Post-Traumatic Instability of theMetacarpophalangeal Joint of the Thumb*

BY RICHARD J. SMITH, M.D.S"

ABSTRACT:. Of eighty-six patients with collateralligament instability of the metacarpophalangeal jointof the thumb, sixty-six (77 per cent) had ulnar andtwenty (23 per cent) had radial instability, while addition twenty-fou~" had fractures and twenty-ninehad volar subluxation of the proximal phalanx. Of thesixty-nine patients operated on, sixty-five had an ab-normality of the ulnar or radial collateral ligamentproper or of its attachment; two, subluxation of the ex-tensor pollicis longus; and two, stretching of theadductor expansion. Stability was restored by collat-eral ligament repair or reconstruction, by fixation of afracture fragment with a Kirschner wire, or by ar-throdesis in all but five thumbs. Of the five patientswho did not have stability of the metacarpophalangealjoint following surgery, three had had the collateral lig-ament sutured more than three weeks after injury andtwo had had reconstruction of the collateral ligamentusing a tendon graft. Early surgical treatment is rec-ommended for all patients with post-traumatic instabil-ity of the metacarpophalangeal joint greater than 45degrees.and for those with volar subluxation of theproximal phalanx or a displaced fracture of the base ofthe proximal phalanx. Collateral ligament repair is in-dicated for patients operated on within three weeks ofinjury, and reconstruction of the ligament by means ofa tendon graft is recommended for those treated morethan three weeks after injury.

Injuries to the collateral ligaments of.the metacar-pophallangeal joint of the thumb are common, and in mostcases respond well to conservative treatment. Despite ade-quate treatment, however, chronic post-traumatic instabil-ity of this joint is frequent and often quite disabling. Themechanism of injury, the precise location of the lesion, theindications, for operative repair, the technique of repair,and the prognosis after these injuries remain controversial.The purpose of this retrospective study was to attempt tosetde some of these controversies.

Materials and Methods - ’

Eighty-six patients with instability of the metacar-

pophalangeal joint of the thumb were studied: sixty-sixwith ulnar and twenty with radial instability. These pa-tients included all those with metacarpophalangeal-joint

* Read at the Annual Meeting of the American Society for Surgeryof the Hand, San Francisco, California, February 28, 1975.

~" Hand Surgery Service, Department of Orthopaedic Surgery,Massachusetts General Hospital, Boston, Massachusetts 02114.

, BOSTON, MASSACHUSETTS

instability referred to me for office care (from August 1972through January 1975), all such patients admitted to theHospitalfor Joint Diseases, New York City, for surgicaltreatment (August 1963 through July 1972), and thoseadmitted to the Massachusetts General Hospital, Boston,for surgical care (August 1972 throtigh January 1975). Pa-tients referred to the Emergency Ward or the clinics ofthese hospitals who did not require admission or surgerywere not included. The patients considered in this review,therefore, were those who were most seriously injured andthose who continued to have symptoms after receivingconservative care.

Tihe patients’ ages ranged from fourteen to sixty-seven years. Eleven were less than twenty years old;forty-three were twenty to thirty-nine years old; thirtywere forty or older; and no age was recorded for two.Fifty-two patients were male and thirty-four were female.

Mechanisrn of Injury

No patient was included in this series who had evi-de.rice of rheumatoid arthritis affecting the hand.’ Elevenpatiems could recall no specific injury preceding the onsetof symptoms. Forty-one had injured the thumb in a fall,twelve while skiing. Nineteen had injuries caused by theimpact of a moving object such as a ball or falling box.Eight had struck an object with the thumb, some whileboxing. Seven had been injured when the thumb waspushed, deflected, or twisted by a friend or spouse. Fewpatients could recall precisely the direction of the injuringforce, but most believed that the thumb had been pushed"backwards" (into extension). None of the patients weregamekeepers. ,

