Associations of the Oxford Knee Score and knee arthroplasty revision at long‐term follow‐up

Abstract

AbstractBackgroundSelf‐reported outcome measures are increasingly being collected for healthcare evaluation therefore it is prudent to understand their associations with patient outcomes. Our aims were to investigate: (1) if Oxford Knee Score (OKS) is associated with impending revision at long‐term (5 and 10 years) follow‐up, and (2) if decreased OKS at subsequent follow‐ups is associated with higher risk of revision.Patients and MethodsAll total knee (TKAs) and unicompartmental knee arthroplasties (UKAs) between 1999 and 2019 in the New Zealand Joint Registry with an OKS at 6 months (TKA n = 27 708, UKA n = 8415), 5 years (TKA n = 11 519, UKA n = 3365) or 10 years (TKA n = 6311, UKA n = 1744) were included. Logistic regression determined associations of the OKS with revision within 2 years of each score. Change in OKS between timepoints were compared with revision risk.ResultsFor every one‐unit increase in OKS, the odds of TKA and UKA revision decreased by 10% and 11% at 6 months, 10% and 12% at 5 years and 9% and 5% at 10 years. For both procedures a decrease of seven or more OKS points from previous follow‐up was associated with higher risk of revision (5 years: TKA 4.7% versus 0.5%, UKA 8.7% versus 0.9%; 10 years: TKA 4.4% versus 0.7%, UKA 11.3% versus 1.5%; all P < 0.01).ConclusionThe OKS had a strong negative association with risk of impending TKA and UKA revision from early to long‐term (10+ years) follow‐up. A decrease of seven or more points when compared with the previous follow‐up was also associated with higher revision risk.