In Vitro Verification of Simulated Daily Activities Using Implant-Specific Kinematics from In Vivo Measurements

The mechanism and boundary conditions used to drive experimental joint simulators have historically adopted standardized profiles developed from healthy, non-total knee arthroplasty (TKA) patients. The purpose of this study was to use implant-specific in vivo knee kinematics to generate physiologically relevant boundary conditions used in the evaluation of cadaveric knees post-TKA. Implant-specific boundary conditions were generated by combining in vivo fluoroscopic kinematics, musculoskeletal modeling-generated quadriceps loading, and telemetric knee compressive loading during activities of daily living (ADL) to dynamically drive a servo-hydraulic knee joint simulator. Ten cadaveric knees were implanted with the same TKA components and mounted in the knee simulator to verify the resulting load profiles against reported fluoroscopic kinematics and loading captured by an ultra-congruent telemetric knee implant. The cadaveric simulations resulted in implant-specific boundary conditions, which accurately recreate the in vivo performance of the like-implanted knee, with Root Mean Square Error (RMSE) in femoral low point kinematics below 2.0 mm across multiple activities of daily living. This study demonstrates the viability of in vivo fluoroscopy as the source of relevant boundary conditions for a novel knee loading apparatus, enabling dynamic cadaveric knee loading that aligns with clinical observations to improve the preclinical development of TKA component design.