Bone Injury

A bone injury at the site of attachment of the collat-eral ligament was visible on the roentgenograms oft~enty-four thumbs: in nineteen with ulnar and five withradial instability (Fig. 1). In these twenty-four thumbs thebone lesion was a fracture fragment that involv.ed moreflaan i0 per cent of the articular surface of the proximalphalanx in nine and was a small avulsion fragment or bonedefect at the site of attachment of the collateral ligament tothe proximal phalanx in eleven and to the metacarpal headin four. The nineteen bone lesions associated with ulnarinstability included eleven avulsions and eight articularfractures, while the five lesions associated with radialinstability were four metacarpal avulsions and onephal~aageal articular fracture. All of the metacarpal avul-.,;ion :fractures were associated with ulnar instability. All of

THE JOURNAL OF BONE AND JOINT SURGERY

POST-TRAUMATIC INSTABILITY OF THE METACARPOPHALANGEAL JOINT OF THE THUMB 15

of the twenty-nine thumbs with volar subluxation also had~

~fractures. The volar subluxatiOninjury tenWaS first recognized less

@ @ \ \ (~ than three weeks after in patients and more thanthree weeks after injury in nineteen.

Treatment

Of the eighty-six patients, sixty-nine were operatedon and seventeen were treated successfully with an Or-thoplast splint or plaster gauntlet cast that immobilized thethumb, :including the interphalangeal joint. Of the sixty-nine,, patients treated surgically, forty-eight were operated

@ ~~ ~ on inore than three weeks and twenty-one, less than three¯ weeks after injury. The forty-eight patients operated on

" more than three weeks after injury included twenty-two in’" / / whom fl:le thumb had been immobilized in a piaster cast

immediately after injury (twelve for three weeks and tenfor less than three weeks); two who had declined surgicaltreatment initially but were eventually operated on whensymptoms persisted after three weeks of immobilization;and twenty-four in whom the thumb had not been im-

Diagram showing types of ulnar and radial collateral ligament injuriesof the right thumb. With instability on the ulnar side (a, b, and c), the mobilized by a splint or cast after injury.rupture may be at the base of the proximal phalanx either without a hone Of the twenty-one patients w.ho were operated on lessfragment (a), with a small avulsion fracture (b), or with a larger fracturefragment (c) (1. anteroposterior, 2. lateral). When a fracture occurs, it than three weeks after injury, nineteen (eighteen withinvolves the volar and radial or ulnar margin of the base of the proximal ulnar ir,~stability and one with radial instability) had eitherphalanx. With radial instability (d, e. and f), avulsion may be from eitherthe metacarpal head or the base of the proximal phalanx, with or without the collateral ligament or the avulsed bone fragment reat-a small avulsion fragment, tached at the site of rupture using one or two Kirschner

wires, a pull-out wire, or interrupted sutures, and two hadthe phalangeal fractures were located at the palmar and a tendon graft to reconstruct the ulnar collateral ligament.ulnar margin of the base of the phalanx when there was in two of these patients, a Kirschner wire was also passedulnar instability and at the palmar and radial margin when through the joint to maintain reduction of a volarly sub-there was radial instability, luxated proximal phalanx after ligament repair by suture.

Of the forty-eight patients who were operated on forVolar Subluxation ̄ post-trauinatic instability more than three weeks after in-

Volar subluxation of the proximal phalanx was evi- jm~ or for chronic instability without known trauma, six"". dent in sixteen of the sixty-six patients with ulnar instabil- had the collateral ligament sutured (four, the radial coIlat-

ity and in thirteen of the twenty with radial instability. Se- eral arid two, the ulnar collateral ligament), thirty-eigh~_tvere subluxation (defined as more than three millimeters of had tendon-graft reconstruction of either the radial or thevolar displacerrient of the dorsum of the proximal phalanx ulnar collateral ligament, four had arthrodesis of the

.,:, with respect to the dorsum of the metacarpal) was present metacarpophalangeal joint as the first operative procedure~"’:-:";: in four of the Sixteen with volar subluxation and ulnar in- (two with radial and two with ulnar !,nstability), and one~ stability and in eleven of the thirteen with volar subluxa- had Kirschner-wire fixation of the joint at the time of

tion and radial instability (Figs. 2-A, 2-B, and 2-C). Ten tendon-graft reconstruction.

