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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.

The teratogenic mechanisms of radial ray deficiency were investigated. Radial ray deficiencies were induced in WKAH/Hkm rat foetuses by maternal administration of myleran on day 10, 10.5, or 11 of pregnancy. The skeletal anomalies in rats were similar to those in human beings, suggesting that exposure to some environmental factors at a sensitive period of embryogenesis may cause radial ray deficiency in humans. Ulnar ray deficiency has also been induced in rat foetuses by maternal administration of myleran, so it is suggested that radial deficiency and ulnar deficiency are caused by a common teratogenic mechanism in humans. However, the critical period for radial deficiency is one day later than that for ulnar deficiency in rats, which may contribute to the greater frequency of radial deficiency than ulnar deficiency in clinical cases.

A method of repair of boutonnière deformity is described, using the transverse retinacular ligament. Six fingers in five patients were treated by this procedure. The deformity was improved in all fingers; complete or almost complete correction was obtained in four fingers and incomplete correction in two. However, severe limitation of flexion of the D.I.P. joint appeared in two fingers after surgery. This procedure is not indicated for boutonnière deformities with severe contracture of the lateral band; its best indication is in cases in which the central slip is defective and conservative treatment is not effective.

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