THE EFFECT OF DORSALLY ANGULATED DISTAL RADIUS FRACTURES ON DISTAL RADIOULNAR JOINT CONGRUENCY AND FOREARM ROTATION

A biomechanical cadaver study was performed to evaluate the effect of dorsally angulated distal radius fractures on the distal radioulnar jo int. Frykman I distal radius fractures were simulated, and laxity meas urements were taken with and without sectioning the triangular fibro-c artilage complex and the interosseous membrane. The findings of this s tudy were threefold. First, measured in terms of radial diastasis, inc ongruency of the distal radioulnar joint occurred with increasing dors al tilt of the distal radius. It became most dramatic with a change of more than 20 degrees of dorsal angulation of the distal radius. This corresponds to approximately 10 degrees of dorsal tilt of the articula r surface of the distal radius, as measured on an x-ray film. Second, increased dorsal angulation caused interosseous membrane tightness and limited maximum pronation and maximum supination. Third, distal radio ulnar joint dislocation did not occur until both the triangular fibroc artilage complex and interosseous membrane were sectioned. These resul ts reveal the importance of anatomic reduction of the distal radius fr acture and evaluation of damaged soft tissue structures.