Model Analysis of Artificial Knee Joint : Comparison of Cruciate Retaining Type and Posterior Stabilized Type

The objective of this study is to analyze statics and kinematics of artificial knee joint at deep flexion to compared the difference between cruciate retaining (CR) type and posterior stabilized (PS) type. We performed a 3D model analysis with conditions of point contact and force/moment equilibrium. The motion to be subjected was passive knee flexion at the flexion angle from 30° to 150°. As a result, patellofemoral and tibiofemoral forces of PS type were smaller than CR type. Besides, with CR type, femoral rollback and tibial internal rotation were observed when the posterior cruciate ligament (PCL) stiffness was large, which are usually observed the physiological knee kinematics. It indicated that CR type can not reproduce such physiological motion without enough PCL. With PS type, femoral rollback was larger than CR type and it obtained wide range of motion. However, femur did not roll back over 90° of flexion angle. Moreover, contact force on post and cam increased much during deep knee flexion. If the PCL stiff enough, we should use the CR type. For PS type, it is necessary to design with consideration for acquiring femoral rollback and preventing breakage in the deep flex region.