Kinematics of the human wrist: Configuration space as an aid in understanding the joint mechanism

Configuration space analysis indicates that motion of the wrist joint may be fully described using fewer than six parameters, thus simplifying the description and interpretation of the joint kinematics. Tests were conducted to assess the suitability of a proposed functional wrist model that assumes all motion of the joint is provided by rotation about two axes that are stationary relative to the joint anatomy. Pronation-supination was not considered to be a motion of the wrist joint, thus all tests were conducted with a fixed radio-ulnar position. Potential additional uses of configuration space methods are also investigated.

Optoelectronic motion data were obtained from intact human wrist joints performing specific motions and processed using standard rigid body kinematic analyses to express the hand relative to the arm. Both healthy volunteers, and volunteers with rheumatoid arthritis and dysfunctional wrists participated in the study.

Movement of the wrist was characterized by a planar motion that is not aligned with either of the traditional planes of motion of the wrist, thus minimizing the chances of hidden degrees of freedom. Some non-planar 3-D motions were also considered. The joint degree of freedom was determined from the dimension of the configuration space. Parametrized surfaces were fitted to the data in order to determine the dimension of the space.

All motions studied (planar and non-planar) of the intact, healthy wrist, could be described using only two degrees of freedom. Wrists affected by rheumatoid arthritis were not found to require additional degrees of freedom to perform the specific planar motion which was studied. (Abstract shortened by UMI.)