THE IMPACT OF BODY MASS INDEX ON THE OUTCOME OF THE UNICOMPARTMENTAL KNEE ARTHROPLASTY

Introduction Obesity has been considered a relative contra-indication in unicompartmental knee arthroplasty (UKA) due to fear of high wear rates, loosening and tibial collapse. The aim of this study was to investigate the impact of high body mass index (BMI) on ten-year survivorship and five-year functional outcome after Oxford UKA, a fully congruous mobile bearing design with large contact area and low wear rate. Methods This prospective study examines a consecutive series of 595 knees (mean age 66 years, range: 33-88) undergoing Oxford UKA with a minimum 5-year follow-up. Patients were divided into three groups; Group I (Normal body weight), BMI Results The mean follow-up was 6.3 years. There was no significant difference in the 10-year survivorship between groups (96% for all groups). Although numbers were small there was no significant difference in revision rates for patients with BMI ≥35 (n=1/38). Group III patients had a lower pre-operative OKS and lower post-operative OKS compared to groups I and II, although DeltaOKS was similar (p= .977). At last follow-up the Functional KSS was lower in group III (p=.11), although Objective KSS was not significantly different between groups (p=.954) Conclusion Oxford UKA can be safely used in obese and morbidly-obese patients. Design features of congruous bearing and large contact area ensure low wear rates. Summary No significant difference in revision rates noted between groups of increasing body mass index in this prospective study of outcome in patients undergoing medial Oxford unicondylar knee replacement.