Obesity should not be considered a contraindication to medial Oxford UKA: long-term patient-reported outcomes and implant survival in 1000 knees

PurposeSome health providers ration knee arthroplasty on the basis of body mass index (BMI). There is no long-term data on the outcome of medial mobile-bearing unicompartmental knee arthroplasty (UKA) in different BMI groups. This study aimed to determine the effect of patient body mass index (BMI) on patient-reported outcomes and long-term survival of medial UKA in a large non-registry cohort. Our hypothesis is that increasing BMI would be associatedwith worse outcomes.MethodsData were analysed from a prospective cohort of 1000 consecutive medial mobile-bearing Oxford UKA with mean 10-year follow-up. Patients were grouped: BMI<25, BMI 25 to <30, BMI 30 to <35 and BMI 35+. Oxford Knee Score (OKS) and TegnerActivity Score were assessed at 1, 5 and 10 years. Kaplan-Meier survivorship was calculated and compared between BMI groups.ResultsAll groups had significant improvement in OKS and Tegner scores. BMI 35+kg/m(2) experienced the greatest overall increase in mean OKS of 17.3 points (p=0.02). There was no significant difference inten-year survival, which was, from lowest BMI group to highest 92%, 95%, 94% and 93%.ConclusionThere was nodifference in implant survival between groups, and although there was no consistent trend in postoperative OKS, the BMI 35+group benefited the most from UKA. Therefore,when UKA is used for appropriate indications, high BMI should not be considered to be a contraindication. Furthermore rationing based on BMI seems unjustified, particularly when the commonest threshold (BMI 35) is used.Level of evidenceIII.