Acute Traumatic Pseudo-pointing Index Finger Due to an Isolated Second Metacarpal-Trapezoid Dislocation: A Case Report.

Introduction: An isolated second metacarpal dislocation is one of the least reported injuries of the hand. This particular injury assumes clinical significance as they occur subsequent to high energy direct trauma and are usually missed with associated carpal and metacarpal bone fractures. We describe this unique case of an isolated metacarpal-trapezoidal disruption with clinical presentation as the pseudo-pointing index finger and also describe a novel radiological sign to ascertain the rotational deformity of metacarpals on plain radiographs.

Case Report: A 32-year male information technology employee experienced a road traffic accident and developed pain, localized swelling over dorsum of the left hand. He exhibited an inability to form a complete fist with the index finger lagging behind, giving a pointing index finger like appearance. Plain radiographs showed isolated disruption of second metacarpal-trapezoid articulation. The computed tomography (CT) scans were used to confirm the absence of associated carpal injuries. The patient was managed successfully by closed reduction and Kirschner wiring. All the deformities resolved and regained normal hand functions in the follow-up period of 13 months with no recurrent episodes or evidence of arthritis.

Conclusion: Although a rare presentation, astute clinical examination and systematic radiological evaluation are the key to diagnose second through fourth carpometacarpal disruptions. The asymmetrical appearance of the metacarpal head tuberosities on anteroposterior radiographs is a strong indicator for rotational deformity of hands. These injuries must be evaluated with CT scans due to the increased potential for associated carpal injuries and poor prognosis when missed. More than often, an open reduction may be required to obtain stable concentric reduction.