Abstract
Limited evidence is available on mid-term follow-up for patients with body mass index (BMI) ≥ 40 receiving a unicompartmental knee arthroplasty (UKA). The primary objective of this study was to investigate survival of the UKA in patients with BMI ≥ 40. Secondary objectives were to assess functional and patient reported outcome measures (PROMs). Survival analysis with endpoint revision of any component for any reason was conducted using Kaplan–Meier technique on 121 knees (103 patients) that underwent UKA with Oxford Phase 3 implant (Oxford Knee, Biomet, Swindon, United Kingdom) between September 2001 and March 2014 by seven surgeons. Survivorship differences were compared using Log Rank (Mantel-Cox) tests, and Cox Proportional Hazard Model was used to assess predictors of failure. Preoperative PROMs were compared at 2 and 5 years postoperatively using paired t-tests. Mean age of patients was 58 years (43–75), mean BMI 43 kg/m2 (40–51), and mean follow-up 7 years (2 months to 15 years). Survival rate for the whole cohort was 92% at 2 years and 86% at 5 years. Females had a significantly higher revision rate than males (p = 0.043). A total of 19 knees required revision (16 to TKA, 2 polyethylene liner exchanges, and 1 femoral component and liner revision). With respect to PROMs, there was a significant improvement at 2 and 5 years (p < 0.001) on 4 of 5 knee injury and osteoarthritis outcome score subscales. The mid-term survival rate for the Oxford UKA in patients with morbid obesity is similar to that of other nondesigner patient series with BMI ≥ 30, which provides further evidence for the safety of the implant in this patient population with significant improvements on PROMs at short and mid-term follow-up.
Keywords
unicompartmental knee arthroplasty - body mass index over 40 - survivorship - revision - patient-reported outcome measures
