Quantitative in vivo analysis of the kinematics of carpal bones from three-dimensional CT images using a deformable surface model and a three-dimensional matching technique

The purpose of this study was to obtain quantitative information of the rel ative displacements and rotations of the carpal bones during movement of th e wrist. Axial helical CT scans were made of the wrists of 11 volunteers. T he wrists were imaged in the neutral position with a conventional CT techni que, and in 15-20 other postures (flexion-extension, radial-ulnar deviation ) with a low-dose technique. A segmentation of the carpal bones was obtaine d by applying a deformable surface model to the regular-dose scan. Next, ea ch carpal bone, the radius, and ulna in this scan was registered with the c orresponding bone in each low-dose scan using a three-dimensional matching technique. A detailed definition of the surfaces of the carpal bones was ob tained from the regular-dose scans. The low-dose scans provided sufficient information to obtain an accurate match of each carpal bone with its counte rpart in the regular-dose scan. Accurate estimates of the relative position s and orientations of the carpal bones during flexion and deviation were ob tained. This quantification will be especially useful when monitoring chang es in kinematics before and after operative interventions, like mini-arthro deses. This technique can also be applied in the quantification of the move ment of other bones in the body (e.g., ankle and cortical spine). (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)02409-3].