Subcutaneous rupture of the flexor tendon of the little finger associated with anomalous flexor digitorum superficialis.

A 59-year-old man suffered from subcutaneous rupture of the flexor tendon of the little finger associated with fracture of the hook of hamate. He could not flex his little finger completely at the distal interphalangeal joint, but incomplete flexion of the proximal interphalangeal joint was possible. Surgical exploration revealed anomaly of the flexor digitorum superficialis of the little finger, as it originated from the palmar aspect of the carpal ligament, and a small portion of the muscle belly was traversed toward the A1 pulley over the profundus tendon and then it ran into the A1 pulley as a normal superficialis tendon. The flexor digitorum superficialis of the little finger is well known to show variations, but our case is extremely rare, and furthermore there are no reports in the available literatures about the function of this anomalous muscle.