Lateralized position of femoral and tibial components during posterior-stabilized total knee arthroplasty leads to better functional outcomes

TL;DR

This study found that positioning knee implants more laterally during surgery improves patient outcomes like mobility and strength.

Contribution

The study is the first to show that lateral positioning of knee implants correlates with better functional outcomes after surgery.

Findings

Lateral femoral component position correlates with better knee function scores and faster movement times.

Lateral tibial component translation correlates with improved knee extension strength.

Lateral positioning is recommended when implant width doesn't match the resected bone surface.

Abstract

The mediolateral position and postoperative translation of the femoral and tibial components relative to the respective bones after total knee arthroplasty (TKA) have not yet been investigated. The purpose of the current study was to investigate the effect of the mediolateral position of the femoral and tibial components on clinical outcomes including muscle strength and ambulatory function.

A total of 86 consecutive knees were included. The mediolateral positions of the femoral and tibial components were measured on the postoperative long-leg radiographs. The mediolateral position of the femoral and tibial components was defined relative to the femoral distal anatomical axis and the tibial mechanical axis. The lateral position of the component was denoted as positive. The lateral translation of the femoral and tibial components was defined as the distance between the preoperative femoral and tibial centers and the postoperative center of the respective component. The Knee Society Score (KSS), New Knee Society Score (2011 KSS), and the Timed Up and Go (TUG) test results were evaluated 2 years postoperatively. Spearman’s correlation coefficient was calculated.

The lateral position of the femoral component was significantly positively correlated with KSS function score (ρ = 0.250, p = 0.020), 2011 KSS functional activities (ρ = 0.258, p = 0.017), and TUG values (ρ = − 0.241, p = 0.027). The lateral translation of the tibial component was significantly correlated with knee extension strength (ρ = 0.259, p = 0.017).

The lateralized position of the femoral and tibial components positively influenced postoperative knee function. When the width of the component does not fit the resected surface, a lateralized position of the femoral and tibial components with respect to the respective bones can be recommended for better functional outcomes.

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