Switching From a 6° to a 20° Valgus Prosthetic Trochlear Groove Improved the Forgotten Joint and Oxford Knee Scores After Kinematically Aligned Total Knee Arthroplasty

TL;DR

Changing to a 20° valgus prosthetic trochlear groove in knee surgery improves patient-reported outcomes like the Forgotten Joint and Oxford Knee Scores.

Contribution

Demonstrates that a 20° valgus PTG in kinematically aligned TKA improves clinical scores compared to the traditional 6° design.

Findings

The 20° valgus group had a 6-point higher Forgotten Joint Score than the 6° group.

The 20° valgus group had a 16% lower incidence of poor FJS (<40) compared to the 6° group.

The 20° valgus PTG showed better Oxford Knee Scores for excellent and good outcomes.

Abstract

In kinematically aligned (KA) total knee arthroplasty (TKA) using a femoral component with the traditional 6° valgus prosthetic trochlear groove (PTG), patients reported a lower Forgotten Joint Score (FJS) when the quadriceps line of pull was laterally misaligned to the groove, with an incidence of 89%. It remains unclear whether switching to a KA-optimized femoral component with a 20° valgus PTG, which properly aligns the quadriceps line of pull, can improve the FJS and the Oxford Knee Score (OKS).

The analysis of single-surgeon series of KA TKAs included 145 cases with a KA-optimized 20° valgus PTG and 292 cases with a 6° valgus PTG. Each participant reported their FJS and OKS at 2 years and underwent a postoperative coronal long-leg scan.

The 20° group had a 6-point higher FJS (79) and a 16% lower incidence of poor FJS (<40) (8%) compared to the 6° group. Additionally, 73% and 22% achieved an excellent (48-42) or good (41-34) OKS, compared to 64% and 20% with a 6° valgus PTG. The FJS in the 20° group was 7 and 20 points higher in the coronal plane alignment of the knee (CPAK) types 2 and 3.

Surgeons performing KA TKA should consider switching to a KA-optimized femoral component with a 20° valgus PTG, as this option improves the FJS and OKS, lowers the risk of a poor FJS, and is especially useful for CPAK 2 and 3, with no apparent disadvantages in CPAK 1, 4, and 5.

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