Lameness - Diagnostic Tests

Lameness: Diagnostic Tests Articles

Extracorporeal Shock Wave Therapy in Horses: What We Know Flex Test Forelimb Flexion Test The Use of Thermography in Lameness Evaluation Scintigraphy Arthroscopic Surgery: is it for treatment, diagnosis or both?

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Extracorporeal Shock Wave Therapy in Horses: What We Know

by By Scott R. McClure, DVM, PhD, Diplomate ACVS

A shock wave is an acoustic (pressure) wave with very high amplitude and rapid rise time. The original use of shock waves to fragment uroliths was expanded to orthopedic applications when, following a safety study, the density of a portion of the pelvis within the treatment area increased. Subsequently, the original musculoskeletal applications were associated with stimulation of nonunion fractures to heal. Multiple studies have documented the effectiveness of extracorporeal shock wave therapy (ESWT) in treating hypertrophic nonunions. Investigations into multiple other areas have led to the FDA approval of ESWT for heal spurs and recently tennis elbow.

There are multiple ways to generate a shock wave. The pressure wave can be instituted by vaporization of fluid across a spark gap (electrohydraulic), expansion of piezoelectric crystals (piezoelectric), or pushing a membrane with opposite electrical current (electromagnetic). In all three mechanisms, the pressure wave is brought to a focal point by lenses or a parabolic reflector. This mechanism allows the energy in the wave to aim at a specific point within the tissue. An alternative mechanism, radial pressure waves, has been developed. This utilizes a pneumatically driven device to strike the surface. This creates a pressure wave, but the parameters of the wave are different from that of a shock wave.

The mechanisms by which ESWT provides a therapeutic outcome are minimally understood. In vitro studies have shown that shock wave can stimulate the production of cytokines by cells and increase cellular division. In vivo studies have shown increased bone formation and healing of nonunions and neovascularization of bone-tendon junctions.

In the horse, multiple applications have been tried. One of the first case series completed was in a group of horses with bone spavin where 59 of 74 horses (80%) improved at least one lameness grade. Data from bone-healing studies would indicate ESWT would be beneficial in treating stress fractures in horses. While multiple users of this technology report good outcomes in stimulating stress fractures to heal, there have been no published reports. Similarly, multiple veterinarians have reported success in stimulating suspensory desmitis to heal and decrease lameness. The first clinical reports from two separate universities indicated seven of eight and five of six horses improved following treatment. A controlled study with collagenase-induced suspensory desmitis found that the defects filled in faster as determined by ultrasonography. So far there is data supporting the use of ESWT for suspensory desmitis, bone spavin, stress fractures and navicular syndrome. There are also multiple discussions as to the use of ESWT for tendonitis, subchondral bone cysts and for sore backs. With time, more controlled studies will be completed for a more thorough and objective assessment of outcome.

While the positives of this therapy are being evaluated, the negatives must be considered. Most importantly there is a period of analgesia following treatment. Humans treated with ESWT report an initial decrease in pain in the area treated, lasting up to a week, then some return of the original pain that gradually decreases as the underlying problem heals. In a study funded by the Grayson Foundation at Iowa State University, we found that in the horse, a period of analgesia appears to be present for about four days after treatment. The analgesia is not profound like a local anesthetic, but there is a decrease in pain perception. The exact mechanism is not known. There is some inflammation in the nerves in the treatment field. Researchers at Louisiana State University have found a decrease in sensory nerve conduction velocity following radial shock wave treatment.

Multiple racing jurisdictions have instituted or are considering regulations concerning when a horse can compete after being treated. Most are in the neighborhood of seven days. The FEI has determined that ESWT should not be used for five days prior to competition. This should allow the analgesia to regress. Additionally, the indications for shock wave therapy would indicate most horses should be on a decreased level of activity while healing.

The data indicate that there are benefits associated with ESWT. Additional controlled studies are indicated to fully evaluate this new therapeutic modality.

Dr. McClure is assistant professor at the Iowa State University College of Veterinary Medicine and has been a member of the AAEP since 1993

posted: 5/19/2003. Last updated: 5/19/2003.

