

1. Mille r TR: Principles of therapeutics, Vet Clin N Am Equine 8:479,1992.

2. Andrew SE, Brooks DE, Biros D1, et al: Posterior lamellar keratoplasty for treatment of deep stromal abscesses in nine ho rses, Vet Ophthalmol 3:99, 2000.

3. Brooks DE: Equine ophthalmology. In Gelatt KN, ed itor: Veterirlary ophthalmology, ed 3, Philadelphia, 1999, Lippincott , Williams & Wilkins.

4. Slatter D, Hanson S, deLahunta A: Neurooph­tha lmology. In Slatter D, edi tor: Fundamelltals of veterinary ophthalmology, ed 3, Philadelphia, 2001, WB Saunders.

5. Millichamp N1: Ocular trauma, Vet Clin N Am Equine 8:52 1, 1992.

6. Samuelson D: Ophthalmic anatomy. In Gelati KN. ed itor: Veterinary ophthalmology. ed 3. Philadelphia. 1999, Lippincott. Will iams & Wilkins.

7. Slatter D: Principles of ophthalmic surgery. In Slatter D, ed ito r: FUrldamentafs of veterillary oplltllalll1ology, ed 3, Philadelphia, 2001, WB Saunders.

8. Miller TR: Eyelids. In Auer 1. Stick J, editors: Equine surgery, ed 2. Philadelphia, 1999, WB Saunders.

ALE ROGENITAL URGERIES

181

CHAPTER 35

Cryptorchid Castration Joanne Kramer

INDICATIONS

Cryptorchid castration is performed to prevent breeding and to modify behavior.

EQUIPMENT

Emasculators are used to crush and sever the spermatic cord. White's modified, Serra, and Reimer emasculators are commonly used. All ca n be used effectively; we commonly use Serra emas­culators. Sponge forceps can be used to evert the vaginal process.

POSITIONING AND PREPARATION

Cryptorchid castration is performed with the horse in dorsal recumbency under general anesthesia.

ANATOMY

Normal testicular descent involves enlargement and then regression of the gubernaculum, a mes­enchymal condensation within the genital fold connected to the developing testes. This enlarge­ment of the gubernaculum extends through the vaginal ring and inguinal canal and is invaded by an extension of peritoneal lining forming the vaginal process. During the process of testicular descent, the gubernaculum differentiates into the

196

proper ligament, the ligament of the tail of the epididymis, and the scrotal ligament (inguinal extension of the gubernaculum ).1 Cryptorchid surgery is based on the identification of one or more of these structures and the use of these structures to locate the retained testicle.

The retained testicle may be within the inguinal ca nal or within the abdomen. Complete abdominal cryptorchids have the epididymis and testicle with in the abdomen. Incomplete or partial abdominal cryptorchids have the tail of the epi­didymis within the inguinal canal and the testes within the abdomen (Figure 35-1). For complete or incomplete abdominal cryptorchids. the prox­imity of the testicle to the vaginal ri ng varies depending on the length of the ligament of the tail of the epididymis and proper ligament.

PROCEDURE

The cryptorchid testicle is removed first. A IO-cm skin incision is made over the superficial inguinal ring (Figure 35-2). Electrocautery is used if nec­essary to control subcutaneous bleeding. The depth of the incision is extended by palpating the deep inguinal ring through the subcutaneous tissues and inguinal canal with the index finger of both hands and then spreading the tissues in one layer. Dissecting bluntly is important because of the superficial caudal epigastric vessels that lie lateral to the incision. Dissecting the deeper tissues in one layer keeps the surgical field simpler and makes it easier to identify the inguinal exten-

Cryptorchid Castration 197

A B c >

Figure 35~1 Three differen t positions of a retained testicle (cryptorchidism). A. Inguinal retention within the inguinal canal. B. Incomplete or partial abdominal retention. C. Complete abdominal retention.

Superficial iguinal

>

Figure 35-2 Location of the superficial ingu inal ring. Straigh t dotted line indicates the cranial border of the pubis.

-

Figure 35-3 Schematic view of the inguinal exten­sion of the gubernaculum.

sion of the gubernaculum or the vaginal process (Figures 35-3 and 35-4).

[f the testicle is inguinal, it will be identified at th is point and can be removed using emasculation (Figure 35-5). The vaginal tunic should be opened to confirm the presence of a testicle. Incomplete

Figure 35-4 The inguinal extension of the guber­naculum (small arrow) has been used to locate the vaginal process (large arrow) in a cryptorchid.

abdominal cryptorchids will have only the epi­didymis present in the vaginal tunic, and with gentle traction and occasional enlargement of the vaginal ring, the testicle can be found and removed. It is important that the descended tail of the epididymis not be mistaken for a small testi­cle and removed without removal of the abdom­inal testicle (Figu res 35-6 and 35-7).

Noninvasive Inguinal Approach

If the testicle is abdominal, the cranial medial aspect of the superficial inguinal ring is searched for the inguinal extension of the gubernaculwn

198 MALE UROGEN ITAL SURGERIES

A Figure 35-6 The taiJ of the epididymis exposed in an

B Figure 35-5 A, First view of an inguinal testicle (arrow). B, An ingu inal t.esticle after exterio rization (arrow).

(scrotal ligament).2 The inguinal extension of the gubernaculum is palpable as a fibrous band such tha t when tension is placed on it, it ca n be observed to descend into the inguinal canal. The size of the inguinal extension of the gubernacu­lum varies but is generally less than 1 cm. Light traction on the inguinal extension of the guber­naculum and blunt dissection to loosen tissue around the structure in the inguinal ca nal result in exposure of the vaginal process (see Figures 35-3 and 35-4). The vaginal process is then incised, and the epididymis or ligament of the tai l of the epididymis is used to retr ieve the testicle from the abdomen.

incomplete abdomi nal crypto rchid .

Figure 35-7 Afte r iden tification of the tail of the epididymis in Figure 35-6, traction on a long proper ligament resu lted in exteriorization of the abdominal testicle.

if the inguinal extension of the gubernaculum is not located, the vaginal process can often be fo und by palpat ing a thin cord like structure in the depression of the deep inguinal ring and by plac ing a curved sponge forceps in the deep inguinal ri ng and carefully everting the vaginal processM (Figure 35-8) . Opening the vaginal process reveals the lig­ament of the tail o f the epididym is, which ca n be used to find the epididymis and testicle. In some cases the vaginal ring must be enla rged to allow the testes to be exteriorized. This can be done manually with a finger or with Metzenbaum

• SC issors.

process

of the tait ;$f epididymis

~roper fig. of the tail of the epididymis

. (i"t

<'!', Y ' f-: .&-:J • .o::-_, ..... v~·tk'lo>--

Figure 35-8 Schematic view of eversion of the vaginal ring with sponge forceps

A

Cryptorchid Castration 199

The testicle is removed by emasculation or lig­ation and transection. Some testicles will not be able to be exteriorized sufficiently to effectively apply emasculators and will require ligation. If the vaginal ring has been opened or is wider than one finger width) the superficial inguinal ring should be closed with No.2 or 3 synthetic absorbable suture material in an interrupted pattern. Further closure of the subcutaneous tissues and skin is optionaL

Modified Parainguinal Approach

This approach can be used when the location of the testicle is known to be abdominal or when the noninvasive method has been attempted but the vaginal process not located.5 A lO-cm skin inci­sion is made 2 cm parallel to the medial border of the superficial inguinal ring beginning 3 to 4 cm cranial to the cranial extent of the ring (Figure 35-9, A). A 4-cm incision is made into the aponeu-

c

Lig. of the tail of

B

Tail of epididymis

Proper lig. of testis

Figure 35-9 Modified para inguinal approach for removing an abdominal testicle. A, Tncision in the aponeurosis of the external abdominal oblique. B, Schematic view of sweeping the deep inguinal ring for testicular attachments. C, Closure of the aponeurosis of the external abdominal oblique.

•

200 MALE U ROGENITAL SURGER IES

rosis of the external abdominal oblique muscle. Th is incision should be 1 to 2 cm medial to the superficial inguinal ring and centered over the cranial aspect of the ring. The index and middle fi nger are inserted through this incision and bluntly through the internal abdominal oblique, transverse fascia, and peritoneum and into the peritoneal cavity. The area of the deep inguinal ring is swept with the finger for either the epi­didymis, ductus deferens, proper ligament, or lig­ament of the ta il of the epididymis (Figure 35-9, B). Once one of these attachments is exteriorized, traction is used to exteriorize the testicle fro m the abdomen. The testicle is removed by emasculation or ligation and transection.

The aponeurosis of the external abdominal oblique muscle is closed with No. 2 or 3 synthetic absorbable suture material (Figure 35-9, C). The skin and subcutaneous tissue are closed with No. 2-0 absorbable synthetic suture material.

POSTOPERATIVE CARE

Postoperative Care

Exercise Reslridions: All horses should be stall rested for 24 hours. Further restriction of activity depends on the approach used and the antici­pated incisional healing. Horses that undergo a noninvasive approach with minimal dilation of the vaginal ring can be allowed turnout after the initial 24 hours of stall rest and can return to use in 2 weeks. When the superficial ring has been closed, horses should have stall rest for 24 hours followed by 1 week of handwalking and 2 weeks of small­paddock turnout. When the abdomen has been entered through a limited parainguinal approach, horses should have stall rest for 24 hours followed by 3 weeks of small-paddock turnout. Medications: Horses should receive a tetanus toxoid booster if it has been longer than 6 months since the previous vaccination. Phenylbutazone (4.4 mg/kg BID) therapy is provided for 24 hours. Antibiotic therapy is case dependent but typically is given only perioperatively. other: Recently gelded horses should be isolated from mares for a minimum of 2 days and prefer­ably up to 1 week after castration.

EXP~CTED OUTCOME

Cryptorchid castrations vary in the diffic ulty and time required to perform. In general, the time requi red or level of difficulty cannot be pre­dicted preoperatively. Many inguinal cryptorchids requi re li ttle more than routine castrations. Some abdomi nal cryptorchids require significant time, careful exploration, and closure. Best results come when the surgeon is prepared fo r either situat ion.

COMPLICATIONS

Complications are similar to those discussed for routine castration. When invasive procedures are necessary, the risk of incisional problems and eventration is greater than for routine castration. Addit ionally, if significant tissue trauma and manipulation occur during explorat ion fo r abdominal testicles, adhesion formation near the inguinal ring may cause colic. Using non invasive approaches when possible and entering the abdomen through approaches that can be closed di rectly (e.g., the modified parainguinal incision) decrease the risk of incisional complications and eventration. Rarely, greatly enlarged testicles, ter­atomas, or cystic testicles are identi fi ed and require removal through an enlarged incision.

Monorchidism is rare but possible. If a retained testicle is not identified after a thorough search, two options are ava ilable. The horse can be referred for further surgery, preferably laparoscopy, or the descended testicle can be removed and hormonal testing carried out to confirm the absence of testicular tissue.

ALTERNATIVE PROCEDURES

Alternative procedures for removing cryptorchid testicles include invasive inguinal, suprapubic paramedian, and flank approaches. The invas ive inguinal approach involves entering the abdomen th rough the inguinal canal. This procedure ca n extensively disrupt the deep inguinal ring and vaginal ri ng, which cannot be closed directl y. Therefore, the authors prefer the parainguinal approach to the invasive inguinal approach. Suprapubic paramedian laparotomy has been well described and is preferred by some authors.6.

7

With the exception of laparoscopic approaches, cryptorchid castration is not routinely performed through a flank approach.

Laparoscopy is a safe and effective way to iden­tify and remove abdominal cryptorchid testicles. Advantages include performing the procedure through small incisions with secure closure, ease of locating the testicle, and the ability to examine both sides of the abdomen when the side of the retained testicle is unknown. Disadvantages include expense of the equipment and the need to learn a specialized technique.

COMMENTS

Geldings that present with stallion-like behavior should have serum testosterone measurements before and 30 to 120 minutes after the adminis­tration of at least 6000 IV human chorionic gonadotropi n (HCG) intravenously to determine if testicular tissue is present. Geldings have serum testosterone levels of less than 40 pglml. Cryp­torchids have serum concentrations of greater than 100 pg/mL' Horses younger than 18 months or horses tested during winter may respond poorly to HCG and may need to have an addi­tional sample tested 24 hours after HCG admin­istration or be retested when older or during the spring.9 Previous surgical exploration often makes identification of surgical landmarks difficult, and when the side of cryptorchidism is not known, surgery can be prolonged. In these situations, laparoscopic exploration of the abdomen is the recommended approach.

Left cryptorchid testicles are more likely to be abdominal, whereas right cryptorchid testicles are more likely to be inguinal.!O Rectal examination of the inguinal region may also be useful in deter­mining the location of the testicle. Horses with abdominal testicles will have a small or indis­cernible inguinal ring. A larger ring with evidence

Cryptorchfd Cdstration 20 J

of the ductus deferens entering the canal indicates the horse is an incomplete abdom inal cryp­torchid, is an inguinal cryptorchid, or has a descended scrotal testicle. 4 Decision to perform diagnostic rectal examination is based on the size and temperament of the horse and the anticipated surgical approach. Bilateral cryptorchidism occurs in up to 15% of cryptorchid horses. These cases may have inguinal, incomplete abdominal, or abdominal retention .9

REFERENCES

I. Dyce KM, Sack WO, Wens ing C1G: The urogenital apparatus. In Dyce KM, Sack WO, Wensing CJG, editors: Textbook of veterillary allatomy, Philadel­phia, 2002, WB Saunders.

2. Valdez H, Taylor TS, McLaughlin SA, Martin TM: Abdom inal crypto rchidectomy in the horse using inguinal extension of the gubernaculum testis,] Am Vet Med Assac 174: litO, 1979.

3. Adams OR: An improved method of diagnosis and castration of cryptorchid horses, ] Am Vet Med Assac 145:439, 1964.

4. Adams SB, Fessler IF: Noninvasive inguinal cryp­to rchidectomy. In Adams S8, Fessler JF, editors: Atlas of eqlline surgery, Philadelphia, 2000, WB Saunders.

5. Wilson OG, Reinertson EL: A modified parain­guinal approach fo r cryptorchidectomy in horses. An evaluation in 107 horses, Vet 5urg 16:1, 1987.

6. Bladon B: Surgical management of cryptorchidism in the horse, In Practice 24: 126, 2002.

7. Cox J: A surgica l approach to the cryptorchid horse, III Practice 10:11, 1988.

8. COX JE: Cryptorchid castration . In McKinnon AO, Voss lL, editors: Equine reproductioll, Philadelphia, 1993, Lea & Febiger.

9. Mueller EPO: Cryp torchidism. In Wolfe OF, Moll DH, editors: Large animal Ilrogellital surgery. Philadelphia, 1999, Williams & Wilkins.

10. Stickle RL, Fessler JF: Retrospective study of 350 cases of equine cryptorchidism,] Am Vet Med Assoc 172:343, 1978.

CHAPTER 36

Circumcision Joanne Kramer

INDICATIONS

Circumcision is indicated for removal of neoplas­tic tissue, granulomas. or other masses from the sheath (Figure 36- 1), It is also indicated for removal of preputial scar tissue that prevents penile retraction or extension.

EQUIPMENT

A tourniquet is optional.

POSITIONING AND PREPARATION

The horse is positioned in dorsal recumbency under general anesthesia. The penis is extended, and the prepuce and shaft of penis a re prepared for aseptic surgery.

ANATOMY

The prepuce has two infoldings, which allow for retraction of the penis into the preputial cavity. The first of these infoldings is the external fold of the prepuce consisting of the external lamina, preputial ostium, and internal lamina. The second infolding is the preputial fold consisting of the outer lamina of the preputial fold, the preputial ring, and the inner lamina of the preputial fold (Figure 36-2), Circumcision can be

202

performed when lesions are located anywhere from the internal lamina of the external fold to the inner lamina of the preputial fold.

PROCEDURE

Two parallel circum ferential incisions are made around the prepuce proximal and distal to the affected region (Figure 36-3), A plane of dissec­tion is established deeper than the affected tissue but superficial to the deep fascia of the penis, The enti re region between the circumferential inci­sions is undermined and removed by creating a longitudinal incision between the circumferential incisions (Figure 36-4). Subcutaneous vessels may require ligation. If a tourniquet has been used, it

Figure 36-1 prepuce. This

, , , Ci rcumCISion.

Squamous cell carcinoma involving the lesion was removed successfully by

ring Outer

Urethral

Preputial ostium

Fossa glandis

-

Preputial fold

Outer lamina

lamina Preputial

ring

preputiallam~i~n~a----- -------------­

External preputial lamina

¥ • " oJ

Circumcision 203

Figure 36-2 A, External aspect of the penis and prepuce. S, Median section through the penis inside of the prepuce.

Figure 36-3 Circumferential incisions lIsed for removal of a lesion invo lving the prepuce.

A

B

204 MA LE U ROGEN ITAL SURGER IES

Figure 16~4 Intraoperative view before a longitudi­nal incision (dotted IiI/e) is created between the hori­zontal incisions to complete the removal of a squamous cell carcinoma les ion during circumcision.

Figure 36-5 Multiple-layer closure after circumci-.

slon.

should be released at th is point and the area checked carefully before closure. Simple superfi­cial resections can be closed in one layer wi th an interrupted pattern that apposes the remaining epithelium . Resection of larger amo unts of prepuce o r resections with greater depth need to be closed in layers using short runs of continuous suture patterns with absorbable suture in the deeper layers and an interrupted pattern in the epithelium ' (Figures 36-5 and 36-6). Care should be taken to maintain alignment during closure.

Figure 36~6 In traoperative view after closure during a circumcision procedure.

POSTOPERATIVE CARE

Postoperative Care

Exercise Restridions: Exercise is limited to handwalking or small-paddock turnout for 2 weeks. Light daily exercise is important to mini­mize edema formation. Stall ions should be iso­lated from rnares for 3 to 4 weeks. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and 2.2 mg/kg BID for an additional 3 days. Antibiotic therapy is given preoperatively and for 3 to 5 days postoperatively. Horses should receive a tetanus toxoid booster if it has been longer than 6 months since the previous vaccination. Suture Removal: Sutures used are absorbable but can be removed 12 days postoperatively.

EXPECTED OUTCOME

The most common reason fo r circumcision is removal of squamous ceU ca rcinoma lesions involving the prepuce. If the extent of neoplasia is limited and confined to the preputial tissues and

wide surgical margins are taken, the prognosis for survival without recurrence appears to be good.2

COMPLICATIONS

Edema commonly develops and generally resolves with time and low-grade exercise. Recurrence of squamous cell carcinoma lesions is possible. Dehiscence of the incision ca n be managed by second-intention heal ing. but extensive dehis­cence may cause stricture and require further resection.

ALTERNATIVE PROCEDURES

Laser excision of neoplastic tissues of the prepuce has been described and has the advantages of increased hemostasis and ablation of the underly­ing tumor bed.) Surgical excision has been com­bi ned with topical 5-fluo rouracil and cisplatin

Circumcision 205

injection in a limited number of cases and has had good reported success.4

•S

REFERENCES

1. Allen DA: Conditions of the penis and prepuce. In Wolfe DF, Moll HD, edito rs: Large allimal urogenital surgery, Philadelphia, 1999. Williams & Wilkins.

2. Mair TS, Walmsley JP, Phillips Tl: Surgical treatment of 45 horses affected by squamous cell carcinoma of the penis and prepuce, Equine Vet J 32:406, 2000.

3. Palmer SE: Use of lasers in urogenital su rge ry. In Wolfe DF, Moll HO, editors: Large animal urogenital surgery, Philadelphia, 1999, Williams & Wilkins.

4. Fortier LA, MacHarg MA: Topical use of 5 fluo­rouracil for treatment of squamous cell carcinoma of the external gen italia of horses: 11 cases, J Am Vet Med Assoc 295: 1183, 1994.

5. Theon AP. Pascoe JR, Meagher DM: Peri-operative intratumoral administration of cisplatin for t reat­ment of cutaneous tumors in equids, J Am Vet Med Assoc 205: 1170, 1994.

==

CHAPTER 37

Penile Amputation Joanne Kramer

INDICATIONS

Neoplastic lesions (primarily squamous cell carci­noma) and other masses involving the shaft of the penis (Figure 37-1), permanent penile paralysis, paraphimosis, or priapism.

EQUIPMENT

A tourniquet and urinary catheter are required for this procedure.

POSITIONING AND PREPARATION

The horse is positioned in dorsal recumbency under general anesthesia. The penis is extended and maintained in extension using gauze or umbilical tape around the glans. The penis, prepuce, and caudal abdomen in the area where the penis is extended should be prepared for aseptic surgery. A urinary catheter is placed before surgery to facilitate identification of the urethra during surgery.

ANATOMY

The urethra is located on the most ventral aspect of the penis and palpable if a urinary catheter has been placed. The urethra is surrounded by the corpus spongiosum penis. The corpus caver-

206

nosum penis surrounded by the tunica albuginea is the largest vascula r space. The primary blood vessels (the dorsal arteries and veins of the penis) encountered in penile amputation a re on the dorsal aspect of the penis between the deep fascia and the tunica albuginea. The veins on the dorsal aspect of the penis and the cross-sectional anatomy of the penis are shown in Figu re 37-2.

PROCEDURE

WilHam's technique is commonly used and is well described. ! A triangular skin incision is made on

Figure 37~1 Extensive melanoma on the distal shaft of the penis.

Dorsal

A

Obturator

External pudendal v.

Penile Amputation 207

Internal pudendal v.

Bulbospongiosus m.

v. of penis

m.

