Solid Model Prediction Of The Range Of Motion Of The Wrist Following A Proximal Row Carpectomy

In this paper, 3-D computer solid models of a complete carpus are generated from CT scans and used to predict the kinematics of the wrist after a proximal row carpectomy. The initial data for this study was obtained through CT scans of a fresh cadaver wrist specimen scanned in ten different positions. The wrist was scanned at 1 mm intervals through seven different positions from 80" extension to 70" flexion, and in three positions from ulnar to radial deviation. The digital CT data was converted to profile sections through the use of an edge following algorithm [1,2]. The profile information was then analyzed by two teams. Each team independently built solid models of the wrist in all ten positions using two different software packages. The volume, principal axes, and three principal moments of inertia of each of the eight bones of the wrist were determined from the computer models using two software techniques. Reconstruction of the wrist bones from digital data to computer generated, 3-D models produced an average relative difference of 3.1% for volume, 6.7% for the first principal moment of inertia, 6.5% for the second principal moment of inertia, and 6.6% for the third principal moment of inertia between the two methods. The computer models predicted that, with a proximal row carpectomy, the maximum range of motion as determined by bone configuration is 64' of extension (80% normal), and 65' of flexion (94% normal).