Flex Test

by David W. Ramey, DVM

David W. Ramey, DVM

You’ve decided to sell your horse and the potential buyer has sent a veterinarian to our farm to perform a purchase exam. As you stand beaming with satisfaction next to who you hope will be the new owner, the veterinarian picks up your horse’s left front leg. Bending it at the knee, he holds it for about 60 seconds, returns it to the ground and asks that the horse be jogged down your asphalt drive. In astonishment, you watch as the horse moves off most decidedly lame. What happened?

What you have witnessed is a phenomenon not necessarily of the veterinarian’s creation, but something that can sometimes occur following a procedure called a forelimb flexion test. In a forelimb flexion test, various joints and soft tissue structures of the lower limb are stretched and/or compressed for a brief period of time by bending the limb. Afterward, the horse is immediately trotted off and observed for signs of lameness.

Forelimb flexion tests were described in Swedish veterinary literature as early as 1923. They appear to have become an integral part of the evaluation of the horse intended for sale. In performing the tests, a veterinarian will likely pick up the horse’s leg and bend it, with the bending force centering around the fetlock joint. He or she will hold the leg for a period of 30 seconds to 60 seconds, and then let go, asking the horse to trot off immediately.

The test is not unlike wht you might experience if someone asked you to sit in a crouch for sixty seconds and then run right off. Usually, you can run off just fine, but occasionally, you might experience some soreness or pain in the joint that results in some initial stiffness when you first try to run. You may be normal or the soreness could signal a problem (such as a bad knee).

While forelimb flexion tests are quite commonly performed, veterinarians have not agred on the optimum duration of the test, which can vary from 30 seconds to three minutes. Although there are devices available to measure the force applied during the test, these are not widely used in practice. A study involving 50 horses has been conducted to determine the effects that force of the test may have on the result. The study suggests that reliance on forelimb flexion tests for a diagnosis of impending lameness or other problems may not be reasonable. The study also indicates that a positive response to the test does not correlate well with other indicators, such as x-rays of the lower limb.

A positive response to forelimb flexion tests, meaning lameness was evident after the limb was released, is one reason horses may be deemed unsuitable for purchase during the prepurchase exam. There seems to be a wide range of significance attributed to these tests that varies according to opinion and the experience of the examiner. There have been many purchase exams discontinued solely because a positive response to a flexion test in one or both forelimbs. Because of the variable response to the test depending on such things as the force applied, duration of the test, age of the horse and the day of examination, demonstrated in this and other studies, discontinuation of a prepurchase examination based solely on a failed forelimb flexion test is probably unwarranted.

Owners and trainers have become increasingly skeptical of the significance of forelimb flexion tests during the examination. Horses can and do perform well for a variety of riding endeavors even then they do not perform well on a forelimb flexion test.

If you horse does respond to forelimb flexion test, don’t stop there. Further examination of the horse through the use of x-ray may be warranted. Look for other signs of a problem, such as lameness, loss of limb flexibility or a painful response to palpation and/or manipulation of the area that you suspect may be a problem. With a complete examination, you will likely receive the answer you need and could be looking for.

Dr. David Ramey is a 1983 graduate of Colorado State University. After completing an internship in equine medicine and surgery at Iowa State University, he entered private practice in southern California. His practice is devoted to the care of pleasure and performance horses of many different breeds and occupations. He is the author of numerous books and articles on horse health. He presented his findings during the 1997 AAEP Convention in Phoenix, Arizona.

Posted: July 2000

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Forelimb Flexion Test

by David Ramey, DVM

You've decided to sell your horse and the potential buyer has sent a veterinarian to your farm to perform a purchase exam. As you stand beaming with satisfaction next to who you hope will be the new owner, the veterinarian picks up your horse's left front leg. Bending it at the fetlock, he or she holds it for about 60 seconds, returns it to the ground, and asks that the horse be jogged down your asphalt drive. In astonishment, you watch as the horse moves off most decidedly lame. What happened?

