Experimental validation of a 3D dynamic finite-element model of a total knee replacement

A 3D forward-dynamics model of a total knee replacement was developed using an explicit finite-element package. The model incorporated both a tibiofemoral and a patellofemoral joint and allowed full 6-DOF kinematics for both joints. Simulated quadriceps contraction was used to drive the model. For validation, a unique experimental apparatus was constructed to simulate an open-chain extension motion under quadriceps control. The ligamentous constraints of the MCL and LCL were simulated using tension springs. The kinematics of the tibia and patella were recorded along with the net forces and moments applied to the femur. Several ligament and inertial configurations were simulated. The RMS differences between the experimental data and model predictions across all simulations were excellent for both the kinematics (angles: 0.3 - 1.6 degrees, displacements: 0.1 - 0.8 mm) and kinetics (forces: 5 - 11 N, moments: 0.2 - 0.6 Nm). The validated model will be extended with physiologically realistic ligaments and utilized in surgical planning simulations.