Fm. 2-A FiG. 2-B FIG. 2-CFigs. 2-A, 2-B, and 2-C: Demonstration of volar subluxation of the proximal phalanx which occurred in twenty-nine of the eighty-six patients

examined.Fig. 2-A: The metacarpal is supported with one hand and the proximal phalanx is held with the other.Fig. 2-B: With volar pressure on the oroximal phalanx the head of the metacarpal becomes palpable dorsally if there is volar subluxation.Fig. 2-C: ~th volar subluxation, a lateral roentgenogram shows incongruity of the surfaces of tlae metacarpophalangeal joint in extension and

translocation of the proximal phalanx volarly.

Operative Findings

¯ Of the fifty-two patients surgically treated for ulnarinstability, twenty-one were operated on within threeweeks of injury and thirty-one; after three weeks. The fol-lowing lesions were found: a ligament ruptured or avulsed

with or without a fracture fragment in forty-eight patients(forty-seven with a distal and one with a proximal lesion)(Figs. 3-A and 3-B) and an apparently uninjured ulnar col-lateral ligament in four patients, of whom two had astretched or torn adductor apparatus and two had subluxa-tion of the extensor pollicis longus.

F~G. 3-A FIG. 3-BFig. 3-A: Marked instability on the ulnar side of the metacar-

pophalangeal joint of the thumb, demonstrated by mild stress on the dis-tal fragment. If need be, local infiltration of Xylocaine (lidocaine) on theulnar side of the joint may be used to decrease pain and adductor spasm.

Fig. 3-B: An anteroposterior roentgenogram showing a fracture of thebase of the proximal phalanx at the site of attachment of the collateralligament.

All of the twenty-one patients operated on early hadrupture of the ulnar collateral ligament or an avulsion of itsphalangea~ attachment. The ruptured ulnar collateral liga-ment was found to be superficial and proximal to theadductor apparatus, as described by Stener11, in three ofthese twenty-one patients (Fig. 4). The adductor expan-sioh was torn, stretched, or thin inthree of the patients op-erated on early.

All df the seventeen patients who were operated onfor radial instability had a damaged radial collateral liga-

FxG. 4The distal end of the avulsed ulnar collateral ligament may lie either

.deep (top) or superficial (bottom) to the adductor-dorsal apparatus.

FIG. 5-A FIG. 5-BRadial instability of the metacarpophalangeal joint due to injury of the

radial collateral ligament or its attachments. There is marked instabilityff’ig. 5-A) several months after rupture of the collateral ligament, but noassociated fracture (Fig. 5-B).

rrtent (Figs. 5-A and 5-B). In six patients the ligament wastorn from its phalangeal attachment and in four, from itsrctetacarpal attachment. In the remaining seven patients,tl~te site of detachment could not be determined but the lig.-

ament appeared stretched and attenuated. In two patients,the abductor-dorsal expansion was also thin or stretched.In two others, operated on more than six weeks after in-j~try, there was a small convex sulcus in the articular car-tillage on the dorsal third of the head of the metacarpal, ap--parently caused by pressure of the subluxated dorsal ar.-titular margin of the proximal phalanx. In no patient wasthere evidence of severe osteoarthritis or extensive carti-l~tge erosion.

Surgical Technique

The techniques used in this.series varied somewhatsince forty-six of the patients Were treated by me and.twenty-three, by other members of the staffs of the twohospitals. The principles of surgical technique for.recon-struction of the collateral ligament, however, were simi-lar. Ifi the patients operated on within three weeks, eitherthe ulnar or the radial collateral ligament was resutured orreattached (except for two who had reconstruction of theligament by tendon graft). In the forty-eight patients oper-ated on late, a tendon graft was used for reconstruction ofthe ulnar collateral or the radial collateral ligament inthirty-eight; a tendon suture was performed in six; and ar-

throdesis, in four.The techniques to be described are those used by me.Primary repair: Under regional block anesthesia, a

mid-axial incision three centimeters in length and centeredat the metacarpophalangeal joint of the thumb is made onthe injured side. After sensory branches of the radial nerveare identified and retracted, the dorsal expansion is

