Reconstruction of Wassel type IV thumb duplication.

The most common thumb duplication is a Wassel type IV with duplication of the proximal and distal phalanges. The term "split-thumb" seems more appropriate as neither element is as robust as a normal thumb. The split parts may share bony elements, tendons, ligaments, joints, neurovascular structures, and nails. The surgical principles are preservation and augmentation of the dominant thumb and ablation of the lesser counterpart. The soft tissue(s) from the ablated thumb are used to augment the retained thumb. This article will discuss the indications, timing, and technique of surgical reconstruction for the Wassel type IV thumb duplication.