Anatomy of the distal radioulnar joint.

The distal radioulnar joint (DRUJ) is of the utmost importance in treatment of fractures of the distal radius. To improve the treatment of these fractures, knowledge of the anatomy and biomechanics of the DRUJ is essential. Three major findings from anatomic specimen studies of the DRUJ are discussed. The radius of the curvature of the sigmoid notch is 4-7 mm larger than that of the ulnar head, and consequently pronation and supination are a combined rotation and sliding movement in the DRUJ. The ulnar head has an average inclination of 20 degrees relative to the long axis of the ulna. Being parallel to the ulnar head, the sigmoid notch of the radius should have the same inclination. In the DRUJ, stability supported by joint surface architecture is minimal, and the ligament is therefore of particular importance to the stability.