Propensity Score Matching: A Robust Adjustment Strategy for Outcome Comparisons in Bilateral Total Knee Arthroplasty Timing Studies (Motivated by the Patient-Determined Interval Study by Lv et al.)

Propensity score matching has become a critical tool for improving causal inference in observational studies, particularly where randomized controlled trials are impractical. This report, motivated by the patient-determined interval study on staged bilateral total knee arthroplasty by Lv et al., illustrates the application of propensity score matching to reduce confounding and improve the validity of surgical timing comparisons. By carefully selecting clinical and demographic variables, calculating propensity scores, and matching patients across groups, the study achieved strong covariate balance, minimizing selection bias. Key results demonstrated that longer intervals between surgeries were associated with better postoperative outcomes, including shorter hospital stays and reduced analgesic requirements. Baseline characteristics, matching efficiency, and outcome comparisons were evaluated through structured tables and standardized mean difference plots. Strengths, limitations, and future directions for propensity score research are also discussed. This case highlights the value of matching methods in generating reliable, real-world clinical evidence where randomized studies are not feasible.