Metabolic syndrome increases the length of stay and medical complications after hip and knee arthroplasty: results from a prospective cohort study of 2,901 patients

BACKGROUND AND PURPOSE: Metabolic syndrome (MetS) affects more than 60% of the patients having a hip or knee arthroplasty due to osteoarthritis. As it is debated whether metabolic syndrome increases the risk of complications, we aimed to investigate the length of stay (LOS) and risk of readmission at 30 and 90 days after surgery, including causes of readmission. METHODS: We conducted a prospective cohort study of 2,901 patients undergoing hip and knee arthroplasty from May 2017 to November 2019. Physical examination, blood samples, and medical history from national registries determined the diagnosis of metabolic syndrome from the International Diabetes Federation definition. We used multivariate linear regression to investigate differences in LOS according to MetS, and binary regression to investigate the risk and causes of readmission within 30 and 90 days, including 95% confidence intervals (CI) and P values. RESULTS: Patients with MetS showed a slightly longer LOS (0.20 days, CI 0.10-0.29) and had an increased risk of readmission within 90 days (adjusted relative risk [RR] 1.2, CI 1.0-1.4; P = 0.02), but not within 30 days (adjusted RR 1.1, CI 0.9-1.4; P = 0.3) after surgery. Cardiovascular disease was the dominant cause of readmission. CONCLUSION: Although patients with MetS do not experience a clinically relevant longer LOS after hip and knee arthroplasty, they have an increased risk of 90-day readmission mainly due to cardiovascular complications, which should be considered when planning surgical care in this group of patients.