(3) The retrospective design lacks critical covariates—including RA disease activity [Disease Activity Score-28 (DAS28), C-reactive protein (CRP)/erythrocyte sedimentation rate (ESR)], disease-modifying antirheumatic drugs (DMARDs)/biologics exposure, and surgical technical details—thereby precluding etiological stratification; thus, residual confounding is inevitable and the study can only generate real-world evidence rather than establish causality. Here, CRP is linked to rheumatoid arthritis.