What you have witnessed is a phenomenon not necessarily of the veterinarian's creation but something that can sometimes occur following a procedure called a forelimb flexion test. In a forelimb flexion test, various joints and soft tissue structures of the lower limb are stretched and/or compressed for a brief period of time by bending the limb. Afterward, the horse is immediately trotted off and observed for signs of lameness.

Forelimb flexion tests were described in Swedish veterinary literature as early as 1923. They have become an integral part of the evaluation of the lame horse and are routinely included in prepurchase evaluations of the horse intended for sale. In performing the tests, a veterinarian will likely pick up the horse's leg and bend it, with the bending force centering around the fetlock joint. He or she will hold the leg for a period of time, then let go, asking the horse to be trotted off immediately.

The test is not unlike what you might experience if someone asked you to sit in a crouch for sixty seconds, then run. Usually, you can run just fine, but occasionally, you might experience some soreness or pain in the joint that results in some initial stiffness. You might be normal or the soreness could signal a problem (such as a bad knee).

While forelimb flexion tests are quite commonly performed, veterinarians have not agreed on the optimum duration of the test, which according to reports can vary from 30 seconds to three minutes. Although there are devices available to measure the force applied during the test, these are not widely used in practice. A study involving 50 horses has been conducted to determine the effects that force of the test might have on the result. The study suggests that reliance on forelimb flexion tests for a diagnosis of impending lameness or other problems is not reasonable. The study also indicates that a positive response to the test does not correlate well with other indicators, such as X rays of the lower limb.

A positive response to forelimb flexion tests, meaning lameness was evident after the limb was released, is one reason horses might be deemed unsuitable for purchase during the prepurchase exam. There seems to be a wide range of significance attributed to these tests that varies according to opinion and the experience of the examiner. There appears to have been many purchase exams discontinued solely because of a positive response to a flexion test in one or both forelimbs. Because of the variable response to the test depending on such things as the force applied, duration of the test, age of the horse, and the day of examination (demonstrated in this and other studies), discontinuation of a prepurchase examination based solely on a failed forelimb flexion test probably is unwarranted.

Owners and trainers seem to have become increasingly skeptical of the significance of the forelimb flexion test during these examinations. Horses can and do perform well for a variety of riding endeavors even when they do not perform well on a forelimb flexion test.

If your horse does limp after a forelimb flexion test, don't stop there. Further examination of the horse through the use of such techniques as X ray might be warranted. Look for other supporting signs, such as lameness, loss of limb flexibility, or a painful response to palpation and/or manipulation of the area that you suspect could be a problem. With a complete examination, you will likely receive the answer you are looking for.

David Ramey, DVM, has a practice devoted to the care of pleasure and performance horses in Glendale, Calif., and he is the author of numerous books and articles on horse health. He presented his findings of this study during the 1997 AAEP Convention in Phoenix, Ariz. For a copy of this article and other articles of interest, check out AAEP Online at http://www.aaep.org.

American Association of Equine Practitioners4075 Iron Works PikeLexington, KY 40511

(606) 233-0147www.aaep.org


The Use of Thermography in Lameness Evaluation

by Tracy A. Turner, DVM, MS, Dipl. ACVS

Lameness diagnosis can be very frustrating when the source of pain is located in the upper leg and is not associated with a synovial structure, or the lameness is too subtle to utilize diagnostic analgesic injections, or the patient is not amenable to these injections, or the lameness is difficult to eliminate by local analgesic injection. These cases usually require the practitioner to treat the horse symptomatically or to perform other diagnostic techniques to try and determine possible areas of injury.

Thermography is one such technique. It is the pictorial representation of the surface temperature of an object. It is a non-invasive technique that measures emitted heat. A medical thermogram represents the surface temperatures of skin, making thermography useful for the detection of inflammation. Although thermographic images measure only skin temperature, they also reflect alterations in the circulation of deeper tissues. This ability to assess inflammatory change non-invasively makes thermography an ideal imaging tool to aid in the diagnosis of certain lameness conditions in the horse. The purpose of this paper is to describe the use of thermography as an aid to clinical lameness diagnosis.

