Introduction: Socioeconomic factors such as poverty may mediate racial disparities in health outcomes after total hip arthroplasty (THA) and confound analyses of differences between blacks and whites.
Methods: Using a large institutional THA registry, we built models incorporating individual and census tract data and analyzed interactions between race and percent of population with Medicaid coverage and its association with 2-year patient-reported outcomes.
Results: Black patients undergoing THA had worse baseline and 2-year pain and function scores compared with whites. We observed strong positive correlations between census tract Medicaid coverage and percent living below poverty (rho = 0.69; P < 0.001). Disparities in 2-year Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function were magnified in communities with high census tract Medicaid coverage. For blacks in these communities, 2-year WOMAC function scores were predicted to be -5.54 points lower (80.42 versus 85.96) compared with blacks in less deprived communities, a difference not observed among whites.
Conclusion: WOMAC pain and function 2 years after THA are similar among blacks and whites in communities with little deprivation (low percent census tract Medicaid coverage). WOMAC function at 2 years is worse among blacks in areas of higher deprivation but is not seen among whites.
Level of evidence: Level II - Cohort Study.