To investigate the clinical efficacy and intraoperative attention of on-top-plasty technique for treatment of Wassel type Ⅵ thumb duplications.

From April 2012 to June 2018, 8 cases of Wassel typeⅥ thumb duplications were treated by on-top-plasty. Postoperative objective evaluation included whether the thumb was deflected, passive range of motion of the metacarpophalangeal (MP) joint, interphalangeal (IP) joint and the first carpometacarpal (CMC1st) joint. Radiographic examination was used to evaluate the force line of thumb, bone healing time and the development of the first metacarpal bone. Subjective evaluation was completed by the parents of the patients with functional and appearance satisfaction questionnaire.

The follow-up period ranged from 2 to 36 months, with an average of 19.5 months. No deflection of thumbs occurred. The range of passive motion of MP, IP and CMC joints was not significantly decreased compared with the healthy side. Postoperative X-ray showed that the force line of the first metacarpal bone was good in 7 cases and malunion in 1 case. The bone healing time ranged from 5 to 7 weeks with an average of 6.2 weeks. There was no retardation in the development of the first metacarpal bone. The function of subjective satisfaction survey was excellent in 4 cases, good in 3 cases, fair in 1 case and the appearance was excellent in 4 cases, good in 2 cases, fair in 1 case, poor in 1 case.

On-top-plasty technique is an effective method to treat Wassel typeⅥ thumb duplications. The full preoperative evaluation, different incisions according to the contracture of thumb web, clear identification of anatomical structures and protection of vascular pedicles are the basic guarantee for restoring thumb function.

Hand deformities, congenital; Treatment outcome; Thumb duplications; Wassel type Ⅵ; On-top-plasty