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POST-TRAUMATIC INSTABILITY OF THE METACARPOPHALANGEAL JOINT OF THE THUMB

visualized and transected in the mid-axial line. Dorsal artdvolar flaps of the expansion are then freed from the under-lying soft tissue and retracted, exposing the joint capsule.If a ligament rupture is found, it is repaired with inter-rupted horizontal mattress sutures of 4-0 nylon. A smallavulsion fracture is replaced with a figure-of-eight pull-outwire; a large fracture fragment is replaced and fixed withone or two Kirschner wires. The dorsal expansion isclosed with horizontal mattress sutures of 4-0 nylon. Post-operatively, a plaster-of-Paris thumb-spica gauntlet castextending from thumb tip to mid-forearm is applied andworn for three weeks. The thumb is then protected with aremovable splint for five more weeks.

Secondary repair: Using the same exposure describedfor primary repair, remnants of the collateral ligament ~reidentified. If the ulnar collateral ligament is ruptured,there is usually a sturdy remnant of ligament still attachedto the metacarpal neck. In this event, a 2.8-millimeter holeis drilled transversely across the base of the proximalphalanx from its radial to its ulnar side and votar to theaxis of motion (Fig. 6). A figure-of-eight pull-out suture passed through one end of a tendon graft (usually from thepalmaris longus), drawn through the hole in the base of theproximal phalanx, and tied over a button on the oppositeside of the thumb. The free portion of the graft is then runto the metacarpal head, where it is secured by makingparallel longitudinal incisions in the remnant of the collat-eral ligament and weaving the graft through the portion ofthe ligament between these incisions. If the collateral lig-ament remnant is not firm, the graft is secured proximallyby making two adjacent drill holes in the metacarpal head,connecting them, and then passing the graft through theresulting tunnel. In either event, the remaining free por-tion of the graft is then run distally so that it lies paralM,volar, and adjacent to the portion of the graft coming fromthe phalangeal drill hole. Any deformity at the metacar-pophalangeal joint is corrected and the tendon graft is su-tured to the renmants of the collateral ligament. The parM-lel segments of the graft are also sutured to each other.Thus, the collateral ligament reconstruction duplicates thenormal collateral ligament passing distally and volarlyfrom the metacarpal head to the base of the proximalphalanx. Reconstruction of either the ulnar or the radialcollateral ligament prevents volar subluxation of the prox-

FIG. 6For late reconstruction of a radial or ulnar collateral ligament from its

phalangeal attachment, a tendon graft should be placed volar to the mid-shaft plane of the proximal phalanx so that the graft will prevent volardisplacement of the phalanx. Proximally, the graft is woven through theremnant of the ruptured collateral ligament.

VOL. 59-A, NO. 1, JANUARY 1977

17

FIG. 7Diagram showing the steps in the reconstruction of the ulnar collateral

ligament for late post-traumatic instability: (a) a mid-axial incision made; (b) the adductor dorsal expansion is transected; (c) the expansionis retracted; (d) a hole is drilled volar to the midline of the proximalphalanx; (e) (dorsal view) a tendon graft is drawn through the hole; parallel incisions are made in the remnant of the collateral ligament; (g)the tendon graft is woven through the collateral ligament remnant (orthrough the bone if the remnant is not present) and the two parallel limbsof the graft are sutured to each other; and (h) the adductor-dorsal ap-paratus is closed and "double-breasted" if lax.

imal phalanx as well as excessive radial or ulnar deviationat the metacarpophalangeal joint. The adductor-dorsal ex-pansion is then resutured in patients with reconstruction ofthe ulnar collateral ligament. In a radial collateral ligamentreconstruction, the abductor-dorsal expansion is resutured

in similar fashion. The expansion is "double-breasted" ifit is lax, by using mattress sutures (Fig. 7). Postopera-tively, the thumb is held for four weeks in a plaster-of-

Paris gauntlet cast extending from the thumb tip to themid-forearm. At the end of that time, the sutures are re-moved and the thumb is protected with a removable splintfor five additional weeks.

