The Influence of Obesity on Unicompartmental Knee Arthroplasty Outcomes: A Systematic Review And Meta-Analysis

Obesity is associated with a greater prevalence of symptomatic knee osteoarthritis. Obese patients are thought to have worse outcomes following unicompartmental knee arthroplasty (UKA).The aim is to compare clinical and functional outcomes of UKA in obese to non-obese patients. A systematic review on six databases (PubMed, MEDLINE, Embase, Web of Science, Scopus, and CENTRAL) from inception through July 2020 was performed. We extracted data to determine revision risk (all-cause, septic, and aseptic), complication risk, and infection risk, functional outcome scores (Knee Society Score [KSS], Oxford Knee Score [OKS], and range of movement [ROM]) in patients with obesity (BMI >30kg/m2) to non-obese patients (BMI <30kg/m2). Meta-analysis was performed using a random effects model. The MINORS criteria was used for quality assessment. Twelve of 715 studies were eligible. Compared with non-obese patients, obese patients had a higher risk ratio for all-cause revision (RR 1.49; 95% CI 1.04 to 2.13; p = 0.03); aseptic revision (RR 1.36; 95% CI 1.01 to 1.81; p=0.04) and complications (RR 2.12; 95% CI 1.17 to 3.85; p=0.01). No significant differences were found in risk of septic revision and overall infection. Obese patients also had lower KSS scores (MD -3.21; 95% CI -5.52 to -0.89; p<0.01), OKS scores (MD -2.21; 95% CI -3.94 to -0.48; p=0.01), and ROM (MD -7.17; 95% CI -12.31 to -2.03; p<0.01). The average MINORS score was 14.2, indicating a moderate quality of evidence. In conclusion, the risk of revision, aseptic revision, and complications are higher in obese patients. The clinical significance of a lower functional score in obese may not be appreciable. Despite the greater risks, there is no conclusive evidence that obesity should be a contraindication to UKA. Further studies are required to corroborate the current conclusions with higher-quality study designs. Level of evidence: III