Attritional rupture of flexor tendons by the head of the ulna associated with a chronic longitudinal radioulnar dissociation.

A 62-year-old woman sustained multiple attritional ruptures of the flexor tendons at the wrist caused by displacement of the head of the ulna. She had had injuries of the wrist and elbow when she was young, which were thought to have caused chronic longitudinal radioulnar dissociation with palmar dislocation of the head of the ulna. Attrition of the flexor tendons by the dislocated ulnar head during pronation and supination was the major mechanism for the ruptures in this case. She was successfully treated with tendon transfer and resection of the ulnar head.