Body of penis Cranial v. of

penis

\----4---B

r------5 ------~· r--------- 6 -------+ c

~~~~~,... --- Dorsal process of glans penis ----'

5

6

D

-«'{ P.->vot;.J:<c, . >

Figure 37-2 A, Anatomy of the penis with transverse sections that extend through the B, glans penis, C, cranial penis, and D. caudal penis. 1, Retractor penis muscle; 2, bulbospongiosus muscle; 3, ureth ra; 4, corpus spongiosum penis; 5, albuginea; 6, corpus cavernosum penis.

the ventral aspect of the penis proximal to the intended site of amputation (Figures 37·3 and 37· 4). The base of the triangle is distal and about 3 em wide. The sides of the triangle are 4 to 5 em long. This incision is continued through the sub­cutaneous tissue. The skin and underlying tissues are discarded.

A longitudinal incision is made the length of the tr iangle between the retractor penis muscles, through the corpus spongiosum penis, and into

the lumen of the urethra (Figure 37·5) . The sides of the urethra are sutured to the skin edges with a simple interrupted pattern using No. 2-0 absorbable monofilament suture material (Figure 37-6). When the amputation is performed in the more proximal portions of the penis, it may be helpful to close the subcutaneous tissue to the tissue just deep to the urethral mucosa before closure of the mucosal epithelium to the skin. Closure of this layer decreases tension on the ure-

208 MALE UROGEN ITAL SURGEIUES

Figure 37-3 Triangular skin incis ion used in William's technique for amputation.

Figure 37-4 Intraoperative view of the triangular skin incision used in WilJiam's technique for amputa­tion.

Figure 37-5 A longitudinal incision is made into the lumen of the urethra.

thral mucosa) minimizes dead space) and helps control hemorrhage from the corpus spongio­sum. When this layer is closed) a simple continu­ous pattern with absorbable suture material is used.

The penis is then transected at the base of the tr ia ngle in an oblique manner so that the dorsal aspect of the penis is slightly longer than the ventral aspect (Figure 37-7). Branches of the dorsal artery and veins of the penis are ligated. The tunica albuginea is closed over the corpus

Figure 37-6 The sides of the incised urethra are sutured to the epithelium using an interrupted pattern.

I

~r; C.f "~

Figure 37-7 The base of the penis is transected so that the dorsal aspect is slightly longer than the ventral aspect.

Figure 37-8 The tunica albuginea is closed to com­press the corpus cavernosum.

cavernosum to compress the vascular spaces using a simple interrupted pattern with No. 0 or No.1 absorbable suture (Figure 37-8). The fi rst suture is placed on midline, and the subsequent sutures bisect the halves (Figure 37-9). The sutures should be closely spaced. Generally) seven or eight sutures are used. Blood loss from the corpus cavernosum can be extensive) and this seal should be checked carefully after release of the tourniquet.

The subcutaneous tissue deep to the skin is closed to the tissue just deep to the urethral

Figure 37-9 Intraoperative view of the initial suture placed to close the corpus cavernosum.

mucosa in a simple continuous pattern with absorbable suture material. The urethral mucosa is then closed to the skin at the base of the trian­gle in a simple interrupted or simple continuous pattern using No. 2-0 monofilament absorbable suture material (Figures 37-10 and 37-11).

POSTOPERATIVE CARE

Postoperative Care

Exercise Restrictions: Stall rest with handwalk­ing should be provided for 10 days, followed by small-area turnout for 10 days. Medications: Phenylbutazone is administered at 4.4 mg/kg BID for the initial 24 hours and 2.2 mg/kg BID for an additional 3 days. Antibiotic therapy is given perioperatively and for 3 to 5 days postoperatively. Horses should receive a tetanus toxoid booster if it has been longer than 6 months since the previous vaccination. Suture Removal: Sutures are absorbable but can be removed 12 days postoperatively. Other: Amputation is not usually performed on stallions because of potential incisional problems. Ideally, stallions should be gelded several weeks before surgery. If the procedure is performed on a stallion, exposure to mares should be avoided for 4 weeks. Artificial collection will be necessary when breeding is resumed.

EXPECTED OUTCOME

With appropriate associated with the

hemostasis, surgery are

complications not common.

Penile Amputation 209

Figure 17-10 Final appearance after performing William's technique.

Figure 37-11 Intraoperative view of final appear­ance after performing William's technique.

Recurrence or metastasis of squamous cell carci­noma is a significant problem, and owners should be forewarned of this . Reported survival rates for squamous cell carcinoma include a 60% to 71% survival rate of longer than 1 year. 2

,3 Involvement of the urethra decreases the prognosis; one study shows only a 30% IS-month survival rate when urethral tissue was involved. 2

COMPLICATIONS

Hemorrhage, dehiscence, urethral stricture, minor swelling, and recurrence or metastasis of neoplastic lesions are possible. Mild incisional hemorrhage during urination may be common during the first 2 to 3 days postoperatively.1.4 Per­sistent bleeding or hemorrhage that is dissecting into the incision line should be controlled surgi-

210 MALE UROGEN ITAL SURGERI ES

cally.4 Minor dehiscence of the suture line usually results in adequate healing by second intention. More extensive dehiscence may result in urethral stricture. Recurrence or metastasis of neoplastic lesions carries a poor prognosis and requires further surgery.

ALTERNATIVE PROCEDURES

Alternative techniques for amputation have been described and include Scott's and Vinsot's tech­niques.l ,s In Scott's technique, a full circumferen ­tial incision is made at the intended site of resection. Dissection is carried down to but not into the urethra. Approximately 4 to 6 em of urethra is freed distal to the site of peniJe ampu­tation. This is the most difficult aspect of the entire procedure, because the wall of the urethra is intimately associated with the corpus spongio­sum. The vascular spaces of the corpus caver­nosum are closed by apposing the tunica albuginea with simple interrupted sutures using No. 0 o r 1 absorbable suture material. The ure­thral stump is separated in to three triangular por­tions, folded back, and sutured to the epithelium.' Advantages and disadvantages of this technique are similar to those for William's technique.

With Vinsot's technique, a triangular portion of epithelium and underlying tissue with the base proximal to the apex is removed. A modification of th is procedure performed in standing horses involves making a longitudinal incision directly to the urethra.' A non absorbable ci rcumfe rentiallig­atu re is placed around the penis, and the penis is transected distal to the ligature. After longitudinal incision, the urethral mucosa is sutured to the skin as previously described. The penile stump is allowed to heal by second intention. The advan­tages of this technique are the decreased surgery time and the potential to perform the procedure standing. The disadvantage of this technique is the tendency for stricture formation and the potential for inadequate hemostasis. '

COMMENTS

Amputation in the distal portion of the penis is considerably less complicated than in the more proximal portions. In the proximal portions, the diameter of the penis is larger and the redundant tissue of the prepuce must be dealt with, which increases surgical and anesthetic time. In cases of squamous cell carcinoma, every attempt must be made to assess the horse for evidence of metasta­sis and to identify small satell ite lesions elsewhere on the penis or prepuce. For horses with lesions too proximal to amputate or requiring preputial ablation and inguinal lymph node removal , more involved procedures have been described.6

•s

REFERENCES

I. Schumacher J: The penis and prepuce. In Auer JA, Stick JA, editors: Equille surgery, Philadelphia, 1999, WB Saunders.

2. Howarth S, Lucke VM, Pearson H: Squamous cell ca rcinoma of the equine exte rn al genitalia: a review and assessment of pen ile amputation and urethros­to my as a surgical lrea tment, Equine Vet J 23:53, 1991.

3. Mair 1'S, Walmsley JP, Ph ill ips TJ: Surgical treat­ment of 45 horses affected by squamous cell carci­noma o f the pen is and prepuce, Equine Vet J 32:406, 2000.

4. Adams S8 , Fessle r 1F: Penile amp uta tion. In Ada ms S8 , Fessler JF, ed itors: Atlas of eqlline surgery, Philadelphia , 2000, WB Saunders.

5. Scott EA: A technique for amp uta tion of the equine penis, J Am Vet Med Assoc 168: 1048, 1976.

6. Archer DC, Edwa rds GB: En bloc resection of the pen is in five geldings, Equine Vet Edllc J 6: 12,

2004. 7. Doles J, Williams JW, Yarbrough TB: Penile amputa­

tion and sheath ablation in the horse, Vet 5urg 30:327,200l.

8. Markel MD, Wheat JD, Jones K: Gen ital neoplasms treated by en bloc resection and pen ile retroversion in horses: 10 cases (I977- 1986),J Am Vet Med Assoc 192:396, 1988.

CHAPTER 38

Perineal Urethrotomy in Males Gal Kelmer

INDICATIONS

Treatment of urolithiasis involving the bladder and urethra, urethral rents causing hemospermia in stallions and hematuria in geldings, and tem­porary urine divers io n for urethral obstructive lesions, such as hematoma, neoplasia (e.g.) squa­mOllS cell carcinoma), o r parasitic granuloma (e.g., habronemiasis ).1.)

EQUIPMENT

A male urinary catheter is helpful fo r urethra iden­tificat ion during surgery. When using urethro­tomy to treat urolithiasis, special equipment such as a custom-made lithotrite may be necessary.

PREPARATION AND POSITIONING

The horse should be standing in stocks with the use of systemic sedation and epidural analge­sia. An alternative to epidural anesthesia is an inverted-V block using local anesthetic. Manual emptying of feces from the rectum is followed by dipping, tail wrapping, and surgical preparation of the perineal region.

ANATOMY

The male pelvic urethra is about 12 cm long and tapers in diameter from 3 em near the prostate to

211

1.5 em in the urethral isthmus and penile urethra. The urethralis muscle envelops the pelvic urethra. The corpus spongiosum penis surrounds the urethra, and the bulbospongio511s muscle lies caudal to the pelvic urethra and becomes ventral to the pen ile urethra d istally. The symmetrical retractor penis muscle covers the bu lbospongio ~

sus and lies beneath the subcutaneous tissue at the perineal region.

PROCEDURE

A vertical incision starts 4 to 6 cm distal to the anus and extends ventrally for 8 to 10 cm through the median raphae skin and subcutaneous tissue (Figure 38-1). The incision should not extend ventral to the ischium in order to prevent urine spraying on the limbs and subsequent scald for­mation. The retractor penis muscles are separated on midline and reflected laterally (Figure 38-2) . The bulbospongiosus muscle is exposed and incised. Hemorrhage is expected, at this stage, and is controlled by applying light pressure using surgical gauze. The incision continues through the corpus spongiosum penis and the ureth ral wall. Urethral lumen entry is verified by visualiz­ing and palpating the urinary catheter (Figure 38-3). The catheter helps to prevent both acci­dental deviation from midline and penetration of the cranial urethral wall .104

212 MA LE U ROGENITAL SURGERIES

Figure 38-1 View of the hind quarters of a gelding. The interrupted line depicts the approach for perineal urethrotomy.

~........"t.:;,.1..... -

Figure 38-2 Intraoperative view, showing perineal urethrotomy of a gelding with a urinary ca theter in place. The illustration depicts the incision through the skin and subcutaneous tissue and between the retrac­tor penis muscles. The deep layer shown at the center of the incision is the bulbospongiosus muscle.

A

B

Figure 38-3 A, Postoperative view of perineal ure­throtomy in a gelding. At the center of the incision the uri nary catheter is visible within the urethral lumen. 8, Close-up view of a completed perineal urethrostomy. The second layer of suture is shown depicting simple interrupted sutures between the urethral mucosa and the perineal skin.

POSTOPERATIVE CARE

Postoperative Care

Protection and Cleaning: The surgery site should be kept clean, and petrolatum jelly is applied to the perineal region and the medial aspect of both upper hind limbs to prevent urine sCilld. Medications: Broad-spectrum systemic antibi­otics and nonsteroidal anti inflammatory medication such as phenylbutazone are given perioperatively for 3 to 5 days. Exercise Restrictions: Stallions need to avoid sexual activity for 4 to 6 weeks. Dietary Modifications: Adding salt to the feed, at 10/0 of the horse's diet, may encourage drink­ing and aid in preventing recurrence of urolithia­sis.5

other: Hemorrhage should be monitored for the first 24 hours. Dripping of blood from the incision and terminal hematuria are expected for up to 2 weeks postoperatively.

EXPECTED OUTCOME

Cystic urolithiasis carries a favorable prognosis, but owners should be forewarned about the pos­sibility of recurrence. 6

.8 Urethral urolithiasis can be treated successfully if diagnosis and treatment are performed early, thus avoiding urethral obstruction and bladder rupture. The success of urethrotomy for treatment of other urinary obstructive lesions depends primarily on the nature and extent of the lesion.

COMPLICATIONS

Excessive bleeding in the form of a continuous stream of blood warrants intervention. Applica­tion of light pressure with gauze or cold packing for 10 to 15 minutes is usually sufficient. However, if significant bleeding persists, surgical explo­ration is indicated. If the corpus cavernosum penis is the source of bleeding, suturing the tunica albuginea is indicated for prompt, effective hemo­stasis. Urine scald is a common sequel that can generally be avoided by keeping the distal end of the incision proximal to the ischial arch . Scald should be cleansed, and affected areas should be treated with silver-sulfadiazine cream, zinc-oxide, or other nonirritating cream-ointment on a daily basis. Unilateral urine scald caused by asymmet­ric urine flow may be eliminated by applying sutures at the contralateral side of the urethro­tomy in an attempt to redirect the urine stream straight caudally. Stricture formation can gener­ally be prevented by careful attention to tech­nique, making one straight incision of adequate length. Recurrence of urolithiasis may be more common following urethrotomy than with laparocystotomy due to incomplete fragment removal.9 Other reported complications include rectal or urethral damage, orchitis, peritonitis, incontinence. and bladder rupture.9

ALTERNATIVE PROCEDURES

Urethral rents can be treated by perineal release incision. The procedure is identical to that of per­ineal urethrotomy but avoids entering the ure­thral lumen. The incision through the corpus spongiosulll penis presumably provides a tem­porary alternative route for the blood, while allowing the urethral rent to heal by second in tention. 3. \0

Perineal Urethrotomy in Males 213

Urethrostomy for permanent urine diversion is created by a two-layer closure over the above described urethrotomy (see Figure 38-3 B). Ini­tially, a hemostatic layer is performed by suturing the bulbospongiosus muscles and the corpus spon­giosum penis, using No. 3-0 synthetic absorbable suture, in a simple continuous pattern. The second layer is performed in a simple interrupted pattern, using No. 2-0 polypropylene, connecting the urethral mucosa to the perineal skin. Meticu­lous, tensionless apposition of the mucosa to the skin is crucial to prevent dehiscence and lateral urine diversion causing scald formation. ],2

Laparocystotomy is an effective method for cystic calculi removal. The primary disadvantage is the need for general anesthesia. The primary advantages are reduced trauma to the bladder and urethra and decreased recurrence rate from com­plete calculi removal and the less traumatic nature of the procedure.5,9

Laparoscopy has also been used for cystic calculi removal. The procedure necessitates general anesthesia, special equipment, and expe­rience with the technique. However, it enables excellent visualization and access to the bladder. II

COMMENTS

As a treatment for urolithiasis, urethrotomy can be performed for retrieving small uroliths or crushing larger ones using a lithotrite. l Most cystic calculi are large enough that they must be crushed or broken into smaller pieces to allow removal through a urethrotomy incision. This can result in a long and somewhat traumatic proce­dure. Other, less traumatic, options for eliminat­ing uroliths via urethrotomy include laser (e.g., pulsed-dye) and electrohydraulic lithotripsy.'-' Performing the urethrotomy 24 to 48 hours before lithotripsy may provide for better visualization with less hemorrhage. Following calculi fragmen­tation, thorough bladder irrigation is indicated and may be repeated postoperatively to decrease recurrence and prevent cystitis.

REFERENCES

1. van Harreveld PO, Gaughan EM. Lillich JO: Urethral surgery in horses, Camp Cant Educ Pract Vet 20;739, 1998.

2. Lillich JO, OeBowes RM: Ureth ra. In Aller JA, Stick JA, ed itors: Eqllille 5l11gery, ed 2, Philadelphia, 1999, WB Saunders.

214 MALE UROGENITAL SURGER IES

3. Schumacher J, Schumacher J: Surgical management of urolithias is in the equine ma le. In Wolfe OF, Moll HO, editors: Large animal urogenital surgery, ed 2, Baltimore, 1998, Williams & Wilkins.

4. Adams SB, Fessler JF: Perinea l urethrotomy and removal of cystic calculi In Adams SB, Fessler 1F, editors: Atlas of equine surgery. Philadelphia, 2000, WB Saunders.

5. Schumacher J, Schumacher J, Schmitz 0: Macro­scopic haematu ria of horses. Equine Vet Edllc 4:255, 2002.

6. Howard RD, Pleasant RS, May KA: Pulsed dye laser lithotripsy: treatment for urolithiasis in 2 geldings. J Am Vet Med Assoc 212:1600.1998.

7. Judy CEo Galuppo LD: Endoscopic-assisted disrup­tion of urinary calculi using a holmium:YAG laser in standing horses, Vet Surg 31 :245, 2002.

8. Eustace RA, Hunt 1M: Electrohydraulic lithotripsy fo r the treatment of cystic calculi in tvvo geldings, Equine Vet J 20:221. 1988.

9. Laverty S, Pascoe JR, Ling GV, et al: Urolithiasis in 68 horses, Vet Surg 2 J :56. 1992.

10. Schumacher T, Varner DO, Schmitz DG, et al: Urethral defects in geldings with hematuria and stallions with hemospermia, Vet Surg 24:250, 1995.

11. Ragle CA: Laparoscopic removal of cystic calculi in 10 horses. In Fischer AT, editor: Equi1/e diagllostic and surgical laparoscopy, Philadelphia, 2002, WB Saunders.

EMALE ROGENITAL URGERIES

215

CHAPTER 39

Caslick's Procedure (Vulvoplasty) John C. Janicek

INDICATION

Pneumovagina resulting from abnormal perineal conformation.

EQUIPMENT

No special equipment is required.

POSITIONING AND PREPARATION

The mare is restrained stand ing in a stock or backed into a stall doorway. The tail is held out of the way by an assistant or wrapped and tied forward. Following aseptic preparation of the per­ineal region, local anesthetic (15 to 20 mL lIsing a 22-gauge needle) is infiltrated along the vulvar labial mucocutaneous margin (Figure 39- 1), Excessive local anesthetic infiltration should be avoided to prevent distortion of the mucocuta­neous margins.!

PROCEDURE

Beginning at the level of the ischiatic tuber and extending to the dorsal commissure, a th in band of mucosa approximately 3 to 5 mm wide is excised from each side of the vulva along the mucocutaneous margin2 (Figure 39-2). The exact length of tissue removed depends on the

216

mare's conformation.) To reduce the likelihood of removing an excessive width of mucosa, thumb forceps may be used to apply downward tension o n the band of excised mucosa. Excessive mucosal removal results in excessive scar tissue forma­tion, making future easlick's procedures more difficult.,,4

Once the mucosa has been excised, the exposed surfaces are apposed beginning at the dorsal COI11-

'<l r f"J~.c~_

Figure 39-1 Infiltration oflocal anesthetic along the vulvar mucocutaneous margin.

/

( \

~P"'AI>t...i_ ...... ~

Figure 39-2 Excision of vulvar mucosa along the mucocutaneous junction using sc issors.

I

'9 f'~f; •. i. .. _. _

Figure 39-3 Apposition of vulvar mucosa Ford interlocking pattern.

• usmg a

missure with No. 0 non absorbable suture using a continuous pattern. Simple continuous or Ford interlocking patterns are commonly used (Figure 39-3). A single "breeding stitch" may also be placed just distal to the suture line with No. I non­absorbable suture material using a loose single interrupted suture to protect the repair during assisted live cover or artificial insemination (Figure 39-4). The "breeding stitch" should not be so ventral that it prevents urination or assisted live cover breeding. A «breeding stitch" should not be placed in mares in which pasture breeding is intended.

(aslick's Procedure (Vulvoplasty) 217

'<jj p...t_l_",~. -Figure 39-4 Addition of a "breeding stitch" just distal to the Caslick suture line.

POSTOPERATIVE CARE

Postoperative Care

Medications: Antibiotic and antiinflammatory therapies are generally not necessary. Suture Removal: Sutures should be removed 10 to 14 days after surgery. other: No exercise restrictions are necessary. Prior to foaling (3 to 5 days), an episiotomy should be performed to minimize perineal da­mage during parturition.

EXPECTED OUTCOME

Resolution of pneumovagina is likely followi ng a Caslick's procedure in mares with normal to mildly abnormal perineal conformation. Mares with moderate to severe abnormal perineal con­formation or persistent pneu movagina may require perineal body reconstruction.

COMPLICATIONS

Min imal complications are associated with this procedure; however, dehiscence and suture sinus tract development are possible. Excessive ventral closure may result in urovagina. Unpredictable vulvar tearing may occur if episiotomy is not per­formed before parturition.

218 FEMALE UROGENITAL SURGERIES

COMMENTS

For maximum reproductive funct ion, the dorsal commissure of the vulva should extend no more than 4 to 5 cm dorsal to the ischiatic tuber, meaning that approximately two thirds of the vulvar cleft is below the ischiatic tuber.4 The vulvar labiae should be oriented vertically with a cranial-to-caudal slope of no more than 10 de­grees from vertical.s A distance of more than 4 cm between the dorsal commissure of the vulva and the ischiatic tuber and/or an angle of more than 10 degrees in the declination of the vulvar labiae is associated with poor perineal conforma­tion and increases the likelihood of pneu­movagina.s Variations in perineal conformation have many causes, including inherent conforma­tion, poor physical condition, and age. A flat croup, elevated tail set, under-developed vulvar labiae, and sunken anus all contribute to faulty perineal conformation.s Poor physical condition intensifies the problem and can result in abnor­mal conformation in mares with otherwise

normal conformation. Improving the physical condition of these mares results in improved per~ ineal conformation. With age and repeated foal­ings, the vulva lengthens and vulva conformation becomes more horizontal relative to the pelvic brinl because of general organ and muscle relax­ation in the pelvic region. 4

REFERENCES

I. Anasari MM: The Caslick's operation in mares, Comp Cont Edllc Vet 5:s107, 1983.

2. Beard W: Standing urogenital surgery, Vet Clill N Am

Equine Pmct 7:669, 1991. 3. Turner AS, McI lwrath CW: Techniques ill large

allimai surgery, ed 2, Philadelphia, 1989, Lea & Febiger.

4. Trotter GW, McKinnon AO: Surgery for abnormal vulvar and perineal conformation in the mare, Vet Clill N Am Equine Pmct 4:389, 1988.

5. Easley J: External perineal conformation. In McKin­non AO, Voss JL, editors: Equi/le reprodllction, Philadelphia, 1993, Lea & Febiger.

•

CHAPTER 40

Perineal Body Reconstruction (Episioplasty) John C. Janicek

INDICATION

Pneumovagina or persistent endometritis follow­ing easlick's procedure.

EQUIPMENT

No special equipment is required.

PREPARATION AND POSITIONING

The mare is restrained standing in a stock, and the procedure is performed with either epidural or local perineal body anesthesia, and sedation if necessary. Once anesthesia is confirmed. the tail is wrapped and securely retracted. Fecal material is removed from the rectum. The perineal region is then rinsed and aseptically prepared. Sterile saline is used instead of alcohol to remove antiseptic soaps, because alcohol may cause excessive irrita­tion.

PROCEDURE

Vulvar retraction is maintained with towel clamps or stay sutures positioned lateral to the dorsal vulvar commissure. In this procedure, triangular areas of mucosa are removed from the perineal body. An incision is made along the vulvar muco­cutaneous margin of both labiae beginning at the dorsal commissure, extending to the desired ventral limit. I The ventral limit of the incision is subjectively chosen by determining the amount of

219

tissue required to develop a dorsal commissure that will provide an adequate vaginal seal. The length required is typically 4 to 6 em. The incision is then extended dorsocranially until the cranial portion terminates on the dorsal midline at the vestibulovaginal junction (Figure 40-1). The tri­angular mucosal flaps are then resected from both sides of the vestibule. The resultant exposed sub­mucosa forms a right-angled triangle with the right angle located along the dorsal commissure of the vulva' (Figure 40-2) .

Closure of the ventral vestibular mucosal margins is performed cranial to caudal with No. 2-o absorbable suture in a simple continuous pattern2

(Figure 40-3). Deeper submucosal tissues are apposed with No. 2-0 absorbable suture using a simple interrupted pattern. Caslick's procedure is performed to appose the vulvar opening (Figure 40-4).

POSTOPERATIVE CARE

Postoperative Care

Exercise Restrictions: Small-paddock turnout should be maintained for 14 days. Medications: Broad-spectrum antibiotics are administered for 7 to 10 days. A nonsteroidal anti­inflammatory agent is administered for 3 to 5 days. Suture Removal: Caslick's sutures are removed 10 to 14 days after surgery. Other: Sexual rest for 4 to 6 weeks is recom­mended. Prior to foaling (3 to 5 days), an epi­siotomy should be performed to prevent perineal damage during parturition.

220 FEMALE UROGENITAL SURGERIES

/

Figure 40-1 Proposed area of vestibula r mucosa to be removed (dotted lilies) for perineal body reconstruction.

Figure 40-2 Caudolateral view of proposed area of vest ibular mucosa to be removed (dotted lines) for perinea l body reconstruction.

Figure 40-3 Cranial-to-cauda l closure of the ven tral vestibular mucosa simple continuous pattern.

• • margin usmg a

.

I

Figure 40-4 easlick's procedure is performed to ove rsew the submucosal perineal tissues and appose the vulvar lips.

EXPECTED OUTCOME

Adequate reconstruction of the mare's perineal region alleviates pneumovagina in most cases of

Perineal Body Reconstruction (Episioplasty) 221

moderate to severely abnormal perineal confor­mation. Occasionally, pneumovagina does not resolve following Caslick's procedure or perineal body reconstruction. In these cases, perineal body transection may be warranted. 2

COMPLICATIONS

Minimal complications are associated with this procedure; however, dehiscence and suture sinus tract development are possible. Excessive ventral closure may result in urovagina. Unpredictable vulvar tearing may occur if episiotomy is not per­formed before parturition.

REFERENCES

I. Beard W: Standing urogenital surgery, Vet Clill N Am

Equille Pract 7:669,1991. 2. Trotter GW, McKinnon AO: Surgery for abnormal

vulvar and perineal conformation in the mare, Vet

CliIl N Am Equine Pract 4:389, 1988.

CHAPTER 41

Urethral Extension (Urethroplasty) John C. Janicek

INDICATIONS

Urine pooling, urovagina.

EQUIPMENT

Long-handled instruments and a 30-Fr Foley catheter are required. Self-retaining retractors (vaginal spatula. Balfour. modified Finochietto) and a good light source (floor lamps. headlamp. or fiberoptic lights) are useful but not necessary.

PREPARATION AND POSITIONING

The mare is restrained standing in a stock, and surgery is performed following epidural anesthe­sia, and sedation if necessary. Once anesthesia is confirmed, the tail is wrapped and securely retracted. Fecal material is removed from the rectum. The perineal region is rinsed, followed by cleansing of the vaginal lumen with a dilute povidine-iodine solu tion. The perineal region is then aseptically prepared, with care taken to not use alcohol, as it may cause excessive irritation.

PROCEDURE

Various repair techniques are described. The goal of all techniques is to create a mucosal tunnel

222

extending from the urethral orifice to near the mucocutaneous junction so that urine enters the vagina caudal to the brim of the pelvis. allowing gravity to assist in voiding urine. In all techniques, it is important to place the first suture cran ial to the urethral orifice to minimize the risk of fistula formation and to appose the dissected tissue shelves with minimal tension. Adequate visualiza­tion is achieved by use of a vaginal spatula posi­tioned along the dorsal aspect of the vaginal lumen along with ventrolateral placement of towel clamps in the vulvar labiae. Retraction may also be provided using Balfour or modified Finochietto retractors.

Monin Te(hnique

This technique involves caudal translocation of the transverse urethral fold l

,2 and is recom­mended only in cases with mild perineal confor­mational abnormalities. The major limitation of this technique is the inability to extend the ure­tlual opening as far caudally as can be done with other techniques, which is necessary in mares with moderate to severe perineal conformational abnonnalities.

The transverse urethral fold is grasped with Allis tissue forceps 1 cm abaxial to each side of midline and retracted approximately 5 cm cau­dally. The lateral aspect of the transverse urethral fold is split horizontally and the incision is extended along the corresponding ventrolateral vaginal wall (Figure 41-1). The transverse urethral fold is sutured to the vaginal floor in the retracted

Figure 41-1 The transverse urethral fold is caudally retracted. On the right side, an incision has been made through the transverse urethral fold and corresponding ventrolateral vaginal wall. On the left side, a dot'ted line indicates the proposed incision line.

position with No. 2-0 absorbable suture using a two-layer pattern. The ventral layer is apposed using a Connell pattern, and the dorsal layer is apposed using a horizontal mattress pattern (Figure 41-2). A simple interrupted suture should be placed at the caudalmost aspect of the two . .. InCISions.

Brown Technique

This is the most common urethral extension tech­nique used.3 Correction of urovagina in mares caused by severe perineal conformation abnor­malities can be achieved with this technique by extending the urethral opening far caudally. However, mares with vaginal scars or vaginal mucosa atrophy are not good candidates fo r this technique because of increased tissue tension.3

