Impact of implant positions in total knee arthroplasty on the postoperative knee kinematics of tibial rotation.

Introduction: In total knee arthroplasty (TKA), the implant positions and knee kinematics, as well as the manifestation of medial pivot motion, play pivotal roles in determining postoperative clinical outcomes. The purpose of the current study was to analyze the correlation between knee kinematics, which was measured during TKA and implant positions derived using computed tomography (CT) examination after TKA.

Methods: This study comprised 64 patients (76 knees) who underwent primary TKA between 2015 and 2022. A navigation system was used in TKA procedures, and intraoperative knee kinematics were automatically calculated with it. Utilizing three-dimensional evaluation software, positioning of implants was quantified with CT images taken pre- and post-operatively. Multiple regression analyses were employed to explore the impact of femoral component position (FP) and tibial component position (TP) on knee kinematics, focusing on the extent of tibial rotational motion (TRM) during passive knee motion.

Results: FP affected TRM between knee extension and 90° flexion ( = 0.003, 95 % confidence interval [CI]: 0.315-1.384) and between knee extension and full flexion ( = 0.0002, 95 % CI: 0.654-1.844) after TKA. FP in internal rotation positively affected internal TRM after TKA. TP was not associated with TRM.

Conclusions: Findings of the current study suggest that FP in internal rotation positively impacts knee kinematics after TKA.