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Dislocations and Fracture Dislocationsof the Metacarpophalangeal Ioint

of the Thumb

Richard ]. Miller, MD*

The thumb metacarpophalangeal (MCP) jointis particularly vulnerable to injury because ofits relatively unprotected position at the baseof the exposed lever arm of the proximal pha-lanx. The severity of these injuries varies con-siderably, with the higher grade lesions beingassociated with the potential for permanentinstability that can be markedly disabling.

The direction and magnitude of the injuringforce determine the site and degree of tissuedisruption in the capsuloligamentous complex;and these parameters, in turn, have tradition-ally formed a useful basis for organizing theclassification and treatment of these injuries.Hyperabduction forces, with varying degrees ofhyperextension load, create injury to the ulnarcollateral ligament (UCL) and volar plate corn-plex, while adduction forces produce tears tothe radial collateral structures. Straight hyper-extension stresses principally tear the volar re-straints and cause dorsal dislocations, often, lear:"ing the collateral ligaments relatively intac’t.Recent reports suggest that straight volar dis-locations may also occur.6z Although some ofthese injuries can occur in combination witheach other, it remains both customary anduseful to discuss them independently. 13eforedoing so, some pertinent aspects of the anatomyof the metacarpophalangeal joint warrant re-view.

FUNCTIONAL ANATOMY

Proper function of the thumb is contingentupon stability at the MCP joint level. Themobility required for thumb function is largely

provided by the basal and interphalangealjoints. Thus, the MCP joint of the thumb isunique in the hand in that functional disabilityfollowing injury to this joint is almost alwaysdue to instability, deformity, or pain, as op-posed to stiffness.

The stability of the MCP joint is. dependentupon the integrity of the collateral ligaments,the volar supporting structures, and the intrin-sic and extrinsic musculotendinous units (Figs.1 to 3). The anatomy of the collateral complexesis particularly important to an understanding ofthe soft tissue injuries that occur about thisjoint. The ulnar collateral ligament arises fi’omthe dorsal ulnar aspect of the metacarpal andpasses distally and palmarward to insert intothe volar ulnar base of the proximal phalanx.The more membranous ulnar accessory, collat-eral ligament takes origin just proximal andvolar to the collateral ligament proper, on themedial neck of the metacarpal. It passes parallelto the proper collateral, but slightly more vo-larly, to attach to the ulnar margin of the volarplate. Some of these insertional fiber~_passfurther volarly to attach to, and help suspend,the flexor sheath of the flexor pollicis longus.Steners7 and others have shown that the collat-eral ligament proper is taut in flexion andsomewhat lax in extension, with just the oppo-site being true for the accessory collateral liga-ment. An entirely analogous and symmetricdisposition of collateral ligamentous fibers isfound on the radial side of the joint. Therelationship of the torn ulnar collateral ligamentto the adductor tendon aponeurosis (Stenerlesion) is of critical importance in the assess-ment and treatment of ulnar collateral injuries,

*Assistant Professor of Orthopaedics, University of Rochester, Rochester, New York

Hand Clinics--Vol. 4, No. 1, February 1988 45

46

Abductor

brevis

Extensor

IVolar plate

Cor~

Richard J. Miller

tCollate,;al ligament

Extensisr pollicisbrevis

Lateralsesamoid

Adductorpotlicis

Figure 1. Lateral aspect of theMCP joint showing the collateral lig-aments and intrinsic tendons. (FromKaplan EB: Functional and SurgicalAnatomy of the Hand. Edition 3.Philadelphia. JB Lippincott. 1984. p118: ~vith permission.)

Extensor

Extensor

brevis

Abductor

Base of Fphalanx

Abductorbrevis -

pollicis

Proximal

~ phalanx

~ Flexor pollicis

~$,~.._~ Abd u c,o r __

~ ,,. brevis .

metacarpa~

Flexorbrevis Collateral ligamertts

A B

. Extensor pollicis ,.. ~ ..:~. ~-"~" . .:: ¯Iongus

Figure 2. A, View of interior of the MCP joint from dorsal perspective with collateral ligaments and dorsal capsuleremoved. The volar plate and sesamoid bones are shown in the depths of the joint. B, Volar view of the joint showingflexor pollicis longus and intrinsic tendons.. (From Kaplan EB: Functional and Surgical.Anatomy of the Hand. Edition 3.Philadelphia. JB Lippincott, 1984, p 119; with permission.)

,,.f the:al lig-(From.~rgicalion 3.984, p

ductorlicis~viS

pollicis

al capsulet showingEdition 3.

Dislocations and Fracture Dislocations of the Metacarpophalangeal Joint of the Thumb 47

Figure 3. A, Volar view of thethumb showing adductor pollicis ten-don itisertion into the ulnar sesa-mold. B, Ulnar aspect showing tri-radiate insertion of adductor pollicisinto the ulnar sesamoid, base of prox-imal phalanx, and dorsal aponeu-rosis. (From Kaplan EB: Functionaland Surgical Anatomy of the Hand.Edition 3. Philadelphia, JB Lippin-cott, 1984, p 141; with permission.)

pollicis

A

First dorsalinterosseous

B

oneurosis

Adductor pollicishead

~Oblique head

and will be discussed further in the sectilonbelo~v that deals specifically with that injury

Volar support for the thumb MCP joint isprovided by the volar plate and its associatedstructures. The volar plate of the thumb MCPjoint is similar to that found in the proxirnalinterphalangeal (PIP) joints of the fingers, butthere are important differences. As in the PIPjoints, the volar plate here consists of a heavyfibrocartilaginous plate of tissue that finds se-cure attachment to the proximal volar marginof the proximal phalanx. It rides freely on thevolar aspect of the metacarpal head duringflexion and extension of the joint. The plate,’ is2 to 3 mm thick distally, but tapers proximallyto become membranous. Unlike the finger PIPjoints, however, the check ligament extensionsof the volar plate are absent in the thumb MCPjoint, and the central portion of the plate ismore membranous. For these reasons, theMCP joint of the thumb is particularly proneto hyperextension injury and subsequentchronic dorsal instability.

Radial and ulnar sesamoid bones are inva:ria-bly present in the distal part of the volar plate.Portions of the short thumb flexor, abductor,and adductor intrinsics insert into these smallbones,s~ The flexor pollicis longus is supportedbetween the two sesamoids. These bones artic-ulate with facets on the metacarpal head andfunction to hold the FPL and intrinsic insertionssomewhat volarly displaced, thus increasingtheir flexor moment arm. The position of thesesamoids, as observed radiographically, can beparticularly helpful in the analysis of hyperex-tension injuries because they mark the positionof the distal portion of the volar plate.

The dynamic support to the MCP joint pro-vided by the intrinsic motor units correlateswell with their geometric distribution about thejoint and their precise manner of insertion intothe periarticular tissues. On the ulnar side, theadductor pollicis has three insertions (Fig. 3).The bulk of the tendon inserts into the ulnarsesamoid and the proximal volar corner of theproximal phalanx. The remainder of the fiberspass dorsally and further distally as an aponeu-rotic sheet to insert into the extensor mecha-nism. A similar situation is present on the radialside of the joint. Most of the insertional fibersof the flexor pollicis brevis and abductor pollicisbrevis insert into the radial sesamoid and radialcorner of the proximal phalanx. A significantportion of the power of these muscles, however,is also transmitted dorsally to the extensor ten-dons via an aponeurotie expansion. These tri-radiate insertions for the ulnar and radial intrin-sits allow them to not only effectively flex theMCP joint and extend the interphalangeal joint,but also to provide strong dynamic protectionagainst varus-valgus and hyperextension loadsdelivered across the joint.

