Understanding the Influence of Single Payer Health Insurance on Socioeconomic Disparities in Total Hip Arthroplasty (THA) Utilization: A Transnational Analysis

Objective: Access to care varies between countries. It is theorized that income-based disparities in access may be reduced in countries with universal health insurance relative to the United States, but data are currently limited. We hypothesized that income-based differences in total hip arthroplasty (THA) utilization and outcomes would be larger in the United States than in Canada. Methods: We retrospectively compared all patients undergoing THA from 2012 to 2018 in Pennsylvania, the United States, and Ontario, Canada. We compared age-standardized and sex-standardized per-capita THA utilization in the United States and Canada overall and across different income strata, where income strata were defined by neighborhood income quintile. We also examined income-based differences in rates of 1-year revision, 90-day mortality, and 90-day readmission. Results: Overall THA utilization per 10,000 people per year was higher across all income groups in Pennsylvania compared with Ontario (15.1 versus 8.8, P < 0.001 in lowest-income quintile; 21.4 versus 12.6, P < 0.001 in highest-income quintile). Income-based differences in utilization in the highest-income vs lowest-income quintile groups were greater in Ontario (43.2%) than Pennsylvania (41.7%). The adjusted odds for the lowest-income group compared with the highest-income group of 1-year revision were greater in Ontario compared with Pennsylvania (P = 0.03), and risk of 90-day mortality and 90-day readmission was similar between the regions. Conclusion: Income-based differences in THA utilization were more notable in Ontario than in Pennsylvania. In addition, patients in low-income communities in Ontario were at equal or greater risk relative to high-income community patients for adverse outcomes compared with patients in Pennsylvania. Income-based disparities in THA utilization and outcomes were smaller in the United States than in Canada, in contrast to what might be expected. Level of evidence: III