Estimation of the finite center of rotation in planar movements

The finite center of rotation (FCR) is often used to assess joint function. It was the purpose of this study to compare the accuracy of the procedure of Crisco et al. [4] for estimating the FCR with a procedure which uses lea st-squares principles. The procedures were evaluated using noisy data rotat ed about a known FCR. Both procedures demonstrated increasing accuracy of F CR estimation with increasing rotation angle. As the centroid of a pair of markers was moved further from the FCR, accuracy of its location decreased. Noise levels had a strong influence on FCR estimation accuracy, with the l east-squares procedure being better able to cope with noise. Increasing the number of landmarks increased FCR estimation accuracy. The accuracy of the procedure of Crisco et al. [4] increased when multiple estimates of the FC R were averaged. On all of the evaluations performed, the least-squares pro cedure gave small improvements in the accuracy of estimating the FCR, but w as not able to circumvent the inaccuracies which arise when landmarks are n ot appropriately positioned, numerous, or if the rotation angle is small. ( C) 2001 IPEM. Published by Elsevier Science Ltd. All rights reserved.