The accuracy of joint surface models constructed from data obtained with an electromagnetic tracking device

Electromagnetic tracking devices are widely used in biomechanics. In this a rticle a method is evaluated to construct models of articular surfaces usin g an electromagnetic tracking device. First, the accuracy of the space trac ker was examined and optimised. Then, from several joint surfaces random po ints were measured and eighth degree polynomials were fitted to these measu rements. To check if the fit converged well, plots of cross sections of the model with corresponding data points were examined. The accuracy of the mo dels was determined by comparing them with computed tomography data and by reproducibility tests. All the fits converged well to the data. The root me an square (RMS) error of the models varied from 0.07 to 0.18 mm, and was pr oportional to the size and complexity of the surface. This was mainly due t o systematic errors made by the space tracker, which were also proportional to the size and complexity of the surface. (C) 2000 Published Elsevier Sci ence Ltd. All rights reserved.