Background: Medicaid payer status has been shown to affect risk-adjusted outcomes and resource utilization across multiple medical specialties. The purpose of this study was to examine resource utilization via readmission rates, length of stay, and total cost specific to Medicaid payer status following primary total hip arthroplasty. Methods: The Nationwide Readmissions Database (NRD) was utilized to identify patients who underwent total hip arthroplasty in 2013 as well as corresponding “Medicaid” or “non-Medicaid” payer status. Demographic data, 14 individual comorbidities, readmission rates, length of stay, and direct cost were evaluated. A propensity-score-based matching model was utilized to control for baseline confounding variables between payer groups. Following propensity-score matching, the chi-square test was used to compare readmission rates between the 2 payer groups. The relative risk (RR) with 95% confidence interval (CI) was estimated to quantify readmission risk. Length of stay and total cost comparisons were evaluated using the Wilcoxon signed-rank test. Results: A total of 5,311 Medicaid and 144,814 non-Medicaid patients managed with total hip arthroplasty were identified from the 2013 NRD. A propensity score was estimated for each patient on the basis of the available baseline demographics, and 5,311 non-Medicaid patients were matched by propensity score to the 5,311 Medicaid patients. Medicaid versus non-Medicaid payer status yielded significant differences in overall readmission rates of 28.8% versus 21.0% (p < 0.001; RR = 1.37 [95% CI, 1.28 to 1.46]) and 90-day hip-specific readmission rates of 2.5% versus 1.8% (p = 0.01; RR = 1.38 [95% CI, 1.07 to 1.78]). Mean length of stay was greater in the Medicaid group than in the non-Medicaid group at 4.5 versus 3.3 days (p < 0.0001), as was the mean total cost at $71,110 versus $65,309 (p < 0.0001). Conclusions: This study demonstrates that Medicaid payer status is independently associated with increased resource utilization, including readmission rates, length of stay, and total cost following primary total hip arthroplasty. Providers may have a disincentive to treat patient populations who require increased resource utilization following surgery. Risk adjustment models accounting for Medicaid payer status are necessary to avoid decreased access to care for this patient population and to avoid financial penalty for physicians and hospitals alike. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: Diabetes is a well-established risk factor for complications following total knee arthroplasty (TKA), and the incidence of type-2 diabetes is increasing. Metformin is considered first-line therapy for type-2 diabetes and has been shown to reduce all-cause mortality and to possess anti-inflammatory properties. The impact of metformin use as it relates to outcomes following TKA is unknown. The purpose of this study was to investigate this relationship. Methods: This is a retrospective cohort study using the Truven MarketScan database. Adult patients undergoing unilateral, primary TKA were identified. We included only patients with a preoperative diagnosis of type-2 diabetes and established 2 cohorts based on metformin status. Propensity score matching was performed to match patients who used metformin to those who did not (1-to-1). Patients were matched on factors including age, sex, insulin status, other diabetic medications, comorbidities, complexity of diabetes, and smoking status. Regression analysis was then performed on matched cohorts to examine 90-day outcomes. A subgroup analysis was performed on 1-year revision rates. Results: After matching, there were 32,186 patients in both the metformin group and the no-metformin group, resulting in a total of 64,372 included patients. Baseline characteristics were similar between groups. Regression analysis, performed on matched cohorts, demonstrated that the no-metformin group had increased odds of readmission (odds ratio [OR], 1.09 [95% confidence interval (CI), 1.04 to 1.15]; p < 0.001), emergency department presentation (OR, 1.09 [95% CI, 1.04 to 1.14]; p < 0.001), extended length of stay (OR, 1.12 [95% CI, 1.06 to 1.15]; p < 0.001), periprosthetic joint infection (OR, 1.30 [95% CI, 1.13 to 1.50]; p < 0.001), deep vein thrombosis (OR, 1.17 [95% CI, 1.09 to 1.26]; p < 0.001), acute kidney injury (OR, 1.21 [95% CI, 1.09 to 1.33]; p < 0.001), hypoglycemic events (OR, 1.25 [95% CI, 1.01 to 1.54]; p = 0.039), and 1-year revision (OR, 1.16 [95% CI, 1.01 to 1.33]; p = 0.033). Conclusions: Metformin use in patients with type-2 diabetes undergoing TKA appears to be associated with lower odds of multiple complications and resource utilization parameters, including periprosthetic joint infection and 1-year revision rates. Given the frequency with which TKA is performed in patients with type-2 diabetes, this knowledge has the potential to improve optimization protocols and outcomes in this group of patients. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.