Objectives: The ideal timing for patients undergoing bilateral total knee arthroplasty (TKA) remains unknown. The purpose of this study was to compare ۹۰-day
outcomes between unilateral, simultaneous bilateral, and staged bilateral TKA.Methods: The PearlDiver database was used to retrospectively identify ۲۳۱,۱۱۹ patients undergoing primary TKA during ۲۰۱۵-۲۰۲۰, of which ۶۷,۹۵۶ (۲۹.۴%) were bilateral. Bilateral TKA patients were divided into cohorts of simultaneous bilateral TKA and staged bilateral TKA at ۱-۱۴ days, ۱۵-۳۰ days, ۳۱-۹۰ days, and ۹۱-۳۶۵ days. Each bilateral TKA cohort underwent one-to-one matching with unilateral TKA patients based on age, gender, year, Elixhauser Comorbidity Index (ECI), and a history of obesity, diabetes, and tobacco use. Ninety-day
outcomes werecompared between matched groups via univariate and multivariate analysis. In staged bilateral TKA groups, outcomes were collected beginning after the second TKA.Results: Compared to unilateral TKA, simultaneous bilateral TKA was associated with higher rates of venous thromboembolism (VTE; odds ratio [OR] ۱.۲۸, ۹۵% confidence interval [CI] ۱.۰۷-۱.۵۴, p=۰.۰۰۷), acute kidney injury (AKI; OR ۱.۴۷, CI ۱.۱۷-۱.۸۴, p=۰.۰۰۱), blood transfusion (OR ۶.۸۱, CI ۵.۴۳-۸.۶۵, p<۰.۰۰۱), and any complication (OR ۱.۶۳, CI ۱.۴۹-۱.۷۸, p<۰.۰۰۱). Staged bilateral TKA at any time interval studied was associated with a similar or decreased risk of individual complications, emergency department visits, readmissions, reoperations, and any complication relative to unilateral TKA.Conclusion: Simultaneous bilateral TKA is associated with an increased risk of adverse events compared to unilateral TKA. However, bilateral TKA staged at a short interval appears safe in appropriately selected patients. Level of evidence: III