Reconstruction of Wassel Type VI Radial Polydactyly with Triphalangeal Thumb Using an On-top Osteotomy

BACKGROUND: The purpose of this study was to present a novel surgical technique using an on-top osteotomy and to assess the clinical and radiographic outcomes for the triphalangeal Wassel type VI thumb duplication patients. METHODS: The surgical technique involves ablation of the radial thumb at distal one-third of the metacarpal, corresponding metacarpal osteotomy of the ulnar thumb, with amalgamation of 2 metacarpals and reconstruction of the ulnar thumb by a series of soft tissue procedures. Clinical and radiologic outcomes were evaluated by using the Japanese Society for Surgery of the Hand evaluation form at a minimum of 30 months. The size of the metacarpal was measured and compared to the opposite one to assess the growth of the thumb. RESULTS: Five patients, including 4 males and 1 female, were observed for an average of 37 months. All amalgamated metacarpal showed bone union in 6 weeks after surgery and revealed growth with the age. The average length of the metacarpal was 86% of the opposite one at the final follow-up. Motion at the metacarpophalangeal and interphalangeal joints showed no restriction after surgery, and they reached excellent function for gripping and pinching. According to the JHHS scoring system, the results were excellent in 3 cases, good in 2. CONCLUSIONS: This novel surgical technique for the reconstruction of Wassel type VI radial polydactyly with triphalangeal shows encouraging results in both clinical and radiologic evaluations; meanwhile long-term results are under evaluation.