Three-dimensional in vivo kinematics of the distal radioulnar joint in malunited distal radius fractures

How malunion of the distal radius affects the kinematics of the distal radioulnar joint in vivo was evaluated. A novel computed tomography image-based technique was used to quantify radioulnar motion in both wrists of 9 patients who had unilateral malunited distal radius fractures. In the injured wrists dorsal angulation averaged 21degrees +/- 6degrees, radial inclination averaged 18degrees +/- 5degrees, and radial shortening averaged 21degrees +/- 3degrees mm. Clinically, the average range of motion of the injured wrists was 75degrees +/- 25degrees pronation and 73degrees +/- 23degrees supination. Kinematics of the radius during pronation and supination in the malunited forearms was indistinguishable from that in the uninjured forearms. In both the axis of rotation of the radius passed through the center of the ulnar head, although it shifted slightly ulnar and volar in supination and radial and dorsal during pronation. In contrast to previous in vitro biomechanical findings, there was no dorsovolar radial translation at the extremes of pronation or supination and no translation of the radius along the rotation axis. Soft tissues may play a larger role in limiting function than previously appreciated, and treatment may require correction of altered soft tissue structures as well as any abnormal bone anatomy. Copyright (C) 2002 by the American Society for Surgery of the Hand.