Motion at the thumb MCP joint shows the.’most variability of any joint in the hand.~ Thisvariability is largely due to the shape of themetacarpal head and the tension of the collateralligaments. ~ The broader and flatter heads tendto be associated with the most stability and theleast motion.~4’ a The motion in flexion variesfrom l0 to 100 degrees--averaging 75 degrees,while extension varies from 0 to 90 degrees,averaging 20 degrees. ~4’ ~" Normal abductionand adduetion, ranges from 0 to 20 degrees,with an average of 10 degrees (measured in 15

48 Richard J. Miller

degrees of flexion). 14 Several degrees of supi-nation and pronation through the joint are alsopossible.

Although small amounts of flexion, abduction,and pronation normally occur in unison whenthe thumb is brought into its working positionof opposition, it is interesting to note that nofunctional deficits have been reported in thosepatients who naturally have limited MCP jointmotion. This correlates well with the clinicalobservation that patients who have had thumbMCP arthrodesis experience little or no dis-ability. Thus, arthrodesis of this joint is anexceptionally good salvage procedure for failedsoft tissue reconstructions.

ULNAR SIDE INJURY

Dislocations and fracture dislocations havebeen estimated to occur about ten times morefrequently on the ulnar aspect of the joint thanon the radial side.~3’ z4, 59. 8e. 10o Often the patient(and sometimes the physician ~vho initially eval-uates the patient) fails to appreciate the signif-icance of the injury, thus setting the stage fordelay in diagnosis and treatment. If left un-treated or inappropriately treated, a high-gradelesion often results in chronic instability, whichin turn may cause marked disability due to painand weakness in pinch and grasp.

Anatomy of Injury

The pathomechanics of ulnar collateral inju-ries have been studied with a variety of cadav-eric models.TM 36, ~. 86. ss Although some of thedetails of the pathomechanics remain contro-versial, there .is general agreement that the

.,basic mechanism Of injury is usually that ofhyperabduction (often with some hyperexten--sion) resulting in tearing of the ulnar collateralligament and at least a portion of the accessorycollateral. Varying degrees of injury to theadductor tendon aponeurosis, dorsal capsule,and extensor tendons have also been reported,a’n. a~. ~6. sz. ss Although the ligament may failanywhere within its substance,~’ 14. 4~. st. 89 mostinvestigators6, ~4. ~0. 8~. as have reported that themajority of failures occur distally, near the siteof the ligament’s attachment to the volar cornerof the proximal phalanx. An avulsion fracture atthis site occurs commonly and serves the usefulpurpose of radiographically marking the posi-tion of the disrupted distal end of the ligament~’14, a6, 8~. 87, s8 (Fig. 4). Smith, on the basis

Figure 4. Radiographs of thumb ~vith ulnar collateral’ligament injury, showing minimally displaced avulsion frac-ture.

combined clinical and cadaveric studies,79 hassuggested that these avulsion fractures onlyoccur if the injuring abduction force is activelyresisted by the adductor pollicis. On occasion,~’larger bone fragment involving more than 10per cent of the articular surface of the proximalphalanx may be avulsed.~a’ ~ The volar plate isalso commonly injured in conjunction with adistal ligament failure, although the plate’s ab-sence of a strong proximal check ligament tethermakes this less likely than in the case of theanalogous injury at the PIP jo.int.

Stener has reported that a shearing type offracture of the radial condyle of the metacarpalhead may occur with UCL injury ffthe proximalphalanx supinates and flexes at the same timethat the abduction load is applied.~ Althoughother authors have confirmed this finding inisolated cases, the incidence seems to b~ low,with Massart~z noting only one case in his seriesof 125 dislocations.

Smith has reported that volar subluxation ofthe proximal phalanx on the metacarpal headoccurs frequently in association with UCL in-juries, sz He reported this finding in 16 of 66cases coming to surgery for acute and chronicrepairs. He felt that this was due to supinationof the proximal phalanx about the intact radial

lar collateral~vulsion frac-

.dies,79 hastures onlyis actively

n occasion,~re than 10~e proximal~lar plate istion with a~, plate’s ab-ment tethercase of the

:ing type of~ metacarpal:he proximal~ same time,~ Althoughs finding ins to be low,in his series

.lbluxation ofacarpal head~ith UCL in-in 16 of 66and chronic

to supinationintact radial

Dislocations and Fracture Dislocations of the

collateral ligament and stressed the need forattention to the repair of the oblique portion of ¯the UCL to correct this deformity (Fig. 5).

It is important to recognize that UCL-~gpeinjuries can occur in the skeletally immaturepatient.~6. 67, 93 Although abduction and. exten-sion blows to the MCP joint of individuals withopen epiphyses typically result in Salter-Harristype II or III fractures at the proximal phalanxlevel, simple soft tissue injuries of all gradeshave been reported.66 Purely cartilaginous avul-sion injuries without bony fi’acture have alsobeen described.93 In many of these cases, theradiographs will be normal despite the presenceof a significant skeletal injury.

Stener Lesion. As previously noted, one ofthe critical features of capsuloligamenl:ous in-juries on the ulnar side of the thumb MCP jointis the possibility for the dorsal extensor aponeu-rosis of the adductor pollicis to become inter-posed between the disrupted UCL and :its bonybed---thereby preventing satisfactory healing ofthe injury with simple immobilization. Stenersr

first called attention to this lesion iu 1962.Working with both clinical material and a ca-daveric model, he observed that after distalfailure of the ulnar collateral ligament under avalgus load, further abduction and flexion of theproximal phalanx could "uncover" the proximalstump of the torn ligament sufficiently to allowthe adductor tendon aponeurosis to becomeinterposed between the ligament and its distalbony bed (Fig. 6). Stener felt that ff this lesionoccurs, satisfactory healing would be prevented.

Metacarpophalangeal Joint of the Thumb 49

He reported finding this lesion in 25 of 39specimens. Other authors6’ ~’ ~a. 70. ~z, 9~, ~o0 haveconsistently confirmed this finding with thereported incidence varying between 14 and 87per cent. If this lesion is present, it must, ofcourse, be corrected if one hopes to achieve apredictably good result. This has lead to thegenerally accepted principle that all completetears on the ulnar aspect of the joint warrantsurgical exploration and repair.

Ulnar Collateral Ligament Injuries in Skiers

The term "gamekeeper’s thumb" refers to achronically unstable UCL. Campbell originallydescribed this as an injury suffered by Scottishgamekeepers due to repeatedly twisting thenecks of hares,n Over the past two decades,however, it has become increasingly apparentthat falls while skiing are the most commonetiology of both the acute and chronic form ofthis injury. During the 1970s, Schultz7~ andBrownes published t~vo reports calling attentionto the relationship between skiing accidents andUCL injuries. Subsequently, Gutman,a°

Young,9~ and Crane~ independently reportedtheir observations that between 10 and 24 percent of all skiing injuries occurred in thethumb.t~, a0. 96 In 1978, we reported on theresults of a survey of 1,008 high school skiersundertaken in an effort to determine the prev-alance and mechanism of skiing injuries to thethumb MCP joint. ~6~ The results of that survey

Figure 5. The collateral ligaments nor-mally resist the volarly directed forces ofthe intrinsics. When one collateral ligamentruptures, the proximal phalanx subluxes vo-larly as it rotates about the remaining intactcollateral. (From Smith RJ: Post-traumaticinstability of the metacarpophalangeal jointof the thumb. J Bone Joint Surg 59A:14--21, 1977; with permission.)

