Diagnosis and Treatment ofFinger Deformities FollowingInjuries to the Extensor TendonMechanism

Martin A. Posner, MDa,b,*, Steven M. Green, MDa,b

KEYWORDS

� Extensor tendon anatomy � Boutonniere deformity � Intrinsic contracture and release

KEY POINTS

� Normal extension of the metacarpophalangeal, proximal interphalangeal, and distal interphalangealjoints depends on the coordinated action of the extrinsic extensor and intrinsic musculotendinousunits as well as the static stabilizers.

� Careful physical examination is critical in the evaluation of injuries to the extensor mechanism.

� Treatment methods include immobilization and surgery.

The extensor digitorum communis (EDC) tendonsto the 4 fingers, together with the extensor indicisproprius (EIP) to the index finger and the extensordigit quinti proprius (EDQP) to the little finger,begin in the forearm, course across the wrist andhand, and end at the metacarpophalangeal (MP)joints. They are independent tendons except onthe dorsum of the hand where there are intertendi-nous connections referred to as juncturae tendi-num. Distal to the MP joints the EDC, EIP, andEDQP tendons become the extrinsic componentof the extensor tendon mechanism of each fingerthat also receives a component from the intrinsicmuscles.

Injuries to the extensor tendons at the level ofthe MP joints and to the extensor tendon mecha-nisms in the fingers are common. These injuriesand their treatment will be discussed at 4 anatomicsites: the MP joints, the dorsum of the proximalsegments of the fingers, the dorsum of the

a Division of Hand Surgery, Hospital for Joint Diseases, NUniversity School of Medicine, New York University, New* Corresponding author. New York University School ofYork, NY 10128.E-mail address: mposner500@yahoo.com

Hand Clin 29 (2013) 269–281http://dx.doi.org/10.1016/j.hcl.2013.03.0030749-0712/13/$ – see front matter � 2013 Elsevier Inc. All

proximal interphalangeal (PIP) joints, and thedorsum of the distal interphalangeal (DIP) joints.

MP JOINT

The extensor tendon in each finger is held in itsnormal midline dorsal position over the MP jointby radial and ulnar sagittal bands that insert intothe sides of the volar plate, forming a closedcylindrical-like tube that surrounds the joint andthe metacarpal head.1 The radial sagittal bandsare usually thinner and longer than the ulnarsagittal bands. The extensor tendons exert theirforce through both sagittal bands to the volarplates to form slinglike structures that extend thejoints. Open injuries to the extensor tendons andsagittal bands are common, and should be re-paired when lacerated. Repair of the extensortendon restores MP joint extension, and repair ofthe sagittal band prevents displacement of the

ew York University, New York, NY, USA; b New YorkYork, NY, USA

Medicine, New York University, 2 East 88 Street, New

rights reserved. hand.th

eclinics.com

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tendon to the opposite side. Even in the absenceof injury to the extensor tendon itself, a sagittalband injury that is not repaired often results in anextension lag of the joint. Postoperatively, a volarsplint is used to immobilize the wrist in moderateextension and the MP joints in approximately 30�

of flexion. Immobilizing theMP joints of all 4 fingersrather than only the MP joint of the operated fingeris preferred for 3 to 4 weeks to protect the surgicalrepair. A splint limited to the injured finger can thenbe used for an additional 2 weeks. Because theMP joints are immobilized in slight flexion, thereis little risk that significant extension contractureswill develop.In some cases, an open injury to the dorsum of

an MP joint is caused by a puncture wound froma tooth when an individual punches another inthe mouth. These injuries are serious because ofthe high risk of infection, especially when treat-ment is delayed. Fist injuries are equivalent tohuman bites and require antibiotics as well as sur-gical exploration, irrigation, and debridement. Thewound is left open, although when extensive, theskin edges can be loosely approximated with 1or 2 sutures. The extensor tendon is rarely disrup-ted in these injuries, but there may be a defect inthe radial or ulnar sagittal band.Closed injuries to the dorsum of MP joints are far

more common than open injuries, and the tendondislocations that ensue are commonly classifiedinto traumatic and spontaneous groups. Traumaticdislocations can follow a direct blow to the area,sudden forceful flexion of the joint, or a forceful tor-sion injury to the joint that frequently occurs inindividuals who, while driving, are tightly grippingthe steering wheel that suddenly spins in theirhand. Patients in the spontaneous group of tendondislocations may not be immediately aware of anyinjury and later recall that the problem followedwhat they thought was a seemingly trivial episode,such as opening a tight jar lid.When discussing traumatic and spontaneous

