Effect of component mal‐rotation on knee loading in total knee arthroplasty using multi‐body dynamics modeling under a simulated walking gait

Mal‐rotation of the components in total knee arthorplasty (TKA) is a major cause of postoperative complications, with an increased propensity for implant loosening or wear leading to revision. A musculoskeletal multi‐body dynamics model was used to perform a parametric study of the effects of the rotational mal‐alignments in TKA on the knee loading under a simulated walking gait. The knee contact forces were found to be more sensitive to variations in the varus–valgus rotation of both the tibial and the femoral components and the internal–external rotation of the femoral component in TKA. The varus–valgus mal‐rotation of the tibial or femoral component and the internal–external mal‐rotation of the femoral component with a 5° variation were found to affect the peak medial contact force by 17.8–53.1%, the peak lateral contact force by 35.0–88.4% and the peak total contact force by 5.2–18.7%. Our findings support the clinical observations that a greater than 3° internal mal‐rotation of the femoral component may lead to unsatisfactory pain levels and a greater than 3° varus mal‐rotation of the tibial component may lead to medial bone collapse. These findings determined the quantitative effects of the mal‐rotation of the components in TKA on the contact load. The effect of such mal‐rotation of the components of TKA on the kinematics would be further addressed in future studies. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1287–1296, 2015.