50 Richard J.

Figure 6. Stener lesion. After the ulnar collateral liga-ment ruptures, the adductor tendon aponeurosis becomesinterposed between the ligament stump and the proximalphalanx.

are summarized in Figure 7. Eleven per centof these skiers reported having sustained askiing-related injury to their thumb, with 89per cent of the injuries occurring on the ulnaraspect of the MCP joint. Only 28 per cent ofthe students who reported a thumb injury hadsought any type of medical treatment acutely.In nearly every case, the individual could relatea history of hyperabduction and/or hyperexten-sion of the joint.

Three specific mechanisms of injury wereidentified (Fig. 8). Thirty-four per cent reportedcatching or abducting the thumb in the strap of

Miller

the pole in the course of a forward or lateralfall. Forty-two per cent reported contacting thesnow with the pole wedged in the first webspace between the thumb and index finger,thus producing forced abduction of the thumb.Fifteen per cent remembered an abduction orextension force at the MCP joint level occurringduring a fall, but did not believe that the polewas a factor.

Seventy-two per cent of the 1,008 skiersindicated that they were using a ski pole gripwith a conventional strap, while 25 per centreported using a pole or grip with a strap orclip across the back of the hand (Fig. 9). Threeper cent reported using a pole without anyrestraint (that is, no strap or dip). The distri-bution of grip types in the skiers with thumbinjuries was essentially the same as the distri-bution in the 1,008 total skier population (Fig.10). This suggested to the authors that the twomajor types of pole grips currently used areequally associated with thumb MCP joint inju-ries.

Numerous subsequent reports~z’ ~’ z,. ~o-. z~. ~.~,, so_ concerning the incidence and mechanism

of UCL injury in skiers have essentially con-firmed the findings reported here.

A definitive means for preventing this injuryin skiers has not been devised. In recent years,there has been general acceptance of the prin-cipal of getting the ski away from the fallingskier to prevent the ski itself from causing lowerextremity injury. Pending the development ofa safer ski pole grip, it is felt that a similarseparation of the pole from the falling skiershould be adopted to control pole-relatedthumb trauma. By removing all straps or other:retention devices from the poles, the unencum-bered thumb should be spared injury during-most skiing falls.

100

SKIER’S INJURY HISTORY--~(N =1008)

50

ALL INJURIES(n = 293)

29%

HA~D(n = 132)

13%

THUMB(n = 112)

11%

Figure 7. Bar graph showin_g thepercentage of skiers r~porting an in-jury, hand injury, and thumb injury.

eralthe

webget,nab.tl or’ringpole

tiersgripcentp orhree

anyistri-.,~umb.istri-(Fi,~~ gvo

i areinju-

, 26. 52,

~nisnacon-

.njury,¢ears,prin-

!ailinglowerent ofinailarskier

elatedother

ii(21.1111-

"3uring

,ring theag an in-b injury..

Dislocations and Fracture Dislocations of the MetacarpoIohalangeal Joint of the Thumb

34%42%

15%

Figure 8. Drawings demonstrating three mechanisms of IvlCP joint injuries of skiers.

Figure 9. Drawing demonstrating the two common types of ski pole grips.

51

52 Richard ]. Mii~,ler

DISTRIBUTION OF POLE TYPES

100 -

72% 7’5%

SKIER SKIER’SPOPULATION THUMB INJURY

Figure 10. Bar grafts comparing the per-centage distribution of the two grip types inthe total population (left) and in the injuredpopulation (right).

Clinical and Radiographic Evaluation

The important aspects of the history andphysical examination in the evaluation of acuteinjuries to the thumb MCP joint have beenemphasized by many authors. In the course ofreviewing the mechanism and timing of theinjury, the patient should be questioned re-garding any history of pre-existing injury orchronic problems with not only the MCP joint,but also with the interphalangeal (IP) and basaljoints of the thumb, and other small joints ofthe hand and wrist.

Concomitant injuriessl or pre-existing diseaseare not uncommon in the adjacent joints, andtheir presence may significantly complicate theman.agement of the MCP joint injury. Figure11 shows a radiograph of a 59-year-old womanwho presented wi~h an acute, third-degree in-jury to her ulnar collateral ligament. Her man-agement was complicated by the presence oflong-standing basal joint arthrosis, an acuteintra-artieular fracture at the IP joint level, andan acute carpal tunnel syndrome. The collateralligament was repaired, the fracture reducedand pinned, and her carpal tunnel decom-pressed. She subsequently had a faseial basaljoint arthroplasty, but only obtained her finalgood result after fusion of the IP joint, whichhad developed post-traumatic arthrosis.

Examination of the thumb with an acute ulnarcollateral ligament injury includes the usualsearch for areas of maximum pain, tenderness,swelling, and deformity. Because the ligament

generally ti~ils at the level of the proximal pha-lanx rather than the metacarpal neck, findingsoften localize to this relatively small area, par-ticularly when the patient is seen soon afterinjury. An assessment of the degree of injury tothe,’ collateral ligament structures is, of course,

Figure 11. Radiographs showing thumb with acute MCPjoint UCL injury with concomitant IP joint fracture andbasa~l joint arthrosis.

ae per-ypes ininjured

pha-:~dings

par-a~}er

ury to’,ourse,

te MCPare and

Dislocations and Fracture Dislocations of the

the cornerstone of the clinical evaluation ofthese injuries, as the degree of injury dictatesthe type of treatment that will be required.Unfortunately, the best method for determiningthat degree, of injury remains somewhat contro-versial.

Most authors agree that clinically stressingthe ulnar collateral ligament is the best meansfor determining the grade of injury, but thereare varying opinions as to how this "stress test"should be performed, and how the resultsshould be judged. Eatonis prefers that thestressing be done with the joint in extensionand feels that valgus laxity in excess of 35degrees or 15 degrees greater than the contra-lateral side constitutes evidence of a third-degree tear. smiths2 concurs with the positionfor the stress testing, but used 45 degrees oflaxity as his upper limit for a second-degreeinjury. Palmer,69 conversely, states that theclinical stress test should be done with theMCP joint in maximum flexion--using 35 de-gree as the criteria for a complete tear. Hefavors this positioning for the test based uponthe results of evaluating the injury with a ca-daveric model. The rationale for performing thetest in flexion is related to the fact that theulnar collateral ligament proper (the integrityof which is under question) is known to besomewhat lax in extension and maximally tightin flexion. In principle, then, a test done in fullextension could produce a false-negative resultin the face of a third-degree ulnar collateral

Figure 12. Drawing illustratingclinical stress test for collateral liga-ment injury.

Metacarpophalangeal Joint of the Thumb 53

proper tear if the accessory ulnar collateralligament has remained completely intact. In myexperience, however, there is often a problemin. attempting to quantify the degree of laxitywith the MCP in full flexion because it isdifficult to determine whether the observedv~dgus angulation of the proximal phalanx isoccurring due to laxity of the collateral ligamentor axial rotation of the metacarpal through thebasal joint.

The author’s preferred method for perform-ing the clinical stress test is illustrated in Figure12. With the MCP joint in extension, a straightline is drawn along the dorsal aspect of thethumb metacarpal and proximal phalanx. Laxityon the ulnar side of the joint is assessed withthe joint held in 15 degrees in flexion. It is feltthat this degree of flexion relaxes the accessorycollateral ligmnent sufficiently to test the integ-rity of the proper collateral ligament, while atthe same time avoiding the practical difficultiesassociated with attempting to measure the de-gree of angular deviation with the MCP jointin full flexion. Laxity in excess of 35 degrees,or more than 15 degrees in excess of the con-tralateral thumb, is judged to represent a third-degree injury to the collateral ligament and isused as a criteria for undertaking operativetreatment. The clinical laxity and "end-pointfeel" are also assessed in full extension and fullflexion because the findings in these positionsare usually confirmatory and may help to furtherdelineate the nature and extent of the injury.

