A rare type of polydactylous thumb and its surgery.

Resently the authors had the opportunity of performing surgery of a trifurcated thumb, an extremely rare morphological polydactylous condition of the thumb. Trifurcated thumb had not been included under classification of polydactylous thumb heretofore. Comments were made on this entity from the standpoint of its morphology and consideration was given to its developmental mechanism. Also as surgery was performed with the intention of creating one thumb out of three polydactylous components, discussion was made of the procedure employed.