Congenital anomaly of the thumb--unusual bifurcation of the flexor pollicis longus and its unusual insertion.

A rare case of bifurcation of the muscle belly of flexor pollicis longus in the distal portion of the forearm is described. The major portion inserted onto the transverse carpal ligament as a tendon, and the lesser portion passed through the normal compartment of the flexor pollicis longus to the terminal phalanx.