extensor tendon dislocations, it is important to un-derstand the anatomy of their relationship to thesagittal bands. Each sagittal band consists of a su-perficial and deep layer. The superficial layers ofthe radial and ulnar sagittal bands form a contin-uous layer superficial to the tendon, whereas thethicker deep layers provide a groove for thetendon as it courses across the MP joint. Thereis no separation between superficial and deeplayers, but there is a separation between thedeep layer and the underlying joint capsule. Theloose connective tissue in this interval can easilybe dissected in order to mobilize the tendon. Trau-matic extensor tendon dislocations are usually theresult of tears in both superficial and deep layers of

the radial sagittal band at a site several millimetersfrom the tendon. Spontaneous dislocations alsoresult from tears in the sagittal band and, as withtraumatic dislocations, it usually involves, theradial sagittal band. However, only the superficiallayer is disrupted and at a site immediately adja-cent to the tendon; the deep layer remains intact.2

Regardless of the cause, most closed traumaticand spontaneous extensor tendon dislocationsinvolve the middle finger, followed in frequencyby the ring finger.3 The index and little fingersare not commonly involved, and the patterns ofdislocations of the 2 tendons in each, the EDCand the proprius, can vary. In the index finger,both tendons can dislocate ulnarly when the tearis in the radial sagittal band, or the EDC can shiftradially and the EIP ulnarly when the tear is be-tween the tendons. In the little finger, dislocationsof the EDC and EDQP can follow similar patterns.However, the little finger differs from the indexfinger in that the EDC is absent in most individualsand is replaced by a junctura tendinum thatattaches the ring finger EDC to the extensoraponeurosis of the little finger just proximal tothe MP joint.4

The treatment of closed traumatic and sponta-neous tendon dislocation injuries depends on theirseverity and the temporal interval between injuryand diagnosis. In many cases, the tendon doesnot actually dislocate into the groove betweenthe metacarpal heads but rather shifts slightlyfrom its normal midline position over the MP joint,usually in an ulnar direction; the tendon subluxatesrather than dislocates. When the subluxation ismild and not accompanied by any snap of thetendon with MP flexion, there is rarely a disabilityand treatment is not required. However, a sublux-ated or dislocated tendon that snaps with jointflexion usually requires treatment. For the acuteproblem, and generally this is considered to bewithin 2 weeks of the injury, the injured finger is im-mobilized in sufficient MP extension to permit thetendon to resume its normal midline position.5

This position is easily determined by passively ex-tending the MP joint and noting the position wherethe extensor tendon spontaneously relocates to itsnormal position. Generally, it is approximately 20�

of flexion, and this is the position that the joint isimmobilized rather than in full extension, which ismore likely to result in an extension contracture.The most comfortable and effective splint is palmbased and fabricated by a hand therapist from athermoplastic material that immobilizes only theMP joint (Fig. 1). The splint should not interferewith interphalangeal joint motions and is worn for4 to 5 weeks. Patients can remove it to bathe pro-vided they do not attempt to flex the MP joint.

Fig. 1. Effective treatment of the acute or subacuteextensor tendon dislocation is achieved with a staticpalm-based splint that immobilizes the MP joint inslight flexion and does not interfere with motions ofthe interphalangeal joints.

Fig. 2. (A, B) A 25-year-old man sustained blunt trauma andearlier. The laceration was sutured in a local emergency dlater, he received no further medical care. He noted that tination showed that the extensor tendons were ulnarly sboth fingers were attenuated, more in the middle fingerboth fingers had undergone secondary contractures. (D)divide the ulnar sagittal fibers in both fingers (probe on cfibers. (E, F) Postoperatively, the extensor tendons were rejoints, and digital mobility was complete.