Of the sixty-five patients who were operate__d on forligament abnormality, twenty-five were not available forevaluation more than three months after operation becausethey often lived several hundred miles away, had been dis-charged from care, and had returned to their regular activi-ties after discharge. The other forty were re-examined four

to. thirty-six months after operation.

Results

" There were five failures for which reoperation was

performed, three of them in patients whose ruptured col-lateral ligament was resutured more th.a~n three weeks afterthe original injury. These three patients were successfullytreated, two by transfer of the extensor indicis proprius, aspreviously reported 5, and one by arthrodesis. The other

two had had tendon grafts for reconstruction of a rupturedulnar collateral ligament by the technique described. Inone of them, the graft had ruptured six months after opera-tion when stability was tested by an "insurance doctor";in the other, the graft gradually stretched over a period ofabout six months, causing recurrent pain when the patientreturned to his original job lifting heavy boxes. Both of

R. J. SMITH18

Fro. 8-A Fro. 8-B FIG. 8-C Fro. 8-D~

Figs. 8-A through 8-D: This eighteen-year-old man ruptured the radial collateral ligament of the right thumb when it was caught in a helmet whilehe was playing football four months previously.

Fig. 8-A: A preoperative photograph shows volar subluxation of the proximal phalanx.Fig. 8-B: Marked radial instability is demonstrated by adduction stress.Fig. 8-C: Four months after tendon graft (opposite palmaris longus) to replace tl’te ruptured radial collateral ligament, subluxation is corrected and

metacarpophalangeal-joint flexion is equal to that of the opposite thumb.Fig. 8-D: Lateral stability is restored so that ulnar deviation of the proximal phalanx under stress is equal to that of the opposite thumb.

these patients were successfully treated by arthrodesis at excellent range of motion complained of continued aching

reoperation.The remaining sixty-four surgically treated patients

all regained excellent stability. None had more than a 15-degree excess of laxity in the involved thumb comparedwith the normal thumb. The stability was assessed bymeasuring the amount of radial deviation of the proximalphalanx while the patient exerted maximum pinch pressurewith the ulnar side of the thumb against the tip of the indexfinger and by measuring the radial or ulnar deviationcaused when the examiner exerted a radial or ulnar deviat-ing force on the distal phalanx while the first metacarpalwas held firmly. Stability was tested in both extension andflexion of the metacarpophalangeal joint. One patientcomplained of persistent dorsal hypesthesia, apparentlydue to injury to a sensory branch of the radial nerve. Two

patients with a tendon-graft reconstruction complained ofa small, paihless lump at the site of the graft, but this wasnot disabling. One patient, with excellent stability and an

pain during heavy work and used a splint intermittently. Inno case did severe subtuxation (more than three millime-ters) or rotatory deformity persist (Figs. 8-A through 9-C).

For forty of the sixty-five patients who were operatedon for ligament repair or reconstruction and did not requiresecondary surgery, data were available that permittedcomparison of the ranges of motion of the metacar-pophalangeat and interphalangeal joints of the injured anduninjured thumbs. In the fifteen patients treated by pri-:ma_ry repair, the metacarpophalangeal joint showed an av-erage loss of 4 degrees of extension (maximum, 30 de-grees) and of 17 degrees of flexion (maximum, 50 de-grees); the interphalangeal joint showed an average loss of5 degrees of extension (maximum, 45 degrees) and of degrees of flexion (maximum, 45 degrees). In thetwenty-five patients who had secondary repair with g-ten-don graft, the average loss at the metacarpophalangealjoint was 8 degrees of extension (maximum, 30 degrees)

FIG. 9-A FIG. 9-B FIG. 9-C

Figs. 9-A, 9-B, and 9-C: A fifteen-year-old boy injured the ulnar collateral ligament of the right thumb in a fall six months earlier.Fig. 9-A: Instability of the metacarpophalangeal joint to radial stress is demonstrated.Fig. 9-B: Three years after replacement of the ulnar collateral ligament with a tendon graft from the extensor indicis proprius, he remains

asymptomatic despite full activities. Extension and flexion of the metacarpophalangeal joints are equal in both thumbs.Fig. 9-C: The right thumb metacarpophalangeal joint is stable to radial stress and the amount of radial deviation with stress is the same in both

thumbs.

