Is unicompartmental knee arthroplasty truly contraindicated in an obese patient? A meta-analysis

Background: Obesity has long been considered a relative contraindication to unicompartmental knee arthroplasty (UKA). However, with improved implants and techniques, the criteria for UKAs have been challenged. This paper aims to assess the impact of body mass index (BMI) on revision rates and functional outcomes in UKAs.Methods: Databases of Pubmed, EMBASE, MEDLINE, CINHL and the Cochrane registries were systematically searched following the PROSPERO protocol. Studies comparing implant survival and functional outcome scores between obese and non-obese patients after a UKA were included.Results: Twenty-five articles reported revision rates or functional outcomes in 42,434 UKA surgeries. There was a trend to higher revision rates in patients with BMI > 30 kg/m(2) (odds ratio [OR] 0.91 [0.79-1.05]), BMI >35 kg/m(2) (OR 0.70 [0.48, 1.01]) or BMI >40 kg/m(2) (OR 0.66 [0.41, 1.07]), although the difference was not significant. There was a significant larger improvement in Oxford Knee Scores in obese patients after a UKA (OR 2.68 [1.79, 3.57], p < 0.00001), but no difference in Knee Society Scores or Visual Analogue Scale scores.Conclusion: With no significant increase in revision rates after a UKA, a significantly greater improvement in Oxford Knee Scores and no differences Knee Society Scores or Visual Analogue Scales, obesity should no longer be viewed as a relative contraindication when performing unicompartmental knee replacements.