Eur J Orthop Surg Traumatol (2007) 17:189–192

DOI 10.1007/s00590-006-0134-8

CASE REPORT

Carpometacarpal dislocations on the ulnar side of the hand following minor injury

Saptarshi Biswas · Ravi Ramachandran · Michael Murphy

Received: 23 December 2005 / Accepted: 5 July 2006 / Published online: 9 November 2006© Springer-Verlag 2006

Abstract We present a case of a fourth and Wfthcarpometacarpal (CMC) joint dislocation followingminor trauma and a review of current literature con-cerning diagnosis and treatment modalities. Such dislo-cations are rare and seldom seen in the setting of minortrauma. The patient, a 24-year-old male, sustained theinjury following a fall on outstretched hand accident athome. He was treated with closed reduction and dis-charged with a short arm cast. At a 6 month follow up,all CMC joints were non-tender with full range ofmotion in all digits. Neurovascular examination wasnormal. Since, he has returned to full working dutieswithout any compromise in the grip strength.

Keywords Hand · Wrist · Carpal Joints · Dislocations · Bone Fractures

Luxations carpo-métacarpiennes côté ulnaire après traumatisme léger

Résumé Les auteurs présentent un cas de luxation del’articulation entre les 4e et 5e métacarpiens survenue à

la suite d’un traumatisme mineur et font une revue dela littérature en ce qui concerne le diagnostic et le trait-ement. Ce type de luxation est rare et ne se voit pastrès souvent à la suite d’un traumatisme léger. Lepatient, âgé de 24 ans, subit le traumatisme en faisantune chute à son domicile, sur la main tendue. Il futtraité par réduction à ciel fermé et put quitter l’hôpitalavec une courte attelle. Après six mois toutesses sesarticulations étaient indolores et tous les doigts avaientune mobilité complète. L’examen neuro-vasculaire étaitnormal. Depuis, il a retrouvé son travail à plein tempssans aucune diminution de la force de préhension.

Mots clés Main · Poignet · Articulations du carpe · Luxations · Fractures

Introduction

Carpometacarpal (CMC) dislocations on the ulnarside of the hand following minor trauma are seldomdescribed in the literature. All CMC dislocations areusually associated with signiWcant, high kineticenergy, trauma and with fractures of the involved oradjacent metacarpals. Due to the high likelyhood ofsevere concominant injuries, CMC dislocations areoften overlooked, resulting in delays in treatment.Reports on the most common carpal dislocation vary,citing dislocations of the Wfth alone, and the fourthand Wfth together [4] or the dorsal dislocation of allfour ulnar metacarpals as the most commonly seen ofthese injuries [23]. The following case describes a raredislocation of the fourth and Wfth CMC joints associ-ated with minor trauma. We believe the particularposition of the hand and wrist during the injury may

S. Biswas (&)Department of General Surgery, Stanford University Medical Centre, 300 Pasteur Drive, H3691, Stanford, CA 94305-5641, USAe-mail: saptarshibiswas@comcast.net

R. RamachandranStanford University Medical School, 300 Pasteur Drive, Stanford, CA 94305-5641, USA

M. MurphyDepartment of Orthopedics Surgery, Tralee General Hospital, Tralee, County Kerry, Republic of Ireland

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have allowed this dislocation pattern to occur withrelatively minor trauma.

Case report (materials, methods and results)

The patient was a 24-year-old left hand dominant engi-neer who fell on his outstretched left hand while athome. The previous day, the patient sustained an unre-lated injury of his right hand, resulting in a deep lacera-tion requiring several sutures for closure. The patientwas discharged with a heavy bandage, a collar and acuV. In order to avoid further injury to his right handthe patient bore the majority of his weight onto his lefthand during the subsequent fall.

On examination in the casualty department, markeddeformity of the dorsal ulnar aspect of the left hand wasnoted, accompanied by local tenderness. Clinically, thepatient had brisk capillary reWll and radial, ulnar andmedian nerve function was intact. X-rays revealed dor-sal and proximal dislocations of the fourth and Wfthmetacarpal at the corresponding CMC joints. There wasan associated transverse, nondisplaced fracture of thehamate (Fig. 1). The remaining carpal bones were intact.

Closed reduction was attempted in the causallydepartment under a local block using 2% lidocaine. Thereduction was stable as was demonstrated radiographi-cally. Clinical examination revealed no carpal instabil-ity. Flexion, extension, abduction and adduction of thedigits were within normal limits post reduction.

The patient was discharged home with a short armcast and seen in the orthopedic outpatient department with radiographic monitoring at 3–4 week intervals

(Fig. 2 Top). At 6 months, all CMC joints were non-tender with normal range of motion and normalappearance radiographically (Fig. 2 Bottom). Neuro-vascular examination remained normal. The patientsustained no enduring eVects from this injury, includ-ing no compromise in range of motion or grip strength.

