Wedging osteotomy to correct metacarpal adduction for the treatment of Wassel types V and VI duplicated thumb: surgical strategy, outcomes, and anatomical findings

This study presents a wedge osteotomy technique for correcting metacarpal adduction in the treatment of Wassel types V and VI thumb polydactyly, evaluating its clinical efficacy and reporting intraoperative anatomical abnormalities. A retrospective analysis of 37 thumbs treated between January 2016 and June 2023 was performed. Preoperatively, the median inter-metacarpal angle (IMA) was 0°, and the median radial deviation angle of the metacarpophalangeal (MCP) joint of the ulnar thumb was 30°. All cases underwent excision of the hypoplastic radial thumb, thenar muscle relocation, and a radial closing wedge osteotomy at the base of the ulnar thumb metacarpal to achieve a corrected IMA exceeding 40°. The ulnar capsule and collateral ligament were reinforced, and one or two Z-plasties were performed to enlarge the first web space in most cases. Mean follow-up was 51.4 months (range, 12-120). Postoperative IMA and MCP joint angle improved significantly to a median of 40° (IQR: 35-42°) and 0° (IQR: 0-10°),respectively. Mean range of motion at the MCP and interphalangeal joints was 40° (IQR: 30-45°) and 60° (IQR: 45-75°). According to the modified Tada score, 31 thumbs were rated good, 5 fair, and 1 poor. In conclusion, wedge osteotomy to correct metacarpal adduction deformity in type V/VI thumb duplication yields encouraging results, with good functional outcomes and a low reoperation rate.