Unicompartmental Knee Arthroplasty Is Not Associated With Increased Revision Rates in Obese Patients

There is controversy among arthroplasty surgeons in regard to performing unicompartmental knee arthroplasty (UKA) in obese patients based on current literature. The aim of this study is to investigate whether UKA is associated with increased complications and revision rates in obese (body mass index [BMI] > 30 kg/m²), morbidly obese (BMI > 40 kg/m²), and super morbid obese (BMI > 50 kg/m²) patients.

We retrospectively reviewed all UKAs performed at our institution from January 2008 to December 2017. A total of 2178 UKA procedures were performed during this period. The patients were categorized based on BMI to include normal weight (BMI = 20-30 kg/m²), obese (BMI ≥ 30.1-40 kg/m²), morbidly obese (BMI ≥ 40.1-50 kg/m²), and super morbid obese (BMI ≥ 50.1 kg/m²) groups. Record review was performed to obtain demographic data, need for revision (timing, type, and etiology), and complication rate and cause.

The 2178 UKA cases were eligible for inclusion in this investigation. We performed 2028 medial UKAs and 150 lateral UKAs. The mean clinical follow-up period was 3.7 years, and the mean time from index surgery to revision was 7.2 years. Of the 2178 UKA cases, 1167 had a 3-year minimum follow-up. The overall revision rate in all patients was 2.2%. There was no significant difference (P > .05) in revision rates among normal weight (3.0%), obese (2.7%), morbidly obese (1.9%), and super morbid obese patients (1.8%). Most failures in all groups were secondary to progression of osteoarthritis requiring total knee arthroplasty.

Similar rates of revision were found for UKAs performed on obese, morbidly obese, or super morbid obese patients (≤2.0% revision rate) vs normal BMI (2.7% revision rate) patients. Progressive osteoarthritis was the most common mechanism of UKA failure. Obesity is not a contraindication for UKA despite previous recommendations to the contrary.