Discussion

CMC joint dislocations are present in less than 1% ofhand injuries [5]. The inciting injury usually involvessigniWcant force and is often associated with fracture ofthe involved or adjacent metacarpals [6]. Such injuriesoften also cause disruption of the palmar arches result-ing in intrinsic and extrinsic muscle imbalance. CMCjoint dislocation in the context of relatively minortrauma and unaccompanied by a metacarpal fractureas described in this case report is a rare event. As men-tioned, the patient had a prior, unrelated injury of thecontralateral hand, causing him to bear the majority of

Fig. 1 Top Dorsal dislocation of fourth and Wfth metacarpal atCMC joint. Bottom AP view of the same

Fig. 2 Top Two weeks post injury in pop cast. Bottom Six weekspost injury after removal of cast

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his weight on his uninjured hand during his fall. Wepostulate that this particular mechanism of injuryallowed the hand and wrist position required to cause aCMC dislocation in the context of such minor trauma.In this particular patient, a dorsal avulsion fracture ofthe hamate was observed. It is also a possibility thatloss of ligamentous integrity from this possibly prece-dent injury was suYcient to allow the fall on out-stretched hand injury to subsequently dislocate themetacarpals.

The structure of the carpal-metacarpal joint contrib-utes to its stability and makes joint dislocation unlikely.The CMC joints of the Wrst four digits are arthrodialdiarthroses (gliding joints) while the 5th is a modiWedsaddle joint [7]. Proximal metacarpals articulate withthe distal row of the carpal bones and with each otherin complex interlocking conWgurations. Intermetacar-pal and CMC ligaments strengthen these joints dorsallyand volarly. Additional reinforcement is provided byinsertion of wrist Xexors and extensors into the bases ofthe second, third and Wfth metacarpals [18]. Essentiallyno movement is possible in the third metacarpal capi-tate joint, which functions as the stable central post ofthe hand [8], while limited amounts of AP gliding ispermitted at the base of the second metacarpal trape-zoid joint. Several tendinous insertions, the six dorsaland volar CMC ligaments, and the four intermetacar-pal ligaments that bind the metacarpal bases providecompressive stability of the CMC joints.

The bases of both the fourth and Wfth metacarpalsarticulate with the hamate. This articulation enablesrotation of the Wfth metacarpal, allowing for powergrip and cupping of the hand. Flexion and extension ofthe fourth CMC joint range from 8° to 15° and between15° and 40° for the Wfth CMC joint [4, 12, 17]. Thisgreater mobility predisposes these joints to injury. Theobliquely oriented, sloping articular surface of the WfthCMC joint and the pull of the extensor carpi ulnarisinserting into the base of the Wfth metacarpal are majorfactors that create instability.

Detection of CMC injuries often requires specialradiologic views. In order to properly visualize theinjured joint, radiographs of the hand should includethe standard AP, lateral and oblique views [21]. Thenormal CMC joint on the AP view should demonstratearticular parallelism with each joint space spanning1.0–2.0 mm. Any bony overlap is suggestive of subluxa-tion or dislocation. A lateral x-ray of the hand actuallyreveals only a true lateral view of The CMC joint of thethird digit. In addition, oblique views should beincluded for evaluations of CMC joint injuries, with thehard pronated and supinated 30°, respectively, fromthe true lateral view.

Treatment of CMC joint injuries is controversialbecause the literature consists primarily of anecdotalreports or small case series. Additionally, there is alack of studies comparing treatment modalities. Ana-tomic, or at least acceptable, closed reduction can beaccomplished if the injury is recognized and treatedearly. If closed reduction and cast immobilization isselected as the method of treatment, careful radio-graphic monitoring must he done for the subsequent 3–4 weeks to detect resubluxation. Complications arise incases involving signiWcant swelling, as these suVer ahigh rate of resubluxation, resulting in weak gripstrength, wrist pain or tenderness over the subluxeddorsal bony prominence [11].

Numerous studies have demonstrated successfulmaintenance of closed reduction of CMC joint disloca-tions with the placement of percutaneous Kirschnerwires [2, 10, 13, 22]. Such results have also been dem-onstrated in patients with concomitant carpal bonefracture [9]. Recent studies recommend open reduc-tion and internal Wxation as the primary method ofapproaching CMC dislocations, as these injuries com-monly involve damage to intra-articular surfaces [1, 9,14, 19]. Complications are possible with an openapproach as the deep (motor) branch of ulnar nervelies immediately volar to the Wfth CMC joint as it windsaround the hook of hamate.

In the case described here, the CMC joint was sta-ble after closed reduction. The literature suggests thatunder such circumstances, operative treatment is notindicated. De Waard et al. [3] and Storm [20] eachpresented one case in which stable reduction led tosatisfactory resolution. A study comparing openreduction with internal Wxation to closed reductiondemonstrated that patients who received conservativetreatment did not have any functional complaintsalthough arthrosis of the fourth and Wfth CMC jointmight be present [19].

CMC dislocations are often diYcult to asses [15, 16],and frequently missed due to unfamiliarity with theinjury and inaccurate interpretation of conventionalradiographs. Delays in adequate treatment necessitatemore invasive forms of treatment, as closed reductionis only successful if attempted early. Familiarity withthe radiographic appearance and clinical presentationof CMC dislocations will lead to faster and more eVec-tive treatment for aVected patients.

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