Evaluating Knee Replacement Mechanics during ADL with PID-Controlled Dynamic Finite Element Analysis

INTRODUCTION: Validated computational knee simulations are valuable tools for design phase development of knee replacement devices. Recently, a dynamic finite element (FE) model of the Kansas knee simulator (KKS), an electro-hydraulic whole joint mechanical simulator, was kinematically validated during gait and deep flexion activities. In order to operate the computational simulator in the same manner as the experiment, a proportional-integral-derivative (PID) controller was interfaced with the FE model to control quadriceps actuator excursion and produce a target flexion profile regardless of implant geometry or alignment conditions. In the current study, the control system was expanded to operate multiple actuators simultaneously in order to produce in vivo loading conditions (compressive load, internal-external (I-E) moment, varus-valgus (V-V) moment, anterior-posterior (A-P) force) at the joint during dynamic activities. Subsequently, the fidelity of the computational model was improved through additional muscle representation and inclusion of relative hip-ankle A-P motion.