Greater risk of all-cause revisions and complications for obese patients in 3 106 381 total knee arthroplasties: a meta-analysis and systematic review

Background: Obesity is a major public health issue and has considerable implications on outcomes of total knee arthroplasty (TKA). However, there has been conflicting evidence and conclusions on the effects of obesity on TKA. This meta-analysis compares the outcomes, complications, and peri-operative parameters of TKA in the obese (body mass index [BMI] ≥ 30 kg/m²) versus non-obese (BMI < 30 kg/m²) population as well as subgroup analysis of morbidly obese (BMI ≥ 40 kg/m²) versus non-obese population. Methods: A meta-analysis was conducted with a multi-database search according to PRISMA guidelines on 12 September 2019. Data from all published literature meeting inclusion criteria were extracted and analysed. Results: Ninety-one studies were included, consisting of 917 447 obese and 2 188 834 non-obese TKA. Obese patients had higher risk of all-cause revisions (odds ratio [OR] = 1.15, 95% CI: 1.08–1.24, p < 0.0001), all complications (OR = 1.21, 95% CI: 1.06–1.38, p = 0.004), deep infections (OR = 1.47, 95% CI: 1.27–1.69, p < 0.0001), superficial infections (OR = 1.59, 95% CI: 1.32–1.91, p < 0.0001), wound dehiscence (OR = 1.46, 95% CI: 1.24–1.72, p < 0.0001) and readmissions (OR = 1.21, 95% CI: 1.05–1.40, p = 0.009). Subgroup analysis of morbidly obese patients revealed greater risks of all-cause revisions (OR = 1.25, 95% CI: 1.10–1.43, p = 0.0009), deep infections (OR = 1.98, 95% CI: 1.05–3.75, p = 0.04), superficial infections (OR = 2.44, 95% CI: 2.08–2.88, p < 0.0001) and readmissions (OR = 1.33, 95% CI: 1.20–1.47, p < 0.0001). No analysis was performed on patient reported outcome measures due to heterogeneous reporting methods. Conclusion: Obese and morbidly obese patients have higher risks of revisions and infections post TKA. Surgeons should counsel patients of these risks during the informed consenting process and adopt preventative strategies into clinical practice to reduce risks where possible. In conclusion, obesity is a significant, modifiable risk factor for increased complications following TKA.