A 30-Fr Foley catheter is placed in the urinary bladder and the cuff is inflated. The transverse urethral fold is split horizontally, and the mucosal incision is extended caudally along the left and

Urethral Extension (Urethroplasty) 223

'\

\

A

B

Figure 41-2 A, The right side of the transverse ure­th ral fold and corresponding ventrolateral vaginal wall are split horizontally in an interrupted manner. Arrows

indicate the direction of tissue mobilization. The left side of the transverse urethral fold has been sutured to the corresponding ventrolateral vaginal wall . B, Close­up view of a two-layer closure. The ventral layer is apposed using a Connell pattern, and the dorsal layer is apposed using a continuous horizontal mattress pattern.

right vaginal walls to a point approximately 3 cm cranial to the vulvar labiae (Figure 41-3). Under­mining of the ventral and dorsal mucosal layers is performed to decrease tension. The ventral mu­cosal layer is closed with No. 2-0 absorbable su­ture using a Connell pattern, everting the tissue ventrally (Figure 41-4). Submucosal tissue is closed with No. 2-0 absorbable suture using a simple continuous pattern (Figure 41-5). Finally, the dorsal mucosal layer is everted dorsally with No. 2-0 absorbable suture using a continuous horizontal mattress pattern (Figure 41-6).

Shires Technique

Although simple and efficient, this technique4 is limited in that it may be used only in mares that have redundant vestibular folds that may be pulled together to form a tunnel without the need for dissecting and undermining tissue flaps to form a shelf.'

224 FEMALE UROGENITAL SURGERIES

Figure 41-3 Horizontal splitting of the transverse urethral fold and caudal extension of the vaginal mucosa incision (dotted line) alo ng the left and right vaginal walls.

Figure 41-4 Inversion of the ventral mucosal layer using a Connell pattern.

Figure 41-5 Submucosal tissue closure using a simple continuous pattern.

A

B

Figure 41-6 A, Eversion of the dorsal mucosal layer using a continuous horizontal mattress pattern. B, Close­up view of the completed three-layer closure.

A 30-Fr Foley catheter is placed in the urinary bladder and the cuff is inflated. Before any inci­sion is made, two lines of the ventral vaginal mucosa are dorsa lly everted and sutured over the Foley catheter with No. 0 absorbable suture using an interrupted horizontal mattress pattern, leaving adequate mucosa to allow excision and further suturing (Figure 41-7). Suture placement is continued caudally to approximately 2 em cranial to the vulvar labiae. The two lines of dor­sally everted mucosa are excised to create four fresh-cut edges of vaginal mucosa (Figu re 41-8). These debrided edges are then apposed with

Figure 41-7 Dorsal eversion of ventral vaginal mucosa over 30-Fr Foley catheter and sutured using an interrupted horizontal mattress pattern.

Figure 41-8 Excision of dorsally everted vaginal mucosa, creating four fresh-cut edges of vaginal mucosa.

Urethral Extension (Urethroplasty) 225

No. 2-0 absorbable suture using a simple contin­uous pattern (Figure 41-9) .

McKinnon Technique

Correction of urovagina in mares caused by severe perineal conformation abnormalities can be accomplished with this technique5

,6 by providing a wide, long, and strong urethral extension. This technique is recommended when the urethra opening needs to be extended far caudally and increased tissue tension is present. Minimal tissue tension is exerted o n the completed tunnel. Ini­tially, a steep learni ng curve for this tech nique is encountered, but it can be easily performed with experience. In addition, disruption of the blood supply should be avoided during the tissue flap dissection.

A 3D-Fr Foley catheter is placed in the u rinary bladder and the cuff is inflated. The caudal border of the transverse urethral fold is grasped on midline with All is tissue forceps and retracted caudally. A horizontal mucosal incision is made 2 to 4 cm cranial to the caudal edge of the trans­verse urethral fold extending slightly dorsocau­dally along the left and right vaginal wal ls (Figure 41-10). This incision should end at the vulvar labia half to two thirds of the distance between the vaginal floor and vaginal roof. The transverse ure­thral fold and vaginal wall mucosal tissues are undermi ned so that the free tissue flaps are reflected caudally and axially, respectively. Dis­section of transverse urethral fold tissue should

Figure 41-9 Apposition of freshly debrided mucosal edges using a simple continuous pattern.

226 FEMALE UROGENITAL SURGERIES

Figure 41-10 Caudal retraction of the transverse urethral fold allowing an incision to be made into the transverse urethral fold. The proposed incision is shown with dotted lines. The incis ion should end at the vulvar labia half to two thirds of the distance between the vaginal floor and roof.

allow 3 to 6 em of caudal reflection, while the vaginal wall tissues are reflected past midline without tension (Figure 41-11) . The final config­uration is in the shape of a Y, with the base of the Y caudaL Beginning at the right cranial junction of the transverse fold and vaginal wall incision, reflected tissues are apposed with No. 2-0 ab­sorbable suture using a Connell pattern, ending at the midpoint of the transverse urethral fold reflection (Figure 41-12). The second suture line is performed on the left side in the same manner, continuing caudally ending at the caudal edge of reflected vaginal wall (Figure 41-13). It is impor­tant to maintain minimal suture tension on the suture line and invert all tissue edges. Exposed submucosal tissues created dorsally by transverse fold and vaginal mucosal dissection are allowed to heal by second intention.

When indicated, a Caslick's procedure is per­formed after all urethroplasty techniques.

>;t.S~ ;1;.. ~ •

Figure 41-11 Caudal reflection of the transverse urethral fold and axial reflection of the vaginal wall mucosa after dissection.

1¥,S .. ;(~.

Figure 41-12 The reflected transverse urethral fold and vaginal wall are apposed using a Connell pattern beginning at their cranial junctions.

•

•

•

,

•

,

,

Figure 41-13 The second suture line begins on the opposite side in the same manner, continuing caudally ending at the caudal edge of the vagina walL The com­pleted urethral extension is in the shape of a Y, with the base of the Y pointing caudal.

POSTOPERATIVE CARE

Postoperative Care

Exercise Restridions: Small-paddock turnout should be maintained for 30 days. Medications: Broad-spectrum antibiotics are administered for 7 to 10 days. A nonsteroidal anti­infiammatory agent is administered for 3 to 5 days. Catheter Removal: Mares should be monitored closely to determine their ability to urinate ade­quately. The Foley catheter is removed within 3 days postoperatively. Other: The reproductive tract should not be examined for 2 to 4 weeks after surgery, and the mare should have 45 to 60 days of sexual rest.

EXPECTED OUTCOME

Primary healing is reported to occur in appro­ximately 85% to 89% of urethroplasty proce-

Urethral Extension (Urethroplasty) 227

dures. 3•S Short-term complications such as dehis­

cence or fistula formation are reported to occur in 11 % to 15% of all described techniques.'" When complications arise, subsequent surgeries are essen­tial to improve the chances for complete healing. Postoperative conception rates are reported to be 64% to 92% within 1 year postoperatively.3's Recur­rence of urovagina is uncommon, unless a signifi­cant change in perineal conformation occurs.

COMPLICATIONS

Suture dehiscence and fistula development along the suture line are the most common complica­tions. Fistula development is most commonly observed at the junction of the transverse urethral fold and vaginal wall reflexion. These complica­tions can be avoided by precise dissection, metic­ulous suture placement, and reduced tension on apposed tissues. If a fistula develops, an attempt to repair the fistula should be pursued to minimize the risk of endometriti s, persistent urovagina, and infertility.

Leaving the indwelling urinary catheter in place for longer than 3 days may result in cystitis. If cystitis does occur, the catheter is removed, the urine is cultured, and appropriate antimicrobials are administered until bacteria are no longer isolated .}

REFERENCES

I. Beard W: Standing urogenital surgery, Vet Clill N Am Equine Pmct 7:669,1991.

2. Baird AN: Surgical management of urovagina in the mare, Southwest Vet 38:36,1987.

3. Brown MP, Colahan PT, Hawkins DL: Urethral extension for treatment of urine pooling in mares, ] Am Vet Med Assoc 173: 1005, 1978.

4. Shires GM, Kaneps AJ: A practical and simple surgi­cal technique for repair of urine pooling in the mare, Proc Am Assoc Eqllil'le Pract 32:51, 1986.

5. McKinnon AO, Belden JO: A urethral extension technique to correct urine pooling (vesicovaginal reflux) in mares, J Am Vet Med Assoc 192:647,1988.

6. Easley JK: Diagnosis and treatmen t of vesicovaginal reflux in the mare, Vet Clin N Am Equine Pmct 4:407, 1988.

CHAPTER 42

Third-Degree Perineal Laceration Repair John C. Janicek

INDICATIONS

Dystocia, traumatic breeding, or conversion of a rectovaginal fistula into a third-degree perineal laceration for subsequent repair.

EQUIPMENT

Long handled instruments and monofilament absorbable suture materials are required. Self­retaining retractors (Balfour, modified Finochietto) and a good light source (floor lamps, headlamp, or fiberoptic lights) are useful but not required.

PREPARATION AND POSITIONING

Surgery is delayed for 4 to 6 weeks following the laceration to allow wound contraction and inflam­mation to subside. Delaying surgery for this period allows the wowld edges to strengthen and become clearly defined before repair is attempted. A gruel or pasture diet is fed 3 to 5 days prior to surgery, and the mare is fasted 1 day before surgery.

The mare is restrained standing in a stock, and surgery is performed following epidural anesthe­sia, and sedation if necessary. Once anesthesia is confirmed, the tail is wrapped and securely retracted. Fecal material is removed from the rectum and vagina. The perineal region is rinsed, followed by cleansing of the rectal and vaginal lumens with a dilute povidone-iodine solution. The perineal region is then aseptically prepared.

228

The preparation solution should be rinsed with ster ile saline, not alcohol, as alcohol may cause excessive irritation.

PROCEDURE

One- and two-stage repair techniques are described. A one-stage repair is preferred; however, a two-stage repair should be performed if excessive tension is present during surgery. No distinct advantage or disadvantage exists between techniques. Principles for all techniques include initial creation of rectal and vaginal shelves, minimal tissue tension, and maintaining a soft manure consistency after surgery. All repair tech­niques close the defect from cranial to caudal. Modification of the techniques can be performed based on surgeon preference.

Towel clamps or retention sutures are posi­tioned along the dorsolateral and ventrolateral aspects of the laceration to provide exposure. The cranial extent of the laceration is extended approximately 3 cm, creating a rectal and vaginal shelf. Dissection is continued laterally and cau­dally along the scar tissue line into the submucosa until the tissue flaps created can be apposed on midline without tension (Figure 42-1). Both mucosal surfaces are dissected 2 cm or more.

One-Stage Repair

Goetz Technique Using No.1 absorbable suture, a six-bite pattern is used to close the rectovaginal shelf.l The suture

------------------------------------------------------------...............

,

Figure 42-1 Surgical dissection of a third-degree peri nea l lace ration prior to surgical repair. The recto­vaginal shelf is reflected with the proposed incis ion line (dotted lille) shown.

pattern begins with in the vaginal lumen, allowing the knot to be secured within the vaginal lumen (Figure 42-2). Sutures are positioned approxi­mately 1 em apart; the suture pattern includes the vaginal mucosa but does not penetrate the rectal mucosa. The vaginal mucosa is closed over the newly created rectovaginal shelf with No. 0 absorbable suture using a continuous horizontal mattress pattern. The rectal mucosa is left to heal by second intention. Closure of the rectovaginal shelf and vaginal mucosa should extend to the cutaneous perineum. Caslick's procedure is then performed to appose the vulvar opening.

Modified Goetz Technique The vaginal mucosa is inverted into the vaginal lumen with No. 0 absorbable suture using a Connell or Lembert pattern.2

-4 This suture pattern

is continued caudally to reconstruct the cranial half of the defect and then tied but not cut. Using No. I absorbable suture, purse-string sutures are used to close the rectovaginal shelf (Figure 42-3). Sutures are positioned approximately 1 cm apart and should not pass through the vaginal or rectal mucosa. O nce the cranial half of the rectovaginal

Third-Degree Perineal Laceration Repair 229

Figure 42-2 The rectovaginal shelf is closed with a six-bite pattern. The pattern should begin and end in the vaginal lumen without penetrating the rectal mucosa.

Figure 42-3 The vaginal mucosa is inverted into the vaginal lumen using a Connell pattern and the recto­vaginal shelf is closed using a purse-string pattern.

shelf is reconstructed, closure of the vaginal mucosa is completed. followed by closure of the remaining caudal half of the rectovaginal shelf. The rectal mucosa is everted into the rectal lumen with No. 0 absorbable suture using a

•

230 FEMALE UROGENITAL SURGERIES

Cushing or Lembert pattern (Figure 42-4). Closure of the rectovaginal shelf and mucosal sur­faces should extend to the cutaneous perineum. A Caslick's procedure is then performed to appose the vulvar opening.

Semitransverse Closure Technique Small marker incisions are made at the ventral aspect of the perineal body along the left and right mucocutaneous junctions5

; these markers will be used as the ventrocaudal points of the triangle used to construct the perineal body. The scar tissue mucosal junction along the rectovaginal shelf is incised longitudinally and divided in its entirety. Rectal and vaginal mucosae are under­mined approximately 7 to 10 cm from the recto­vaginal shelf. Beginning approximately 4 cm cranial to the external anal sphincter, a mucosal incision is made from the lateral edge of the rec­tovaginal shelf ventrocaudally toward the original marker incision. A triangle-shaped section of mucosa is excised; the exposed triangular section of submucosa will form the perineal body when sutured. The center of the rectovaginal shelf is grasped with Allis tissue forceps, pulling the shelf caudally to the cranial border of the proposed perineal body. The final configuration is in the shape of a Y, with the base of the Y pointing caudal. Beginning at the deepest corner on the right side, the rectovaginal shelf is reconstructed with No. 2 absorbable suture using a simple

-

/ J1t-_ ;f. •.•. r.-~ .... _

Figure 42-4 The rectal mucosa is everted into the rectal lumen using a Cushing pattern.

continuous pattern ending at the center of the shelf. The left side is closed in the same manner. Rectal and vaginal mucosa surfaces should not be penetrated.

Perineal body reconstruction begins at the caudal edge of the newly formed rectovaginal shelf and is continued caudally. The first suture incorporates the caudal end of the newly formed rectovaginal shelf and the right and left sides of the perineal body. The dorsal portion of the per­ineal body is closed first with No. 2 absorbable suture using a Cushing pattern. Incorporation of the rectal, vaginal, or anal mucosa should be avoided during closure. The remainder of the perineal tissue is closed with No. 2-0 absorbable suture using a simple interrupted pattern. Caslick's procedure is performed to appose the perineal skin and vulvar opening.

Two-Stage Repair

Aanes Technique The vaginal mucosa is inverted into the vaginal lumen with No. 0 absorbable suture using a Connell or Lembert pattern.6

,7 This suture pattern is continued caudally to reconstruct the cranial half of the defect and then tied but not cut. Using No.1 absorbable suture, purse-string sutures are used to close the rectovaginal shelf (see Figure 42-3). Sutures are positioned approximately 1 cm apart, avoiding the vaginal and rectal mucosa. If an excessive amount of tension or dead space is present, partial tightening of the purse-string sutures along with sagittally oriented simple inter­rupted sutures will help obliterate dead space (Figure 42-5). Once the cranial half of the recto­vaginal shelf is reconstructed, closure of the vaginal mucosa is completed, followed by closure of the remaining caudal half of the rectovaginal shelf. Optionally, the rectal mucosa may be inverted into the rectal lumen with No. 2-0 absorbable suture using a Cushing or Lembert pattern. Closure of the rectovaginal shelf is COI1-

tinued to the level of the cutaneous perineum. Closure of the perineal body is performed 3 to

4 weeks after the first surgery if the rectovestibu­lar shelf is completely healed. If dehiscence occurs or a fistula is present, the first stage must be repeated. Local anesthesia of the perineal body or epidural anesthesia is used. Closure of the per­ineal body is performed as described in the per­ineal body reconstruction technique (see Chapter 40). A triangular section of the vestibular mucosa

,

,

,

A Figure 42~5 A, Suture pattern placement in the cranial area of a third-degree perineal laceration repair when excessive loss of tissue or thick, inelastic connec­tive tissue is present. When the purse-string suture is tightened, tension on the connective tissue produces a transverse ridge in the rectal submucosa that reduces the diameter and elast icity of the rectum.

c Figure 42-5 C, Sagittally oriented simple inter­rupted sutures are then placed from rectal submucosa to vaginal submucosa to obliterate dead space.

Third-Degree Perineal Laceration Repair 231

B Figure 42-5 B, To prevent this complication, the purse-string suture is tied before the ridge starts to

form.

D "'$i.e- .(_ ... £(#..,., ,

Figure 42-5 D, Tissues are approximated without excessive tension. Several of these purse-string sutures with their associated simple interrupted sutures may be necessary in mares that have suffered excessive tissue loss or that have developed excessive fibrosis.

232 FEMALE UROGEN ITAL SURGERIES

is reflected ventrally and removed from each side. with the triangle apex pointing cranially and the base along the mucocutaneous junction of the perineum (Figure 42-6). Closure of the ventral vestibular mucosaJ margins should be performed in a cranial-to-caudal manner with No. 2-0 ab-

(

A

•

, ,

sorbable suture in a simple continuous pattern (Figure 42-7). Deep perineal tissues should be apposed with No. 2-0 absorbable suture using a simple interrupted pattern. Perineal ski n is apposed with No. 0 nonabsorbable suture using Ford interlocking pattern (Figure 42-8).

B

Figure 42-6 A, Proposed area of vestibular Illllcosa to be removed (dotted lilies) for perineal body reconstruction. B. Caudolateral view of pro­posed area of vestibular mucosa to be removed (dotted lilies) for perineal body reconstruction.

Figure 42-7 Cranial-to-caudal closure of the ven tral vestibular mucosa margin using a simple con­tinuous pattern .

Figure 42-8 Apposition of submucosal perineal tissue is shown using a ser ies of simple cont inuous patterns. Casli ck's procedure is performed to oversew the submucosal perineal tissues and appose the vulvar lips.

POSTOPERATIVE CARE

Postoperative (are

Exercise Restrictions: Sma ll-paddock turnout should be maintained for 30 days. Medications: Broad-spectrum antibiotics are administered for 7 to 10 days. A nonsteroidal anti­infiammatory agent is administered for 3 to 5 days. Suture Removal: Perineal and Caslick's sutures should be removed 10 to 14 days after surgery. Dietary Modifications: Free-choice access to grass, a gruel diet, or both should be provided for 30 days, with gradual return to normal diet. Occa­sionally, mineral oil may be added to the diet to maintain a soft manure consistency. Other: Sexual rest is recommended until the fol­lowing breeding season.

EXPECTED OUTCOME

Primary healing is reported to occur in approxi­mately 75% to 90% of repaired third-degree per­ineal lacerations.2

-7 Short-term complicat ions

Third-Degree Perineal laceration Repair 233

such as dehiscence or fistula formation are reported to occur in 12% to 24% of all surgical repairs. 2,4,6,7 Subsequent surgeries are essential when complications arise to improve the chances for complete healing. Conceptio n rates are reported to be 75% to 92% with in 1 year after surgery.2.4,6,7 Third-degree lacerations recur in 5% to 50% of foal ing mares due to the inelasticity of the resultant scar t.issue.2

-4

,6.7

COMPLICATIONS

Suture dehiscence and subsequent fistula devel­opment are possible. These complications can be avoided by precise d issection, adequate tissue pur­chases) and reduced tension on apposed tissues. Fistula formation may result in fa ilure to conceive due to endometritis) pneumovagina) or contin­ued fecal contamination of the vaginal lumen. Urovagina may be a consequence of the mare)s natural perineal conformatio n or the result of altering the perineal confo rmation during a rec­tovaginal fistula repair and can be addressed with a urethroplasty procedure.2 Mares should be mo nitored closely during subsequent foa lings because the fibrous tissue from the repair may reduce the elasticity of the birth canal and predis­pose the mare to additional birthing trauma.7 As the sutures are progressively placed in the caudal tissues) care must be taken to avoid narrowing of the rectal lumen) which will predispose the mare to tenesmus and constipation.

COMMENTS

Epidural anesthesia is occasionally insufficient for some rectovaginal procedures. Local anesthetic techniques have been developed to ei ther supple­ment or replace epidural anesthesia. The perineal area can be desensitized by infiltrating local anes­thetic laterally between the rectum and the pelvis. A needle long enough to extend approximately 1 inch cranial of the area to be desensitized sho uld be used. One hand is inserted in to the rectum and the needle is inserted through the skin at the 9 to 10 o'clock position lateral to the rectum. The needle is then advanced parallel to the rectum in the loose connective tissue lateral to the rectum. Twenty to 40 mL of local anesthetic are injected as the needle is withdrawn. The procedure is then

234 FEMALE UROGENITAL SURGERIES

Pudendal n.

Caudal rectal n.

e;" (>,..-.-t;" .1.-"", ____ Figure 42-9 Illustration for performing subsacral anesthesia in the horse. The left hand is placed in the rectum to identify the ventral sacral foramina and a needle is inserted on midline a third of the distance from the anus to the base of the tail, directed toward the foramen identified by the left hand.

repeated on the other side at the 2 to 3 o'clock position.

Another technique of subsacral anesthesia has been described. The tail is wrapped and retracted dorsally. One hand is inserted into the rectum to locate the sacral promontory. The hand is drawn back along the sacrum 2 to 3 em from midline to locate the ventral sacral foramina. By counting back, the third ventral foramen (exit of the pudendal nerve) is found. The index or middle finger remains on this point (Figure 42-9) . With the other hand a needle (LIp to 6 inches in length) with a short beveled point is inserted on midline a third of the distance from the anus to the tail base, and directed toward the ventral sacral foramen. A syringe is attached to the needle and approximately 20 mL of anesthetic solution is injected. The syringe is removed and the needle withdrawn 5 to 6 em until the point reaches the fou rth sacral foramen (exit of the caudal rectal nerve) and 20 mL of anesthetic solution is like­wise injected. The entire procedure is repeated on the other side so that a total of 80 mL of anaes­thetic is required. Within 5 to 20 minutes areas

desensitized by this block include the perirectal region, the entire caudal region overlying the semitend inosus and semimembranosus muscles, and most of the perineum excluding the vulva and the area immediately surrounding the vulva. In males, the penis and retractor penis muscles will be desensitized. 8

REFERENCES

I. Beard W: Standing urogenital surgery, Vet c/in N Am Equine Pract 7:669, 1991.

2. Belk nap JK, Nickels FA: A one-stage repair of third­degree perineal lacerations and rectovestibular fistu­lae in 17 mares, Vet Surg 21 :378, 1992.

3. Stjck1e RL, Fessler JF, Adams SB: A single-stage tech­nique for repai r of rectovestibular lacerations in the mare, Vet SlIrg 8:25, 1979.

4. O'Reilly JL, Maslean AA, Lowis TC: Repair of third­degree perineal laceration by a modified Goetz tech­nique in twenty mares, Equille Vet J 10:2, 1998.

5. Phillips TN, Foerner JJ: Semitransverse closu re tech­nique for repair of perineal lacerations in the mare, Proc Am Assoc Equine Pract 44: 191, 1998.

6. Aa nes WA: Surgical management of foaling injuries, Vet Clill N Am Equine Pract 4:417, 1988.

7. Colbern GT, Aanes WA, Stashak TS: Surgical man­ageme nt of perinea l lace rations and rectovestibular fi stulae in the mare: a retrospective study of 47 cases, ] Alii Vet Med Assoc 186:265. 1985.

Third-Degree Perineal l aceration Repair 235

8. Popescu P, Paraipan V, Nicolescu V: Anestezia sub­sacrala 1a taur si la cal. Probleme ZootelJl/ice SI Vet­erillare Of. 3:46, 1958. In Westhues M, Fritsch R: Anilllal allaesthesia, Vol. 1, p. 180, Edinburgh and London, 1964, O liver and Boyd. ("Local Anaeste­sia" translated from German by A.D.Weaver)

CHAPTER 43

Rectovaginal Fistula Repair John C. Janicek

INDICATIONS

Dystocia. traumatic breeding, or unsuccessful third-degree perineal laceration repair resulting in rectovaginal fistula formation.

EQUIPMENT

Long-handled instruments and monofilam ent absorbable suture materials are required . An SO­degree scalpel handle is helpful for the direct repair technique described. Self-retaining retrac­tors (Balfour, mod ified Finochietto) and a good light source (floor lamps) headlamp, or fiberoptic lights) are useful but no t required.

PREPARATION AND POSITIONING

Surgery is delayed fo r 4 to 6 weeks following fistula formation to allow wound contraction and inflammation to subside. Delaying surgery for th is period allows the wound edges to strengthen and become clearly defined before repair is attempted. A gruel or pasture diet is red 3 to 5 days prior to surgery, and the mare is fasted 1 day before surgery.

The repair can be performed with the horse standing or under general anesthesia. For stand­ing procedures, the mare is restrained in a stock, and surgery is performed folJowing epidural anes­thesia) and sedation if necessary. Once anesthesia

236

is confirmed) the tail is wrapped and securely retracted. Fecal material is removed from the rectum and vagina. The perineal region is rinsed, followed by cleansing of the rectu m and vagina with a d ilute povidine-iodine solution. The per­ineal region is then aseptically prepared. The preparatio n solution should be rinsed wi th sterile saline) not alcohol) as alcohol may cause excessive irritation.

PROCEDURE

Vario us repair techniques are described. Princi­ples for all techniques include complete debride­ment of the fistula margin, minimal tension on the repair, and maintaining a soft manure consis­tency after surgery. Modi fi cation of the techniques can be performed based on surgeon preference.

Direct Repair

Fistulas up to 10 em have been repaired usin g this technique. I This technique preserves the perineal body and anal sphincter) resulting in good primary healing and minimal swell ing and pain after surgery. Complete fistula margin debride­ment, which can be difficult in cranially located fistulas) is the major limitation of the direct repair.

The anal sphincter is dilated with self- retaining retractors o r by placing umbilical tape through the anal sphincter 2 cm lateral to each side of dorsal midline and securing the tape around the base of the tail. Towel clamps or retention sutures are

positioned along the ventrolateral aspect of the sphincter fo r retraction if self-reta ining retractors are not used (Figure 43~ 1). The fistula margin is incised circumferentially (Figure 43-2), exposing the submucosal tissue and incised edges of the rectal and vaginal mucosae (Figure 43~3). Taking large, closely spaced ( 6~ to 8~mm) bites, the

Figure 43-1 Dilat ion of the anal sphincter using umbilical tape secured around the base of the tail and ventrolateral positioning of towel clamps allows good visualization of the rectovaginal fistula.

--

v

Redovaginal Fistula Repair 237

submucosa is apposed transversely with No. 1 absorbable suture using a simple interrup ted pattern. The submucosal sutures should be pre­placed beginning in the lateral aspects of the fistula and tightened after all sutures have been preplaced. Care should be taken to avoid purchase of the rectaJ and vaginal mucosa within these bites (Figure 43~4). The rectal mucosa is then apposed transversely with No. 0 absorbable suture using a continuous horizontal mattress pattern (Figure 43-5), Closure of the vaginal mucosa is optional.

Schiinfelder Technique

FistuJas up to 6 em have been repaired with this technique.2 As long as principles of flap develop-

..

~U;;",";C. •• l'4"­

Figure 43-3 Exposure of fresh submucosal tissue and incised edges of the rectal and vaginal mucosae,

Figure 43-2 Circumferential inci­sion of the fi stula using an 3D-degree scalpel handle.

•

238 FEMALE UROGENITAL SURGERI ES

A B ~~~ ... ~. -

Figure 43-4 A, Preplacement of submucosal suture pattern in a transverse direction beginning in the corners of the fistula using a simple interrupted pattern. B, Sagittal cross section of submucosa suture place­ment. Avoid penetrating the rectal and vaginal mucosae.

A

B ~~.-~­

Figure 43-5 A, Transverse apposition of the rectal mucosa using a continuous horizontal mattress pattern. B, Sagittal cross section of rectal mucosa suture place­ment.

ment are respected, this technique avoids exces­sive tension on wound closure and minimizes swelling and pain after surgery.

Following full-thickness fistula debridement, a U-shaped vaginal tissue (mucosa and submucosa) pedicle flap is made from the lateral vaginal wall closest to the fistula (Figure 43-6). The base of the flap should be as wide as the fistula and at least two-thirds the length of the flap. The flap length should provide sufficient length to achieve rota­tional transfer to cover the fistula without tension on the flap. The base of the flap should be I to 2

