the ideal timing of bilateral total knee arthroplasty: simultaneous versus staged

Objectives: the ideal timing for patients undergoing bilateral total knee arthroplasty (tka) remains unknown. the purpose of this study was to compare 90-day outcomes between unilateral, simultaneous bilateral, and staged bilateral tka.methods: the pearldiver database was used to retrospectively identify 231,119 patients undergoing primary tka during 2015-2020, of which 67,956 (29.4%) were bilateral. bilateral tka patients were divided into cohorts of simultaneous bilateral tka and staged bilateral tka at 1-14 days, 15-30 days, 31-90 days, and 91-365 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] 1.28, 95% confidence interval [ci] 1.07-1.54, p=0.007), acute kidney injury (aki; or 1.47, ci 1.17-1.84, p=0.001), blood transfusion (or 6.81, ci 5.43-8.65, p<0.001), and any complication (or 1.63, ci 1.49-1.78, p<0.001). 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