Extensor Tendon Mechanism Injuries 271

For chronic injuries of more than 2 weeks dura-tion, surgery is usually necessary unless theextensor tendon still spontaneously shifts backto its normal midline position with MP extension.In such cases, a splint is used. However, splintimmobilization is not as effective for chronic in-juries as it is for acute injuries, and patients shouldbe informed that they could require later surgery.When surgery is performed, all that is necessary,in most cases, is to mobilize the extensor tendon,restore it to its midline position over the MP joint,and repair the tear in the radial sagittal band tomaintain the tendon in its correct position. Insome chronic cases, the fibers of the intact ulnarsagittal band have contracted and they must bedivided via a longitudinal incision to permit reloca-tion of the extensor tendon. It may also be neces-sary to imbricate the radial sagittal fibers tostabilize the tendon after it is restored to its properposition (Fig. 2). When imbrication of the radialsagittal band is not feasible because the tissuesare too attenuated, a different procedure is

a laceration to the dorsum of his right hand 2 monthsepartment; following removal of the sutures 1 week

he index and middle fingers were deviated, and exam-ubluxated. (C) At surgery, the radial sagittal fibers inthan the index finger, and the ulnar sagittal fibers inTo relocate the extensor tendons, it was necessary tout fibers in middle finger) and reef the radial sagittalstored to their normal midline positions over the MP

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required to stabilize the tendon in its normal posi-tion. A variety of operative techniques have beendescribed that generally report favorable results.6

Most techniques involve using a strip of theextensor tendon, either from its radial or ulnarside, that is looped around the lumbrical or theradial collateral ligament or is passed through thedeep transverse metacarpal ligament.7–10 Re-gardless of the technique, postoperative immobili-zation is similar to that used for acute closedinjuries; the MP joints of all fingers are immobilizedas well as the wrist that is positioned in moderateextension for the first 3 to 4 weeks followed by apalm-based splint confined to the injured fingerfor another 2 weeks.

DORSUM OF PROXIMAL SEGMENT

The distal extension of the extrinsic EDC in thefinger is the central tendon (often referred to asthe central slip) that courses over the proximalphalanx and inserts into the base of the middlephalanx. Attached to the radial and ulnar sides ofthe central tendon are transverse and oblique fi-bers from the lateral bands that arise from theintrinsic muscles. The extrinsic central tendonand the intrinsic lateral bands, together with theirtransverse and oblique fibers, cover approximately75%of the circumference of a proximal phalanx onits dorsal, radial, and ulnar surfaces. The only sur-face of the phalanx not covered is the volar surfacethat is the site of attachment for the flexor tendonsheath and where the flexor superficialis and pro-fundus tendons course distally to their insertionson the middle and distal phalanges, respectively.Scarring of the extrinsic (central tendon) andintrinsic components (lateral bands and their trans-verse and oblique fibers) of the extensor tendonmechanism are common following fractures ofthe proximal phalanx or following less severe in-juries that result in swelling that leads to scarringand adhesions. In most cases, either the extrinsicor intrinsic component is scarred to the underlyingbone; in some cases both components arescarred. Identifying the scarred component isdetermined by clinical examination. With scarringof the extrinsic tendon component, there is anextension contracture of the PIP joint that is un-changed regardless of the position of the MP joint.With scarring of the intrinsic tendon component tothe radial and/or ulnar side of the phalanx the clin-ical examination can be identical with respect tothe extension contracture of the PIP joint. Howev-er, most cases of scarring of the intrinsic compo-nent are more proximal in the interossei musclesthemselves, which is evident by performing theBunnell test for intrinsic tightness.

The Bunnell test is a completely passive test thathas 2 parts and is performed with the patient’shand totally relaxed. In part one, the examiner po-sitions the MP joint in maximum extension that isusually hyperextension that results in the intrinsicsto the finger being stretched because they arevolar to the axis of MP motions. The examinerthen attempts to passively flex the PIP joint anddetermines if there is any limitation and the degreeof that limitation. When passive PIP flexion is com-plete with the MP joint maximally extended, the in-trinsics are normal and are not contracted.However, when passive PIP flexion is limited,part two of the test is performed to determine ifthe limitation in passive PIP flexion is caused bythe contracture of the joint capsule. The examinernow positions the MP joint in full flexion, which re-laxes the intrinsics, and again attempts topassively flex the PIP joint. When passive PIPflexion is limited with MP hyperextension but notwith MP flexion, there are contractures of the in-trinsics and not the joint capsule. Often, theintrinsic on one side of a finger is more contractedthan the intrinsic on the opposite side, which canbe determined by not only hyperextending theMP joint but also pushing the proximal phalanx inits hyperextended position as far ulnarly aspossible and then as far radially as possible. Theeffect when pushing the phalanx ulnarly is thatthe intrinsic on the radial side of the finger isstretched more than the intrinsic on the ulnarside of the finger. Pushing the phalanx radiallydoes the opposite; the intrinsic on the ulnar sideof the finger is stretched more than the intrinsicon the radial side. For example, hyperextendingthe MP joint of an index finger and pushing theproximal phalanx as far ulnarly as possible putsthe radial intrinsic, the first dorsal interosseousmuscle, under greater stretch than the ulnarintrinsic, the first volar interosseous muscle. Hy-perextending the MP joint and pushing it as farradial as possible has the opposite effect, it putsthe first volar interosseous muscle under greaterstretch than the first dorsal interosseous muscle(Fig. 3).When PIP flexion is limited with the MP joint