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Thermography has most commonly been used to evaluate horses with back or hind limb lameness. The second most common use of thermography was to evaluate the horse for performance or pre-purchase. In this capacity, the horses were examined to determine if any area of inflammation that would account for decreased performance or determine a source of pain that might explain a horse’s change in attitude toward work or to try to identify subclinical areas of inflammation could be detected. Thermography has been used least frequently for investigation of forelimb problems. Thermography has provided significant information in 86% of the horses examined. Temperature changes were identified as either “hot spots” or “cold spots.” The thermographic image was very useful in localizing the area of injury, but did not characterize the specific nature or etiology of the injury. Investigation of the upper limb lameness was the region where thermography was most useful. The most frequent upper limb problems were located over large muscle masses and thought to be either muscle strains or muscle inflammation. In the upper foreleg, the most common areas of temperature asymmetry were located over the pectoralis muscles or the biceps brachii (shoulder). In those cases, showing increased heat over the shoulder region, meant we were able to identify specific lesions within the biceps tendon or bicipital bursa utilizing ultrasonography.

In the upper hind leg, abnormal thermal patterns of three distinct regions were commonly seen: cranial thigh, caudal thigh, and croup region. In the cranial thigh, distinct hot spots were associated with the quadriceps musculature just proximal to the insertion on the patella. In each of the cases, we subsequently have been able to find evidence of muscle damage utilizing ultrasonography. The caudal thigh thermography showed several common areas of abnormal heat: The most common was at the musculotendinous junction of the semitendinosus muscle. A third area of abnormal thermal patterns was commonly seen in the caudal thigh, just caudal to the third trochanter of the femur directly over the biceps femoris. The thermal changes noted were both a “hot spot” and an intense “cold spot.” We have not correlated any sonographic findings with this injury to date. The croup area injuries involved hot spots over the loin region, over the sacroiliac region, over the body of the gluteal muscle, and over the third trochanter. Ultrasonography has been used in these cases to characterize a “muscle cramp,” dorsal spinous ligament desmitis, and suspect sacroiliac desmitis. Fasciitis was diagnosed in one case based on muscle biopsy. In the assessment of horses that “tie up,” thermography indicated that the longissimus and gluteal muscle regions had the most intense heat. Further, the behavior the horse showed during the “tying-up” episode correlated with the thermal patterns. Horses that became stiff showed the most intense heat over the longissimus muscles, whereas horses that would stop and be very reluctant to move showed the most intense heat over the gluteal region.

New, more portable thermographic equipment is now available. Because of this, we have used thermography more frequently in the evaluation of forelimb lameness and in the evaluation of various exercise-related problems. Thermography is being used in the evaluation of forelimb lameness to assess the intensity of inflammation as well as to gain insight into stresses or inflammatory nature of various lamenesses. In addition, we can evaluate various problems at the barn under the conditions where the horse actually shows the problem. This has allowed several tack-related problems to be identified by the

thermal patterns caused by the tack while the horse is being ridden. It has been our experience that thermography specifically increases the accuracy of diagnosis by confirming inflammation in palpably sore areas and by providing objective data that indicate in which area to concentrate further diagnostic testing such as sonography, radiography, or muscle biopsy. Heat is one of the cardinal signs of inflammation and is associated with thermographic “hot spots.” “Cold spots,” however, may also be a sign of injury and reflect the presence of marked swelling or result from decreased circulation in damaged tissue or of the presence of dense scar tissue. Thermography, when combined with a thorough clinical examination by your veterinarian, is an excellent imaging technique for assessing lameness. It is particularly helpful in determining areas of inflammation in the upper limbs, but can also be readily used to assess inflammation of the lower limbs. It has been useful in assessing cases of palmar foot pain and has helped identify areas other than the navicular bone that may be sources of pain. It has been useful in the assessment of joint problems as well as tendon and ligament problems. Since the modality is non-invasive, it can readily be used. With recent technological advances, the equipment is completely portable and can readily be taken to farms, arenas, etc.