POST-TRAUMATIC INSTABILITY OF THE METACARPOPHALANGEAL JOINT OF THE THUMB 19

and 11 degrees of flexion (maximiam, 40 degrees). Withgin ot! the base of the proximal phalanx. Most likely, a pot-

the exception of the patients requiring secondary surgery,tion of the volar plate was also ruptured adjacent to its at-

almost all patients were able to return to full activity, in- tachment to the fracture fragment.

cluding manual labor and athletics, within three months of 1Ulnar instability of the thumb following ski injuries is

surgery; none sought further care either for late stretchingoften produced by a ski-pole strap 9. Most ski instructors

or rupture of the repaired ligament, or for late recurrencerecommend passing the fingers through the loop of the

of the deformity,strap, grasping the pole with the strap in the palm. Whenthe skier falls with the ski pole caught in the snow, the

Discussion strap across the palm may push the thumb into extension

Although chronic post-traumatic instability of the and radi~.~l deviation, rupturing the supporting structures

thumb metacarpophalangeal joint is relatively commonon the u]~nar and volar side of the metacarpophalangeal

and often quite disabling, controversy persists as to thejoint. If the strap is allowed to dangle at the wrist and the

mechanism of injury, the exact nature of the lesion, thepole is grasped without the strap in the palm, a fall is less

" treatment, and the prognosis,likely to cause thumb injury since the strap will not en-

Campbell concluded that so-called gamekeeper’stangle or twist the thumb (Figs. 10-A and 10-B). Recent

thumb is due to gradual stretching of the ulnar collateral changes in design of the ski pole and strap may decrease

ligament. All of his patients had subjected their thumbs tothe incidence of these injuries.

repetitive abduction maneuvers over a long period of time.Fourteen patients in this series were treated by ira-

None had had an acute injury. Moberg ~,7 and Stener 3,11,13 mobilization in a plaster cast for more than three weeks

described avulsion of the collateral ligament with its distal and subsequently had continued complaints necessitating

end often displaced proximal to the intact adductor-dorsalsurgery. Although retraction of the avulsed collateral lig-

expansion, but almost all of their patients were operated ament proximal to the dorsal expansion, as described by

on within three weeks of an acute injury. Kaplan found inSterter, :may be a factor, it seems likely that if there is

two patients that the adductor-dorsal expansion hadcomplete rupture of the collateral ligament, it will not heal

stretched, with radial dislocation of the extensor polliciswith conservative treatment even if the ligament is only

longus, but that the ulnar collateral ligament was intact, mildly displaced.

However, both of his patients had been operated on pre- The collateral ligaments of the thumb have two prin-

viously, some months after the original injury, and theirciple functions: one, to provide lateral stability and the

collateral ligaments had been resutured. The adductor- other, which is equally important, to provide dorsal sup-

’ dorsal expansion therefore may have been injured at theport for the proximal phalanx 10. Volar subluxation of the

time of the original surgery. Neviaser and associates alsometacarpophalangeal joints of the fingers due to attrition

called attention to the stabilizing influence of theof the coHateralligaments causedby rheumatoid disease is

adductor-dorsal expansion and recommended its repair inwell known. In the thumb, the collateral ligaments, which

:icases of ulnar instability, pass distally and volarly, are of great importance for the

~ The experimental defects created by stress on the.dorsal support of the proximal phalanx. If the collateral

metacarpophalangeal joints in cadavera, as reported in the ligamertts do not provide sufficient support, the thum-b-

.... literature, have varied. The variability of these findings flexors, rather than flexing the phalanx about an axis,

may have been due to the differences in the experimentaltranslocate it toward the palm, causing volar subluxation