positioned in hyperextension and also in flexion,the reason is almost always a capsular contractureof the PIP joint, although it can also be caused byisolated scarring of the central tendon to thedorsum of the proximal phalanx. Differentiatingbetween the two diagnoses may not be possibleon a clinical examination but can usually be antic-ipated when considering the nature of the injury.For example, a patient who sustained a fractureof the proximal phalanx that healed with bonycallus under the central tendon is more likely to

Fig. 3. (A) The MP joint when hyperextended and deviated radially results in tension on the first volar inteross-eous that is tight. (B) Deviating the hyperextended MP joint ulnarly showed that there was no tightness of thefirst dorsal interosseous muscle.

Extensor Tendon Mechanism Injuries 273

have scarring of the central tendon than having acontracture of the PIP joint capsule, although acapsular contracture can develop as a secondaryproblem in chronic cases. At surgery, attention isfirst directed to lysing the adhesions of the centraltendon to the underlying proximal phalanx. A PIPcapsulectomy is necessary when PIP passiveflexion remains limited after the tenolysis iscompleted (Fig. 4). An extension contracture of aPIP joint also does not exclude the possibilitythat there are also intrinsic contractures because

Fig. 4. (A, B) A 6-year-old child had sustained a crush-typeleft index finger several months earlier. The child was unato passive flexion. (C) A lateral radiograph showed periostsurgery, the central tendon was scarred to the phalanx. (almost complete finger mobility.

both problems frequently coexist. It is, therefore,important to perform the Bunnell test at surgeryfollowing a PIP joint capsulectomy to determine ifthere are concomitant intrinsic contractures.When present, intrinsic releases are necessary.

There are 2 types of intrinsic releases that areclassified according to the site where they are per-formed. When performed proximal to the MP joint,they are referred to as proximal intrinsic releasesand when performed distal to the MP joint, distalintrinsic releases (Fig. 5). The indication to perform

injury to the dorsum of the proximal segment of herble to actively flex the PIP joint, and there was a blockeal bone formation beneath the central tendon. (D) AtE) A tenolysis was performed, and the child regained

Fig. 5. (A) A lateral band and its transverse and obli-que fibers that attach to the central extensor tendon.(B) A proximal intrinsic release. (C) The triangle oftissue consisting of the lateral band and its oblique fi-bers that are excised in a distal intrinsic release. (D)The results of a distal intrinsic release that preservesthe transverse fibers arising from the lateral band.

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one type of intrinsic release versus the other de-pends on the site of the contracture and that isdetermined by a clinical examination. Becausethe intrinsics flex the MP joints and extend thePIP joints, active and passive motions of thesejoints are evaluated. When active MP joint exten-sion and active PIP flexion are limited, the intrinsiccontracture is proximal to theMP joint, and it is thisarea that the intrinsics must be released, both attheir insertions into the proximal phalanx and thelateral bands. Proximal intrinsic contractures arecommon in patients with inflammatory types ofarthritis, such as rheumatoid arthritis, whose MPjoints are often volarly subluxated. Arthroplastiesof the MP joints with the insertion of siliconeimplants are proximal releases because with exci-sion of the metacarpal heads, there is a significantdecrease in the distances between the origins andinsertions of the intrinsic muscles.Most patients with intrinsic contractures have no

