Abstract
PURPOSE: The decision to perform a second surgery in staged bilateral total knee arthroplasty (BTKA) remains undetermined. While previous studies have investigated the timing of the second surgery, they have not reached a consensus on the optimal interval and lack self-controlled comparisons between the first and second surgeries to minimize bias. This study aimed to address these gaps by evaluating postoperative outcomes across patient-determined intervals and conducting internal comparisons between sequential surgeries to optimize the timing of the second procedure in staged BTKA. METHODS: We retrospectively reviewed 528 patients (1,056 knees) who underwent staged BTKA between January 1, 2015, and December 31, 2019. Considering the different intervals, all patients were divided into 3 groups using 3 different cut-off points: group A (≤ 180 days), group B (> 180 days and ≤ 365 days), and group C (> 365 days). Comparison was done among the 3 groups for the second arthroplasties (A2 vs. B2 vs. C2). In each group, comparison was conducted between two surgeries (A1 vs. A2, B1 vs. B2, and C1 vs. C2, respectively).All data were retrieved retrospectively.This study utilized the propensity score matching (PSM)was performed to minimize confounding factors when comparing outcomes among groups.The matching variables included age, sex, BMI, height, comorbidities (hypertension, diabetes, coronary heart disease, chronic obstructive pulmonary disease, liver cirrhosis, and smoking status), ASA score (American Society of Anesthesiologists classification), and surgeon (C.X.W. or G.D.). Patients with same Kellgren-Lawrence (K-L) grades (grade 4)were included during the initial screening to ensure homogeneity in osteoarthritis severity. We evaluated demographics and clinical outcomes, major complications, and hospital adverse events. RESULTS: There were no statistically significant differences in any of the clinical outcomes, major complications, and hospital adverse events among the 3 groups (A2 vs. B2 vs. C2)( all P > 0.05). When C1 and C2 were compared, LOS (12.23 ± 3.41 vs 10.12 ± 2.76, P < 0.0001), drainage volume (115.62 ± 45.67 vs 101.26 ± 49.28, P = 0.003), additional morphine analgesics consumption (131.52 ± 259.11 vs 69.78 ± 159.89, P = 0.016), and the rate of hospital adverse events (58.33% vs 46.15%, P = 0.026) were significantly better in group C2. CONCLUSION: The time frame of staged BTKAs has no influence on postoperative outcomes when the intervals are determined by patients. However, prolonging the interval between the surgeries may be beneficial for a faster recovery after the second knee arthroplasty. Benefits such as reduced intraoperative blood loss, lower postoperative analgesic use, and shorter hospital stays are especially evident when the interval exceeds one year, showing statistically significant differences. Therefore, if patients are willing to wait, we recommend scheduling the second surgery at least one year after the first. TRIAL REGISTRATION NUMBER: ZE2020-139-01, for retrospectively registered trials. LEVEL OF EVIDENCE: Retrospective cohort study, LEVEL III.