Atypical thumb polydactyly with duplicated metacarpal bone: a report of 2 cases.

We report 2 cases of patients with thumb polydactyly that were difficult to classify into either Wassel type VI with a remarkable hypoplastic metacarpal or Wassel type VII (triphalangeal thumb). The radial digit was functional but hypoplastic, and the ulnar digit presented a dominant appearance but no active motion. The operative findings revealed that the radial and ulnar MP joints were completely independent and the metacarpal bones were separated, simulating Wassel type VI thumb polydactyly. In both cases, the ulnar digit was transported to the top of the radial metacarpal, accompanied by tendon transfer from the radial to the ulnar digit and rotation flap for web plasty. One year after surgery, the postoperative results showed good appearance and function of the preserved ulnar thumb in both cases.