Socioeconomic Disadvantage, Body Mass Index, Rurality and Postoperative Outcomes Following Hip and Knee Arthroplasty in a Regional Australian Cohort

BACKGROUND: Socioeconomic disadvantage, body mass index (BMI) and geographic location influence healthcare access and outcomes. This study examined associations between socioeconomic status, rurality and BMI with outcomes following total hip arthroplasty (THA) and total knee arthroplasty (TKA) in a regional public referral centre. METHODS: A retrospective cohort study of all primary THA and TKA admissions between 2017 and 2024 was performed. Variables included socioeconomic indices (SEIFA), rurality (Modified Monash Model classification), age, sex and BMI. The primary outcome was unplanned 90-day readmission. Secondary outcomes were length of stay (LOS) and intensive care unit (ICU) admission. Multivariate regression was performed. LOS was analysed as a continuous variable, and BMI and socioeconomic indices were modelled continuously to assess dose-response relationships. RESULTS: A total of 3364 admissions were analysed (1862 THA; 1502 TKA). Mean age was 66.63 years (THA) and 69.22 years (TKA). Mean BMI was 30.87 and 34.02, respectively. Increasing BMI demonstrated a dose-response association with 90-day readmission, with a stronger effect in THA (OR 1.08, p < 0.01) than TKA (OR 1.03, p = 0.05). Increasing age and BMI were independently associated with longer LOS in both cohorts (all p < 0.01). Socioeconomic disadvantage was associated with longer LOS in THA (p < 0.01) but not TKA. Higher BMI was associated with ICU admission in both cohorts (THA p = 0.01; TKA p = 0.02). CONCLUSION: In this regional arthroplasty cohort, obesity was associated with increased readmission and longer LOS, while socioeconomic disadvantage was associated with longer LOS. Rurality was not associated with LOS or readmission.