problems with MP joint motions, only PIP joint

motions. Because their MP motions are normal,the components of the intrinsics that affect thatjoint, namely, the insertions of the intrinsic muscleson the bases of the proximal phalanges and thetransverse fibers that extend from the lateralbands to the central tendon and assist in MPflexion, need not be disturbed. These patients donot need proximal intrinsic releases but ratherdistal intrinsic releases. For each involved finger,it consists of excision of the triangle of tissuecomposing one or both lateral bands and their ob-lique fibers; the transverse fibers are preserved. Adistal intrinsic release is performed through a lon-gitudinal incision on the dorsum of the proximalsegment of the finger. Visualizing the lateral bandwith its transverse and oblique fibers is not difficultand is facilitated by deviating the finger in theopposite direction that puts the fibers understretch (Fig. 6). The Bunnell test that was per-formed preoperatively is repeated at surgery todetermine if the intrinsic on one side of the fingeris more contracted than the intrinsic on the otherside of the finger. When they are contracted onboth sides and the contractures are of equalseverity, it is dealer’s choice in deciding whichintrinsic lateral band and oblique fibers are excisedfirst. In those cases when there is deviation of theMP joint to one side, it is preferable to first excisethe intrinsic on that side because it is usuallytighter than the intrinsic on the opposite side. Insome cases, intrinsic tightness is not relievedfollowing excision of one lateral band and its obli-que fibers, and it is then necessary to excise thelateral band and oblique fibers on the other sideof the finger. A distal intrinsic release is not a diffi-cult surgical procedure, and its beneficial effectsin eliminating the contracture are immediatelyevident by performing a Bunnell test.

PIP JOINT: THE BOUTONNIERE DEFORMITY

In 1930, Mason11 succinctly explained the patho-physiology of the deformity: “It is the middleportion of the dorsal aponeurosis which ruptures,the two lateral slips now loosen from their attach-ment about the joint slip palmarward, and the jointcomes to lie between them as in a ‘buttonhole’.”11

The deformity in English-speaking countries isreferred to by the French word for buttonhole,that is, boutonniere; in French-speaking countries,it has been curiously Anglicized and is referred toas deformite buttonhole. The deformity consistsof weakness and loss of extension of the PIP jointand hyperextension and diminished active andpassive flexion of the DIP joint (Fig. 7). It beginswith disruption of the central tendon (Fig. 8) thatis often caused by sudden forced flexion of a PIP

Fig. 6. (A) Surgical sequence for a distal intrinsic release of the ulnar intrinsic (third dorsal interosseous) in a mid-dle finger following similar surgery for the index finger. The operative incision is longitudinal over the middle ofthe proximal finger segment that provides excellent visualization of the central tendon, the ulnar lateral band,and its transverse and oblique fibers. (B) The triangle of tissue consisting of the lateral band and the obliquefibers is outlined before excision. (C) Following excision of the triangle of tissue, a Bunnell test is performedto insure that the preoperative intrinsic contracture was eliminated.

Extensor Tendon Mechanism Injuries 275

joint that is actively being extended, resulting in aneccentric load on the finger. The central tendoncan also be injured by an open injury, such as alaceration (Fig. 9), follow an infection, chemicalor thermal injury, or result from an inflammatorytype of arthritis (Fig. 10). In some cases, the cen-tral tendon disruption is accompanied by volardislocation of the PIP joint (Fig. 11), or (rarely) thetendon avulses with a fragment from the dorsalbase of the middle phalanx. The triangular liga-ment that connects the 2 lateral bands may be

Fig. 7. Boutonniere deformity with flexion of the PIPjoint and hyperextension of the DIP joint.

initially injured together with the central tendon orit subsequently becomes stretched, permittingthe lateral bands to shift volar to the axis of thePIP joint. Contractures of the oblique retinacularligament, the volar plate of the PIP joint, and thecollateral ligaments of the DIP joint then ensue(Figs. 12 and 13).

Boutonniere deformities have been classifiedinto 5 stages.12,13

Stage 1: Active extension of the PIP jointmay beweak, and the joint may be in a slightly flexedposition; but active extension is still possiblevia the lateral bands that essentially remainin their normal anatomic positions.

Stage 2: The triangular ligament has attenuated,and there is a volar shift of both lateral bandsvolar to the axis of joint motions. Activeextension of the PIP joint is now seriouslyaffected.

Stage 3: There is progressive hyperextensionof the DIP joint because the extensionforce of the intrinsic muscles is exclusivelyto that joint. Active and passive flexion ofthe DIP joint is also limited because of thecontracture of the oblique retinacularligaments.

Fig. 8. Normal static and dynamic components. TRL, transverse retinacular lig; OBL, oblique retinacular lig.

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Stage 4: There is a fixed flexion contracture ofthe PIP joint because of the contracture ofthe volar plate.

Stage5: Theboutonnieredeformity isassociatedwith articular degeneration of the PIP joint.

