Closed tendon rupture as a result of Kienböck disease.

Closed tendon rupture is a well-known complication of Kienböck disease, but only 11 cases have been reported. We reviewed six cases of Kienböck disease with subcutaneous rupture of a tendon. There were five cases of 4th extensor tendons and one case of the flexor digitorum profundus tendons of the ring finger and little finger. Radiographs showed protrusion of the segmented lunate or the deformed lunate in all cases. Intraoperative findings confirmed rupture of the wrist joint capsule by these lunate lesions. We then reviewed 11 reported cases in English and 48 cases in Japanese and confirmed that all cases had similar clinical characteristics and radiological features to our own, except the involved digits of flexor tendon rupture. Our case was unique in that the ulnar side tendons were ruptured, while in the reported cases the radial flexor tendons were more susceptible to rupture than the ulnar ones. Closed rupture of tendons should be recognised as a complication in patients over middle age with stage IIIb or IV asymptomatic or less symptomatic Kienböck disease.