Treatment for Wassel Types V and VI Thumb Polydactyly.

Background: Polydactyly of the thumb is the most common congenital anomaly of the hand, but there have been few reports regarding Wassel types V and VI. The purpose of this study is to present our surgical strategies and outcomes for cases of Wassel types V and VI polydactyly of the thumb. Methods: Twenty-nine thumbs of 29 patients were included in this study; 17 cases were Wassel type V and 12 cases were type VI. Our strategies for initial surgery were appropriate tendon and muscle relocations. Opponensplasty with the abductor digiti minimi or the flexor digitorum superficialis and osteotomy were not performed in the initial surgery. We evaluated pinch motion ability and the number of additional surgical procedures. The first web space and radial instability of the metacarpophalangeal (MCP) joint were measured by radiography while the patient held a polystyrene foam cone. Results: Twenty-two patients were able to perform a pulp pinch. Narrowing of the first web defined as the angle between the first and second metacarpus (1-2 MCA) 20 degrees occurred in seven cases. Additional surgery was performed in seven cases (24%) to improve insufficient thumb opposition, radial instability of the MCP joint, and narrowing of the first web. Patients in all reoperation cases were able to perform a pulp pinch. Conclusions: Our strategies for initial surgery often had satisfactory outcomes, but careful follow-up observations and appropriate reoperation for cases with poor initial outcomes were more important.