IIlIII

54 Richard

Regardless of the precise method used in stress-ing the joint, it is essential that the intrinsicand extrinsic musculature that supports thejoint be fully relaxed. Usually, this type ofrelaxation requires a median and radial sensorynerve wrist block.

As with any injury of this type, radiographicexamination is an essential part of the initialclinical evaluation. Obviously, films should beobtained prior to clinically stressing the joint,to avoid displacing an undisplaced intra-articu-lar fracture or disturbing an epiphyseal injuryin a skeletally immature patient. Routineanteroposterior and lateral x-rays are obtainedinitially. Oblique views are added as necessa~.to help delineate the nature and position of anyfractures visualized on the initial films.

As previously noted, the small avulsion frac-tures that commonly accompany distal ligamentfailures are helpful in guiding treatment, as theposition of the torn end of the ligament can bedetermined ~vith relative certainty based uponthe plain radiographs alone (see Fig. 5). If thefragment is undisplaced, one can be certain thatthe Stener lesion is absent and proceed withnonoperative treatment, confident of the prog-nosis for a good result. Coonrad and associates1~

and Smithsz found that one third of their pa-tients presenting with ulnar collateral ligamen-tous injury had had some type of an avulsionfracture from their proximal phalanx. In Smith’sseries, 50 per cent of these fractures involved10 per cent or more of the articular surface.The size of the fracture fragment and the degreeof displacement that necessitate surgical inter-vention (aside from the Stener lesion criteria)has remained controversial and ultimately be-comes a matter of clinical judgment. If thefragment is larger than 10 per cent of the"articular surface and/or is sufficiently displacedto create joint incongruity, the author favorssurgical reduction and K-wire fixation.

The role of stress x-rays in the evaluation ofthese injuries is another controversial issue,aT,,~, ~4 Although in principle they offer an objec-

tive means for quantifying the degree of liga-mentous laxity produced when the injured jointis stressed, in actual practice there may beproblems that can limit their usefulness. Forreasons already discussed, stability fs best as-sessed with the joint in at least some flexion. Ifthe stress x-rays are made with the joint stressedin flexion, however, variation between the ac-tual angular deviation present and that recordedon the x-ray film is influenced by both errorsassociated with the planar projection of a flexedjoint and errors introduced by any rotation

Miller

along the long axis of the flexed thumb. In theauthor’s experience, these problems have beensignificant. If the study is to be used, thephysician who is to interpret the films shoulddirectly supervise the positioning of the hand.

Arthrography is yet another radiographictechnique that some authors have found to beuseful in helping to make the critical determi-nation as to presence of a third-degree lesion.The details and merits of the technique havebeen described by Bowers and Hurst a andothers.-~o. 47. 61.73. 74. 92 If contrast is detected inthe soft tissues external to the joint, one can becertain that the capsuloligamentous integrityhas been breached; but the goal of making thediagnosis of a Stener lesion with this techniquehas proved difficult to achieve. Bowers andHurst have reported some success in this questby combining special stress films with arthrog-raphy. ~

Treatment~Acute Injuries

Although Coonrad~4 and Neviaser64 felt thatacute complete rupture of the UCL could bemanaged satisfactorily with closed treatment,most authors-~a, ag, ~6, ~a. ~, ~9. s-,, sv, 8s, 94, i0o agreethat operative intervention is ~varranted forthird-degree lesions if one wishes to achieveconsistently good to excellent results. Until ameans is achieved for consistently diagnosingthe Stener type of lesion, only with operative¯ exploration can one make certain that all ofthese lesions are identified for surgical repair.A second indication for open repair of an acuteinjury is the finding of a displaced intra-articula__r...fracture that exhibits sufficient size and dis-placement to warrant operative reduction andfixation. Smith felt that volar subluxation of theproximal phalanx on the metacarpal head wasalso a surgical indication,s~ ,

The surgical technique used by the author inthe exploration and repair of acute injuries isrelatively straightforward and entirely consis-tent with what has been detailed previously bym’any other authors. Either a lazy s-shapedincision on the dorsal-ulnar aspect of the-jointor a dorsally based gently curved flap incisionis used. The subcutaneous dissection is donebluntly, with care taken to identify and protectan invariably present dorsal branch of the radialsensory nerve that courses along the ulnar as-pect of the extensor mechanism. If a Stenerlesion is present, it can frequently be identifiedat this time as an edematous, hemorrhagic rriassof ligamentous tissue just proximal to the mar- "

b. In theave beentsed, theis shouldae hand.iographiemd to bedetermi-

.~e lesion.que have.irst 6 and~tected inne can beintegrity

aking the:eehnktuewers andthis questx arthrog-

’ felt thatcould be

reatment,¯ 10o agree

anted foro achieves. Until aliagnosingoperativehat all of?al repair¯f an acutea-articular

and dis-teflon and:ion of thehead was

~ author ininjuries is,qy consis-viously by

s-shapedf the jointtp incision,n is donetad protect." the radial.~ ulnar as-: a Steneridentified

hagic rriass~ the mar-

Dislocations and Fracture Dislocations of the

gin of the adductor aponeurosis. The aponeu-rosis is tagged and released from its insertioninto the extensor pollicis longus tendon andreflected ulnarly, thus exposing the remainderof the capsuloligamentous injury.

The precise nature of the repair is dependentupon the location of the lesion within the col-lateral ligament. Usually the tear is at or nearthe distal insertion into the volar ulnar cornerof the proximal phalanx. In this case, the inser-tional bed is freshened with a currette, and theligamentous stump is repaired with a pull-outwire tied over a button on the radial aspect ofthe proximal phalanx. ~4. ~s. ~o, ~,~, s~, sa If the tearhas extended into the accessory collateral liga-ment and corner of the volar plate, this area isrepaired with interrupted sutures. If the pri-mary ligamentous damage has occurred in themidsubstance or at the metacarpal head origin:.then primary soft tissue repair with horizontalmattress sutures is often all that is required. I:~"there is an insufficient proximal soft tissuestump to hold the suture, a pull-out wire teeh--nique using a drill hole through the metacarpalhead may be requiredY When an articularfi’acture is present, and a decision has been~made to reduce it (as opposed to excise it), thisreduction can often be facilitated with the tipof a 16-gauge needle. The needle holds thefracture reduced while an 0.045 or a 0.035 K-wire is passed through the needle, exiting onthe dorsal radial aspect of the proximal phalanx.There it is cut short, but left protruding throughthe skin, and then sealed with collodion.

Because it is difficult to protect the ulnarcollateral repair with a thumb spiea cast alone,it is recommended that the joint be temporarilytransfixed with a 0.045 K-wire in a slightlyoverredueed (varus) position and in 15 degreesof flexion. The author has found it helpful toset the K-wire in the proximal phalanx beforereducing and fixing any intra-articular fractures.All necessary ligamentous sutures are thenplaced, but left untied until the transarticularK-wire is passed.

If volar subluxation of the proximal phalanxon the metacarpal head is part of the pathoan-atomy found at the time of surgery, then thissubluxation should, of course, be reduced priorto passing the transarticular wire. As previouslymentioned, Smiths~ has emphasized the need

attention to the repair of the oblique por-of the proper and accessory collateral

to correct this deformity.At the completion of the articular and cap-

repairs, the adductor tendonaponeurosis is repaired to the extensor pollieis

Metacarpophalangeal Joint of the Thumb ¯ 55

longus tendon with interrupted 4.0 nonabsorb-able suture.