~~~.l>" -

Figure 43-6 Transverse cross section of a dorsally based U-shaped vagina l tissue flap originating from the lateral vaginal waU.

mm from the fistula margin. Once the flap is rotated, the vaginal mucosa faces dorsally into the rectum and its margins should extend at least 2 mm beyond the fistula margin (Figure 43-7). The flap is circumferentially secured to the edges of the fistula with No. 0 absorbable suture using a simple interrupted pattern. The rectal mucosa should not be penetrated when securing the flap to the fistula margin. Closure of the rectal mucosa is not required.

Bemis Technique

This technique can be used to repair large fistu­las.'" Caudally located fistulas can be easily and efficiently repaired, leaving the caudal rectum and anal sphincter intact. The major limitations of this technique are reduced exposure and difficult closure of large cranially located fistulas. Addi­tionally, increased scar tissue formation in the perineal region may compromise the elastic nature of the dorsal vaginal region.

An 8- to lO-cm transverse perineal incision is made equidistant from the ventral surface of the anal sphincter and the dorsal commissure of the

I

Figure 43-7 Transverse cross section of a vaginal tissue fla p rotated into position so that the vaginal mucosa is facing dorsally and its margins are at least 2 mm beyond the fistula margin. The flap is circu rn ­ferentially secured to the edges of the fistula using a simple interrupted pattern.

vulva. Dissection is continued cranially in a hori­zontal plane through the perineal body and rec­tovagi nal shelf, attempting to separate the fistula into two equal-thickness fistulas (rectal and vaginal) (Figure 43-8). The rectal and vaginal mucosae are circwnferentiaUy dissected approxi­mately 2 to 3 em from the underlying tissue sur­rounding the fistula. Avoiding the rectal mucosa) the rectal fistula is transversely closed with No.1 absorbable suture using an interrupted Lembert pattern. The sutures are preplaced beginning in the lateral aspects of the fistula and tightened after all have been prep laced. The vaginal fistula is then longitudinally closed with No. I absorbable suture using an interrupted Lembert pattern. The sutures are preplaced beginning in the rostral and ca udal aspects of the fistula and tightened after all have been preplaced (Figure 43-9). After both fistulas have been closed) the remaining tissue surround­ing and caudal to the fistulas is closed with No. 0 absorbable suture using a simple interrupted pattern. The transverse perineal skin incision can be left to heal by second intention or primarily closed with No. 2-0 nonabsorbable suture using a simple interrupted pattern. The rectal mucosa is transversely apposed with No. 0 absorbable suture

Redovaginal Fistula Repair 239

/

-.;;.e ...... l.J' u -

Figure 43-8 Complete horizontal dissection between the ventral surface of the anal sphincter and dorsal commissure o f the vulva extending through the fis tula to create rectal and vaginal shelves. The dotted lines indicate proposed areas of dissection.

using a continuous horizontal mattress pattern. The vaginal mucosa is longitudinally or trans­versely apposed with No. 0 absorbable suture using a continuous horizontal mattress pattern.

Huber Technique

This technique is a combination of the Bemis and conversion to third-degree laceration techniques that can be used to repair large fistulas.5

.6 Longi­

tudinal division of the vaginal shelf provides exceUent exposure and surgical access for suture placement. Healthy tension-absorbing rectal tissues located between the fistula and perineum are preserved) and broad) generous shelves of perirectal and perivaginal tissues are created.

An 8- to lO-cm transverse perineal incision is made equidistant fro m the ventral surface of the anal sphincter and the dorsal commissure of the vulva. Dissection is continued cranially in a hori­zontal plane through the perineal body and rec­tovaginal shelf) attempting to separate the fistula into two equal-thickness fistulas (rectal and vaginal) (see Figure 43-8) . The rectal and vaginal mucosae are circumferentiaUy dissected approxi-

240 FEMALE UROGENiTAL SURGER IES

-

Figure 43-9 After dissection , the rectal fistula is transversely closed and the vaginal fistula is longitudi­nally closed using an interrupted Lembert pattern. Suture preplacement should begin in the lateral and cranial aspects, respectively, of each fistula. Submucosal tissue surrounding and caudal to the fistula is closed using a simple interrupted pattern. The perineal skin incision can be left to heal by second intention or pri­marily closed using a simple interrupted pattern.

mately 2 to 3 em from the underlying tissue sur­rounding the fistula.

A longitudinal midline incision is made through the vaginal shelf from the fistula caudally to the exterior (Figure 43- 1 0) . The vaginal mucosa is inverted toward the vaginal lumen with No. 0 absorbable suture using a Connell pattern. This suture pattern is continued caudally to recon­struct the cranial half of the defect and then tied but no t cut. If desired, the rectal mucosa is trans­versely apposed from the vagin al side with No. 0 absorbable suture using a Connell pattern from the vaginal side. The rectovaginal shelf is closed with No. 1 absorbable suture using a six-bite purse-st ring pattern. Successive bites are taken in the rectal submucosa, lateral perivaginal tissue, and vaginal submucosa o n each side with the knot tied deep to the rectal mucosa (Figure 43-11 ).

~e-""t.-. t.~ ...... ~­Figure 43-10 Appearance of the surgical area afte r a longitudinal midline incision is made thro ugh the vaginal shelf.

Figure 43-11 Vaginal mucosa inversion towards the vaginal lumen using a Connell pattern. A six-bite purse­string pattern is lIsed to close and el iminate dead space between the rectal and vaginal shelves.

Sutu res are positioned approximately 1 em apart, avoiding the vaginal and rectal mucosa. Once the cranial half of the rectovaginal shelf is recon­structed, closure of the vaginal mucosa is com­pleted, fo llowed by closure of the remaining caudal half of the rectovaginal shelf. The trans­verse perineal skin incision is closed with No. 2-0 nonabsorbable suture using a simple interrupted pattern . If indicated, easlick's procedure is per­formed to appose the vulvar opening.

Klug Technique

Fistulas up to 6 em have been repaired using this technique.7 The KIug technique provides good visualization, a durable and stable closure, and good first-time healing success rate without dis­rupting the in tegr ity of the anal sphincter. Repair­ing a large fistu la using this technique should be attempted with caution. Tissue mobilization is difficult in large fistula repairs and may require an alternative repair method. Cranially located fistu­las shouJd not be repaired with this technique because of inadequate visualization and limi ted working room.

Beginning at the caudal edge of the fistula, an incision approximately 1 cm in depth is made through the vaginal mucosa and submucosa extendi ng caudally to the dorsal commissure of the vulva (Figure 43-12). The vaginal mucosa caudal to the fistula is dissected approximately 2 em and ventrally reflected. The cranial and la teral aspects of the fistula are then horizontally split through the line of scar tissue and separated into rectal and vaginal shelves (Figure 43-13). Dissec­tion of the rectal and vaginal shelves sho uld extend approximately 2 to 3 cm lateral and cranial to the fi stula. Sl ight caudal traction is applied to the cra nial vaginal shelf, and an interrupted vest­over-pants pattern using No.1 absorbable suture is used to close the fi stula (Figure 43-14). The cranial vaginal shelf provides the ventral layer, while the caudal rectal shelf provides the dorsal layer of the repair. A shelf overlap of at least 2 cm should be obtained (Figure 43-15). The remain­ing vaginal submucosa should be apposed with No. 0 absorbable suture using a simple inter­rupted pattern. The reflected vaginal mucosa should be apposed with No. 2-0 absorbable suture usi ng a continuous horizontal mattress pattern. The rectal mucosa is allowed to heal by second intention.

Redovaginal Fistula Repair 241

• A

, ,

)

B ~Ro/T>V"l~ ce~~­Figure 43-12 A, An incision (dotted lilies) approxi­mately 1 em deep is made through the vaginal mucosa and submucosa beginning at the caudal edge of the fistula and extended to the dorsal commissure of the vu lva. Essentia lly, a second-degree per ineallacera tio l1 is created. B, Sagittal cross section indicating the length and depth of the incis ion (dotted lille) made through the dorsal vaginal mucosa and submucosa.

Conversion to Third-Degree Perineal laceration

When fistulas have large diameters or are located very cranial or if minimal perineal tissue is present, conversion into a third-degree perineal laceration and subsequent repair is often recom­mended. Third-degree perineal laceration conver­sion is initiated by incising from the caudal margin of the fistu la through the perineal ti ssues, anal sphincter, and dorsal vulvar commissure. Repair of third-degree lacerations is discussed in Chapter 42.

242 FEMALE UROGENITAL SURGERIES

A

--J

B

Figure 43 w 13 A, Following creation of a second­degree per ineal laceration , the dorsal vaginal mucosa caudal to the fistula is dissected 2 em and ventrally reflected. B, Sagittal cross section of the ventrally reflected vaginal mucosa. The dotted title depicts hori­zontal dissection through the cranial and lateral aspects of the fistula, allowing separation of the fistu la into rectal and vaginal shelves.

POSTOPERATIVE CARE

Postoperative Care

Exercise Restrictions: Small-pen turnout should be maintained for 30 days. Medications: Broad-spectrurn antibiotics are administered for 7 to 10 days. A nonsteroidal anti­infiammatory agent is administered for 3 to 5 days. Suture Removal: Perineal and Caslick's sutures should be removed 10 to 14 days after surgery. Dietary Modifications: Free-choice access to grass, a gruel diet, or both should be provided for 30 days, with gradual return to normal diet. Occa­sionally, mineral oil may be added to the diet to maintain a soft manure consistency. other: Sexual rest is recommended until the fol­lowing breeding season.

A

B

Figure 43w 14 A, Vest-over-pants (dotted line) is used to close the fistula. The first two sutures are placed through the cran ial aspect of the vagi nal shelf and the caudal edge of the rectal shelf. B, Sagittal cross section indicating caudal traction of the vaginal shelf so that at least 2 em of tissue overlap is obtained.

EXPECTED OUTCOME

Primary healing is reported to occur in approxi­mately 65% to 100% of repaired rectovaginal fist ulas.l-lO Short-term complications such as de­hiscence or fistula formation are reported to occur in 6% to 35% of all surgical repairs. '·'o Subsequent surgeries are essential when complications arise to improve the chances for complete healing_ Post­operative conception rates are reported to be 33% to 92% within I-year postoperatively?,S-9 Recur­rence of rectovaginal fistulas and third-degree perineal lacerations during subsequent foalings are reported in 8% to 10% of mares as a result of stress on inelastic tissues secondary to excessive scar tissue deposition.

A

B

Figure 43-15 A, Closure of the fistula. B, Sagittal cross section of suture placement for closure of the fistula.

COMPLICATIONS

Suture dehiscence and subsequent fistula devel­opment are possible. These complications can be minimized by precise dissection, adequate tissue purchases, and reduced tension on apposed tissues. Fistula recurrence may result in failure to conceive due to endometritis, pneumovagina, or continued fecal contamination of the vaginal lumen. Urovagina may be a consequence of the

Rectovaginal Fistula Repair 243

mare's natural perineal conformation or the result of altering the perineal conformation during a rectovaginal fistula repair, and may be addressed with a urethroplasty procedure.' Mares should be monitored closely during subsequent foalings because fibrous tissue may reduce the elasticity of the birth canal and predispose the mare to addi­tional birthing trauma.s As the sutures are pro­gressively placed in the caudal tissues, care must be taken to avoid narrowing of the rectal lumen, which will predispose the mare to tenesmus and const ipation.

REFERENCES

1. Adams S, Benker F, Brandenburg T: Direct rec­tovestibular fistu la repair in five mares, Proc Am Assoc Equine Pmct 42:156,1996.

2. Schonfelder AM, Sobiraj A: A vaginal mucosal pedicle flap technique for repa ir of rectovaginal fistu la in mares, Vet Surg 33:517, 2004.

3. Aanes WA: Surgical management of foaling injuries, Vet eli" N Am Equine Pract 4:417, 1988.

4. Beard W: Standing urogenital surgery, Vet Clin N Am Equine Pract 7:669,1991.

5. Huber MJ: Modified technique for single stage rec­tovestibular fistula closure in three mares, Equine Vet J 30:82, 1998.

6. Schofield WL: Surgical repair of rectovaginallacer­ations and fistulae in 20 mares, Irish Vet J 5 1 :468, 1998.

7. Klug E, Almdida-Sampaio AlS, Aupperle H: Repair of the rectovaginal fistula in the mare a new sur­gical approach, Pferdeheilktmde 17:600,2001.

