The thumb in syndactyly.

Syndactyly of the thumb is a rare but very serious malformation. It produces a loss of the grasping function of the thumb, which is the main function of the human hand. The author presents different methods for the reconstruction of the first web space and a functional thumb. The surgical methods of reconstruction depend upon the extend and type of the malformation. The opening of the deep intermuscular fascia of the first web is a most important step of the procedure.