Risk Factors for Readmission Following Same-Day Discharge in Primary Total Hip Arthroplasty.
INTRODUCTION Same-day discharge (SDD) following primary total hip arthroplasty (THA) is increasingly utilized and has been shown to be safe in appropriately selected patients. However, limited data compare whether specific patient risk factors for postoperative readmission exert different magnitudes of influence in the SDD versus in the non-same-day discharge (NSDD) cohorts. Identifying risk factors that disproportionately affect SDD patients may refine SDD selection criteria and improve postoperative safety.: METHODS: This retrospective cohort study evaluated 11,245 patients who underwent primary elective THA at a single institution between 2017 and 2024. Patients were grouped by discharge timing into SDD (n = 2,318) and NSDD (n = 8,927). The primary outcome was orthopaedic-related hospital readmission within 90 days. Multivariable logistic regression models were constructed separately for SDD and NSDD cohorts to identify independent predictors of readmission. Adjusted odds ratios were compared between cohorts using z-tests to assess differences in effect magnitude. A sub-analysis was performed among cases by high-volume surgeons (≥ 100 THAs/year). RESULTS The SDD patients had a significantly lower 90-day readmission rate compared with NSDD patients (0.8 versus 2.1%, P < 0.001). In SDD patients, smoking (odds ratio (OR) 13.98, P < 0.01) and older age (OR 1.13, P < 0.01) were strongly associated with readmission, while women were protected. In NSDD patients, higher body mass index and American Society of Anesthesiologists score ≥ III increased readmission risk, whereas partner status, higher hemoglobin, and non-White race were protective. Effect-size comparisons demonstrated that smoking (z = 4.34, P < 0.001) and age (z = 3.65, P < 0.001) had stronger associations with readmission in SDD patients than in NSDD patients. Readmission etiologies were similar between groups. Findings were consistent in the high-volume surgeon sub-analysis. CONCLUSIONS While SDD after primary THA is associated with low overall readmission rates, smoking and advanced age confer disproportionately greater readmission risk when same-day discharge is pursued. These findings suggest that smoking status and age may warrant additional attention during preoperative counseling and individualized same-day discharge decision-making, while recognizing that absolute readmission rates remain low.