The effects of wrist distraction on carpal kinematics

Changes in carpal kinematics under wrist distraction were studied in fresh cadaveric specimens. A magnetic tracking device measured kinematic motions of the scaphoid, lunate, and third metacarpal relative to the fixed radius in 3 planes of passive motion (coronal, sagittal, and "dart throwers") unde r progressive distraction loads. The change in percent contribution of the radiocarpal and midcarpal joints was calculated. Radiocarpal motion during extension was decreased as increasing traction was applied, but it increase d with flexion. Motion of the scaphoid relative to the lunate was smaller i n the oblique plane, resulting in less radiocarpal motion than in the sagit tal plane. In the coronal plane, traction had little effect on radial devia tion, bur ulnar angulation of the scaphoid was greater with ulnar deviation of the wrist. These results suggest that different degrees of tension exis t in the palmar and dorsal ligaments with the wrist under traction and duri ng different planes of wrist motion. If wrist motion is desired during fixe d traction, such as used clinically with external fixation, the dart-throwe rs motion (wrist extension with radial deviation and wrist flexion with uln ar deviation) appears to have the least impact on radiocarpal motion. If gr eater radiocarpal motion is desired, however, such as during postoperative mobilization, flexion-extension and radioulnar deviation will create more r adiocarpal motion than the dart-thrower's motion. (I Hand Surg 1999;24A:113 -120. Copyright (C) 1999 by the American Society for Surgery of the Hand.)