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

Abstract

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.

Fig. 1.

Preoperative evaluation showed that both ulnar and radial thumbs were functional.

Fig. 2.

Surgical techniques. A, Transposition of the ulnar digit to the radial ray. “V shape” osteotomy of the radial and ulnar metacarpals was performed (black area was resected). B, The ulnar digit was transported to the top of the radial metacarpal bone and fixed with a K-wire.

Fig. 3.

Intraoperative photographs (case 5). A, Exposure of radial and ulnar metacarpals. B, “V shape” metacarpal osteotomy. C, Amalgamated metacarpals were fixed with a longitudinal k-wire. D, Reconstruction of the APB and FPB. E and F, The appearance after surgery.

Fig. 4.

A 33-month-old boy (case 1) with right Wassel type VI radial polydactyly with triphalangeal thumb. A, Preoperative appearance photograph. B, The satisfactory appearance of thumbs with almost the same sizes between the operative and the opposite side after surgery. C–E, The patient had 10-degree active extension deficit at the IP joints (white arrow) but reached excellent gripping and pinching function.

Fig. 5.

A, Preoperative x-ray. B, Six-week postoperative x-ray showed amalgamated metacarpals and good bone union. C and D, During the 45-month follow-up, it showed the proximal metacarpal epiphysis had normal growth with the age (white arrow; case 1).