Carpometacarpal Joint Dislocation

55 Carpometacarpal Joint Dislocation

Andrew L. Haas and Kevin D. Plancher

History and Clinical Presentation

A 19-year-old right hand dominant male college student presented to the emergency room with complaints of pain and swelling of his right hand and thumb. He stated that he had injured it 3 months previously in a skiing mogul competition and had an open reduction and internal fixation (ORIF) of his index metacarpophalangeal (MP) joint and proximal phalanx and third MP. He complained of a persistent painful lump on the dorsum of his right thumb. He denied any weakness or numbness.

Physical Examination

The patient was noted to have a dorsal deformity of the thumb with subluxation and instability of the thumb. He had tenderness to palpation with mild weakness secondary to pain. Full active range of motion of the fingers and wrist was intact. Sensation was intact to soft touch. He had 2+ radial and ulnar pulses and less than 2-second capillary refill throughout the hand. He was found to have difficulty with activities of daily living secondary to pain and inability to hold and grab objects.

Diagnostic Studies

Anteroposterior, lateral, and oblique radiographs of the right hand were obtained. These radiographs revealed a carpometacarpal dislocation of the thumb (Fig. 55–1).

Figure 55–1. (A) Anteroposterior (AP) view of a previously injured hand with dislocated thumb carpometacarpal (CMC) dislocation. (B) Close-up view of dislocated thumb CMC.

Differential Diagnosis

Carpometacarpal joint fracture and dislocation

Metacarpal fractures

Carpal fractures

With appropriate radiographic evaluation, the diagnosis of carpometacarpal joint dislocation is rarely mistaken. It is important to rule out associated fractures, as fractures of the bases of the metacarpals are frequently encountered along with this injury (Fig. 55–2). Isolated fractures of the metacarpals and/or the carpus can present with marked generalized swelling with pain and tenderness of the hand. High clinical suspicion needs to be maintained so as not to miss these injuries. Prolonged periods of untreated dislocations have an adverse effect on the future function of the hand and early osteoarthritis.

PEARLS

Obtain true lateral radiographs to obtain a correct diagnosis.
Each carpometacarpal joint, when pinned leaves the intermetacarpal ligament intact
Reduction and stabilization of the third carpometacarpal joint are key to reduction of the remaining carpometacarpal dislocations.
Attempt closed reduction early, before swelling occurs.

PITFALLS

Maintain high clinical suspicion of a CMC dislocation to avoid a missed diagnosis.
Persistent subluxation often presents after closed reduction attempt
Nonanatomic reduction leads to impairment of mechanical function of the hand.

Diagnosis

Carpometacarpal Dislocation of the Thumb

Carpometacarpal joint dislocations are a relatively rare injury. They are often associated with high-energy trauma or occur as a result of another direct force to the hand, such as in a fall or with punching. The key to making the diagnosis of a carpometacarpal joint dislocation is clinical suspicion. In the event of a high-energy trauma, often other more serious injuries take precedence and the hand injury can be overlooked. In addition, the failure to obtain appropriate radiographs often leads to a failure of diagnosis.

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