Elson described a diagnostic clinical examina-tion technique to evaluate the integrity of the cen-tral slip by positioning the PIP in 90� of flexion andcomparing the resting position of the DIP joint withthe same joint in the contralateral uninjured digit.14

He then asked the patient to actively extend thePIP joint of the injured finger against resistance;he noted that when the central tendon was disrup-ted, the active PIP joint extension was weak. TheDIP joint also hyperextended, and passive flexionwas restricted. Boyes15 noted that with centraltendon ruptures, active flexion of the DIP jointwas limited when the PIP joint was passively posi-tioned in full extension. Rubin16 evaluated thediagnostic effectiveness of the Elson and Boyesmethods, as well as other methods, using cadaverdigits and concluded that the Elson test was themost effective diagnostic test.16–19

Treatment of a boutonniere deformity dependson its stage. For the acute injury (within the first2 weeks), immobilization of the proximal interpha-langeal joint in full extension for 4 to 5 weeks usinga static splint that permits active and passiveflexion of the DIP joint is usually effective(Fig. 14). Surgery is recommended only for anacute laceration of the central tendon or for a

Fig. 9. Laceration of the central tendon.

closed injury when the tendon avulses with a frag-ment from the dorsal base of the middle phalanx.Subacute injuries (2–8 weeks) may present with

either supple or stiff joints. When the PIP is suppleand can be passively extended and there is nolaceration or fracture, extension splinting, as forthe acute injury, is the treatment of choice. How-ever, when the injury is caused by a laceration orthere is a displaced fracture fragment, surgery isnecessary. Often, there are early flexion contrac-tures in subacute injuries that are not yet fixedand respond to dynamic and/or static progressiveextension splints. Frequently, sufficient joint mo-tions can be restored with these splints that sur-gery can be avoided.The treatment of the chronic injury (more than

8 weeks) is significantly more complicated be-cause disruption of the central tendon is no longeran isolated problem. The triangular ligament hasbecome attenuated, and the lateral bands havedisplaced volar to the axis of the PIP joint wherethey usually become fixed because of secondarycontractures of the transverse retinacular liga-ments. The oblique retinacular ligaments usuallyalso contract together with the volar plate of thePIP joint and the collateral ligaments of the DIPjoint. In those patients whose interphalangealjoints remain supple, an anatomic repair is recom-mended to restore active PIP joint extension. Theoperation is performed through a curved dorsalskin incision with its apex midaxial on either the

Fig. 10. Rheumatoid pannus (arrow) seen after reflec-tion of the central slip.

Fig. 11. Volar PIP joint dislocation.

Fig. 13. Elson test. Note exaggerated DIP extension ofthe injured right middle finger.

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radial or ulnar side of the finger. Elevation of theskin flap permits excellent visualization of the cen-tral slip that is usually retracted, the subluxatedradial and ulnar lateral bands, and the contractedtransverse retinacular ligaments. Incisions aremade on the volar margins of both lateral bands,releasing them from their connections to the trans-verse retinacular ligaments. This release permitsthe lateral bands to be shifted back to their normalanatomic positions dorsal to the axis of PIP jointmotions. The scarred and attenuated triangular lig-ament is excised, and the lateral bands are suturetogether at that site with 2 or 3 sutures of a finegrade (4–0 or 5–0). It is important not to insertany sutures proximal to the PIP joint that wouldlikely result in an extension contracture. If pos-sible, the central tendon and redundant scar tissueare elevated off the middle phalanx, and the cen-tral tendon is reattached into the middle phalanxusing a small bone anchor (Fig. 15). In somecases, the central tendon has retracted and itmay not be possible to reattach it. The PIP jointis temporarily stabilized with a Kirschner wire tofacilitate early mobilization of the DIP joint. Thewire is removed in 4 to 6 weeks, when active PIPexercises are encouraged.

When the integrity of the central tendon has beenseverely compromised, a variety of operative pro-cedures have been described to restore its func-tion. Mattev20 recommended cutting one lateralband at the distal extent of the triangular ligament

