[page 6] [Orthopedic Reviews 2012; 4:e2] Orthopedic Reviews 2012; volume 4:exxxx2Differences in tibiofemoralkinematics between theunloaded robotic passive pathand a weightbearing kneesimulator

Cadaveric in vitro studies are essential to test hypotheses concerning surgical manipula-tions in the same individual. Robotic technolo-gies as well as different knee-models have been developed to get an in-depth comprehen-sion of knee joint kinematics. The purpose of this study was to compare utilization of these different established principles. Ten human cadaveric knee specimens were used to measure the kinematics during a weight-bearing flexion in a 6-degrees-of-free-dom knee simulator. While flexing the knee, joint quadriceps muscle forces were dynami-cally simulated to reach a vertical ground reac-tion force of 100N. Fourteen knee specimens were mounted in 6-degrees-of-freedom robotic manipulator with a universal force sensor. The unloaded flexing motion of each specimen was measured by finding positions for each degree of flexion where all forces are minimal (pas-sive path). The kinematic data of the knee-simulator and the robot concerning internal-external rotation, anterior-posterior transla-tion, varus-valgus motion, and medial-lateral translation was examined. For all investigated degrees of freedom the kinematics of the robotic passive path differed from the loaded kinematics in the knee simu-lator. Simulated bodyweight as well as the exami-nation method used has a substantial influ-ence on joint kinematics during flexion which has to be considered when interpreting biome-chanical studies as well as clinical tests