The Forgotten Joint Score after total knee arthroplasty with a kinematic alignment-optimized femoral component matches total hip arthroplasty.

Abstract

Purpose: In kinematic alignment (KA) total knee arthroplasty (TKA), 50% of patients treated with a femoral component that has a 6° valgus prosthetic trochlear groove (PTG) show an abnormal quadriceps line of pull directed laterally to the groove. Lateral misalignment is reported to decrease the Forgotten Joint Score (FJS) by 17-24 points. Therefore, this study aimed to determine whether using a femoral component with a 20° valgus PTG, which minimizes the risk of lateral misalignment, can achieve a mean FJS that meets the 70-point threshold for a successful outcome in total hip arthroplasty (THA) and the mean value of 67 points for knees in the U.S.

Population:

Methods: The study analyzed the first 127 patients who underwent KA TKA with the 20° valgus KA-optimized femoral component. At a minimum 2-year follow-up, patients were sent an online survey to complete the FJS and Oxford Knee Score (OKS) to assess function and report instances of revision knee surgery. Ten of the 127 cases were excluded: two required revision surgery. Four patients did not complete the questionnaire but reported no reoperations. The families of two individuals who passed away provided the same response. Two patients could not be contacted.

Results: The analysis focused on 117 KA TKAs, with a mean FJS of 75 points, 5 points higher than the 70-point threshold considered successful for THA and exceeding the normative value of 67 points for knees. The mean OKS was 43 points.

Conclusion: Primary KA TKA with a 20° valgus PTG can achieve an FJS comparable to THA with high functionality, as shown by 70% and 25% of subjects receiving an excellent (48-42) or good (41-34) OKS.

Level of evidence: Level III.