Rotatory subluxation of the metacarpophalangeal index finger joint: a case report.

We report a case of rotatory subluxation of the metacarpophalangeal joint (MCPJ) of the finger. A 40-year-old man sustained an open injury to his index finger following an explosive injury. Radiographs showed rotatory subluxation of the index finger MCPJ. The index finger extensor digitorium was found interposed in the MCPJ, with a complete tear of the radial collateral ligament. Treatment was by open reduction and repair of the collateral ligament and the extensor tendon. A high level of clinical suspicion is needed to diagnose this entity.