Tracy A. Turner, DVM, MS, Dipl. ACVS, Department of Clinical and Population Sciences, University of Minnesota, 1365 Gortner Ave, St. Paul, MN 55108


(606) 233-0147www.aaep.org


Scintigraphy

by Greg Roberts, DVM, MS, Dipl. ACVR

Not too many years ago, advanced imaging techniques such as radiography, ultrasonography, and scintigraphy only were available in human medicine or in veterinary university teaching hospitals. Now, these tools can be found in veterinary referral centers as well as private practices throughout the country. That is good news for horse owners, because the ability to combine information from a hands-on lameness evaluation with information from a variety of images might lead to an earlier and more reliable diagnosis.

Lameness Evaluation

In a lameness evaluation, a number of steps might be required before the diagnosis can be confirmed and treatment prescribed:


Signalment: age, breed, gender History: the current problem and the horse's current situation (workload, environment,

etc.)

Physical examination: observation at rest, during in-hand movement, on the longe line, and under saddle, if appropriate; palpation, manipulation, and flexion tests, if necessary

Regional anesthesia: a blocking agent can be injected near sensory nerves (even nerves inside a joint) to numb an area, then the veterinarian observes for improvement in the horse's way of going

Imaging: scintigraphy can be used as a screening test at this point to be followed up with radiographs or ultrasound the next day

Which steps are performed, and in what order, will depend on the nature of the lameness, the demeanor of the patient, and the budget of the client. A logical and thorough work-up, however, might return a horse to performance sooner and less expensively than guessing what is wrong and treating inappropriately. In addition, a complete examination might detect a sub-clinical problem (one not yet manifesting signs) before it develops into a more serious situation. Scintigraphy is particularly useful in this regard.

Scintigraphy is the process of intravenously administering low levels of a safe radioactive agent, then obtaining images with a special (gamma) camera for evaluation and display. There are three phases in the process: the vascular (blood) phase, which occurs immediately; the soft tissue phase, which can be visualized five minutes after the injection; and the bone phase, which occurs three to four hours later. The radioactive agent ends up in bone tissue because it is tagged with phosphorous, a normal component of bone.

In normal tissues, the injected compound is distributed evenly; abnormal tissues take up more (or less) of the compound. This difference in uptake is detected by the gamma camera and translated as "hot spots" or "cold spots" on a screen or printout. Hot spots are caused by anything that increases the blood supply, while cold spots are caused by anything that decreases the blood supply. Hot spots in soft tissue usually relate to inflammation--an injury to a muscle, tendon, or ligament is one example. Cold spots in soft tissue indicate a disruption in circulation--a blood clot, for example. Hot spots in bone indicate active bone turnover or remodeling, while cold spots in bone indicate diminished bone turnover or remodeling. Causes of increased bone activity include growth in young horses, fractures, joint disease, and cancer, among others. Cancer also is one of the causes of decreased bone activity.

Because scintigraphy is based on the function of tissues, it is a highly sensitive tool, especially for detecting early musculoskeletal problems such as navicular syndrome, stress fractures, and degenerative joint disease. It also is useful when more than one lesion is suspected; when the problem area cannot be pinpointed; for upper limb, pelvis, and back injuries; and to evaluate healing. However, as described earlier, it merely indicates that there is increased or decreased activity in an area, it does not provide any information about what might be causing the change in activity.

Scintigraphy is not unlike your smoke detector. Both are capable of picking up very small amounts of evidence that something is wrong, prompting you to determine the cause. This limitation is the reason a complete lameness evaluation--including additional imaging techniques--must be performed on the unsound horse.

Think of other imaging techniques such as radiography and ultrasonography as being like your home's alarm system--when it goes off, it tells you exactly which door or window the burglar has

already broken open to get in. Both are very specific--if you see a fracture in a bone or a defect in a tendon, there can be no doubt of the cause of the lameness. But these modalities are not very sensitive--it might be weeks before enough damage is done to a bone or tendon for these techniques to be able to detect it.

