Author(s)

A. Bouafia & J. Dimnet

Abstract

The purpose of this paper is to compare the kinematics of the same knee joint in different successive states: intact, after A.C.L. (Anterior Cruciate Ligament) ruptures, and then replaced by a prosthetic implant. To attain this objective required working on a cadaver limb, using a speciality designed simulator to reproduce continuous flexion-extension cycles under realistic loading conditions. The successive positions of the knee adjacent segments (femur and tibia) are measured using a motion analysis system that computes the three dimensional trajectories of a set of reflective markers screwed directly into the bones. The motion analysis system is made up from the following components: a SUN workstation, five video cameras, an electronic interface that allows the conversion of the optical signal into an electronic signal and the synchro between the different signals (force, electro–myograph ....), and one software set for 3D reconstruction. We then apply the theory of solid kinematics in order to calculate the relative displacement between the two adjacent segments, assumed to correspond to the knee joint movement. Specific tests have been executed in order to quantify the errors due to the measurement protocol, so that the results obtained for the various knee states under scrutiny can be assigned to the actual changes in the functioning joint. In this paper we first describe the experimental material and conditions, then the method used to assess the joint kinematics and then quantifying the errors due to the measurement protocol is explained. Finally, the most representative results of the comparison between the different knee states are displayed and commented on from a clinical point of view. Keywords: anatomic piece, optoelectronic system, simulator, knee kinematics, three dimensional motion, the finite helical axis.

Keywords

anatomic piece, optoelectronic system, simulator, knee kinematics, three dimensional motion, the finite helical axis.