8. Colbern GT, Aanes WA, Stashak TS: Surgical man­agement of perineal lacerations and rectovestibular fistulae in the mare: a retrospective study of 47 cases, J Am Vet Med Assoc 186:265, 1985.

9. Belknap lK, Nickels FA: A one-stage repair of third­degree perineal lacerations and rectovestibular fis­tulae in 17 mares, Vet Slirg 21:378, 1992.

10. Hilbert J: Surgical repair of recto-vaginal fistulae in mares, Aust Vet J 57:85, 1981.

IMITED BDOMINAL

URGERIES

245

CHAPTER 44

Inguinal Herniorrhaphy David A. Wilson

INDICATIONS

Repair of congenital inguinal hernias is indicated for hernias that have not resolved by 3 to 6 months of age, for hernias that are gradually increasing in size, or in cases in which owners request elective repair.' -4 Foals with large hernias that have rup­tured into the subcutaneous space or exhibit clinical signs of abdominal pain should not be repaired in the field because of the difficulty in reducing these hernias and the potential need for abdominal exploration.

EQUIPMENT

No special equipment is requi red.

PREPARATION AND POSITIONING

The horse is placed under general anesthesia and positioned in dorsal recumbency. Preoperative administration of antibiotics (e.g., penicillin and gentamicin) and nonsteroidal antiinflammatory agents are recommended. The caudoventral ab­domen is clipped and prepared for aseptic surgery, with care taken to not damage or irritate the sensitive inguinal skin. Aggressive scrubbing and the use of alcohol should be avoided. Sterile saline should be used to ensure complete removal of any surgical soap. If there is any concern that the reduction may be prolonged, the bladder should be catheterized to minimize urine conta­mination of the surgery site.

246

ANATOMY

The primary structures involved in congenital inguinal hernia repair are the superficial and deep inguinal rings, the inguinal canal, the vaginal tunic and vaginal ring, the testicles, and the in­testine within the hernial sac. The superficial inguinal ring is formed by a slit in the aponeuro­sis of the external abdominal oblique. Its lateral border continues as the femoral fascia, which is the medial fascia of the thigh. The deep inguinal ring is formed by the internal abdominal oblique muscle and arcus inguinalis (inguinal ligament). The inguinal canal is a potential space between the deep and superficial inguinal rings. The vaginal tunic is an evagination of peritoneum that encases the testicle and spermatic cord. The vaginal ring, a transition between the peritoneum and the vaginal tunic, is a thickened ring that plays the role of a limiting barrier against indirect herniation.

PROCEDURE

Congenital inguinal hernias in the foal are gener­ally classified as indirect inguinal hernias in that the intestines pass through an intact vaginal ring and are usually contained within the vaginal canal and cavity (the virtual space between the parietal and visceral layers of the vaginal tunic) (Figure 44-1 ). The approach is directly over the affected inguinal canal. A 10-cm incision is made centered over the superficial inguinal ring, starting at its cranial margin and extending caudal to the

Small

Testicle ~t;,.k",-_

Figure 44-1 Indirect inguinal hernia viewed from the abdomen, and skin cut away from scrotum showing intestine and testicle within the scrotum.

scrotum. Intestine is typically noted within the vaginal tunic. Occasionally, the parietal vaginal tunic or peritoneum in the region of the vaginal ring tears and the intestine is directly under the skin. Ruptures of the tunic or peritoneum can be very large and are an indication that surgical repair is indicated (Figure 44-2). The skin of very young foals is thin. Stretching and thinning of the skin can lead to blood supply disruption, ischemic necrosis, and subsequent sloughing of the skin.

If the vaginal tunic is intact, a combination of blunt and sharp dissection is used to free the tunic and internal spermatic fascia from the external spermatic fascia. The vaginal tunic and testicle are twisted in order to "milk" the intestine back into the abdominal cavity (Figure 44-3). A transfixa­tion suture is then placed. while maintaining the twist, within the inguinal canal. The testicle and tunics are then emasculated distal to the ligature.

For ruptures of the vaginal tunic, the tear is identified and the intestines are replaced into the

• abdomen. "Last-out, first-in" is the guideline for feeding the loops of bowel back in the abdomen. This may require enlargement of the vaginal ring depending on the condition of the intestine. Care should be taken to not inadvertently disrupt the delicate intestinal mesentery. The testicle and tunic are then emasculated in a routine manner.

Inguinal Herniorrhaphy 247

Vaginal tunic and testicle

Figure 44-2 Direct inguinal hernia showing in­testines outside the abdomen next to the vaginal tunic containing the testicle.

7Le~t.J.-__ . -

Figure 44-3 For indirect inguinal hernias. the vaginal tunic can be tvvisted, starting at the testicle and tvvisting the vaginal tunic to force the intestines into the abdomen.

The superficial inguinal ring is then closed with preplaced absorbable sutures (Figure 44-4) . A simple interrupted or cruciate pattern using No. 1 or No.2 absorbable monofilament suture mate­rial is recommended for closure of the superficial inguinal ring. Use of a blunt-point hernia needle (The Torrington Company, Torrington, Conn.) reduces the risk of inadvertently penetrating the large vessels in the surgical field. The sutures

248 L IMITED ABDOMINAL SURGERIES

~t....,t-... ~.~-

Figure 44-4 Prep laced sutures in the superficial inguinal ring to close inguinal hernia.

should be placed at varying distances from the edges of the ring to avoid creating excessive tension in one fascial plane. The subcutaneous tissues and skin may then be closed with absorbable sutures. Pass ive drains may be consid­ered in the presence oflarge dead spaces. Alterna­tively, the subcutaneous tissues and skin may be left open to heal by second intention, particularly in cases with extensive preoperative subcutaneous dissection, a large amount of dead space, or com­promised integrity of the overlying skin.

POSTOPERATIVE CARE

Postoperative Care

Exercise Restrictions: The foal should be rested in a stall or small paddock for at least 2 weeks prior to returning to unrestricted pasture turnout or turnout with other foals. Medications: Broad-spedrum antibiotics and non­steroidal antiinflammatory agents are generally not necessary. However, the presence of complicating fadors may alter this decision. Tetanus prophylaxis should be current. In most cases, adequate antibod­ies to tetanus will be achieved by passive transfer via colostrum from an appropriately vaccinated mare. other: If placed, drains should be removed within 2 days. Drainage from the drains or from the sui>­cutaneous tissues of open incisions rnay cause scalding of the skin between the legs. The skin surrounding the incision and between the legs should be coated with petroleum jelly to minimize this scalding.

EXPECTED OUTCOME

Edema of the incision site and prepuce may be extensive but generally resolves with conservative therapy. In uncomplicated and elective cases, re­covery is usually straightforward and uneventful.

COMPLICATIONS

The prevalence of complications is low. Seroma formation is probably the most common compli ­cation.s Failure to resect devitalized bowel is prob­ably the most serious complication.6 This can be avoided by careful evaluation of the intestine with or without exploratory celiotomy to evaluate the intestines. In neonates, exploratory celiotomy has the added advantage of being able to remove the umbilical remnants to reduce the incidence of septicemia. If there is preoperative concern about the systemic health of the foal, the viability of the intestine, or the anticipated length or difficulty of the procedure, the repair should be performed at an equine surgical facility, where potential com­plications can be readily addressed.

Uncommon complications include incisional infections, wound dehiscence with evisceration, intestinal prolapse, paralytic ileus, bronchopneu­monia, abdominal adhesions, peritonitis, and colic. In an unpublished review of inguinal hernia repair by the author, the incidence of complica­tions following repair was 13% (4 of 31 cases). [n the only published report identified, the survival rate following inguinal herniorrhaphy was only 50%.'

ALTERNATIVE PROCEDURES

Laparoscopic techniques have been developed to repair readily reducible inguinal hernias and pos­sibly salvage the affected testicle.' "

COMMENTS

Congenital inguinal hernias occur primarily in males. Most resolve spontaneously by 3 to 6 months of age. The cause of congenital inguinal hernias is unknown. but a hered itary predisposi­tion may exist and it is generally agreed that cas­tration should accompany the hernia repair. Development of the hernia is likely related to

increased abdominal pressure and large vaginal rings. In the perinatal period the vaginal rings are large to allow the testicles to descend into the scrotum, but normally contract to less than 2 em during the first 2 weeks of life. Increased abdomi­nal pressu re during parturition may force the sm all intestines into the inguinal canal or scrotum as the foal passes through the birth canal. Strain­ing to pass meconium may also increase abdomi­nal pressure and increase the likelihood for intestines to pass into the inguinal canal. Occa­sionally. the parietal vaginal tunic or the peri ­toneum in the vaginal ring region tears, and the intestines migrate subcutaneously under the skin. Individual intestinal loops may be seen under the skin.

Foals with inguinal hernia(s) generally present with non painful swelling or enlargement of the scrotum or inguinal region. Usually the hernias are reducible, do not cause any clinical signs such as colic, and resolve within a few days to a few months. Conservative therapy including daily monitoring and frequent reduction of the hernia is recommended until the vaginal rings close down and the hernia resolves. There is some concern that foals treated conservatively for inguinal hernias may be predisposed to evisce­ration following castration. Therefore, owners should be aware of this potential complication and instructed to inform their veterinarian at the time of castration. Additionally, the presence of a

Inguinal Herniorrhaphy 249

congenital inguinal hernia should be recorded in the medical record to remind the veterinarian of this potential complication.

REFERENCES

I. Spurlock GH, Robertson JT: Congenital inguinal hernias associated with a rent in the common vaginal tunic in five foals, J Am Vet Med Assoc 193:1087,1988.

2. Hance SR, DeBowes RM, Clem MF, et al: Umbilical, inguinal, and ventral hernias in horses, Comp Cont Educ Pmct Vet 12:862, 1990.

3. Gaughan EM: Inguinal hernias in horses, Comp Con t Edllc Pract Vet 20:1057, 1998.

4. Dietz 0, Richter W: Etiology, ea rly symptoms and treatment of equine inguinal hernia. Praktische Tierarzt 83:712, 2002.

5. Adams SB, Fessler JF: Neonatal inguinal herniorrha­phy. [n Adams SB, Fessler JF, editors: Atlas of equine SLlrgery, Philadelphia, 2000, WB Saunders.

6. van der Velden MA: Ruptured inguinal hern ia in new born colt foals: a review of 51 cases, Equine Vet J 20: 178,1988.

7. Klohnen A, Wilson DG: Laparoscopic repair of scrotal hern ia in 2 foals , Vet Surg 25:414, 1996.

8. Marien T, va n Hoeck F, Adriaenssen A, et al: Laparo­scopic testis-spa ring herniorrhaphy: a new approach for congenital inguinal hernia repair in the foa l, Equine Vet Educ 13:32, 200 I.

9. Boure LP: Laparoscopic surgical techniques in foa ls, Proc ACVS Vet Symp 13:31,2003.

CHAPTER 45

Umbilical Herniorrhaphy David A. Wilson

INDICATIONS

Uncomplicated congenital umbilical hernias that have persisted until 5 to 6 months of age) gradu­ally enlarged over time, or failed to respond to conservative therapy,l Complications may develop in congenital umbilical hernias, which can significantly increase the complexity and expense of repair. One report has shown a com­plication rate of 8.8%.2 Hernia repair before these complications develop is desirable.

EQUIPMENT

No special equipment is required fo r surgical repair of umbilical hernias.

PREPARATION AND POSITIONING

The surgery is performed with the horse under general anesthesia in dorsal recumbency. The ventral abdomen is clipped, prepared, and draped for aseptic surgery. In males, the bladder may be catheterized in males and the prepuce closed with towel clamps or suture to minimize urine conta­mination of the surgery site.

ANATOMY

An umbilical hernia consists of a midline defect in the body wall and an outpouehing of the skin

250

with a peritoneal lining (hernial sac). The hernial sac generally contains small intestine.

PROCEDURE

Closed Herniorrhaphy

An approximately lO-em fusiform incision is cen­tered over the umbilicus. Generally) intestine will be palpable within the hernial sac and the hernia can be readily reduced. The incision is continued through the subcutaneous tissue with care taken to not penetrate the hernial sac. The skin and sub­cutaneous tissues are dissected from the hernial sac (Figure 45-1). At the attachment of the umbilicus, the hernial sac can be very thin and is easily penetrated. 1f the sac is penetrated, the defect in the sac is closed with No. 2-0 absorbable suture material.

The hern ial sac is then inverted into the abdomen (Figure 45-2). Absorbable sutures (No. I or No.2 depending on the size of the foal) are placed in the fibrous hernial ring, with care taken to not incorporate intestine into the suture line (Figures 45-3 and 45-4). The specific suture pattern for closure of the hernial ring is left to the discretion of the surgeon. Simple interrupted, cruciate, and far-near-near-far patterns are com­monly used.

The advantages of the closed method of repair are the relative ease of the procedure and the reduced risk of postoperative peritonitis or evis­ceration. Disadvantages include not being able to thoroughly assess the contents of the hernial sac,

Umbilical Herniorrhaphy 251

A

B Figure 45~ 1 A, Sharp dissection of skin from hernial sac. S, The hernial sac and overlying skin are held before removal of skin from sac.

~C..f.' __

Figure 45-2 Afte r removal of skin from the hernial sac and before closure, the sac is inverted into the abdomen.

Figure 45-1 The fi rst bite of closure inserts the needle into the edge of the fibrous hernial ring and inverted hernial sac.

~t.e..J!:..0'-

Figure 45-4 The hernial sac is inverted into the abdomen and the thickened fibrous ring (arrow) is closed.

the potential for incorporation of intestine in the sutllre line, and, in large hernial sacs (larger than a tennis ball). the potential for ischemic necrosis of the hernial sac and subsequent aseptic peri­tonitis. The closed technique is indicated for repair of most uncomplicated hernias.

Open Herniorrhaphy

The approach for the open technique is similar to the closed technique until the hernial sac is

252 LIMITED ABDOM I NAL SURGERIES

exposed. At this point, the hernial sac is resected to the level of the fib rous ring of the hernia. Careful palpation of the hernial ring will identify a thinned triangular area on the cranial and caudal borders of the ring with the fibrous por­tions of the linea alba in a fusifo rm shape (Figure 45-5). The tissue within this triangular area may be removed.

Closure of the abdomin al wall consists of appositional absorbable sutures (No.1 or No.2 depending on the size of the foal). The suture pat­terns are similar to those recommended for the closed technique. The vest-over-pants or Mayo mattress suture pattern is not recommended because the pattern tends to excessively focus or increase the tension of the suture line rather than simply closing the space between the fibrous por­tions of the hernial ring.3

The only significant advantage of the open technique is the ability to assess the contents of the hernial sac. The disadvantages of the open technique are the slightly increased risk of post­operative evisceration) abdominal adhesions, and

, ,

Palpable border of defect in linea alba

, •

,- Hernial sac

•

A Figure 45~5 A, Careful palpation of the hernial ring will identify a thinned triangular area on the cranial and caudal borders of the ring with the fibro us portions of the linea alba in a fusiform shape. B, The tissue within this triangular area (black arrow) may be removed along with the fibrous tissue forming the base of the triangle (white arrow), in an open herniorrhaphy, Dotted line indicates the line of incision,

peritonitis. The open technique is indicated for repair of large hernias) irreducible hernias, or hernias complicated by enterocu taneous fistula.

The subcutaneous tissue and skin are closed similarly for both open and closed techniques. The suture material and patterns are left to the surgeon's preference. We use No. 2-0 polydiox­anone, polyglactin 910, or poliglecaprone. A sub­cuticular layer in the skin rather than traditional skin closure or the use of absorbable sutures in the skin eliminates the need for suture removal.

POSTOPERATIVE CARE

Postoperative Care

Exercise Restridions: The foal should be rested in a stall or small paddock for at least 4 weeks prior to returning to unrestricted pasture turnout or turnout with other foals. The incision line should be palpated and examined for ade­quate healing before unrestricted exercise is allowed. Medications: If the procedure is uncomplicated, only preoperative antibiotics and anti-inflammatory agents are indicated. Tetanus prophylaxis should be current. Suture Removal: Nonabsorbable sutures should be removed in 10 to 14 days.

EXPECTED OUTCOME

If the margins of the body wall defect are carefully identified during surgery and adequate ti ssue bites are obtained using strong nonreactive suture material, closed and open hernia repairs have a high success rate. Mild periincisional edema is common during the first postoperative week.

COMPLICATIONS

Reported complication ra tes for either surgical hernia repai r or the clamp technique have been reported to be between 7% and 19%.4,5 Seroma formation is probably the most common compli­cation associated with both surgical techniques and generally occurs as a result of inadequate closure of subcutaneous dead space. Hematomas may also occur if inadequate hemostasis occurred during surgery. Generally, hematomas and seromas regress on their own and require no

,

I

\

specific therapy. However, seroma and hematoma formation may progress to subcutaneous infec­tion, which can be determined by the presence of focal tenderness, persistent inflammation, and moisture or discharge at the suture sites. Sub­cutaneous infections are treated with warm com­presses and systemic antibiotic therapy. If not resolved by 10 to 14 days postsurgery, ultrasonog­raphy may be used to identify subcutaneous abscesses and needle aspiration or lancing of the abscesses considered. Uncommon complications associated with the open technique include evis­ceration, abdominal adhesions, and peritonitis.

ALTERNATIVE PROCEDURES

The advantages of hernial clamping or the appli­cation of elastrator rings have been reported to be ease of application and cost. 1,5,6 The primary dis­advantage of hernial clamping is the risk of incor­porating gut into the clamp and inadequate fibrosis of the abdominal wall defect. The proce­dure should be done under general anesthesia with the foal in dorsal recumbency. Clamping is recommended only for hernias that are uncom­plicated, easily reducible, and less than 8 em in length. Additionally, the hernial sac should be easily palpable to ensure there are no contents within the sac when applying the clamp. Some surgeons believe that clamping is easier in females than in males as the prepuce can get in the way in males. In males, the smallest possible clamp should be selected and carefully padded to prevent injury to the foal's sheath.'

COMMENTS

Umbilical hernias are a common congenital defect in young horses. Females are twice as likely as males to have the defect.7 Many hernias are small and will resolve with time or with more conser~ vative measures such as manual daily reduction, the application of a truss, or umbilical clamps.l Umbilical hernias generally require surgery if they persist until 5 to 6 months of age, if they gradu­ally enlarge over time, or if they fail to respond to conservative therapy. Most hernias are uncompli­cated and reducible. Some (8% to 10%) sustain complications that are life threatening and

Umbilical Herniorrhaphy 253

mandate emergency surgery.2,8,9 Hernias that suddenly increase in size, become edematous or painful, or are associated with depression or colic warrant urgent clinical evaluation and exploratory surgery. Hernias that exhibit these signs are not amenable to field surgery, and the horse should be referred to an appropriate surgi­cal facility. Careful evaluation of the umbilical masses by palpation and ultrasonography will help to differentiate complicated umbilical hernias from the uncomplicated, reducible hernias.

The goals of surgical repair of an umbilical hernia are obliteration of the hernial sac and repair of the defect in the abdominal wall. Alter­natives to surgical repair of hernias include the application of hernial clamps or elastrator rings and the injection of irritating substances around the base of the hernial sac. These alternatives are usually successful in obliterating the hernial sac but do not directly repair the defect in the abdom­inal wall.

REFERENCES

1. Adams SB, Fessler 1F: Umbilical herniorrhaphy. In Adams S8, Fessler JF, editors: Atlas of equine surgery, Philadelphia, 2000, WB Saunders.

2. Freeman DE, Orsini 1A, Harrison TW, et al: Compli­cations of umbilical hernias in horses: 13 cases (1972- 1986), JAm Vet Med Assoc 192:804,1988.

3. Orsini JA: Management of umbilical hernias in the horse: treatment options and potential complica­tions, Eqllil1e Vet Educ 9:7,1997.

4. Wilson DA, Baker G1, Boero MJ: Complications of celiotomy incisions in horses, Vet SlIrg 24:506, 1995.

5. Riley CB, Cruz AM, Bailey ]V, et al: Comparison of herniorrhaphy versus clamping of umbilical hernias in horses: a retrospective study of 93 cases (1982-

1994), Can Vet J 37:295, 1996.

6. Greenwood RES, Dugdale OJ: Treatment of umbili­cal hernias in foals with elastrator rings, Equine Vet Educ 5: 113, 1993.

7. Freeman DE. Spencer PA: Evaluation of age, breed, and gender as risk factors for umbilical hernia in horses of a hospital population, Am J Vet Res 52:637,

1991. 8. Steckel RR, Nugent MA: Parietal hernia in a horse,

] Am Vet Med Assac 182:818, 1983.

9. Markel MD, Pascoe JR, Sams AE: Strangulated umbilical hernias in horses: 13 cases (1974-1985),

] Am Vet Med Assoc 190:692, 1987.

INDEX

2-0 m onofilament nonabsorbable sutures, 162 2-0 PDS, usage, 144 3-0 nonabsorbable monofilament suture material, 52,

162 . See also Simple-interrupted 3-0 monofil ament non absorbable sutures

4.S-mm cortical bone screw, dorsopal mar rad iograph. See Carpus

IS-gauge orthopedic wire, usage, 5 1-52, 51 f 20-gauge I-inch catheter, 55

placement. See Palmar ve in 22-gauge I-inch catheter, 55

placement. See Palmar vein 3D-em ventral midline incision, 158f 30-Pr Foley catheter, placement, 223, 225 60-mL syringe, usage, 21£

A

Aanes technique. See Third-degree perineal laceration • repair

Abcessation. See P3 Abdominal crypto rchid, 198f. See also Incomplete

abdominal cryptorchids Abdominal retention, 197f Abdominal testicle

exteriorizatio n, 198f remova l, modified para inguinal approach, 199f

Abduction, prevention. See Limbs Acepromazine, usage, 30-31, 35t Acrylic hoof material, usage. See Toe Adhesives. See Tissue Adson forceps, 7f. See also Browll-Adson forceps Albuginea, 207f Allis forceps, 8f Allis tissue forceps

schematic,l72f usage. See Soft palate

Alpha2 agonists (a ragonists), 30-32 advan tage, 31-32 dissociative combinations, 35-36 dissociative-guaifenesin combinations, 36

Aminoglycosides, administration, 25 Analgesia. See Epidural analgesia Anal sphincter

dilation, umbilical tape (usage), 237f ventral surface, horizontal dissection, 239f

Anesthesia. See Epidural anesthesia; Field anesthesia; Injectable general anesthesia

induction/recovery. See Injectable field anesthesia

Page numbers followed by t indicate table; f, figure.