Fig. 12. Boutonniere deformity with disruption of the centcontractures of the transverse (TRL) and oblique retinacul

and the other lateral band at the base of the middlephalanx. The shorter of the two lateral bands wasthen passed through the proximal portion of thecentral slip and inserted into the dorsal base ofthe middle phalanx. The longer lateral band thathadbeencut at the triangular ligamentwas then su-tured to the distal portion of the contralateral lateralband, thus creating an elongated lateral band.Littler and Eaton21 suggested a reconstructionthat involved separating the interosseous tendonsfrom the lumbrical tendon and from the oblique ret-inacular ligament. The interosseous tendons arethen rolled dorsally and sutured together at thelevel of the middle phalanx. Distal joint extensionis preserved through the oblique retinacular liga-ment. Hellman and later Aiche and colleagues22,23

described a technique that involved splitting thelateral bands longitudinally and approximating themedial halves together to reconstruct the centraltendon. When local tendon tissue is insufficient, afree tendon graft is usually required. The midpor-tion of the graft is attached to the dorsal base ofthe middle phalanx, and the ends are crosseddorsally and sutured into the lateral bands proximalto the PIP joint.24,25 An alternative technique wouldbe a transfer of a slip of the flexor digitorum super-ficialis tendon to a lateral band (Fig. 16).

ral tendon, volar subluxation of the lateral bands, andar ligaments (OBL).

Fig. 14. A splint that immobilizes the PIP in full exten-sion and permits DIP flexion.

Fig. 16. Transfer of the flexor digitorum superficialis(FDS) to one lateral band.

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For patients who present with an unacceptablefixed flexion contracture of the PIP joint that hasnot responded to dynamic and/or static progres-sive splinting, correction of the joint contractureis the first requirement. Stretching the volar platecan be accomplished using an external fixator orsurgically via a capsulectomy involving the volarplate and accessory collateral ligaments and, insome cases, the volar portions of the collateral lig-aments. The transverse retinacular ligaments aresectioned to mobilize the lateral bands. Correctionof the PIP flexion contracture alone is sometimessufficient. However, if the joint can made supple,a tendon reconstruction is performed for thosepatients unable to regain adequate active PIPextension.For many patients, their main functional

complaint is the hyperextension deformity of theDIP joint rather than the deficit in active PIP

Fig. 15. (A) Intense scarring of central tendon andlateral bands. (B) Anatomic repair of central tendon,and mobilization and imbrication of lateral bands.(Note: sutures in the lateral bands are distal to PIPjoint).

extension. In such cases, a tenotomy of the lateralbands distal to the insertion of the central slip im-proves the hyperextension deformity of the DIPjoint. A severe mallet deformity does not occurbecause the oblique retinacular ligament remainsintact. The tenotomy, first described by Fowler25

and later reported by others, diminishes the flexionposition of the PIP joint because it increases ten-sion of the lateral bands that is transmitted to thedamaged central tendon (Fig. 17).25–27

When a chronic boutonniere deformity is associ-ated with arthritis of the proximal interphalangealjoint that is painful, an arthrodesis is an effectiveprocedure to relieve pain and position the joint ina functional position. In selected patients whowant to maintain active joint motions and whoseextensor tendon mechanism is amenable toreconstruction, an implant arthroplasty can beconsidered. The procedure requires mobilizationof what remains of the central tendon, mobilizationof the lateral bands, insertion of the implant, fol-lowed by a tendon reconstruction, as previouslydescribed.

DIP JOINT

Extensor tendon injuries at the DIP joint areamong the most frequent injuries that affect thehand. The injury usually results from a suddenflexion force applied to an extended finger thatdisrupts either partially or completely the con-joined lateral bands at or near their insertion into

Fig. 17. (A) Loss of DIP flexion that affected patient’s ability to forcefully grip a hammer. (B) Extensor tenotomyperformed at level of the probe distal to the triangular ligament.

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the base of the distal phalanx. There is a loss ofactive extension of the DIP joint that varies ac-cording to the degree of tendon injury that maysimply be attenuated or completely disrupted. Inmost cases, there is not a complete disruption,and the loss of extension is in the 30� to 40� range.The flexed position of the DIP joint is commonlyreferred to as a mallet finger or baseball finger,although drop finger or droop finger are more ac-curate descriptions.28 These injuries are oftenassociated with degenerative DIP joint arthritisthat, together with the avascular zone in thetendon that is located approximately 1.0 to1.5 cm from its insertion where it passes overthe head of the middle phalanx, compromises itsintegrity and makes it susceptible to rupture witheven minor trauma, especially in the elderly.29 Insome cases, the tendon avulses with a bone frag-ment from the dorsal base of the distal phalanx. Alateral radiograph should, therefore, always betaken.

