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Volar dislocation of the metacarpophalangeal joint. Pathologic anatomy and report of two cases.

Of two cases of volar metacarpophalangeal joint dislocation, the thumb was affected in one. This is the first case of its kind reported in the English-language literature. Patients with this injury are older than patients with the more common dorsal dislocation. The mechanism of injury seems to be direct trauma to the dorsum of the hand with the metacarpophalangeal joint acutely flexed. The pathologic anatomy may be a combination of a dorsal capsular tear, a tear of one or both collateral ligaments, and a tear of the volar plate with interposition in the joint. Attempt at closed reduction, even if a pin is used percutaneously to transfix the joint, almost invariably will lead to recurrence of the deformity. The recommended treatment for such very rare injuries is open reduction through dorsal, or both dorsal and volar, approaches; removal of the incarcerated volar plate from the joint; and repair of all torn ligaments.