255

Anesthetic depth, 37 Anesthetics. See Injectable anesthetics Angiotribe forceps, 157 Angular limb deformity, 50, 52

differentia l diagnoses, 53 origin, 54

Annular ligament constriction. See Palmar annular ligament incision. See Proximal annular ligament proximal border, incision, 69f transection, 69f

scissors, usage, 70f Annular ligament desmotomy

anatomy, 67 bandaging,'lO complications,70-7l equipment, usage, 67 exercise restriction, 70 indications, 67 intrasynovial m ed ications, 70 medications, 70 outcome, expectation, 70 positioning, 67 postoperative care, 70 preparation, 67 procedure, 67 -68

al ternatives, 71 closed technique, 67-68 open technique, 67

references, 71 suture removal, 70

Antebrachial fascia, perforation, 88f Antibiotics, usage. See Distal limb perfusion Antiseptics, usage. See Skin p reparation Arcus inguinal is, 183f Army-Navy retractor, 9f Articular cartil age atrophy, degree, 118

B

Balfour self-retaining retractor, 222, 236 Bandage cast, 116-117

splitting, 117f usage, 116-117, 117f

Bandages application , 28f. See also Tension suture change, 11 7f material, casting material (placemen t),

117f usage. See Robe rt Jo nes bandage

Bandage scissors. See Lister bandage scisso rs design, 5-6

•

256 I N D EX

Bandaging equipment, 25f indication, 11 8

Bard-Parker blade. See No. 10 Bard-Parker blade

Bard Parker handle, No. JO blade (usage), 76 Bard-Parker No.4 handle, 6£ Basi lhyoid bone, 148f, 158f

lingual process, 148f Battery-operated headlight, inclusion, lOb Belpharospasm, 173 Bemis technique. See Rectovaginal fistula repair Bent table knives, usefulness, 99f Benzodiazepines, 32 Betadine surgical scrub, 4 Bilateral fractures. See Interdental space Biomechan ical forces, 25f Bishop-Harmon tissue forceps, 170, 171 Bistoury knife

No. 10 blade, usage, 76 passage, 68, 69f usage, lOS£. See also Medial patellar ligament

transection Black's method. See Neurectomy Black's technique, 110 Blades. See Scalpel blades Bleeding, control, 95 Blepharoplasty. See Hotz-Celsus blepharoplasty Blunt d issection, usage, 172 Blunt-tipped b isto ury. usage. 104 Body reconstruction. See Perineal body

reconstruction Bolsters

inclusion. See Verti cal mattress su tu res usage. See Tension suture

Bone amputation . See Spl int bone diaphysis. 51 fracture, risk (increase). See Deep navicular bone

fracture lateral hemicircumference, 47f rasp. usage, 95f resection. See Distal splint bone resection sequestrati on, 125

Bony orbit, schematic. 171 f Bradycardia, 31 Breakage. result. 119 Breeding stitch

addition. See Caslick suture li ne ventrality. avoidance. 217

Bridging. See Transphyseal bridging Broad-spectrum antibiotics, 25 Brown-Adson fo rceps. 7£ Brown-Adson thumb fo rceps, inclusion, lOb Brown techniq ue. See Urethral extension Bulbospongiosus muscle, 207f, 212f Bupivacaine. usage. 40 Butorphanol

administration, 35

Butorphanol (Contirmed) sedation, 34 usage, 24, 35t

(

Canaliculus, lacerated ends (alignment), 166 Canines

notch, presence, 124f presence, 125£ usage, 124f

Cannulated 4-mm screw, wing nut/adapter (welding), 56f

Cannulated screw, usage, 57, 58f Carbon dioxide laser, usage, 147 Carmalt forceps. inclusion. lOb Carotid artery, 140f Carpus, 4.5-mm corti cal bone screw (dorsopalmar

radiograph ), 53f Car tilaginous ulna, presence, 47f Caslick's procedure (vulvoplasty). See Urethroplasty

techniques comments, 217-2 18 complications, 217 d ifficulty, 216 equipment, usage, 216 indications, 216 medications, 217 outcome. expectation, 217 performing, 22lf, 233f positioning, 216 postoperative care, 217 p repa ration, 216 p rocedure, 2 16-217 references, 2 18 suture removal, 217

Caslick suture line, breeding stitch (addition), 2I7f Cast application, 113-117

acrylic, application, 116f bandaging, 117 com ments, 11 9-120 complications, 11 8-119 equipment, usage, 113 exe rcise restrictions, 117 indica tions, 113

limb position ing/handling, 113 positio ning, 113 postoperative care, 117- 11 8 preparation, 113 proced ure, alte rnatives, 119 references, 120 supplies, 114£

Casting mater ial, placement. See Bandages Casting tape, partial roll, Iisf Cast layers

separate curing, 114f simultaneous cur ing, 114f

Cast material application, 114-115 handling, 114

Cast proximal limit, orthopedic felt (application) I 14f

Castration. See Cryptorchid castration anatomy, 184 closed technique, 184-185

technique, 184f colic, complication, 192 comments, 193- 194 complications, 189-192 cranial inguinal app roach, 193 emasculators, application. See Closed castration equipment. usage, 182 exercise restrictions, ] 88 exteriorization, maintenance. See Modified closed

castration hemorrhage (excess), complication, 190 hydrocele

complication, 192 formation. See Postcastration

indications, 182 infec tion, complication, 190 intestinal even tration, complication, 191 medications, 188 modified closed technique, 184

performing, l8Sf omental prolapse, com plication, 190-191 open technique, 185

performing, 187f outcome, expectation, 189 penile damage, complication, 192 peritonitis, com plication, 190 persistent stallion-like behavior, complication, 191-

192 positioning, 182-183 postoperative care, 188 preparation, 182-183 primary closure, 193 procedure, 184-188

alternatives, 192-193 references, 194- 195 special circum stances, 185- 188 swelling, complication, 189 techn iques. See Half-closed castration techniques

Cast removal, oscill ating saw (usage), 1I8f Casts. See Bandage cast; Distal limb; Foot cast; Half

limb cast monitorin g, 118 removal , 117-118

Cast sores. See Fetlock Catheter

placement. See Dorsal punctum recommendation, 36 removal. See Urethral extension suture. See Nasolacrimal catheter usage. See Sesam oid bones

Caudal epidural injection, needle placement, 39f Caudal maxillary sinus, 128f, 129f

communication, 128 treph ination, 135f

Caudal penis, 207f Cefazolin, 25

Index 257

Celiotomy, advantage. See Exploratory celiotomy Cephalic vein, 87 Cervical region (C 1), transverse section, 140f Check ligamen t. See Distal check ligament

desmotomy. See Distal check ligam ent desmoto my; Proximal check ligament desmotomy

ends, gap fo rmation, 83f exteriorization, curved forceps (usage), 83f

Cheek, drill positioning, 124f Cheek teeth

lateral view. See Mandibular cheek teeth; Maxillary cheek teeth

orientation, 136 tension band wire, insertion, 124f

Chromic catgut, characteristics, 14t Chronic distal limb infection, 56f Circumcision

anatomy, 202 complications, 205 equipment, usage, 202 exercise restrictions, 204 indications, 202 medications, 204 multiple-layer closure, 204f outcome, expectation, 204-205 positioning, 202 postoperative care, 204 preparation, 202 procedure, 202-204

alternatives, 205 closure, intraoperative view, 204f

references, 205 suture removal, 204

Client comm unication, 3 Clipper blades (size 40), 4 Closed castration, emasculators (application), 185f Closed herniorrhaphy, 250-251 Closed technique. See Annular ligament desmotomy;

Castration Coffin joint

hyperextension, 62£ region (perfus ion), intraosseous screw placement,

58f Cold (chemical) sterilization, usage, 10 Colic, complication. See Castration Collateral ligamen t, 51 Collum glandis, 203f Comm unicating branch, 82f

ligation/transection, S8f Compound locking loop. See Modified compound

locking loop Conchofrontal sinus, 128f, 129£ Congenital entropion , 173 Conjunctiva, grasp ing, 171 Connell pattern, usage, 223f, 229. See also Cranial

junctions; No. 0 absorbable suture; Vagi nal mucosa; Ventral mucosal layer

258 INDEX

Continuous horizontal mattress suture pattern, ISf Contralateral limb

bandaging/elevation,IISf support, 65

Corneal pain, 173 Corona glandis, 203f Corpus cavernosum

blood loss, 208 compression, 208f initial suture, intraoperative view, 209f

Corpus cavernosum penis, 207f bleed ing, source, 213

Corpus spongiosum penis. 207f incision, 207

Cor rective shoeing, 85 Corrective trimming, 85. See also Distal check

ligament desmotomy Counte rirritants, injections, 78 Cranial ingui nal approach. See Castration Cranial junctions, Connell pattern (usage), 226£ Cranial penis. 207f Crescen t-shaped skin. removal (schematic), 174£ Cribbing, modified ForsseU's operation

anatomy, 157 complications, 159 drain removal, 159 equipment, usage, 157 exercise rest riction, 159 indications, 157 medications, 159 outcome, expectatio n, 159-160 positioning, 157 postoperative ca re, 159 preparation, 157 procedure, 157-158

alternatives, 160 references, 160 stent removal, 159 suture removal , 159

Cricoid cartilage. 148f Cricothyroid membrane, 148f

incision , 152f laryngeal ventricle, relation, 15lf

Crile forceps, 7f Cross-clamping, usage, 148- 149 Cryptorch id cast ration

anatomy, 196 comments, 20 I compl ications, 200 equipment, usage, 196 exerc ise restrictions, 200 indications, 196 med ications, 200 modified parainguinal approach , 199-200 non invasive ingui nal approach, 197-199 outcome, expectation, 200 positioning, 196 postoperative care, 200

Cryptorchid castration (Continued) preparation, 196 procedure, 196-200

alternatives, 200-20 1 references, 201

Cryptorchid testicle, removal, 196 Curved forceps, usage, 8. See also Check ligamen t Curved Mayo scissors, 7f

inclusion, lOb Curved Metzenbaum scissors, 7f

inclusion, 1 Db usage, 171

Curved sponge forceps, usage, 151 Curvilinear incis ion. See Left distal radial physis Cushing pattern, 73

usage, 230f Cutaneous colli m uscles, 139f

removal, 148f Cu ta neous colli tissues, 143

D

DDFT. See Deep digital flexo r tendon DDSP. See Soft palate Dead space. usage, 20 Debrided mucosal edges (apposition ), simple

continuous pattern, 225f Deep digital flexor tendon (DDFT), 80, 82f

3-cl11 incision, 99, 107 abaxial border, 107 con tractu re, 84f, 98. See also Left fo relimb

improvement, 84 mi ld ness, 85

cross-sectional anatomy, 99f heads, 99 intersection . identification. See Distal check

ligament isolation, 99f, 100f laceration, 62f

Kimzey sp lint support. 63f lateral border, 110 radial head, 88

muscle beliy, visual ization, 89f severe contracture, 98f t ransectio n, 99f, 10 I f

Deep digital flexor tenotomy anatomy, 99 bandaging, 100 commen ts, 101 compl ications, 101 equipment, usage, 98 exercise restrictions, 100 incision location, IOO f indications, 98 medica tions, 100 outcome, expectation, 10 1 positioning, 98 postoperat ive care. 100 preparation, 98

,

,

Deep digital flexor tenotomy (Continued) procedure, 99-100

alternatives, 101 references, 101 -102 suture removal, 100

Deep inguinal r ing. sweeping (schematic view), 199£ Deep navicular bone fracture, risk (increase), l09f Delayed primary closure, 13 Delayed secondary closu re. 13 Dental punch, position, 135f Desmoplasty, 71 Desmotomy. See Annular ligament desmotomy;

Medial patellar ligament desmotomy Detomidine

doses, 35 sedation, 34 usage. 24, 35t, 36

Diagnostic trephination , 129 Diaphyseal fracture. See Section 3 diaphyseal fracture Diaphyseal radial fracture, 27 Dietary modification. See Distal check ligament

desmotomy Digital cushion, fascia, 108f Digital extensor retinaculum, 73f Digital extensor tenectomy. See Lateral digitaJ extensor

tenectomy Digital extensor transection. See Long digital extensor

tendon transection Digital flexor tendon

laceration. See Deep digital flexor tendon laceration partial laceration. See Superficial digital flexor

tendon Digital flexor tenotomy. See Deep digital flexor

tenotomy Digital neurectomy. See Palmar-plantar digital

neurectomy Digital sheath

entrance, skin incision (usage), 69f proximal border, incision, 69f

Diode laser, usage, 147, 153, 157 Direct repair. See Rectovaginal fistula repair Dissociative combinations. See Alpha2 agonists Dissociative-guaifenesin combinations. See Alpha2

agonists Distal attachment, spl int bone (freeing), 94f Distal check ligament

anatomy, 82f DDFT intersection. identification. 83f transection, 83f

Distal check ligament desmotomy anatomy, 80 bandaging, 84 comments. 85 complications, 84-85 corrective trimming. 84 dietary modification. 84 equipment, usage. 80 exercise restrictions, 84

Index

Distal check ligament desmotomy (Continued) indications, 80 medications, 84 outcome, expectation, 84 positioning, 80 postoperative care, 84 preparation, 80 procedure. 80, 83

alternative, 85 references. 85 skin incision. location, 82f suture removal, 84

Distal incision site, 73f Distal interphalangeal joint region, 26f Distal limb

cast, 116 application. 116f usage, 116

extension, 77f infection. See Chronic distal limb infection

Distal limb perfusion anatomy, 55 antibiotics, usage, 55-56 bandaging. 57 comments, 58-59 complications. 58 equipment, usage, 55 exercise restriction, 57 exsanguination, 56-57 indications, 55 medications. 57 outcome, expectation, 57-58 positioning, 55 preparation, 55 procedure. 55-57

alternatives, 58 references, 59 suture removal , 57

Distal pastern region, palmar digital vein injection (contrast),56f

Distal radial physis. 47f dorsopalmar radiograph, 53f identification, hypodermic needle (usage), 5lf

Distal splint bone anatomy, 94f Distal splint bone fractures, 96 Distal splint bone resection

bandaging, 96 comments, 96 complications, 96 equipment, usage. 93 exercise restrictions, 96 indications, 93 medications, 96 outcome, expectation, 96 positioning, 93 preparation, 93 procedure. 93-95

alternatives, 96

259

260 INDEX

Distal splint bone resection (Cofltinued) references, 96-97 suture removal, 96

Distal third metacarpus, 26f Distal third metatarsus, 26f Distal tibial epiphysis, proximal-to-d istal dimension,

50 Disuse osteopenia, degree, 118 Dorsal conchal sin us, 129f Dorsal d isplacement, surgical treatmen t options. See

Soft palate Dorsal displacement of the soft palate. See Soft

palate Dorsal layer, apposition (contin uous horizontal

mattress pattern, usage), 223f Dorsally based V-shaped vaginal tissue flap, t ransverse

cross-section, 238f Dorsal mucosal layer (eversion), continuous

horizontal m attress pattern (usage), 224f Dorsal nasal concha, 129f Dorsal nasal meatus, 129f Dorsal-palm ar splint, incorporation, 119f Dorsal puncta, anatomy (schematic), 163f Dorsal punctum, catheter (placement), 164f Dorsal splint cast combin ation, usage, 26f Dorsopalmar rad iograph. See Carp us; Distal radial

phys is Double-Y incision. See Tracheal mucosa Double-Y pattern, 144 Down testicle, castration, 182 Drains

classificati on, 21-22 removal. See Cribbing usage, 20-21

Drill bit, usage, 58f Drugs

combinations, 35t usage. See Single drugs; Standing sedation

Duct tape, usage, 117f Ductus deferens, 183f Duragesic, 33

E

Edema, formation, 189f Eight wire, figure (placement), 51 f Electric shock collars, usage, 160 Electrocautery, 170 Elevation. See Periosteal transection/elevation Emasculator. See Modified White's emasculator;

Reimer emasculator; Serra emasculator application. See Closed cast ration; Open castration;

Spermatic cord Endoscopic transaction, 71 Entropion

anatomy, 173 complications, 174-175 equipment, usage, 173 indications, 173

Entropion (Continued) positioning, 173 postoperative care, 174 p reparation, 173 procedure, 174 protection, 174 references, 175 suture removal, 174

Enucleation. See Transconj unctival enucleation; Transpalpebral enucleation

Epididym is ligament tail

cutting. See Open cast ration disruption, 187f

long proper ligament, traction, 198f tail, exposure, 198f

Epidural analgesia, 39-40 ana tomy, 39 technique, 29-40

Epidural anesthesia, 39-40 anatomy, 39 technique, 39-40

Epidural d rugs, usage, 40 Epidural injection, 39

needle placement. See Caudal epidural injection repetition, 39-40

Epiglottis, 152f Epinephrine, addition, 40 Episioplasty. See Perineal body reconstruction Epitheli um, urethral sutures (interrupted pattern),

208f Ergot, 94f

ligamen t, 108f Esm arch bandage (proximal end), pneumatic

tourniquet (application), 56f Esophagus, 140f Ethylene oxide, usage, 10 Euthanasia, indication, 28 Eventration. See Castration; Inguinal hernia-

eventration Evosions, 119f

Exploratory celiotomy, advantage, 248 Exsanguination. See Distal limb perfusion Extensor tendon lacerations, 63, 65

PVC splin t support, 63f Extenso r tenectomy. See Lateral digital extensor

tenectomy Exteriorized check ligament, in traoperative view, 83f External abdominal obliq ue, aponeurosis

closure, 199f incision, 199f

External inguinal ring, sutures (preplacement ), 248 External spermatic fascia, st ripping, 184f Extrasynovial transection, 71 Exudate, removal. See Incision site; Wo unds Eyelid

anatomy, schematic, 166f innervation, schem atic, 177f

Eyelid (Colltinued) Lembert sutures, p lacement schematic, 174£

• margin figure-of-eight suture, schematic, 169f subjunctival closure, schematic, 169f

tacking. See Temporary eyelid tacking Eyelid laceration repair

anatomy, 168 com plications, 169 equipment, usage, 168 indications, 168 medications, 169 positioning, 168 postoperative care, 169 preparation, 168 procedure, 168 protection, 169 references, 169

F

Facial crest, 127 rostral end, 129f

Facial nerve auriculopalpebral branch, 176 CN VII paralysis-paresis, 179

Farabeuf ret ractor, 8f Far- near-near-far suture patterns. See Modified

far-near-near- fa r suture pattern Far-nea r-near-far tension suture patterns, 19f Fascia, coverage, 158f Fetlock

buckling, 62f canal, palmar-plantar wall, 68f

contracture. See Left forelimb hyperextension, 60, 62f palmar aspect, cast sores, 11 9£

Fetotomy wires, preplacem ent. See Plastic-covered fetotomy wires

Fiberglass casting material

application, 115f usage, 11 4f

tape, application, 11 5f Fiberglass cast material, 26 FiberWire, 60 Fibrous tarsal plate, 179 Field anesthesia, 30

ind uctionlrecovery. See Injectable field anesthesia references, 40-43

Field su rgery, general pack, 9 contents, lOb

Figure-of-eight suture, schematic. See Eyelid Finger-held retractors, 8f Finger sponge forceps, usage, 151 Finger traction. See Tunic First-intention healing, 13 Fistula repair. See Rectovaginal fistula repair Flaccid epiglottis, 151

Flexion , exaggeration. See Limbs Flexor ca rpi radialis

caudal retraction, 89f muscle, tendon sheath, 89f

Index 261

retinaculum, superficial sheet (incision), BSf tendon sheath, superficial sheet (incision), SSf

Flexor retinacul um closure, 88

deep sheet, 89f superficial sheet, 89£

Flexor tendon free cut ends, 62-63 lacerations, 64-65. See also Mid metacarpal region;

Palmar pastern region sheath , proximal, 61f support, IISf

Flexor tenotomy. See Deep digi tal flexor tenotomy Fluid therapy, 37 Foam cast padding, usage, 114£ Foam padding, appl ication, 11 5f Foley catheter, usage. See Ventral vaginal mucosa Foot cast, JI6

usage, 11 M Foot cysts, detection, 109 Forceps, 7f. See also Adson forceps; Allis forceps;

Brown-Adson forceps; Crile forceps; Forester sponge-holding forceps; Grasp ing forceps; Halstead mosquito fo rceps; Hemostatic forceps; Kelly forceps; Thumb forceps; Tissue

inclusion. See Brown-Adson thumb forceps; Carmalt fo rceps; Oschsner forceps; St raight mosquito forceps

passage, 69f usage. See Check ligament; Perineural sleeve;

Vaginal r ing eversion Ford's interlocking pattern , 17f. See also Vulvar

mucosa Forel imbs

fracture, 26. See also Section 1 fo reli mb fracture; Section 2 forel imb fracture; Section 3 fo rel imb fractures; Section 4 forelimb fractures

moderate SDFT contracture, 87f SDP tendonitis. See Left forelimb

Forester sponge-hold ing forceps, 8f Forssell's operation, modification. See Cribbing Fossa gland is, 203f Fracture patien t

comments, 29 complications, 28 emergency management, 24

references, 29 equipment, usage, 24 indications, 24 initial evaluation/treatment, 24-28 ou tcome, expectation, 28-29 positioning/preparation, 24 procedures, alternatives, 29 referral, p repa ration, 28

262 INDEX

Frontal sinus Heel (Contil/Lled)

communication. 128 trephine sites, limits (identification), 129f

G

Gamma-aminoblltyr ic acid (GABA). 32 GABA-associated chloride channel opening, 34 receptor, 33

Gas ste rilization, 10 Gauze sponges, inclusion. lOb Gelding

hind quarters, view, 212f per ineal urethrotomy

intra-operative view, 212f postoperative view. 212f

Gelpi retractors, 9f usage, 87

Gelpi self-retaining retractors, 147

General anesthesia. See Injectable general anesthesia Gentamic in , 25 Gerald forceps, usage, 107. See also Perineural capping GG. See Glyceryl gllaiacolate GKX. See Guaifenesin ketamine xylazine Glans penis, 207f Glyce ryl guaiacolate (GG), 32 Granulatio n tissue formation. 145 Graspi ng forceps, 8 Groove director, passage, 69f Guai fenesin, 32

10% solution, 32 combi nations. See Alpha2 agonists; Thiopental ­

guaifenesin combinations Guaifenesin ketamine xylazine (GKX) combination,

36 Gubernaculum

inguinal extens ion, usage, 197f testis. inguinal extension (schematic view). 197£

Guillotine technique. III

H

Half-closed castration techniques, 184 Half limb cast, 115

areas, soreness, 119f casting tape, usage, 115 strength. increase, 119f

Half limb cast ing, 117f Halstead mosqu ito forceps. 7f Halstead pattern, 73 Hand-held retracto rs, 9f Hanging drop technique, 39 Hay- net. recommendation, 28 HCG. See Human chorionic gonadotropin Head

lateral view. 133f lavage tube, placement. 166f ventral view, 148f

Heel elevation, 64. 84

acrylic, usage. See Temporary heel elevation extension, 64

appUcation, 118f ground contact, absence, 84f wedge. incorporation, 115£

Hematocrit, dose-dependent decrease, 30 Hemorrhage, excess, 189f

complica tion. See Castration Hemostasis, provision, 171-172 Hemostat ic forceps, 6, 8 Hemostats, usage. See Nerve ending Hernia-eventration. See Inguinal hernia-event ration Hernial ring, palpation, 252f Hernial sac

abdominal inversion, 25 1 f inversion, 250

needle, insertion, 251 f skin dissection, 25 1 f

Herniorrhaphy. See Closed herniorrhaphy; Inguinal herniorrhaphy; Open herniorrhaphy; Umbilical herniorrhaphy

