Background Total hip arthroplasty (THA) is one of the most widely performed surgical procedures in the USA. Safety net hospitals, defined as hospitals with a high proportion of cases billed to Medicaid or without insurance, deliver a significant portion of their care to vulnerable populations, but little is known about the effects of a hospital’s safety net burden and its role in healthcare disparities and outcomes following THA. We quantified safety net burden and examined its impact on in-hospital mortality, complications and length of stay (LOS) in patients who underwent THA.

Methods We analyzed 500 189 patient discharge records for inpatient primary THA using data from the Healthcare Cost and Utilization Project’s State Inpatient Databases for California, Florida, New York, Maryland and Kentucky from 2007 to 2014. We compared patient demographics, present-on-admission comorbidities and hospital characteristics by hospital safety net burden status. We estimated mixed-effect generalized linear models to assess hospital safety burden status’ effect on in-hospital mortality, patient complications and LOS.

Results Patients undergoing THA at a hospital with a high or medium safety net burden were 38% and 30% more likely, respectively, to die in-hospital compared with those in a low safety net burden hospital (high adjusted OR: 1.38, 95% CI 1.10 to 1.73; medium adjusted OR: 1.30, 95% CI 1.07 to 1.57). Compared with patients treated in hospitals with a low safety net burden, patients treated in high safety net hospitals were more likely to develop a postoperative complication (adjusted OR: 1.11, 95% CI 1.00 to 1.24) and require a longer LOS (adjusted IRR: 1.06, 95% CI 1.05, 1.07).

Conclusions Our study supports our hypothesis that patients who underwent THA at hospitals with higher safety net burden have poorer outcomes than patients at hospitals with lower safety net burden.