Fig. 18. (A) A 65-year-old man sustained extensor tendonment. (B, C) A lateral radiograph was negative, and an ejoint. (D, E) Following splinting for 8 weeks, complete ext

Numerous articles have appeared in the medicalliterature regarding the treatment of terminalextensor tendon injuries, and the vast majorityrecommend nonoperative measures. Splintingshould be confined to the DIP joint and shouldnot interfere with motions of the PIP joint. A dorsalsplint is preferable to a volar splint because it isless likely to interfere with prehensile activities(Fig. 18). The splint should obviously be comfort-able because it must be maintained for approxi-mately 6 weeks. Patients must never permit theDIP joint to flex during this period, even for a splitsecond; joint extension must be maintained24 hours a day, 7 days a week. Patients can betaught to remove the splint each day to clean thedorsal skin without permitting the DIP joint toflex. This is easier with a dorsal splint than a volarsplint, although it can also be accomplished with awell-fabricated volar splint (Fig. 19).

Splinting is also the preferred treatment of theclosed extensor tendon injury that occurs with an

injury to middle finger with no avulsion fracture frag-xtension splint was applied to the dorsum of the DIPension restored with no loss of flexion.

Fig. 19. (A, B) Another type of DIP extension splint fabricated by a hand therapist that permits normal motions ofthe PIP joint.

Posner & Green280

avulsion fracture, provided the joint is not volarlysubluxated. However, extension splinting mustbe continued longer than for the nonavulsion injuryuntil there is radiographic evidence of bone healing(Fig. 20). The avulsed fragment usually heals with apermanent bony prominence at the dorsal base ofthe distal phalanx. Although it has no functionalsignificance, patients should still be alerted that itis likely to occur.The only indication for operative treatment is

when the avulsion fracture fragment is large andthere is volar subluxation of the remaining portionof the bone resulting in articular incongruity. Inthose cases, the least invasive procedure that re-duces the subluxated phalanx and stabilizing it ispreferred. This procedure can usually be achievedwith a Kirschner wire that is drilled percutaneouslyacross the joint into the middle phalanx.Individuals with a chronic drop finger often seek

medical attention only because they do not like theaesthetic appearance of their finger. They oftenrefer to it as disfiguring when actually the flexedposition of the DIP joint is far more obvious to

Fig. 20. Extensor tendon injury to index fingers with a larjoint (A, B). A dorsal extension splint was used until therea slight bony prominence at the dorsum of the distal pha

them than to others because when hands arerelaxed, fingers are also relaxed and slightlyflexed; the DIP joints are never fully extended.The treatment of a chronic injury is necessaryonly when the DIP joint is in such severe flexion(generally that is at least 60�) that patients reporta significant disability with important daily activ-ities, such as typing at a computer or playing amusical instrument. In the absence of a significantdisability, surgery should be avoided. Patients willgenerally accept that advice when they are toldthat an operation will not restore normal mobility;may result in an extension contracture that couldcompromise grasp; and, probably what is themost important, that it will result in scarring overthe dorsum of the joint that will be far more notice-able than the current flexed position of the joint.In the rare case of a chronic drop finger that is

disabling, surgery is warranted. It is also warrantedwhen there is hyperextension of the PIP joint thatoften occurs in patients with normal joint laxity.With disruption or attenuation of the terminaltendon, the lateral bands retract proximally and

ge avulsion fragment but with no subluxation of thewas bone healing that took 10 weeks (C). There waslanx, and essentially full mobility was restored (D, E).

Extensor Tendon Mechanism Injuries 281

exert a greater extension force on the lax PIP jointthat becomes hyperextended. The finger assumesa swan-neck appearance, with the hyperextendedPIP joint resembling the neck of a swan and theflexed DIP joint resembling its head. This appear-ance is commonly seen in patients with rheuma-toid arthritis and is usually caused by intrinsiccontractures, whereas in patients with a chronicdrop finger, the deformity is caused by an imbal-ance of extension forces at the PIP joint thatensues after the extension force at the DIP jointhas been damaged. As with surgery for the chronicdrop finger without PIP hyperextension, the sur-gery for the finger with PIP hyperextension is thesame. The scarred segment of extensor tendonover the DIP joint is excised; by closing the gap,the imbalance of extension forces at the PIP jointis corrected, and a greater extension force to theDIP joint is restored.

SUMMARY

Injuries to the finger extensor apparatus are verycommon and may produce chronic deformityand loss of function. The diagnosis is contingenton an understanding of the complex anatomy ofthis region as well as the ability to perform a carefulphysical examination. Immobilization is usually themost effective treatment of acute problems.Surgery is often necessary for chronic conditions,but the results are much less predictablycorrective.

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