ANALYSIS OF IN-VIVO 3-D INTERNAL KINEMATICS OF THE JOINTS OF THE FOOT

This paper describes a methodology for the analysis of three-dimension al (3-D) kinematics of live joints of the foot based on tomographic im age data acquired via magnetic resonance (MR) imaging. A mechanical ji g facilitates acquisition of MR images corresponding to different posi tions of the joint in a pronation-supination motion. The surfaces of t he individual tarsal bones are constructed by segmenting the MR images . A mathematical description of the motion of the individual bones and of their relative motion is derived by computing the rigid transforma tion required to match the centroids and the principal axes of the sur faces. The mathematically described motion is animated via surface ren ditions of the bones, The kinematics of the bones are analyzed based o n features extracted from the motion description and on how they vary with motion. Based on 17 joints that have been imaged, which includes an abnormal joint and the same joint after surgical correction, we con clude that this methodology offers a practical tool for measuring inte rnal 3-D kinematics of joints in vivo and for characterizing and quant ifying with specificity normal kinematics and their pathological devia tions. Some of the 3-D kinematic animations generated using the method s of this paper for normal joints can be seen at: http://www.mipg.upen n.edu.