.... models, some studies having been performed on freshof ’the metacarpophalangeal joint (Fig,. 11). If one collat-

specimens 3,1~, others on embalmed specimens ~,~0, and eral ligament is ruptured, the opposit6 collateral ligamentcontinues to support the proximal phalanx on the uninjuredstill others on s~ecimens preserved in formalin. The

!~: method by which t~he injury was produced also d~ffered m~ ~ these studies. In some the proximal phalanx was stressed

radially s and in others, dorsoradially 1~. Some were sub-jected to impact, while others were tested after serialtransection of pararticular tissues

In many patients in this series, the instability wasby a force on the thumb directed ulnarly or. ra-

t and dorsally: Stener’s observation that both the col-lateral and the accessory collateral ligament prevent ex-

cessive hyperextension of the metacarpophalangeal jointwould suggest that these ligaments may rupture when theproximal phalanx is forced dorsally (and dorsoradially)and that the sudden development of ulnar instability after-~cute trauma may be the result of a radial hyperextension~,jury. In all ten patients in this series with a large fracturefragment, the fracture involved only the volar ulnar mar-

F~. 10-BF~o. 10-A

Figs. 10-A and IO-B: A ski-p~le strap often causes collateral ligamentinjuries of the thumb metacarpophalangeal joint.

Fig. ].0-A: If the strap is passed through the palm and the skier fallswith the pole caught in the snow, the strap may push the thumb intodorsiflenion and radial deviation.

Fig. I~0-B: If the strap is passed about the wrist and not through the.palm, stress by the strap is much less likely to cause thumb-ligament in-

2OR. J. SMITH

F~o. I 1

The collateral ligaments of the metacarpophalangeal joint of thethumb hold the proximal phalanx dorsally, resisting the force of the in-trinsic and extrinsic flexors of the thumb which tend to subluxate theproximal phalanx anteriorly (top). With rupture of a collateral ligament,the proximal phalanx is free to subluxate volarly, rotating around the op-posite, intact collateral ligament (bottom).

side and a rotation deformity is produced. Thus, with rup-ture of the ulnar collateral ligament, the intact radial liga-ment fixes the radial side of the proximal phalanx and thethumb rotates into supination as the ulnar side is displacedvolarly. Similarly, an intact ulnar collateral ligament inthe presence of a rupture of the radial collateral ligamentcauses the subluxating proximal phalanx to rotate intopronation. If volar subluxation is to be corrected, the rup-tured collateral ligament should be reconstructed. The re-constructed ligament, to be most effective, must pass dis-tally and volarly from the metacarpal head to the base ofthe proximal phalanx. With pronounced volar subluxationof the proximal phalanx, a transarticular Kirschner wiremay be used to maintain the position of the relocated prox-imal phalanx for three weeks. One must remember to in-sert the Kirschner wire prior to passing the pull-out suturethrough the proximal phalanx, so that the suture is notbroken.

The extensor pollicis longus and brevis also providesupport for the proximal phalanx, limiting volar displace-ment. The extensor pollicis brevis inserts into the base ofthe proximal phalanx and the dorsal capsule of themetacarpophalangeal joint, and is unlikely to be displacedor ruptured in ulnar or radial injuries of the thumb with orwithout hyperextension. The extensor pollicis longus in-serts onto the base of the distal phalanx. It is held in themidline of the dorsum of the metacarpophalangeal joint byradial and ulnar sagittal bands, both of which attach to thevolar plate, and by the dorsal expansion of the adductorpollicis and abductor pollicis brevis. As a result of radialor ulnar stress, the dorsal expansion of the adductor or ab-ductor may be stretched, allowing the extensor pollicislongus to subluxate from the dorsum of the metacar-

pophalangeal joint. Imbrication and suture of the torn orsr;etched adductor expansion in cases of ulnar instability,or of the abductor expansion in cases of radial instability,will usually relocate the extensor pollicis longus in themidline of the dorsal aspect of the metacarpophalangealjc, int so that it once again contributes to the dorsal stabilityof the proximal phalanx of the thumb. Extensor indicisp:roprius transfer, as described by Kaplan, can also be usedto reinforce the ulnar dorsal expansion of the adductor pol-licis and to hold a displaced extensor pollicis longus in themidline of the dorsum of the joint.

