Thumb duplication: concepts and techniques.

Within the Oberg, Manske, Tonkin (OMT) classification, thumb duplications are a failure of formation and/or differentiation affecting the radial-ulnar axis of the hand plate. The Wassel description of seven types of thumb duplication provides a good structure from which an approach to management is based. The aim of surgical reconstruction is to obtain a stable, mobile thumb of adequate size and appropriate shape. The most common form of reconstruction is removal of the lesser digit and reconstruction of the dominant digit. Surgical techniques address the problems of deviation, instability and lack of size. The disadvantages of the Bilhaut-Cloquet procedure, these being joint stiffness and a nail ridge, may be lesser concerns when reconstruction of one digit will not create a satisfactory thumb of adequate mobility, stability, alignment and size. Complicated problems of triphalangism, triplication, ulnar dimelia and the rare circumstance in which neither of the duplicated thumbs may be adequately reconstructed present specific challenges which demand alternative techniques.