Patient reported outcome measures, healthcare utilization, and survivorship after unicompartmental knee arthroplasty may not be impacted by obesity.

Abstract

Obesity has long been considered a relative contraindication to medial unicompartmental knee arthroplasty (mUKA). However, controversy remains. This study aimed to assess the association of BMI with (i) 1-year patient reported outcome measures (PROMs), (ii) healthcare utilization, and (iii) survivorship and mortality in patients undergoing mUKA. 886 mUKA patients from 2016 to 2022 at a single hospital system were identified. PROMs included Knee disability and Osteoarthritis Outcome Score (KOOS) for Pain, Joint Replacement (JR), and Physical function Shortform (PS), Achievement of the Minimal Clinically Important Difference (MCID), and Patient Acceptable Symptom State (PASS). Healthcare utilization was assessed by length of stay (LOS), discharge disposition (DD), readmission, and emergency department (ED) visits. Survivorship was assessed using 1- and 2-year reoperations and 1-year mortality. Multivariate regression was used to predict the effect of BMI on outcomes of interest. In multivariate analyses, BMI did not predict MCID-JR, PASS-PS, PASS-Pain, PASS-JR, and 90-day ED visits. There were no differences in achievement of MCID-Pain (p = 0.4), LOS (p = 0.62), DD (p = 1), 90-day readmission (p = 0.78), 1-year reoperation (p = 0.75), and 2-year reoparation (p = 1), between cases with BMI above and below 35. Class I obesity was associated with failure to achieve MCID for KOOS-PS (OR = 1.94, 95 % CI [1.02-3.67], p = 0.04). Overall, BMI did not impact healthcare utilization, PROMs, or short term survivorship following mUKA. Therefore, using BMI as a contraindication for mUKA may be unwarranted. With the continued rise in mUKA numbers, enhanced understanding of the influence of morbid obesity on healthcare utilization, survivorship, and PROMs is needed.