Development of Multi-Bundle Virtual Ligaments to Simulate Knee Mechanics after Total Knee Arthroplasty

Preclinical evaluation of total knee arthroplasty (TKA) components is essential to understanding their mechanical behavior and developing strategies for improving joint stability. While preclinical testing of TKA components has been useful in quantifying their effectiveness, such testing can be criticized for lacking clinical relevance, as the important contributions of surrounding soft tissues are either neglected or greatly simplified. The purpose of our study was to develop and determine if subject-specific virtual ligaments reproduce the same kinematics as native ligaments surrounding TKA joints. Five TKA knees were mounted to a motion simulator. Each was subjected to tests of anterior-posterior (AP), internal-external (IE), and varus-valgus (VV) laxity. The forces transmitted through major ligaments were measured using a sequential resection technique. By tuning the measured ligament forces and elongations to a generic non-linear elastic ligament model, virtual ligaments were designed and used to simulate the soft tissue envelope around isolated TKA components. The average root mean square error (RMSE) between the laxity results of TKA joints with native versus virtual ligaments was 2.9 mm during AP translation, 6.5{degrees} during IE rotations, and 2.0{degrees} during VV rotations, and there was no statistically significant difference between the results of both methods. Interclass correlation coefficients (ICCs) indicated a good level of reliability for AP and IE laxity (0.85 and 0.84). To conclude, a virtual ligament envelope around TKA joints can mimic natural knee behavior and is an effective method for the preclinical testing of TKA components.