LOCATION AND GEOMETRIC DESCRIPTION OF CARPAL BONES IN CT IMAGES

The carpal regions of ten cadaver extremities were imaged by CT. The i mages were combined into a 3-dimensional model Of the carpus using a t echnique based on a dynamic programming algorithm to find an Optimal e stimate of the location of the bone boundaries in the CT images. The r esulting set of surface points on each bone was used to compute volume s and principal and antipodal axes for the bones. A spatial coordinate system was established based on the positions of the centroids of thr ee bones in the distal carpal row. The angular orientations of all car pal bones were determined with respect to this system. The principal a xes for the same bone among ten wrist specimens proved to be more wide ly dispersed than the antipodal axes for the same bones. The antipodal axes also correspond more closely to an intuitive notion of the ''lon gest axis'' of the bones. We conclude that the antipodal axis is a mor e reliable and useful measure of bone orientation than the principal a xis.