Polydactyly and the triphalangeal thumb.

Polydactyly associated with triphalangeal thumb is not rare, as among the records of 1,269 patients with congenital deformation of the upper extremity at the University of Iowa there were 21 patients with 32 hands with such involvement. More detailed classification based on Wassel's work was made. Treatment should be early, with removal of the radial digit if equal in size, excision of all accessory parts including delta bone when present, reconstruction of joint ligaments or joint fusion and osteotomy for correction of deviations. Care should be taken to avoid leaving a narrow first web space.