Postoperatively, the thumb is supported for4 weeks with a thumb spica cast, after whichan orthoplast splint is used on an intermittentbasis for an additional 4 weeks. Both the castand the splint leave the IP joint free to allowearly active IP joint motiou. The immobilizationshould maintain the thumb index web. To avoidstressing the ulnar soft tissue repair, this is bestdone by holding the thumb ray in extension asopposed to palmar abduction. The sutures areremoved at 2 weeks, and the transartieular K-wire is removed at 4 weeks¯ Between 4 and 6:weeks, the orthoplast splint is worn continu-ously except for range-of-motion exercises per-formed 4 times a day. These exercises focus on

MCP flexion and extension, with active thenarabduction and opposition motions being intro-duced only gradually¯ The patient is slowlyweaned from the splint between 6 and 8 weeks,at which time progressive resistive strengthen-ing exercises are emphasized by the hand ther-apist. Patients are advised that it is often 8 to 4months before they can return to full function,and that swelling and some low-grade symptomsare likely to persist for several more months.

The reported results following this type ofsurgical treatment of acute (up to 2 to 3 weeksold) grade III lesions has been uniformly goodto excellent. ~6, ~4. ~. ~. ~, s~, ~

Grade I and grade II lesions are virtuallyalways treated successfully nonoperatively.Nonoperative treatment, however, does notmean no treatment. The general guidelines forour nonoperative treatment of grade II lesionsare very similar to the rehabilitation programoutlined above for the postoperative manage-_.ment of grade III lesions. The MCP joint is.splinted in 30 degrees of flexion, and because atransarticular pin is not used, extra care mustbe taken to assure that the cast and splint:immobilization do not allow either passive oractive stress to develop in the ulnar collateraltissues.

Grade I lesions require less immobilization,and ,the rehabilitation is obviously more rapid.The resolution of tenderness in the soft tissues]provides a useful guide in determining the]ength of cast immobilization required.

Chronic Injuries

Like ligaments elsewhere in the body, collat-eral ligament injuries in the thumb are notamenable to acute repair if more than 2 to 31

56 Richard ].

weeks have elapsed from the time of injury.Those patients who present late for their eval-uation and treatment may benefit from a trialwith cast immobilization for several weeks untilall of the swelling and soft tissue tenderness hasresolved. An effort should then be made tomaximally strengthen the intrinsic musculature,with particular emphasis on the adductor polli-eis. If disabling instability, pain, and weaknesspersist despite these measures, some patientsmay benefit from a thumb spica orthosis thatsupports the MCP joint, but leaves the IP jointfi’ee. In our experience, most patients find thisunacceptably awkward, and for this reason aninitial trial ~vith an orthoplast splint is usuallyadvised before prescribing an expensive customleather brace. If the patient remains disableddespite these measures, he or she should beconsidered for operative intervention.

Operative treatment for chronic instability ofthe ulnar collateral ligament consists of eitherreconstruction of the ligament or arthrodesis ofthe joint. The best choice of treatment is de-pendent both upon the status of the joint andthe functional demands that the patient antici-pates placing upon the joint. If the articularsurfaces are well preserved, the patient antici-pates only moderate stresses on the articulation,and the joint on the uninjnred hand shows goodmotion, then the patient will almost certainlybe best treated with one of the many differentligament reconstructions. If, on the other hand,the joint shows evidence of arthrosis, or thepatient is engaged in very head-/manual activ-ities, or the opposite (normal) thumb MCP jointshows very little motion, then the patient willvery likely be best served by arthrodesis.

Arthrodesis. As previously noted, arthrodesisof the MCP joint permits retention of excep-tlonally good function. In my experience, it hasbeen helpful to make a point of discussing;arthrodesis as an option that may need to beexercised at the time of a planned ligamentreconstruction. Unless this option has beendiscussed preoperatively, the surgeon may bepresented with a dilemma if unanticipated ar-throsis is encountered at the time of arthro-tomy.

The position of the arthrodesis is important.When the normal thumb is brought into oppo-sition:, the MCP joint usually shows a fewdegrees of flexion, palmar abduction, and pro-nation. Fusion in this position will provide goodresults. Fusion of the joint in too much flexionor any adduction will seriously diminish thequality of the result. Although any of the estab-lished techniques for fusing this joint should

Miller

produce a satisfactory, result if carefully imple-mented, the author has found the "ball andcup" method to be most useful as it permitsfine adjustments of angular alignment in allthree planes just prior to transfixion of the joint.

Soft Tissue Reconstruction. There are a num-ber of methods available for reconstruction ofthe ulnar collateral ligament. These includeefforts at repair of the scarred ligament; recon-struction with a free tendon graft; reconstruc-tion with a static tendon transfer; and recon-struction with a dynmnic tendon transfer.Although some authors have reported satisfac-tory resnlts following simple mobilization andrepair of the scarred ligament stumps,~s’ ~ most’.have felt this type of repair to be inadequateand have favored one of the more formal typesof reconstructions.

Several techniques have been described forthe reconstruction of the ulnar collateral liga-ment employing free tendon grafts. Eaton hasdescribed his method using the pahnaris longusas a free graft interwoven through drill holes inthe metacarpal head and proximal phalanx.~Alldred~ described a similar technique nsing atoe extensor as the graft material. Smith favorsa slightly dit-}~rent procedure, again using thepalmaris longus as the free tendon graft mate-rial. sz His method consists of weaving the graftthrough the residual stump of the proximalligament on the metacarpal head and thenthreading it through a drill hole in the proximalphalanx, thereby reconstructing both theoblique and transverse components of the liga-ment (Fig. 13). He has reported satisfactoryresults in 25 cases. The author has had favorableexperience using this technique. If there isinsufficient soft tissue at the metacarpal origin--of the ligament, another drill hole can be madeat that position, and the reconstructed ligamentanchored there with a second pull-out wire.

A variation on the free tendon graft type ofreconstruction involves the’use of so-called"static tendon transfers." This group of recon-structions also reconstitutes the ligaments withtendon grafts, but with these procedures oneend of the graft material is left attached to itsbony insertion. This allows the graft (in theory)to retain some of its blood supply and simplifiesthe anchorage of one end of the repair. Proce-dures of this type have been described byStrandelP~ using the extensor pollicis brevis, ¯Frykman~ using a slip of the abductor pollicislongus, and Lamb4z using the palmaris longusleft attached distally. These authors have re-ported satisfactory results with their methodsin small numbers of patients, but there is no

Dislocations and Fracture Dislocations of the MetacarpophalangeaI Joint of the Thumb 57

~ly imple-"ball andt permitsmt in allthe joint..re a num-ruction ofe includent; recon-.~construc-nd reeon-

transfer.d satis~:ac-:ation and

aadequate’real types

cribed for.feral liga-Eaton hastris longusill holes inphalanx. 29.m using aaith favorsusing the

;ra~?: mate-g the graft, proximaland then

e proximalboth the)f the liga-~atisfactory~ favorableif there isrpal originn be maded ligamentat wire.aft type off so-called> of recon-nents with,’dures oneched to its(in theory,)t simplifies,air. Proce-~eribed bylois brevis,.,tor pollicisaris longus¯ s have re-ir methodsthere is no

technique for Smith’s method of recon-structing the collateral ligaments. Note thatthe reconstructed ligament restores theproximal-dorsal to distal-velar orientation ofthe normal collateral ligament. (From SmithRJ: Post-traumatic instability of the meta-carpophalangel joint of the thumb. J BoneJoint Surg 59A:14-21, i977; with permis-sion.)

evidence that these grafts performed betterthan the free grafts previously mentioned.