H ibiclens. 4 Hind limb fracture. See Section 1 hind limb fracture;

Section 2 h ind limb fracture; Section 3 hind limb fracture

Hock extension, 77f hyperflexion. 73f

Hohmann retractor, blades (inclusion), 9f Hoof angle. change, 84 Hor izontal mattress pattern. See Suture Hor izontal mattress su tures

pattern, 28f placement, polyethylene supports, 22f

Horizontal periosteal transection. connection. 47f Hotz-Celsus blepharoplasty, 173, 174

suture placemen t. bisecting method. 174f Huber technique. See Rectovaginal fistula repair Human chorionic gonadotropin (HCG).

administration, 191 Hydrocele

complication. See Castration formatio n. See Postcastration

Hydrogen peroxide gas plasma, usage. 10 Hydrolysis, constant rate, 16 Hyperflexion. See Hock Hypodermic needle

I

usage. See Distal radial physis wire guide, 123f

Incision Line avoidance. See Primary incision line ventral site, trocar usage, 21 f

Incision site. See Periosteal transection distal site, drain, 22£ exudate, removal, 21£

,

•

•

I

Incisors fractures, 123 involvement. See Rostral mandibular fractures

Incomplete abdominal crypto rchids, 197 Indirect inguinal hernia, 247f

abdo minal view, 247f i nduction, 38. See also Injectable field anesthesia Infection, complication. See Castration Inferomedial subpalpebrallavage tube placement

anatomy, 165 complications, 167 equipment. usage, 165 indications, 165 medications, 167 positioning, 165 postoperative care, 167 preparation , 165 procedure, 165-166 protection, 167 references, 167

Infraorbital canal, 129f positi on, 128f

relative positions, t28f Infraorbital nerve, blockage, 177 Infra trochlear nerve blocks

anatomy, 176 complications, 178 equipment, usage, 176 indications, 176 positioning, 176 preparation, 176 procedure, 176-178 references, 178

Ingu inal canal, inguinal retention, 197f Inguinal hernia. See Direct inguinal hernia

abdominal view. See Indirect inguinal hern ia closure, 248£

Inguinal hernia-eventration, 186, 188 Inguinal herniorrhaphy

anatomy, 246 comments, 248-249 complications, 248 equipment, usage, 246 exercise restrictions, 248 indications, 246 medications, 248 outcome, expectation , 248 position ing, 246 postoperative care, 248 preparation, 246 procedure, 246-248

alternatives, 248 references, 249

Inguinal testicle exteriorization , view, 198f view, 198f

Injectable anesthetics, 33-34 Injectable field anesthesia, inductionlrecovery, 38-39

Injectable general anesthesia, 34-37 supportive care, 37-38 usage. See Patient

Injury, initial assessment, 24

Index 263

Instruments. See Surgical instruments Insurance, communication, 3 Interdental space, b ilateral fractures, 124 Internal abdominal oblique muscle, 183f Internal inguinal region, postcastration adhesion

formation, 192 Internal spermatic fascia, 183f In terosseus ligament, 94f

severing, 95f Interosseus med ius, 94f Interrupted cruciate pattern, 17f Interrupted horizontal matt ress pattern , 18f Interrupted Lembert pattern, usage. See Vaginal fi stula Interrupted vertical mattress pattern, 18-19, 18f Intestinal eventratio n, complication, 191

In testine exposure, 191 milking, 247

Intramuscular injections, 106 Intraoral wire fixation. See Rostral mandibular

fractures; Rostral maxillary fractures Intraosseous perfusion, 57 Intraosseous screw placement. See Coffin joint;

Pastern Intrasynovial medications. See Annular ligament

desmotomy Intravenous perfusion, 57 Intubation, usage, 37 Ischatic tuberosity, 103

J

Jackso n-Pratt nega tive suction drain insertion, 21£ placement, 21 f

K

Kappa agonists, 33 Kappa receptor activation, 32 Kelly forceps, 7f

usage, 6, 8 Ketamine, 33. See also Guaifenesin ketamine xylazine

half dose, 35 Kevlar, 60 Kimzey Leg Saver, 29 Kimzey Splint, 61

disadvantages, 65 Kimzey splint support. See Deep digital flexor tendon Klug technique. See Rectovaginal fistula repair Knee pads, inclusion, lOb

l

Lacerations. See Extensor tendon lacerations; Flexor tendon lacerations

conversion. See Third-degree perineal laceration

264 INDEX

Lacerations. See Extensor tendon lacerations; Flexor tendon lacerations (Continued)

repair. See Eyelid laceration repair; Mid metacarpal-metatarsal tendon laceration repair; Third-degree perineallaceration repair

lavage, 63f skin necrosis, evidence. See Pastern laceration

Lacrimal nerve blocks anatomy, 176 complications, 178 equipment, usage, 176 indications, 176 positioning, 176 preparation, 176 procedure, 176-178 references, 178

Laminitis, 98f Laparocystotomy, 213 Laparoscopy, 213 Large cords, separation/ligation, 185-188 Laryngeal ventr icle, relation. See Cricothyro id

membrane Laryngotomy, surgical approach, ISH Larynx

lateral view, 150f ventral view, 148f

Lateral digital extensor, IO-cm vertical skin incision, 74f Lateral digital extensor muscle, location, 73f Lateral d igital extensor tendon, 47f, 73f

location, 73f pull ing, 72

Lateral digital extensor tenectomy anato my, 72 bandaging, 74 comments, 74-75

complications, 74 equipment, usage, 72 exercise restriction, 74 indication, 72 med ications, 74 outcome, expectation, 74 positi oning, 72 postoperative care, 74 preparation, 72 procedure, 72-73 references, 75 suture removal, 74

Lateral recumbency, 37, 135f Lateral splints

extens ion,27f usage, 27f

Lavage solutions, effectiveness, 12 Lavage tube

footplate, 166f placement. See Head; Inferomedial subpalpebral

lavage tube placement Laxity. See Ligament

degree, 118

Left distal radial physis, medial aspect (curvilinear incision), 51£

Left forelimb DDFT contracture, 81£ fetlock contracture, 87f lateral aspect, 47f pointing stance, 108f SDFT contracture, 87f SDF tendonitis, 87f

Left jugular vein, 139f Left second maxillary molar, rep ulsing, 135f Left tibia, lateral aspect, 47f Leg Saver, usage, 29f Lembert pattern , usage, 230 Lembert sutures

nu mber, variation, 174 placement schematic. See Eyelid

Lidocaine, usage, 40 Ligament

desmotomy. See Annular ligament desm otomy; Distal check ligament desmotomy; Medial pateUar ligament desmotomy

laxity, 11 9

Limbs abductio n, prevention, 27f, 28f appearance, 68f cast. See Distal limb; Half limb cast flexion, exaggeration, 77f functional sections, divis ion, 25f perfusion. See Distal limb perfusion perineural capping, Illf position, stance phase, 77f positioning, ropes (usage), lab

Limb stabilization, 25-28 section 1,25-26 section 2, 26 section 3, 27-28 section 4, 28

Limb support. See Contralateral li mb support Linea, closure, 251 f Lister bandage scissors, 7f Locking loop. See Modified compound locking loo p Locking mechanism, 77f Long digital extensor tendon, 73f

transection, 62f Long-handled instruments, requirem ent, 236 Long-handled scisso rs, usage, 152f Longitudinal fibe rs, palpation, 108f

M

Males, perineal urethrotomy anatomy, 211 cleaning, 212 comments, 213 complications, 213 dietary modifications, 212 equipment, usage, 21 I exercise restrictions, 212

•

Males, perineal urethrotomy (Continlled) indications, 21 1

medications, 2 12

outcome, expectation, 213 positioning. 21t postoperative care, 212

p reparation, 211 procedure. 21 1-212

alternatives, 213

protection, 212 references. 213-214

Mandibular cheek teeth , lateral view, 134f Mandibular fractures, intraoral wire fixation. See

Rostral mandibula r fractures Mandibular tooth, repulsion, 136 Mastication, difficulty, 125

Mathieu retractor, 8f Mattress patterns. See Interrupted horizontal mattress

pattern; Inter rupted vert ical matt ress pattern; Suture

Matt ress suture pattern. See Conti nuous horizontal mattress suture pattern; Horizonta l mattress su ture pattern

Maxillary cheek teeth, lateral view, l34f

Maxillary fractures, intraoral wire fixation. See Rostral maxillary fractures

Maxilla ry sinus, trephi ne sites limits (identification),

129f Maxillary vein, 140f

Mayo-Hegar needle holde rs, 7f McKinnon technique. See Urethral extension

Medial canthus, 129f

Medial patellar ligament desmotomy anatomy, 76

bandaging, 78 commen ts, 78-79

complications, 78

equ ipmen t, usage, 76 exercise restrictions, 78

indications, 76 medications, 78

outcome, expectation, 78

positioning, 76

postoperative care, 78 preparation, 76

procedu re, 76 alternatives, 78

references, 79

skin incision, location, 77f

suture removal , 78 Medial patellar ligament transection, bistoury knife

(usagel,78f Median raphe, removal, 192, 193f

Medulla ry cavity cyst, 109£ Mepivaca ine, usage, 40 Mesofuniculus, ligament ta il (disruption ), 187£

Mesorchium, window (creation ), 186f

Metal splints, usage, 29f

Index 265

Metzenbaum sc isso rs, usage, 83

Meyerding finger retractor, blades (i nclusion ), 8f

Meyerdi ng retractor, 9f Middle metacarpal region, transverse section, 6lf

Middle metatarsal fractu res, 26 Middle metatarsal region, transverse section , 61f

Middle nasal m ea tus, 129f

Midline incis ions. 144 Mid metacarpal-metatarsal tendon laceration repai r

anatomy. 60 assessment, 60-64

comments, 66

compl ications, 65 equipment, usage, 60

indications, 60 outcome, expectation, 65

positioning, 60

postoperative care, 64-65 preparation, 60

procedures, alternatives, 65

refe rences, 66 stabilization, 60-6 1

surgical proced ures, 60-64 synovial structure, involvement, 6 1

vascular status, 61-62

wounds, debr idement/repair, 62-63

Mid metaca rpal region cross-sectional anatomy, 99f

flexor tendon laceration, 61 f Mid metatarsal spli nt bone fracture, 93f

Moderate SDFT contracture. See Forelimbs Modified closed castration, exteriorization

(maintenance),186f

Modified closed technique. See Castration Modified compound locking loop. 64, 64f

Modified far- near-near-far pattern, 64f Modified far- nea r- near-far suture pattern, 63

Modified Finochietto self-retaining retractor, 222, 236

Modified Forssell's operation. See Cribbing Modified Forssell's procedure, 152f

incision site. t58f Modified Goetz technique. See Third-degree perineal

laceration repair

Modified parainguinal approach. See Cryptorchid

castration Modified White's emasculator, 182£ Monin technique. See Urethral extension

Monofilament absorbable suture materials,

requirements, 236 Monorchidism, rarity, 200

Morphine, usage, 35t Mosquito hemosta tic forceps, usage, 52

Mucocutaneous junction, 217f

Mucosal edges (a ppositi on), simple continuous pattern. See Debrided mucosal edges

Muscles severing, 74£

view, 133f

266 INDEX

Muscle-tendon junctions, 73f, 74f Musculotendinous junction, 158f Myectomy. See Omohyoideus myectomy;

N

Sternothyrohyoideus myectomy exercise restrictions. 153 medications, 153 procedures, 148- 153

postoperative care, 153 suture removal, 153

Nasolacrimal catheter suture, 164f usage, 163

Nasolacrimal catheterization, 162 Nasolacrimal duct, 129f

anatomy, schematic, 163f position, 128f relative position, 128f

Nasolacrimal flush anatomy, 162 complications, 164 equipment, usage, 162 indications, 162 medications, 164 positioning, 162 postoperative care, 164 preparation, 162-164 procedure, 162-164 references, 164

Nasolacr imal obstruction, treatment, 164f Nasolacrimal sac, anatomy (schematic), 163f Nasolacr imal system, catheterization, 163 Navicular disease, preoperative image, 108f Nd:YAG lase r, llsage, 147, 153. 157 Near-far-far-near tension suture patterns, 19f

usage, 20 Neck

C4, transverse section, 140f lateral view. IsSf vent ral views, 139f, 144f

Needle holders. 6. See also Mayo-Hegar needle ho lders; Olsen-Hegar needle holders

inclusion, lOb types, 6

Need le placement. See Caudal epidural injection' Negative suction drain, insertion. See Jackson-Pratt

negative suction drain Nerve blocks. See Infratrochlear nerve blocks;

Lacrimal nerve blocks; Ophthalm ic procedures; Palmar-palmar metacarpal nerve block; Palpebral nerve blocks; Supraorbita l nerve blocks; Zygomatic nerve blocks

Nerve ending (grasping), hemosta ts (usage), III f Neu rectomy, Black's method, 107, II0f No. 0 absorbable su ture, ConneU pattern (usage),

240

No.2 synthetic absorbab le suture material. usage,

200 No.3 scalpel handle, inclusion, lOb No.3 synthetic absorbable suture mater ial, usage,

200 No.4 scalpel handle, scalpel blades (shapes), 6f No. 10 Bard-Parker blade, 162 No. 10 scalpel blade, usage, 47 No. 12 hooked scalpel blade, usage, 47 Non invas ive inguinal approach. See Cryptorchid

castration Nonsteroidal inflammatory drugs (NSAIDs),

25 NSAIDs. See Nonsteroidal inflammatory drugs Nucleat ion, indications, 170 Nylon. characteristics. 1St

o Ocular lubricant, usage, 37 Olecranon fractures, 28f Olsen-Hegar needle holders, 7f Omental prolapse, com plication. See Castration Omohyoidectomy

intrao perative view, 149f usage. See DDSP

Omohyoideus dissection, 150 Omohyoideus muscle, retraction. 150f Omohyoideus myectomy, 149-150 One-stage repair. See Third-degree perineal laceration

• repair Open castration

emasculators. application, 187f epididym is, ligament tail (cutting), 187f tun ic, removal, ISSf

Open herniorrhaphy, 25 1-252 usage, 252f

Open technique. See Ann ular ligament desmotomy; Castration

Operating scissors, 6f classification,S

Ophthalmic procedures, nerve blocks anatomy, 176 complications, 178 equipment, usage, 176 indications, 176 positioning, 176 preparation, 176 procedure, 176- 178 references, 178

Opioids, 32-33 Orbital rim, 177f Orchitis, 213 O rthopedic felt

appl ication. See Cast proximal limit usage, 114f

Orthopedic support, 117 Oschsner forceps, inclusion, l Ob

•

Oscillating saw removal. See Cast removal usage, 117

Oxygen supplementation, 38

p

P3, abscessation/sequestration, 10 1 Palmar annular ligament

constriction, 68f

proximal incision. 69f Pa lmar digital artery, 108f Pa lmar digital nerve

distal incision, 110f exposure, proximal/distal incisions, I 1 Of incision, postoperative view, 110 location, 108f transection, 108f, 110£

Palmar digital vein, I08f injection, contrast. See Distal pastern region

Palmar fascia . closure, 83 Palmar metacarpus, anatomy, 82f Palmar-palmar metacarpal nerve block, 98 Palmar pastern region, flexor tendon laceration, 61 f Palmar-plantar annular ligament, 68f Palmar-plantar digital neurectomy

anatomy, 107 bandaging, 109 comments, III complications, 109-110 equipment, usage, 107 exerc ise restrictions, 109 indications, 107 med icat ions, 109 outcome, expecta ti on, 109 positioning. 107 postoperative care, 109 preparation. 107 procedure, 107. 109

alternatives. 110-111 references, 112 suture removal. 109

Palmar-plantar wall See Fetlock Palmar vein , 20-gauge/22-gauge I-inch catheter

(placement), 57f Palpable lateral digital extensor tendon, 3-cm incision.

74f

Palpebral conjunctiva, 166 Palpebral nerve anatomy, schematic. 177f Palpebral nerve blocks

anatomy. 176 complications. 178 equipment. usage, 176 indications. 176 position ing, 176 preparation, 176 procedure, 176-178 references, 178

Paramedian incisions, 144 Parietal lamina. 183£ Parker retracto r, 8f Parotid duct, 133f Passive drains, 2 1-22 Pastern

Index 267

proximal portion, stab incision, 58f • regIOn

flexor tendon laceration. See Palmar pastern .

regiOn perfusion, intraosseous screw placement,

58f Pastern laceration (previously repaired), skin necrosis

(evidence),22f

Patella fragmentation, 78 rel ease. 77f upward fixatio n, 77f

PateUar ligament desmotomy. See Medial patellar ligament desmotomy

Patient emergency management. See Fracture

patient evaluation, 3 monitoring. injectable general anesthes ia (usage).

37 preparation. See Surgery

Penile amputation anatomy, 206 comments, 210 complications. 209-210 equipment. usage, 206 exercise restrictions, 209 indications, 206 medications, 209 outcome, expecta tion, 209 pos itio ni ng, 206 postoperative care, 209 preparation, 206 procedure, 206-209

alternatives, 210 references. 210 suture removal, 209 William's technique, triangular skin incision,

208f appeara nce, 209f intraoperative view, 208f, 209f

Penile damage, com plication. See Castration Penis

anatomy, 207f base, transection, 208f distal shaft, melanoma. 206f external aspect, 203f free part, 203f median section, 203f transection, 208 transverse section, 207f

268 I NDEX

Penrose drain , 22f placement, 149 usage, 21-22

Perfusate loss, prevention, 56f Perfusion. See Distal limb perfusion; Intraosseous

perfusion; Intravenous perfusion Perineal body reconstruction (episiopJasty)

complications, 221 equipment. usage, 2 19

exercise restrictions. 219 indication, 219 medications, 219 outcome, expectation, 22 1 positioning, 219 postoperative care, 219 preparation, 219 procedure, 219 references, 22 1 suture removal, 219

Perineal laceration repair. See Third-degree perineal lace ration repair

Perineal urethrotomy. See Males completion, close-up view, 2 12f postoperative view. See Gelding

Perineural capping, Ill. See also Limbs Gerald forceps, usage, I08f requirement, 107

Perineural sleeve closure, III str ipping, 111£

smooth-tipped fo rceps, usage, III f Periosteal elevato r, usage. See Periosteum Periosteal transection, incision site, 47f Periosteal transection/eleva tion

anatomy, 46 comments, 48-49 complications, 48 equipment, usage, 46 exercise restriction, 48 indications, 46 introduction, 48-49 outcomes, expectation, 48 positioning, 46 postoperative care, 48 procedure, 46-47

alternatives, 48 refere nces, 49 su ture removal, 48

Periosteum transection,47f triangular shaped flaps (elevation), periosteal

elevator (usage) , 47f Per itomy, schematic, 172f Peritonitis. 213

complication. See Cast ration Persistent stallion-like behavior, complica tion. See

Castration Phenylbutazone, 25

Plantar splints cast combination, usage, 26f usage,27f

Plastic-covered fetotomy wires, preplacement, 11 9 Plugs, composition, 135 Plunger, needle placement, 21 f Pneumatic tourniquet, application. See Esm arch

bandage Poliglecaprone 25, cha racteristics, 14t Polydioxanone, 16

characteristics, 14t Polyester, characteristics, 1St Polyethylene supports. See Horizontal mattress sutures Polyglactin 9 10, 16

characteristics. I4t Polyglacti n acid , characteristics, 14t Polyglecaprone. 16 Polyglycolic acid, 16 Polyglyconate, 16

characteristics, 14t Polymerized capro lactum, characteristics. 1St Polypropylene, cha racteristics, 1St Polyvinyl chloride (PVC)

splint support. See Extensor tendon lacerations tubing, placement. 122 usage, 24

Postcastration adhesion formation, impact, 192f hydrocele, formation. 192f

Postoperative hematoma, min imization , 153f Potassium penicillin, 25 Preoperative radiographs, 54 Prepuce

circumferential incisions, 202 external aspect. 203f involve ment. See Squamous cell ca rcinoma lesion removal, ci rcumferential incis ions, 203f med ia n section, 203f

Preputial ring, 203f Primary anatomic entropion , 173 Primary closure, 13 Primary incis ion line, avo idance, 22f Primary suture line, excess tension. 22 Propofo!' 34 Proximal amputation site. 9S Proximal annular ligament. 67

incision. 69f Proximal check ligament

intraoperative view, 88f transection. 89f

Proximal check ligament desmotomy anatomy, 86 bandaging, 90 comments, 91 complications. 90 equipment, usage, 86 exercise restrictions. 90 incision, location, 98f

•

Proximal check ligament desmotomy (Colltillued) ind ications, 86 medicatio ns, 90 o utcome, expectation, 90 position ing, 86 postoperative ca re, 90 preparation, 86 p roced ure, 86-88

alternatives, 90-91 references, 91-92 suture re moval, 90

Proximal metata rsal fractu res, 26 Proximal radial artery, palmar carpal branch, 89f Prox ima l radial fracture, 27. See also Section 3

p rox imal rad ial fracture Prox imal radial vein, deep communicating branch, 89f Proximal sesamoid bones, abaxial surfaces, 68f Proximal splint bone, edge (removal), 95f Proximal tendon sheath, incision, 68 Proximal tib ia

insertion , 104f medial aspect, 103

Pul leys. See Three-loop pulley Purse-stri ng pattern

tigh tening, 231 f usage. See Rectovagina l shelf

Purse-st ring suture, simple interrupted sutu re (association),23 1f

PVc. See Po lyv inyl chloride

R

Rad ial fract ure. See Section 3 proximal radial fracture Radiographs, 134f Recovery. 38-39. See also Injectable field anesthesia Rectal damage, 2 13 Rectal fis tu la, transverse closure, 240f Rectal lumen, 230f Rectal mucosa

inve rsion , 230f transverse apposition , 238f

Rectal shelf creation , 239f vagina l shelf, dead space (elimination ), 241 f

Rectovaginal fi stula circumferential incision, 80-degree scalpel handle

(usage),237f closure, 243f

suture placement, sagittal cross-section, 243f vest-over-pants, usage, 242f

cranial/lateral aspects, horizontal dissection, 242f margin , 239f submucosal sutures pattern , preplacement, 238f visualization, 237f

Rectovaginal fistu la repair Bemis techniq ue, 238-239 complications, 243 dietary modifications, 242 direct repair, 236-237

Index 269

Rectovaginal fi stula repair (Continued) equipment, usage, 236 exercise restrictions, 242 Huber technique, 239-24 1 indications, 236 Kl ug technique, 24 1-242 medications, 242 outcome, expectation, 242 positioning, 236 postoperative ca re, 242 p reparatio n, 236 procedure, 236-242 references, 243 Scho nfelder technique, 237-238 sutu re removal, 242

Rectovaginal shelf, closure purse-string pattern , usage, 229f six-b ite pattern. usage, 229f

