Evaluation of the performance of a motion capture system for small displacement recording and a discussion for its application potential in bone deformation in vivo measurements.

The aim of this study is to evaluate the performance of a motion capture system and discuss the application potential of the proposed system in in vivo bone-segment deformation measurements. In this study, the effects of the calibration procedure, camera distance and marker size on the accuracy and precision of the motion capture system have been investigated by comparing the captured movement of the markers with reference movement. The results indicated that the system resolution is at least 20 microm in a capture volume of 400 X 300 X 300 mm3, which mostly covers the range of motion of the tibia during the stance phase of one gait cycle. Within this volume, the system accuracy and precision decreased following the increase of camera distance along the optical axis of the cameras. With the best configuration, the absolute error and precision for the range of 20 microm displacement were 1.2-1.8 microm and 1.5-2.5 microm, respectively. Small markers (Ø3-8 mm) yielded better accuracy and repeatability than the larger marker (Ø10.5 mm). We conclude that the proposed system is capable of recording minor displacements in a relative large volume.