The final mode of reconstruction uses dy-namic tendon transfers to compensate for theloss of ligamentous integrity. An early report ofa procedure of this type was provided by Ka-plan.as He transferred the extensor indieus pro-prius to the adductor tendon aponeurosis, re-~orting a good result in one ease. Probably the

~nost popular transfer is that described by Nev-iaser and eoworkers.~ His method (Fig. 14)advances the adductor tendon insertion fromthe volar ulnar base of the proximal phalanx toa drill hole placed transversely in the proximalphalanx, 1 em distal to the IP joint. The scarredligament is also reefed. He reported good re-sults in six of eight patients. Sakellarides andDeWeese~’ ~7 have described a different tech-nique that makes use of the extensor pollicisbrevis. They reroute the tendon of the EPBdeep to the EPL and then passed it throughdrill holes in the proximal phalanx to provide adynamic backupto their static ligament recon-struction (Fig. i5). They have also reported favorable experience in 20 eases. Finally, Ah-mad and DaPalma~ outlined yet another methodof using the extensor pollieis brevis as a dynamictendon transfer, but reported experience withonly one case.

Osterman and coworkers~ have pointed outthat although the literature suggests that goodresults can be obtained with all of the recon-

cited above, most of the reports areon rather subjective criteria. In their

review, they presented a somewhat more rig-orous follow-up study that included a compar-ative analysis of nine patients who had had UCL

reconstruction using a free tendon graft, andfive patients who had had an adductor tendonadvancement. They found that both techniquesgave similar results with good restoration of

Figure 14. Drawing showing Nevaiser’s method~ ofdistally advancing the adductor pollicis to reinforce dynam-ically the reefed repair of a scarred chronic UCL injury.(From Green DP: Dislocations and ligamentous injuries inthe hand. In Evarts CM (ed): Surgery of the Musculoskel-etal System. New York, Churchill Livingstone, 1983 p2171; with permission.)

58

uln~ collai:~Pal

/ t pll~cu~ ~ons~s

Figure l& A-P, Sake]larides and Deweese’s method ot"UCL reconstruction using the extensor pollicis brevis.(From Sakellarides HT, DeWeese ]W: Instability of themetacarpophalangeal joint of the thumb. Reconstruction ofcollateral ligaments using the extensor pollicis brevis ten-don. J Bone Joint Surg 58A:10f~-112, 1976; with permis-sion.)

RichardJ.

motion and strength. For the athlete, theysuggest that the two methods might be com-bined to yield an optimal result.

RADIAL SIDE INJURY

Compared to injuries of the ulnar collateralcomplex, very little has been written abouteither acute or chronic injuries to the radialaspect of the joint. Based upon the author’sexperience, and that which has been docu-mented in the literature, it is apparent that theevaluation and treatment of these injuries canproceed in a manner similar to that alreadyoutlined for the evaluation and treatment ofulnar collateral injuries. There are, however,important differences.~ The reported incidence of injury to the radial

side varies between 10 and 30 per cent of thatreported for the ulnar side.~°’ 14, 19, ~a, 28, aT, 41, 58, 82The mechanism of injury involves adduction

Miller

with or without an element of hyperextension--usually occurring with a sports injury or fall.Problems with pinch and grip are often absent,and presuraably for this reason, the patientscommonly present late for evaluation and treat-ment with chronic symptomatology.I° Theselate symptoms include a cosmetic deformityconsisting of prominence of the radial marginof the metacarpal head due to ulnar and volarsubluxation of the proximal phalanx on themetacarpal, and pain on the radial aspect of thejoint when the joint is loaded in adduction, lo. ~Examples of painful activity include pressureon the flattened hand (as occurs when polishinga tabletop), and pressure on the radial aspect ofthe thumb tuft (as occurs when pressing on theopening latch on a car door or twisting the lidof a jar). The surgical pathology consists oftearing or attenuation of the radial and accessorycollateral ligaments, which may fail at eitherbony attachment or within their midsub-stance, lo Like its companion injury on the ulnarside, volar subluxation often occurs about theintact contralateral collateral ligament.l°’ s,zSmith found this in 65 per cent of his 20patients,se This results in a pronation deformitythat contributes to the dorsal radial prominenceof the metacarpal head, so often noted onclinical exam. Although Camp~° noted no intra-articular fractures in his 26 patients, Smithfound that 5 of 20 patients in his series hadavulsion fractures, ~vith four of these noted onthe metacarpal side of the joint. Althoughstretching of the extensor aponeurosis may oc-cur, a disturbance analogous to the Stener le-sion seen with ulnar-sided injuries has not beenreported, lo, la, ~, s2

Evaluation and Treatment

The clinical assessment of this injury mayproceed in a fashion similar ;to that detailed forproblems on the ulnar side of the joint. Aclinical "stress test" with the joint held in 15degrees of flexion usually suffices to establishthe grade of the injury. Laxity in excess of 45d~grees, or greater than 15 degrees more thanthat found on the contralateral thumb, indicatesa complete tear of the radial collateral liga-ment.lo, sz The presence or absence of volarsubluxation with pronation of the proximal pha-lanx on the metacarpal head should also bedetermined. Plain x-rays are helpful and mayfurther assist in the documentation of volarsubluxation. Stress x-rays and arthrograms aregenerally not ne6essary.

~sion--or fall.absent,~atientsd treat-

These:fortuitymarginLd volar

state that most third-degree injuries can also be brevis in the treatment of chronic radial injuries

on the ~ satisfactorily managed with simple cast immo- was originally described by Sutro~° and has

.’t of the ~bilizati°n’~4’ ~ Others, however, have recom- recently been advocated by Neviaser,~

:ion.~°’~ i~mended acute operative repair as the best Green,~ and Camp.~° The surgical technique

~ressuremeans of assuring reliably good results,e~’ s~ If d.escribed by Camp starts with a 5-cm incision

olishing volar subluxation is apparent on evaluation of on the radial aspect of the joint, with the

tspect of the acute third-degree injury, this may consti- subcutaneous dissection identifying and pro-

~ on the tute a more definitive indication for open sur- tecting superficial branches of the radial sensory

~ the’lidgical repair.

~sists of~ If acute surgical intervention is undertaken, from the extensor tendons, the capsuloligamen-~ the repair proceeds in a manner analogous to tous plane is identified and cleared, and the

ceessorytt either ~

that outlined for ulnar-sided injuries. Midsub- short abductor tendon detached from its inser-

midsub- ~ stance tears and avulsions from the origin at the tion into the proximal volar corner of the prox-

I metacarpal level are more apt to be encoun- imal phalanx. The abductor pollicis brevis is:he ulnar tered here than with ulnar collateral injuries,m mobilized from the surrounding soft tissue tobout the ~ allow it to be advanced distally. Campm makes~ent. m,f his 20

the point that visualization of the radial collat-

[eformitvChronic Injuries eral ligament from the interior of the joint often

¯ helps to identify the site of the rupture, whichmlinence~oted onno intra-

and findings of radial or radial-volar instability taken down, and the ligamentous tissue fresh-

s, Smithare candidates for ligament reconstruction

~ries had ~:~noted on ,..i; The principles of soft tissue reconstruction A aA~-inch drill hole is then made in the radial

Although for chronic radial instability are similar to those cortex of the proximal phalanx, 1 cm distal to

~ may oc-;tener le-not been : ;::: "

Ljury mayetailed for Figure 16. CamP’s teehmque for, joint. A pair of the chronic radial collateral tear.

leld in 15 A,B, Ligamentstumpisfreshenedand~!

