Extensor tendon rupture associated with osteoarthritis of the distal radioulnar joint.

Non-rheumatoid osteoarthritis of the distal radioulnar joint can cause extensor tendon rupture. We analysed the radiographic morphology of the distal radioulnar joint to identify the risk factors for this complication. Forty-one wrist X-rays of 37 patients with extensor tendon rupture caused by distal radioulnar joint osteoarthritis were evaluated retrospectively for the severity of osteoarthritis by the Kellgren/Lawrence scoring system. Measurements were obtained from posteroanterior views. All but one wrist had severe osteoarthritic changes exceeding grade 3. The radiographic features that were different from those of the contralateral wrists included deepening and widening of the sigmoid notch, radial shift of the ulnar head and dorsal inclination of the sigmoid notch. There was no significant association between tendon rupture and the morphology of the ulnar head or ulnar variance. The scallop sign, dorsal inclination of the sigmoid notch and radial shift of the ulnar head are radiological risk factors for extensor tendon ruptures.