Introduction - Video-based
motion analysis systems have been used successfully in clinical analysis of
gait [2]. A similar system could prove useful in applications involving the
foot and ankle [1].
In this study, a four-segment rigid body model was developed to describe the
kinematics of the foot and ankle. 12 retroreflective markers were placed on
bony landmarks of the foot and ankle. The 3-D marker coordinates were then determined
during a complete gait cycle using VICON video analysis system (Vicon, Oxford,
England). The model was employed to transform the 3-D data into a set of angular
kinematic relationships. Various methods for describing the relative angular
positions of the segments were investigated including Euler angles, helical
axis, and a set of three independent angles [3].