~ establish advanced distally or proximally to bone.

:tess of 45 i G, Overlapping flap repair for midsub-stance tear. (From Camp RA, Weather-

more than wax RJ, Miller EB: Chronic post-trau-

, indicates matic radial instability of the thumb~teral liga- metacarpophalangealjoint. J Hand Surge of volar 5A:’221-225, 1980; with permission.)

ximal pha-Id also be1 and mayn of volar)grams are

60 Bichard J.

the articular surface. The abductor pollicisbrevis tendon is advanced into this hole andsecured with a suture tied over a bony bridgeon the ulnar aspect of the mid-proximal phalanx(Fig. 17). Any volar subluxation of the jointshould be corrected, and an 0.045 K-wirepassed to transfix the joint prior to securing theligamentous and tendon sutures. The abductortendon aponeurosis is repaired, recentralizingthe extensor tendons if they have subluxedulnarly. Postoperative rehabilitation is virtuallythe same as that mentioned for the ulnar inju-ries. Camp reported good results with thistechnique in eight patients with excellent res-toration of stability and satisfactory maintenanceof mobility.

DORSAL DISLOCATIONS

The mechanism of dorsal dislocation is forcedhyperextension. The degree of resulting dorsalinstability is dependent upon the extent o:f thevolar and collateral soft tissue disruption. Usinga cadaver model, Stener showed that an intjurylimited to the volar plate could result in hyper-extensibility of the MCP joint, but that a truedorsal dislocation with bayoneted positioning ofthe proximal phalanx on the metacarpal couldnot be produced without the addition of acomplete rupture of at least one collateral liga-ment.S,s

Failure of the volar plate in a dorsal disloca-tion may occur either proximally or distally:. Ifthe failure occurs proximally, the metacarpalhead herniates through the thin men~tbranouscentral portion of the proximal volar plate,usually passing between the adductor pollicisand flexor pollicis brevis tendons.~ The ]!ong

Miller

thumb flexor is displaced by the metacarpalneck either radially or ulnarly. The intrinsicsnormally retain their insertion into the sesa-molds, and this tends to prevent the volar platefrom becoming incarcerated within the joint.This fact, together with the absence of completetendon and ligament encirclement of the meta-carpal head, usually prevents an irreducibledislocation.

Alternatively, if the volar plate ruptures dis-tally at its junction ~vith the volar base of theproximal phalanx, the intrinsics and volar platemay retract volarly as a unit, thereby disruptingboth the principal passive and active wrist re-straints to hyperextension of the joint. Thisleaves the joint particularly prone to hyperex-tension instability. Some authors believe thatthis situation is an indication for surgical repairin the acute setting. As previously mentioned,the position of the sesamoids relative to theproximal phalanx, as seen radiographically onthe lateral projection, provides valuable infor-mation.as to the exact anatomic site of the volarsoft tissue tear. If the sesamoids have remainedin their anatomic position adjacent to the base.of the proximal phalanx, then the volar disrup-tion must have occurred proximally; whereas,if the sesamoids have retracted proximally, thenone can be certain that the volar plate andintrinsics have ruptured at their insertionalpoint into the volar base of the proximal pha-lanx. Failure through the sesamoids has alsobeen reported.~, ss

Although uncommon, complex (irreducible)dorsal dislocations of the thumb MCP joint dooccur. ~, ~7, ~, _~s, ~ The irreducibility of this typeof dislocation is caused by interposition of thevolar plate between the proximal phalanx andmetacarpal head. Unlike the situation with a

Figure 17. Suture technique for ab-ductor pollicis brevis advancement. A,Tendon advanced to transverse drill holein proximal phalanx. B,.Tendon suturetied over ulnar cortical bony bridge.(From Camp RA, WeatherwaxM filer EB: Chronic post-traumatic radialinstability of the thumb metacarpopha-langeal joint. J Hand Surg 5A:221-225,1980; with permission.)

.etacarpalintrinsicsthe sesa-olar platethe joint.completethe meta-reducible

tures dis-Lse of theolar platetisruptingwrist re-

.int. Thishyperex-

[ieve that.cal repairentioned,ce to theaicalty onble infor-! the volarremained~ the basear disrup-whereas,

~ally, thenplate andnsertional:imal pha-; has also

reducible)P joint do[ this typeion of the~alanx and3n with a

~ique for ab-

ncement. A,,rse drill hole~ndon suture~ony bridge.:herwax B.J,umatie radialetaearpopha-5A:2~1-29~5,

Dislocations and Fracture Dislocations p]~

simple dorsal dislocation where the MCP jointis often fixed in hyperextension, in complexdislocations the alignment of the thumb raymay be minimally disturbed. The metacarpalhead is prominent beneath the votar skin, andthere is associated volar skin dimpling.~ Thediagnosis is confirmed by the finding of a wid-ened joint space on radiographic examination.On occasion, the sesamoids may be incarceratedwithin the joint.

Treatment

Although Stener~ recommended that dorsaldislocations be treated with open repair, otherauthors~ have found that simple dorsal dislo-cations of the thumb MCP joint can usually bemanaged satisfactorily with closed reductionfollowed by 3 weeks of cast immobilization withthe MCP joint in 20 to 30 degrees of flexion.The manner in which the closed reduction isattempted is important because there is risk ofconverting a simple dorsal dislocation into acomplex irreducible one.~ After obtaining ad-equate anesthesia with a median and radialsensor3, nerve wrist block, the thumb metacar-pal is flexed and adducted to relax the intrinsics,and the wrist is flexed to relax the flexor pollicislongus. Longitudinal traction is applied to theproximal phalanx, after which the reduction canusually be accomplished by gently flexing theproximal phalanx on the metacarpal. Medialand lateral stability is checked clinically, andthe congruency of the reduction is confirmedradiographically. If the joint easily dislocateswith active movement following closed reduc-tion, or the joint shows more than 40 degreesof radial or ulnar laxity on gentle clinical stress,Eaton suggests that open repair is indicated.X9Excessive hyperextension instability can be cor-rected by repairing the rupture in the proximalportion of the volar plate and suturing any tearsof the intrinsic tendons. In the exceptional casewhere the volar plate has torn from its attach-ment to the base of the proximal phalanx,consideration should be given to t’epairing thiswith a pull-out wire in the manner describedby Eaton~ and othersY" ~s In the absence ofopen treatment, postreduction care includes 4weeks of thumb spica immobilization with thejoint in 20 to 30 degrees of flexion followed byprogressive mobilization and strengthening sim-ilar to that outlined for acute collateral injuries.

If efforts at closed reduction are not success-ful, open reduction is required. ,With a volarapproach, the soft tissues encountered will usu-ally be found to be tightly stretched across the

theMetacarpol)halangeal Joint of the Thumb " 61

metacarpal head, which has herniated into asubcutaneous position. Exceptional care shouldbe taken to identify and protect the radial digitalnerve as it crosses the field at this level. Theincarcerated volar plate, intrinsic tendons, orother soft tissue that are preventing reductionare retracted or released, after which the jointis reduced under direct vision. Following re-duction, the joint is checked for residual insta-bility in both the medial-lateral and flexion-extension planes and repaired as necessary.Postoperative treatment is the same as thatindicated for closed reduction.