The majority of injuries to the collateral ligament canbe successfully treated conservatively z.4. If the ligament

i.s partially ruptured, a plaster-of-Paris splint or cast or anOrthoplast splint worn for three weeks may restore normalstability to the joint. In this series, many of the patientswere referred for treatment either because of gross jointlaxity following relatively severe trauma or because ofpersistent complaints following either conservative care orno care at all. The many thousands of patients with so-called sprained thumbs who are successfully treated in skiareas, emergency rooms, and private offices throughoutthe country attest to the efficacy of conservative therapyfor these incomplete collateral ligament injuries. Surgerywould appear to be indicated in patients who have evi-dence of complete collateral ligament disruption, a dis-placed fracture of the volar part of the base of the proximalphalanx, or volar subluxation of the proximal phalanx, aswell as in patients who have persistent disability severalmonths after collateral ligament injury. If gentle stressapplied on the proximal phalanx, with or without localanesthesia at the site of injury, reveals deviation which ex-ceeds that of the uninjured thumb by more than 45 de-grees, complete disruption of the collateral ligament canbe assumed. Stability should be tested with the metacar-pophalangeal joint both in flexion and in extensib--n. Stressroentgenograms are often helpful in evaluating these in-juries.

Arthrodesis is an alternative to soft-tissue reconstruc-tion for lateral instability of the thumb metacar-pophalangeal joint. Soft-tissue reconstruction results in anaverage loss of 20 to 30 degrees of motion of the metacar-po.phalangeal and interphalangeal joints of the thumb, ardsult that would appear to be preferable to the complete

loss after fusion. Arthrodesis of the metacarpophalangealjoint limits the versatility of the thumb, especially inyoung and active patients. Arthrodesis should probably bereserved for those who have painful or osteoarthriticjoints, or for the few who have persistent complaints after

soft-tissue reconstruction.

Conclusions

1. Post-traumatic radial or ulnar instability of themetacarpophalangeal joint of the thumb is usually due torupture of a collateral ligament or to avulsion or fracture of

its bone insertion.2. Instability of the metacarpophalangeal joint of the

POST-TRAUMATIC INSTABILITY OF THE METACARPOPHALANGEAL JOINT OF THE THUMB

thumb may be due to hyperextension combined with eitherradial or ulnar stress on the proximal phalanx, causing in-jury not only to the collateral ligament but also to the volarsoft-tissue structures about the thumb.

3. Loss of either collateral ligament of the thumbmay result in volar subluxation or rotation of the proximalphalanx.

4. With post-traumatic radial or ulnar instability ofthe thumb metacarpophalangeal joint, early surgery is in-dicated if:

a. Lateral deviation of the stressed thumb ineither flexion or extension is 45 degrees more than that onthe normal side.

b. There is a displaced articular fracture of theproximal phalanx.

c. There is volar subluxation of tl~e proximalphalanx.

21

In all other cases, the thumb should be immobilizedfor three weeks with a plaster thumb-spica gauntlet cast.

Surgical treatment of an acute injury should includeresuturing the collateral ligaments, if ruptured, or replac-ing the avulsed fracture fragment. The intrinsic dorsal ap-paratus may also require repair.

5. With persistent lateral instability or volar subluxa-tion of the metacarpophalangeal joint of the thumb presentfor rnore than one month after injury, surgical reconstruc-tion of the collateral ligaments should be performed. Theintrinsic aponeurosis should also be tightened if it appearsattenuated. The metacarpophalangeal joint of the thumbmay be arthrodesed in the presence of persistent pain orsymptomatic osteoarthritis, or after failure of soft-tissuereconstruction.

NOTE: The author wishes to thank Dr. Robert Leffert of Boston. Massachusetts’. for allow-ing him to review his clinical records. Anatomical studies were performed with Dr. Antonio DeSantolo of Caracas, Venezuela.

6.7.

8.

9.10.

12.

13.

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