Background and objectives Inpatient shoulder arthroplasty is widely performed around the USA at an increasing rate. Medicaid insurance has been identified as a risk factor for inferior surgical outcomes. We sought to identify the impact of being Medicaid-insured on in-hospital mortality, readmission, complications, and length of stay (LOS) in patients who underwent inpatient shoulder arthroplasty.

Methods We analyzed 89 460 patient discharge records for inpatient total, partial, and reverse shoulder arthroplasties using data from the Healthcare Cost and Utilization Project’s State Inpatient Databases for California, Florida, New York, Maryland, and Kentucky from 2007 through 2014. We compared patient demographics, present-on-admission comorbidities, and hospital characteristics by insurance payer. We estimated multilevel mixed-effect multivariate logistic regression models and generalized linear models to assess insurance’s effect on in-hospital mortality, readmission, infectious complications, cardiac complications, and LOS; models controlled for patient and hospital characteristics.

Results Medicaid-insured patients had greater odds than patients with private insurance, other insurance, and Medicare of inpatient mortality (OR: 4.61, 95% CI 2.18 to 9.73, p<0.001) and 30-day and 90-day readmissions (OR: 1.94, 95% CI 1.57 to 2.38, p<0.001; OR: 1.65, 95% CI 1.42 to 2.38, p<0.001, respectively). Compared with private insurance, other insurance, and Medicare patients, Medicaid patients had increased likelihood of developing infectious complications and were expected to have longer LOS.

Conclusions Our study supports our hypothesis that among inpatient shoulder arthroplasty patients, those with Medicaid insurance have worse outcomes than patients with private insurance, other insurance, and Medicare. These results are relatively consistent with previous findings in the literature.