Rectum (elasticity), reduction (problem), 23 1 f Reimer emasculator, 183f Repulsion. See Tooth repulsion Restraint, combinations. See Standi ng sedat ion Restrictive scar tissue. transection , lOSf Retained testicle, location, 197f Retractor penis muscle, 207f Retractors, 8-9. See also Army-Navy retractor;

Fa rabeuf retracto r; Finger-held ret racto rs; Gelpi ret ractors; Hand-held retractors; Mathieu retracto r; Meye rding retractor; Ribbon mall eab le retracto r; Self- retaining ret ractors; Senn retracto r; Weitlaner retractors

b lades, inclusion. See Hohmann ret ractor; Myerding finger retractor

Ribbon malleable retractor, 9f Right angle scissors, usage, 152f Robert Jo nes bandage, usage, 27f, 28f Rochester-Carmalt forceps, 147, 157 Rochester-Pean forceps, 147, 157 Romifidine, usage, 35t, 36 Rongeurs, usage, 134. See also Segmental ulnar

ostectomy Rostral mandibular fractures

incisor involvement, J 24f repair, 124f

techniques, compa rison, 125f wire posi ti oni ng, 123f

Rostral mandibular fractures, intraoral wire fixat ion

anatomy, 122 comments, 125 complications, 125 equ ipment, usage, 122 indications, 122 med ications, 125 outcome, expectation, 125 positi on ing, 122 postope rative care, 125 p reparation , 122

i

270 I NDEX

Rost ral mandibular fractures, intraoral wi re fixation (Continued)

procedure, 122- 125 references, 125-126

Rost ral maxillary sinus, 128f, 129f Rostral neck, ventral view, 148f

5

Sacrococcygeal region, sagittal section. 39f Scalpel blades, 6f

gu ida nce. 69f shapes. See No.4 scalpel handle usage,S

Scalpel handle inclusion. See No.3 scalpel handle sca lpel blades. shapes. See No.4 scalpel handle

Scar tissue, presence, 94 Schonfelder technique. See Rectovaginal fistu la repair Schrodeder-Thomas splint, usage. 27 Scisso rs. 5-6. See also Curved Mayo scissors; Curved

Metzenbaum scissors; Lister bandage scissors; Operating scisso rs; Straight Mayo sc issors

inclusion. See Suture Scrotal ligament, 198 Scrotal region/shea th

postoperative appearance, 189f postoperative swelling, 189f, 190f

SDF. See Superficial digital flexor SOFT. See Superficial digital flexor tendon Seconda ry ent ropion, 173 Second-degree perineal laceration, 242f Second-intention healing, 13 Second premolar. involvement, 123 Section 1 forel imb frac ture, 26£ Section 1 frac tures. stabilization, 29f Section 1 hind limb fracture, 26£ Section 2 forelimb fracture. 26f Section 2 fractu res, 27f Section 2 hind limb fracture, 27f Section 3 diaphyseal fracture, 27f Section 3 forelimb fractures, 27f Sect ion 3 hind li mb fracture. 27f. 28f Section 3 proximal radial fracture, 27f Section 3 tarsal fracture, 28f Section 3 tibia fracture, 28f Section 4 forelim b fractures, 28f Sedation

achievement, 24 restraint, combinations. See Standing sedation

Segmental ulnar ostectomy (performing), rongeurs (usage),47f

Self-retaining retractors, 9f, 222, 236 placement, 15lf

Self- retai ning tracheotomy tube, insertion, 141 f Sem itendinosus myotomy, 103- 104

bandaging, 104f exercise restri ct ions. 104f medications, 104f

Semitend inosus myotomy (ColltiITJ.led) refere nces, 106 suture removal, 104f

Semitendinosus tendo n, location/i ncision , 104f Semitendinosus tenotomy, t03

bandaging, 104 exercise restrictions, 104 medications, 104 references, 106 suture removal, 104

Semitendinosus tenotomy/myotomy anatomy, 103 com ments, 106 com plications, lOS equipment, usage, 103 indications, 103 outcome, expectation, 105 positioni ng, 103 postoperative care, 104 preparation, 103 procedure, t03-J 04

alternatives, 105-106 Semi transverse closure technique. See Third-degree

perineal lace ration repair Senn ret racto r, 8f Septic tenosynovitis, 70 Sequest ration. See Bone; P3 Seroma formation, 190f

minimization, 153f Serra emasculator, 183f Sesamoid bones

abaxial surfaces. See Proximal sesamoid bones catheter, usage, 57f

Shires techn ique. See Urethral extension Shoe, setting, 81£ Shoeing. See Corrective shoeing Silk, characteristics, 13, 1St Silver-sulfadiazine cream, 213 Sim ple continuous pattern, 17f Sim ple-interrupted 3-0 monofilament nonabsorbable

sutures, 164 Simple interrupted appositional suture patterns,

combination. See Vertical mattress sutures; Vertical mattress tension suture

Simple interrupted pattern. 17f Single drugs, usage. 35t Sinus treph ination

anatomy. 127-128 comments, 130 com plications, 130 equ ipment, usage, 127 indications, 127 outcome, expectation, 130 positio ning, 127 postoperative care, 130 preparation, 127, 128-130 procedure. 128-130

alternatives. 130

--------------------------------............................ ...............

Sinus trephination (Continued) references, 130-131

Six-bite pattern, usage. See Rectovaginal shelf Skin

closure. 90f performing. 168

defects, closure, 21 f necrosis, evidence. See Pastern laceration preparation, antiseptics (usage), 11-12 tension, management. 22

Skin incision, 69, 184£ depiction, 212f enlargement, 185 location. See Distal check ligament desmotomy;

Medial patellar ligament desmotomy Skull

latera l view, 128f

ove rview, 128f

transverse section, 129£ Small intestine, adhesion formation (excess), 192f Smooth-tipped forceps, usage. See Perineural sleeve Soft pala te

elevation, IS2f free edge, retraction, 152f

grasping, AJlis tissue forceps (usage), 152f

Soft palate, dorsal displacement (DDSP), 153f impact, 154 omohyoidectomy, usage, 149f

sternohyoidectomy, usage, 149 Soft palate, dorsal displacement (surgical treatment

options) (DDSP) anatomy, 147-148 comments, 154-155

cornplkations. 154 equipment, usage, 147

indications, 147 outcome, expectation, 154

positioning. 147 postoperative care, 153 preparation, 147 procedure, 148-153 references, 155- 156

Soft tissue dissection , 53 Spastic entropion, 173 Spermatic cord, 183f

emasculation, 187f emasculators, application, 184f musculofib rous portion, emasculation, 185f, 188f separation , 185f vascular portion, emasculation, 185f, 188f

Spinal accessory nerve identification, 159f insertion, 158f ventral branch, insertion, 158f

Splint bone amputation, 95f freeing. See Distal attachment removal, 95f

Index 271

Splint bone (Contill/led) resection. See Distal splint bone resection

Spl inting equipment, 25f Spl ints

application, indication, 118 cast combination, usage. See Dorsal splint cast

combination; Plantar splints extension. See Lateral splints usage. See Lateral splints

Sponge forceps, usage. See Vaginal ring eversion Squamous cell carcinoma

incis ions, intraoperative view, 204f prepuce, involvement, 202f

Stabilization. See Mid metacarpal-metatarsal tendon laceration repair

Stab incision, 149. See also Pastern sha llowness, 141

Stainless steel, characteristics, 1St Stance phase. See Limbs Standing sedation

drugs, usage, 35t restraint combinations, 34

Staphylectomy, 150-151 exercise restrictions, 153 medications, 153 procedures

alternatives, 151-153 postoperative care. 153

suture removal, 153 Steel concrete reinforcement rod, usage, 27 Stent bandage. usage, 20 Stent removal. See Cribbing Sternohyoidectomy

intraoperative view, 149f usage. See DDSP

Sternomandibularis muscle axial surface, 158f removal, 139f retraction, 158f

Sternothyrohyoideus muscles, separation, 138 Sternothyrohyoideus myectomy, 148- 150.

IS3f surgical approach, 149f

Sternothyrohyoideus tenectomy. ISO, 153f Sternothyroidectomy, intraoperative view,

149f Sternothyro ideus

insertion. See Thyroid cartilage inserts, usage, 148 musculotendinous section, view, 150f

Steven's tenotomy scissors, 170 Sti fle, extension, 77 Stockinette

double layer, 115 application, 114f

usage, 114f Straight Mayo scissors, 7f

inclusion. lOb

272 INDEX

Straight mosquito forceps, inclusion, lOb Stringhalt gait, 73f, 75 St ringhalt-like gait, 75 Subcutaneous patterns. See Suture Subcutaneous plane, creat ion, 70f Subcutaneous tissue

closure, 83, 90f option, 73

incision, 143, 212f partial closure, 22f walking sutures, usage, 21 f

Subcuticular patterns. See Suture Subjunctival closure, schematic. See Eyelid Submucosal perineal tissue

apposition,221f simple continuous patterns, usage, 233f

oversewing, 221 f Submucosal sutures pattern, preplacement. See

Rectovaginal fistu la Submucosal tissue

closure, 223 simple continuous pattern, usage, 224f

exposure, 237f Submucosa suture placement, sagittal cross, 238f Subsacral anesthesia, performing, 234f Suction drain, insertio n. See Jackson-Pratt negative

suction d rain Superficial digital flexor (SDF) tendonitis, 90. See also

Left forelimb Superficial digital fl exo r tendon (SDFT), 82f

con tracture. See Forelimbs; Left forelimb extrasynovial space, 71 lateral aspect, 67 pa rtial laceration, 62f repair, 64 tens ion, decrease, 113 in vitro strain, 91

Superficial inguinal ring location , 197f medial border, 199

Superficial retinaculum, closure, 90f Superficial structures, view, 133f Supraorbital foramen , location, 177-178 Suprao rbital nerve blocks

anatomy, 176 compl ications, 178 equipment, usage, 176 ind ications, 176 positioning, 176 preparation, 176 procedure, 176- 178 references, 178

Surgery decision , 3

general pack. See Field surgery patient preparation, 3-4

Surgical dissection. See Third-degree perineal laceration

Surgical instruments, 5-9 preparation, 9-10 references, 10

Surgical procedures. See Mid metaca rpal- metata rsal tendon laceration repair

Surgical treatment options. See Soft palate Suspensory ligament disruption, recovery, 62f Suture

continuous patterns, 17-18 horizontal mattress pattern, 18 materials

cha racteristics, 14t-15t usage, 13, 16

pa tterns. See Conti nuous horizontal matt ress suture pattern; Ford's interlocking pattern; Horizontal mattress sutures; Interrupted cruciate pattern; Modified far-near-near-far suture pattern; Simple continuous pattern; Simple interrupted pattern; Tendon lacerations

bolsters, usage. See Tension suture combination. See Vertical mattress sutures;

Verti cal mattress tension su ture impact, 16

placement, b isecting m ethod. See Hotz-Celsus blepharoplasty

placement/patterns, 16-20 scissors, inclusion, lOb securing, 20 simple interrupted patterns, 17·18 subcutaneous patterns, 18f, 20 subcuticular patterns, 20 tension patterns, 19-20 usage. See Tension suture vertical mattress pattern, 18-19

Swelling, complication. See Castration Synovial structure, involvement. See Mid

metacarpal-metatarsal tendon laceration .

repair Synthetic absorbable sutures, 16

T

Tap, usage, 58f Tape tabs, restructuring, 167 Tarsal fracture. See Section 3 tarsal fracture Tarsorrhaphy. See Temporary tarso rrhaphy TeJazol, 32 Temporary eyelid tacking, 174 Temporary heel elevation, acrylic (usage), 84f Temporary tarsorrhaphy

anatomy, 179 cleaning, 180 complications, 180 equipment, usage, 179 indica tions, 179 positioning, 179 postoperative ca re, 180 preparation, 179 procedure, 179-180

Temporary tarsorrhaphy (Coll tilllled) protection, 180 references, 180 sutu re removal, 180

Tendon lacerations. See Extensor tendon lacerations; Flexor tendo n

Kimzey splint support. See Deep digital flexor tendon

repair. See Mid metacarpal- metatarsal tendon laceration repair

sutu re patterns, 63-64 Tendon sheath , 68f

proximal. See Flexor tendon Tenectomy. See Lateral digital extensor tenectomy;

Sternothyrohyoideus tenectomy procedures, 148-153

postoperative ca re, 153 Te nsion-absorbing rectal tissues, 239 Tension band wire

insertion. See Cheek teeth placement, 124- 125

Tension patterns. See Suture Tension su ture

patterns. See Far-near-near-far tension su ture patterns; Near-far-far-near tension suture patterns

bolsters, usage, 18f

usage, 22 supports, bandages (application), 22f usage, 18f

Testicle anatomy, 3184f exposure, 184f exteriorization. See Abdominal testicle; Inguinal

testicle location. See Retained testicle prolapsing. 187f remova l. 199

mod ified parai nguinal approach. See Abdom inal testicle

Testicular attachments, identification, 199f Thiobarbi turate, 33 Thiopental. 33-34 Thiopental-guaifenesin combinations, 36-37 Thi rd-degree lace ration, occurrence, 233 Third-degree perineal laceration

conversion, 24 1 references, 234-235

surgical d issection. 229f Third-degree peri neal laceration repair

Aa nes technique, 230-232 comments. 233-234 complications, 233 cranial area, su ture pattern placement, 23lf dietary modifications. 233 equipment. usage, 228 exercise restrictions. 233 indications, 228

Index 273

Third-degree permeallaceration repa ir (Conti l/lled) medications, 233 modified Goetz technique. 229-230 one-stage repair, 228-230 outcome, expectation, 233 posit ioning. 228 postoperative ca re, 233 preparation. 228 procedure, 228-232 semitransverse closure technique, 230 suture removal, 233 two-stage repair, 230-232

Third metacarpal-meta tarsa l bone, 93 Third metatarsal bone, 27f Third phalanx

frac ture stab ilization, 116f rotation, 98f

Three-layer closure. close-up view, 224f Three-loop pulley. 64. 64f Three-way stopcock, usage, 2 1f. 57f Throat regio n. view. See Ventral th roat region T humb fo rceps. 6 T hyroid carti lage. 148f

sternothyroideus, insertion, 150f Tibia fractu re. See Section 3 tib ia fracture T ibiotarsal joint, entering, 51 Tie-forward procedure, 153 Tie-over bandage, 20 Tiletamine, 33 Tissue

adhesives, 20 forceps. 7f mobilization. direction, 223f removal . 62 walking sutures, usage. See Subcutaneous

tissue Toe

elevation. 62f extension, creation, 8lf

acrylic hoof material. usage, 81 f Tooth removal, 132 Tooth repulsion. See Mandibular tooth

anatomy, 132-133 comments, 137 compl ications, 135-136 equipment, llsage, 132 exe rcise restrictions, 135 indications, 132 medications. 135 outcome, expectation, 135 positioni ng, 132 postoperative care. 135 preparation. 132 procedure, 133-135

alternatives. 136-137 references, 137

Touhy needle, usage, 40 Tourniquet. application. See Esmarch bandage

274 INDEX

Towel clamps inclusion, lOb

--

ven trolateral positioning, 237f Towel stent, suture, 153f Tracheal cartilage, incision lines, 144f Tracheal muc6sa, double-Y incision,

144£ Tracheal mucosa-skin suture line, 145 Trachea l sections. removal, 144f Tracheostomy

anatomy, 143 completion, 144f complications, 145 equ ipment. usage, 143 exe rcise restri ction, 145 incision site, 144f indications, 143 medications, 145 outcome, expectation . 145 positioning, 143 postoperative care, 145 preparation, 143 procedure. 143-145

neck. ventral view, 144f references. 145 site. apposition. 145 suture removal, 145

Tracheotomy anatomy. 138 complications. 141 -142 equipment. usage. 138 incision site, 141 f indications, 138 med ications. 141 positioning, 138 postoperative care. 14 1 preparation, 138 procedure, 138, 14 1 references, 142 si te. view. 141 f tube

fit . 138 management, 141

Tranqui lizers, usage, 30-32 Transconjunctival enucleation

anatomy, 170 complications, 172 equipment, usage, 170 indications, 170 medications, 172

position ing, 170 postoperative care, 172 prepa ration, 170 procedure, 170- 172 protection, 172 references, 172 suture removal, 172

Transdermal delivery systems. 33

Transection . See Extrasynovial transection; Periosteal transection/elevation; Ultraso und guided transection

Transpalpebral enucleation anatomy, 170 approach. 172f com plications, 172 equ ipment, usage, 170 indica tions, 170 medications, 172 positioning. 170 postoperative care, 172 preparation. 170 procedure, 170, 172 protection, 172 references, 172 sutu re removal, 172

Transphyseal b ridging alternative, 53f anatomy, 50 bandaging. 52 comments, 53-54 complications, 52-53 equ ipment, usage, 50 exercise restrictions, 52 indications, 50 olLtcomes, expectation, 52 positioning, 50 postoperative care, 52 procedure, SO-52

alternatives, 53 references. 54 suture removal, 52

Transphyseallag-screw, S3 Transverse ureth ral fold

caudal reflection, 226f caudal retraction, 223f, 226f horizon tal splitting, 224f incision. 223f. 226f m ucosa (stri p), excision, 223f sutu re. See Ventro lateral vaginal wall vaginal wall, apposition , 226f

Trephination. See Diagnostic trephination; Sinus trephination

Trephines sites, limits (identification). See Frontal sin us;

Maxillary sinus usage. 134

Triceps apparatus, disabling, 28f Trigeminal nerve, maxillary branch, 176 Triple drip. usage. 36 Trocar

finger guidance, 166f po int, retraction, 130 usage. See Incision line

Tuber calcis, insertion, 105 Tunic

cran ial aspect, incision, 185f

Tunic (Continued) exteriorization, finger traction , l8Sf incision, 187f removal. See Open castration usage, 186f

Tunica albuginea, 206 closure, 20Sf

Two-layer closure, close-up view, 223f Two-stage repair. See Third-degree perineal laceration

. repair

u Ultrasound guided transection, 85

Umbilical hern iorrhaphy anatomy, 250

comments, 253 complications, 252-253

equipment, usage, 250 exercise restrictions, 252f

indications, 250

medications, 252f outcome, expectation, 252

positioning, 250 postoperative care, 252

preparation, 250 procedure, 250-252

alternatives, 253 references, 253

suture removal, 252f

Umbilical tape, usage. See Anal sphincter Urethra, 207f

involvement, 209

lumen, vertical incision, 207, 208f

sides, suture, 208f Urethral damage, 213

Urethral extension (urethroplasty)

Brown technique, 223 catheter removal, 227f

complications, 227 equipment, usage, 222

exercise restrictions, 227 indications, 222

McKinnon technique. 225-226 m edications, 227

Monin technique, 222-223

outcom e, expectation, 227 positioning, 222

posto perative care, 227 preparation, 222 procedure, 222-226

references, 227

Shires technique, 223, 225

Urethral mucosa, perineal skin (simple interrupted su tures), 212f

Urethral process, 203f

Urethral sinus, 203f

Urethroplasty techniques, Caslick's procedure, 226 Urethrostomy, 213

Urine output, transient increase, 3 1 Urolithiasis. 213

V

Vaginal canal. 183f

Index 275

Vaginal fistula, longitudinal closure (i nterrupted Lembert pattern, usage), 240f

Vaginal floor/roof, distance, 225 Vaginal lumen, pattern. 229f Vaginal mucosa

dissection, 242f dorsal evers ion, excision, 22Sf incision, caudal extension, 224f inversion, Connell pattern (usage), 229f, 241f

Vaginal process location, 197f opening, 198

Vaginal ring eversion (schematic), sponge fo rceps

(usagel, 199f Vaginal shelf

creation, 239f

dead space, elimination. See Rectal shelf

longitudinal midline incision , su rgical area (appearance),240f

Vaginal spatula, 222 Vaginal tissue flap (rotation), transverse cross-section,

239f Vaginal tuni c, twisting, 247f

Vaginal wall m ucosa, axial reflection, 226f suture line, 227f

Vascular status. See Mid metacarpa l- metatarsal tendon

laceration repair Ventral branch, insertion. See Spina l accessory nerve

Ventral canal iculus, obstruction, 164f

Ventral midline skin incision, 150 Ventral mucosal layer (inversion), Connell pattern

(usagel , 224f Ventral nasal concha, 129f

Ventral nasal meatus, 129f Ventral puncta, anatomy (schematic ), 161 f

Ventral throat region, view, 151£ Ventral vagi nal mucosa (dorsal eversion ), 30-Fr Foley

catheter (usage), 225f

Ventral vestibular mucosa margin closure, 219

cranial -to-caudal closure, simple continuous pattern (usage), 220f, 232f

Ventrolateral vaginal wall

incision , 223f transverse urethral fold , suture, 223f

Ventromedial subpalpebrallavage tube placement,

165 Vertical bites, 64

Vertical mattress pattern. See Suture Vertical mattress sutures (bolster inclusion), simple

interrupted appositional sutures (combination),

19f

276 IND EX

Vertical mattress tension suture, simple interrupted

appos itional suture patterns (combination), 19f

Vertical skin incision. See Lateral digital extenso r Vestibular mucosa, removal (proposed area), 220 f,

232f caudolateral view, 220£, 232£

Vestibulum, naso lac rimal pu nctum , 163£ Vest-over-pants, usage. See Rectovaginal fi stula

Vetrap, appl ication, 11 6 Viscera l lami na, 183£

Vulvar labia, incision (ending), 226£ Vulvar Li ps

apposition, 22 1 f, 233f towel clamps, 222

Vulvar mucocataneous margin, local anesthetic (infiltration),2 16f

Vulvar mucosa

apposition, Ford interlocking pattern (usage),

2 17f excision, scissors (usage), 217f

Vulvoplasty. See e asl ick's procedure

w Walking sutures, usage. See Subcu ta neous tissue Weight bearing surface, 115f Weitlaner retractors, 9f

usage, 87

Weitlaner sel f- retaining retractors, 147 Will iam's technique

triangular skin incision. See Penile amputation usage, 206-207

Wi re guide. See Hypodermic needle

Wire positioning. See Rostral mandibular fractures Wi re twists, bending, 51 f

Wounds

x

closure, II , 13 references, 23

debridement, 12-13. See also Mid metacarpal­

metatarsal tendon laceration repair lavage, 12

consideration, 12 preparation, 11 - 12

repair. See Mid metaca rpal- metatarsal tendon

laceration repair sc rubbing, mechanical effect, 12

site dista l site, drain, 2lf exudate, re moval, 2 1 f

Xylazi ne. See Guaifenesin ketamine xylazine

addition, 34

usage, 3 1, 35t

z Zimaloy Epiphyseal Staple, 53 Zolazepam, 32

concen tratio ns, 33

Zygo matic arch , 177f

Zygomatic nerve blocks anatomy, 176

complications, 178

equipment, usage, 176 indications, 176

positioning, 176 preparation, 176

procedure, 176- 178 references, 178