Simultaneous bilateral total knee arthroplasty has higher in-hospital complications than both staged surgeries: a nationwide propensity score matched analysis of 38,764 cases

Purpose To investigate (1) healthcare utilization, (2) in-hospital metrics and (3) total in-hospital costs associated with simultaneous versus staged BTKA while evaluating staged BTKA as a single process consisting of two combined episodes. Methods The national readmissions database was reviewed for simultaneous and staged (two primary unilateral TKAs12 months apart) BTKA patients (2016-2017). A total of 19,382 simultaneous BTKAs were identified, and propensity score matched (1:1) to staged BTKA patients (19,382 patients; 38,764 surgeries) based on demographics, comorbidities, and socioeconomic determinants. Outcomes included healthcare utilization [length of stay (LOS) and discharge disposition], in-hospital periprosthetic fractures, non-mechanical complications, and costs. Staged BTKA was evaluated as one process consisting of two episodes. For each staged patient, continuous outcomes were evaluated via the sum of both episodes. Categorical outcomes were added, and percents were expressed relative to total number of surgeries (n = 38,764). Results Simultaneous BTKA had longer LOS (5.0 days +/- 4.7 vs. 4.5 days +/- 3.5; p < 0.001), higher non-home discharge [36.9% (n = 7150/19,382) vs. 13.6% (n = 5451/38,764)], in-hospital periprosthetic fractures [0.13% (26/19,382) vs. 0.08% (31/38,764); p = 0.049], any non-mechanical complication [33.76% (6543/19,382) vs.15.93% (6177/38,764); p < 0.0001], hematoma/seroma formation [0.11% (22/19,382) vs. 0.05% (20/38,764); p = 0.0088], wound disruption [0.08% (16/19,382) vs. 0.04% (16/38,764); p = 0.0454], and any infection [1.13% (219/19,382) vs. 0.50% (194/38,764); p < 0.0001]. Average in-hospital costs for the two staged BTKA episodes combined were $5006 higher than those of simultaneous BTKA ($28,196 +/- $18,488 vs. $33,202 +/- $15,240; p < 0.001). Conclusion Simultaneous BTKA had higher healthcare utilization and in-hospital complications than both episodes of staged BTKA combined, with a minimal in-hospital cost savings. Future studies are warranted to further explore patient selection who would benefit from BTKA.