Posterior stabilized (PS) total knees are regarded as one classification, although there are considerable differences in condylar and cam-post geometries which may affect their kinematic outputs. Evaluation methods for kinematics have included Oxford type machines , robots , knee simulators [3,4], computer models , and loading rigs specifically designed to measure laxity in line with the ASTM standard on constraint .
We developed a desktop machine for kinematic evaluation of total knee models under a full range of loading conditions and flexion angles, and proposed that the data from the anatomic knee be used as the benchmark .
Our hypotheses were that current PS designs will show a large variation in kinematic output, that these would differ from anatomic characteristics, and that an asymmetric guided motion design could potentially restore anatomic kinematics.
The test machine applied...