Dorsal dislocation of the trapezoid at the scaphotrapeziotrapezoidal joint.

Background Axial dislocations of the trapezoid are rare, high-energy injuries. We present an unusual case of isolated dorsal dislocation of the trapezoid and index metacarpal at the scaphotrapeziotrapezoidal (STT) joint due to steering wheel injury. Case Description A 56-year-old man presented to our office with right hand pain for 10 days after a head-on motor vehicle accident (MVA) in which he suffered an axial load injury to his hand on the steering wheel. X-ray images were reported as unremarkable. Further workup with computed tomography (CT) scan revealed an isolated dorsal dislocation of the trapezoid with its associated index metacarpal at the STT joint. The patient was treated with open reduction, pinning, and dorsal capsulodesis. Literature Review Dorsal dislocation of the trapezoid has been associated with high-energy trauma such as industrial accidents or motorcycle accidents; however, recent case reports have also revealed an axial loading mechanism from a steering wheel injury as an increasingly common mechanism. These cases typically occur concomitantly with other fractures or dislocations of the carpal bones or carpometacarpal (CMC) joints. Multiple reports of delayed diagnoses due to distracting injuries and difficulty of recognition on plain radiographs have been reported. Clinical Relevance Dorsal dislocation of the trapezoid with its associated second metacarpal is a rare, high-energy injury that can often be missed on plain radiography. We report a rare variant with no concomitant injury to the metacarpals or carpal bones. A low index of suspicion for further imaging should exist in the setting of an axial loading injury to the hand.