Correction of Wassel type IV thumb duplication with zigzag deformity: results of a new method of flexor pollicis longus tendon relocation.

The purpose of this study is to present a treatment algorithm and a method of flexor pollicis longus tendon relocation for Wassel type IV thumb duplication with zigzag deformity. Forty-two thumbs in 42 patients were included in this study and the mean follow-up was 4 years. In addition to excision of the extra digit, tendon relocation and metacarpal and/or proximal phalangeal osteotomy were carried out, based on the degree of angulation at the metacarpophalangeal and interphalangeal joints. Tendon relocation was achieved using our pull-out suture technique. The results were assessed using an evaluation form for thumb polydactyly provided by the Japanese Society for Surgery of the Hand. At the time of latest clinical contact, eight cases were rated good, 31 cases fair, and three cases poor. It is useful to decide surgical procedures according to the degree of angulation of the metacarpophalangeal and interphalangeal joints and flexor pollicis longus tendon relocation is important to prevent malalignment at the interphalangeal joint.