Kinematics of the distal radioulnar joint.

The kinematics of the normal distal radioulnar joint (DRUJ) in five fresh frozen cadavers were investigated by means of computerized tomography (CT). Rotation of the radius about the ulna is accompanied by translation so that in supination the ulna is somewhat palmar, and in pronation the ulna is more dorsal relative to the radius. The average ranges of motion of the hand and DRUJ were 260 degrees and 190 degrees, respectively. Significant carpal and metacarpal rotation occurred with pronation-supination of the hand. The DRUJ has both rotational and translational components of movement and does not have a single center of rotation. The pathway of the instantaneous centers of rotation, or centrode, of the DRUJ has a characteristic pattern. The centrode moves in a direction opposite that of the DRUJ movement and is located near the center of the ulnar head. A prosthetic joint for the DRUJ should not have a fixed axis of rotation but should allow the normal translatory motion of the ulna and radius if early joint failure is to be prevented.