Anatomical site of radiographic degeneration is an independent variable influencing outcome of total knee arthroplasty.

ABSTRACT

OBJECTIVES: We aimed to determine whether the site of anatomical degenerative change could be identified as an independent risk factor influencing clinical outcome of total knee arthroplasty (TKA) 12 months postoperatively. METHODS: We compared preoperative, postoperative and the change observed in Oxford Knee Score (OKS) amongst TKA patients categorised as primarily medial, lateral or patellofemoral osteoarthritis (PFJOA). Multivariable regression analysis was conducted on 434 consecutive knees in 333 patients, adjusting for sex, age and body mass index (BMI). RESULTS: Adjusted estimates showed that preoperatively, patients with medial and lateral osteoarthritis (OA) had a lower mean OKS of 2.1 (p â€‹= â€‹0.049) and 2.3 (p â€‹= â€‹0.056) points respectively, while those with PFJOA had mean scores 2.7 points higher (p â€‹= â€‹0.062). There was no statistically significant difference between compartments in absolute postoperative OKS. The greatest improvement of 30.1 points (95% confidence interval (CI) 16.9-36.0, p â€‹= â€‹0.012) in OKS was observed for those with lateral OA, followed by 28.9 points (95% CI 16.7-35.3, p â€‹= â€‹0.049) for those with medial OA. The improvement observed postoperatively in patients with PFJOA was less than that observed for the average of the cohort at 24.5 (95% CI 11.5-29.7, p â€‹= â€‹0.088). CONCLUSIONS: The site of compartmental involvement in knee OA is an independent factor influencing clinical outcome of TKA. With arthroplasty registry adoption of patient-reported outcome measures (PROMs), this study supports precise anatomical categorisation of knee OA in outcome studies. LEVEL OF EVIDENCE Level III, Retrospective consecutive clinical study.