CARPAL BONE KINEMATICS AND LIGAMENT LENGTHENING STUDIED FOR THE FULL RANGE OF JOINT MOVEMENT

Present data on carpal kinematics and carpal ligament behaviour are li mited to flexion and deviation movements of the hand. These motions do not represent all the wrist-joint motions which are important for the activities of daily living. The goal of this project was to obtain in sight into carpal kinematics and carpal ligament behaviour during moti ons of the hand covering the full range of motion of the wrist joint. The carpals and the ligaments of four wrist-joint specimens were provi ded with radiopaque markers. These joints were subjected to Rontgenste reophotogrammetric experimentation in a large number of hand positions to determine carpal positions and ligament lengths. The movements of the carpal bones were described by means of finite helical axes (FHA). It was found that the movements of the carpals in the distal row clos ely resemble those of the hand. Conversely, the motions of the carpals of the proximal row appeared not to be directly proportional to the h and motions and exhibited clear out-of-plane movements. Furthermore, i t could be shown that movements of the hand into the ulnodorsal quadra nt of the full range of hand motion corresponds to larger helical rota tions and translations for most of the carpals than when the hand was moved into any other quadrant. The maximal ligament length changes det ermined did not exceed the length changes reported for pure flexion an d pure deviation movements of the hand.