Conclusion

By combining the physical imaging of radiography and ultrasonography with the physiological imaging of scintigraphy, veterinarians are able to determine the cause of lameness more often and more accurately. Despite these technological advances, it still is the responsibility of an owner to understand when his or her horse is not performing well and present the horse to a veterinarian for a thorough evaluation.


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Arthroscopic Surgery: is it for treatment, diagnosis or both?

by Lydia F. Miller, DVM

Lydia F. Miller, DVM,

Arthroscopic surgery is the best tool veterinarians have for visually inspecting the condition of a joint. That gives it a place not only in the treatment of joint lameness, but also in its diagnosis.

"The typical lameness work-up begins with a history-taking, a general physical examination and an examination of the musculoskeletal system," says Dr. Mark Martinelli, DVM, PhD, Dipl ACVS and clinical assistant professor of equine surgery at the University of Illinois College of Veterinary Medicine.

"The musculoskeletal examination may include palpation, observation in motion and flexion tests," he says. Based on the results, the veterinarian may try to identify the location of the lameness with diagnostic anesthesia, commonly referred to as nerve or joint blocks. Radiographs, or x-rays, may be the next step. Inconclusive findings here may send the horse to scintigraphy, where a computer-generated picture of "hot spots" (inflamed areas that have taken up more of an intravenously injected, safe, radioactive compound) may help localize the problem.

However, none of these techniques ensure that the joint is the root of the lameness or indicate how severely affected the joint is. Because arthroscopic surgery has many benefits and few


disadvantages, veterinarians may often recommend this procedure earlier in the work-up of a lameness that appears to be joint-related.

"Arthroscopic surgery is minimally invasive and has almost no drawbacks," says Dr. Martinelli. Because the horse must undergo general anesthesia for the procedure, there is some risk involved, but with today’s modern screening techniques, safer compounds and improved monitoring during surgery, that risk is slight. In addition, whenever surgery is performed on a horse there is always the risk of infection, but this, too, is minimized with arthroscopy due to high volumes of fluid flushing through the joint as part of the procedure.

Compared to the earlier surgical procedure for examining a joint, arthrotomy, arthroscopy provides:

o a better view of the joint and all its components o decreased aftereffects of surgery (that is, the horse goes home sooner) o improved cosmetic appearance afterwards o quicker return to full function

In medical language, "arth" means joint. "Scope" refers to an instrument for observing or examining and "otomy" refers to a surgical incision into an organ or part. Together, an "arthroscope" is an instrument inserted into the cavity of a joint in order to inspect the contents and an "arthrotomy" is the surgical incision of a joint capsule in order to inspect the contents.

In an arthroscopic surgery, two to three tiny "nicks" are made through the skin and joint capsule in order to insert the arthroscope and other instruments as needed. The joint cavity is inspected, any bone chips or loose cartilage are removed and the area is flushed to remove small fragments and inflammatory products. The "nicks" are usually closed with one suture each and rarely can signs of this surgery be detected afterwards.

On the other hand, an arthrotomy involves one or more large incisions over the entire joint to allow the veterinarian to see inside firsthand, without the aid of a magnifying scope that can reach from one end of the joint to another. Not only does the skin require an entire row of sutures, but the joint capsule itself must be sutured back together. Recovery is prolonged due to pain, swelling and weakened structures. In addition, there may be permanent loss of range of motion and scarring.

"After arthroscopic surgery, most horses don’t usually know they’ve had anything done to them," says Dr. Martinelli. Horses walk back to their stalls following the procedure and most go home the next day. A minimum of two weeks stall rest is usually recommended, but the type and length of aftercare depends on the horse, the specific joint and condition being treated, and the extent of the surgery. While pain-killers are not usually necessary, some joint therapy may be indicated; consult your veterinarian before starting or even continuing injections or oral supplements.

Science and technology continue to provide us with better and better tools for prolonging the athletic life of horses (as well as humans). But in order to get the most benefit out of arthroscopic surgery or any procedure, early recognition that there is a problem is vital. Just as important is knowing what can be done to help prevent problems. In the case of joint disease, proper footing, training and conditioning—together with close observation and regular veterinary care—are your best strategies.


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Lameness - Diagnostic Tests