Comparison of Postoperative Outcomes Following Simultaneous versus Staged Bilateral Total Knee Arthroplasty in Obese Patients: A Database Study.

Abstract

Obesity is associated with higher complication risk after total knee arthroplasty (TKA), and evidence comparing simultaneous versus staged bilateral TKA (BTKA) across obesity severity is limited. Adults undergoing BTKA (2014 to 2024) were identified from a global de-identified research network. Patients were classified by surgical timing (simultaneous; short-interval staged [one to less than four months]; longer-interval staged [four to 12 months]) and body mass index (BMI) (non-obese [less than 30]; obesity classes 1 [30 to less than 35]; 2 [35 to less than 40]; 3 [greater than 40]). Both 30-day and two-year outcomes were evaluated using logistic and linear regressions adjusted for age, sex, ethnicity, and Charlson comorbidity score with interaction testing between BMI category and surgical timing. Among 11,965 patients (5,653 non-obese; 3,096 class 1; 1,870 class 2; 1,346 class 3), BMI category modified surgical timing's association with 30-day composite complications (P < 0.001), readmission (P = 0.017), two-year aseptic loosening (P = 0.011), all-cause revision (P = 0.011) and length of stay (LOS) (P < 0.001). Staged BTKA showed lower odds of composite complications with the largest reductions in class 3 (short-interval [odds ratio (OR) 0.18, 95% confidence interval (CI): 0.09 to 0.35]; comparable for longer-interval). Staged BTKA also showed lower odds of aseptic loosening and revision in classes 2 and 3 with the largest reductions in class 3 (aseptic loosening [OR 0.24, 95% CI: 0.08 to 0.71]; revision [OR 0.13, 95% CI: 0.04 to 0.42]; comparable for longer-interval). In non-obese patients, staged BTKA was conversely associated with higher 30-day readmission ([OR 1.93, 95% CI: 1.17 to 3.17]; comparable for longer interval). The LOS was longer after simultaneous than staged BTKA, decreasing at higher BMI. The BMI category modified surgical timing's association with postoperative outcomes. Staged BTKA showed reductions in 30-day composite complications from class 1 onward and in two-year aseptic loosening and all-cause revision at BMI ≥ 35. The largest reductions for all three outcomes were observed in class 3.