関節運動における瞬間中心の計測

抄録

The instantaneous center of rotation (ICR) is a basic quantity for describing planar motion of rigid bodies and useful for analysis of anatomical joint motion. For example, the ratio of sliding or spinning and rolling at the articular surfaces of the joint has a direct relationship with the location of ICR. Reuleaux's method has been used to determine ICR. So far the position of segments has been measured by means of several X-ray photographs. Reuleaux's method and other methods use data at two consecutive positions. These methods are very sensitive to position error of segments, and therefore few reliable ICR data on joint motion have been reported. However, it has become possible recently to obtain sufficient position data using several electronic techniques including photo-sensitive semiconductor and magnetic sensor. Therefore it is expected that ICR error can be reduced using these data. In this paper, we propose a method of calculating ICR based on smoothing technique. That is, to determine velocity and angular velocity of a segment, we adopted numerical low-pass differentiation. Then we analyzed the error of this method and discussed the optimal sampling interval of position data. We compared this method with other methods by computer simulation, and we applied this method to temporomandibular joint motion.