Although most authors~4, ~s. ~4. ~8, 86 have rec,ommended that a volar or lateral approach beused in the operative treatment or irreducibledorsal dislocations, a good argument4" tv can bemade for considering the alternative use of adorsal approach. In view of the fact that theprinciple block to reduction is usually that ofan incarcerated volar plate, a dorsal approachoffers the distinct advantages of better exposureof the plate, a lessened risk of injury to thedistorted volar neurovaseular structures, andimproved visualization of the interior of thejoint. Although most of the experience with thisapproach in complex dorsal MCP joint disloca-tions has been in the index finger,~ its successfulapplication in the thumb has also been re-ported.~ Regardless of the approach used, thekey to the reduction is retrieval of the volarplate from within the joint. Often a longitudinalincision in the midsubstance of the volar plateis necessary to effect this retrieval, and should[his be the ease, there is reason to believe thatthis may be most easily accomplished througha dorsal approach.

Chronic Dorsal Instability. Like the other_.chronic instabilities about the MCP joint,chronic post-traumatic hyperextension instabil-ity may result in compromised thumb functiondue to weakness and pain in pinching andgrasping activity. If these symptoms do notrespond to the usual conservative measures,including limiting activities, intrinsic strength-ening exercises, and a trial with an orthosis,then the patient becomes a candidate for sur-gical stabilization with either volar soft tissuereconstruction or arthrodesis.

The soft tissue reconstructions are designedto either reanehor the proximal margin of thevolar plate to the metacarpal, or to recreate avolar tether with graft material. Milch,~ in1929, provided us with one of the earliestdescriptions of a technique for reestablishingvolar restraint with a free tendon graft. Morereeer~tly, Kesslera8 has reported his experiencewith nine patients using the extensor pollieis

62 Richard ].

brevis tendon, rerouted to form a sling acrossthe volar aspect of the joint. By taking thistendon for his graft and leaving it attacheddistally, he was able to eliminate one of themain deforming forces while accomplishing thereconstruction in a relatively simple i~ashion,requiring only one drill hole through the met-acarpal neck. A similar technique has beendescribed by Brewood7 for the correction ofcombined volar and radial instability. The alter-native strategy of checking hyperextension byreanchoring damaged existing tissue has beenadvocated by Green.29 He described a modifi-cation of Zaneolli’s99 sesamoid capsulodesis inwhich he anchors the proximal edge of the volarplate to a bony trough created in the volar neckof the metacarpal. Green has found this proce-dure to be effective and simpler than the useof tendon slings.

If the MCP joint is arthritic, then arthrodesisof the joint, as previously described, againprovides a good salvage.

Locked MCP Joint with Partial DorsalDislocation

In addition to simple and complex dorsaldislocations of the thumb MCP joint, partialdislocations resulting in locking of the joint inmild hyperextension can occur. This conditionhas been alluded to by several authors and has

Figure 18. Diagram illustrating MCP joint-locking mech-¯ anism. A, Forced hyperextension of the MCP joint resultsin rupture of the volar plate, B, C, The radial condyleherniates through the radial portion of the volar plateproximal to the radial sesamoid. Joint is locked in mildhyperextension. (From Yamanaka K, et al: Locking of themetacarpophalangeal joint of the thumb. J Bone Joint Surg67A:782-787, 1985; with permission.)

Miller

recently been reviewed and expanded upon byYamanaka96 in his clinical report of 23 patients.Again, the mechanism of injury is hyperexten-sion, but in this case, the volar disuption of thesoft tissue is limited to the isolated herniationof the prominent radial condyle of the metacar-pal head through the midsubstance of the radialaspect of the volar plate just proximal to theradial sesamoid (Fig. 18). The most distal mar-gin of the volar plate’s substance remains intactand becomes tightly drawn across the distalprominence of the radial condyle of the meta-carpal head, thereby locking the joint in mild(30 to 40 degrees) hyperextension. The sesa-molds and volar plate are not entrapped withinthe joint, but do ride very distally on the volarcontour of the metacarpal head. In Yamanaka’sseries, 7 of 23 patients ~vere successfully treatedwith closed reduction under regional anesthesiaby manipulating the proximal phalanx towardsthe volar side of the joint while supinating thethumb on the metacarpal head and simultane-ously flexing the metacarpophalangeal joint. In’16 of his patients, however, surgical release ofthe distalmost margin of the volar plate wasrequirec~ to obtain reduction. Only 2 weeks ofpostoperative immobilization were necessaryfor these patients, and no recurrences werereported.

SUMMARY

Due to its exposed position, the MCP jointof the thumb is particularly vulnerable to dis-locations and fracture dislocations. Dependingon the direction of the injuring force, inju.ri__esto the ulnar, radial, and volar aspect of the jointcan occur. If high-grade lesions are not identi-fied and treated appropriately during theiracute phase, marked instability with associatedlong-term disability due to weakness and painin pinch and grip can result. In the absence ofa reliable method for diagnosing the Stenerlesion, surgical repair of acute, third-degree¯ lesions on the ulnar side of the joint remainsthe treatment of choice. In the presence ofchronic instability, a variety of effec{ive softtissue reconstructive measures are available.The fact that both acute and chronic injuriesenjoy a ~:avorable prognosis with operative re-pair is due to the fact that operative interventionreliably restores stability to the joint. Mild tomoderate loss of motion at .the joint is welltolerated functionally. For this reason, arthro-desis remains an exceptionally satisfactory sal-vage for failed soft tissue reconstructions.

upon by

patients.perexten-ion of themrniationmetacar-

the radialtal to theistal mar-tins intactthe distalthe meta-~t in mildthe sesa-ed withinthe volar

amanaka’s.Iv treatedinesthesiax tmvardsaating the

;imultane-.1 joint. In"release ofplate was:weeks ofnecessary

Ices were

vlCP joint~te to dis-)ependinge, injuries~f the joint

aot identi-ring theirassociated~ and pain

absence ofhe Stenerird-degree

It remainsresence ofeetive soft

available.

le injurieserative re-tervention.t. Mild tont is wellm, arthro-"actory sal-

ions.

Dislocations and Fracture Dislocations of the Metacarpophalangeal Joint of the Thumb

REFERENCES

1. Ahmed O, DePalma F: Treatment of gamekeeper’sthumb by a new operation. Clin Orthop 103:167--169, 1974

2. Aldred AJ: Rupture of the collateral ligament of themetacarpophalangeal joint of the thumb. J BoneJoint Surg 37B:443--445, 1955

3. Bailey RAJ: Some closed injuries of the metacarpo-phalangeal joint of the thumb. J Bone Joint Surg45A:428-429, 1963

4. Becton JL, et al: A simplified technique for treatingthe complex dislocation of the index metacarpopha-langeal joint. J Bone Joint Surg 57A:698, 1975

5. Bell MJ, McMurtry RY, Rubenstein J: Fracture of theulnar sesamoid of the metacarpophalangeal joint ofthe thumb--an arthrographic study. J Hand Surg10B:379-381, 1985

6. Bowers WH, Hurst LC: Gamekeeper’s thumb. Eval-uation by arthrography and stress roentgenography.J Bone Joint Surg 59A:519-524, 1977

7. Bre~vood AF, ,Menon TJ: Combined reconstruction ofvolar and radial instability of a thumb metacarpo-phalangeal joint. J Hand Surg 9B:333-334, i984

8. Browne EA, Dunn HK, Snyder CC: Ski pole thumbinjury. Hast Reconst Surg 58:19-23, t976

9. Burman A: Irreducible hyperextension dislocation ofthe metacarpophalangeal joint of a finger. Bull HospJoint Dis 14:290, 1953

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