Extensor tendon rupture due to osteoarthritis of the distal radio-ulnar joint.

Five cases of closed rupture of the finger extensor tendon due to osteoarthritis of the distal radioulnar joint were studied. Difficulty in extension began at the little finger and extended to the ring and long fingers. Pain and swelling in the dorsal aspect of the wrist preceded the tendon rupture. Osteoarthritic changes at the distal radio-ulnar joint were more severe than those at the radio-carpal and intercarpal joints. The distal end of the ulna showed the plus variant, as well as dorsal dislocation or subluxation. All patients underwent a tendon graft or tendon transfer, with excision of the distal ulna. The tendon rupture was thought to be caused mainly by friction between the displaced distal end of the ulna and osteophytes of the distal radio-ulnar joint.