BIOMECHANICAL INVESTIGATION OF WRIST KINEMATICS

This paper describes a biomechanical investigation to determine the overall kinematic behavior of the human wrist or carpus. The hand and forearm segments are modeled as rigid bodies, and the three-dimensional kinematic characteristics of the wrist are obtained by studying two clinically significant planar motions of the hand relative to the forearm: flexion-extension motion, and radial-ulnar deviation. The three mechanical quantities used to describe the kinematic behavior of the wrist are the functional range of motion, the looseness locus, and the instantaneous center of rotation locus. In vivo and in vitro experimental data are collected using biplanar X-ray films, and a three-dimensional sonic digitizer interfaced with a small laboratory computer. Validation tests using a metal universal joint with known kinematic properties indicate the accuracy and reliability of the experimental results. Data for one normal subject and one rheumatoid patient, examined both pre and post operatively, are presented and discussed. © 1979.