OBJECTIVE: To evaluate the Maryland All-Payer Model's impact on the rate of elective major joint replacement surgery. STUDY DESIGN: A retrospective cohort study of patients in Maryland undergoing elective major joint replacement between 2011 and 2018 was performed using a 20% fee-for-service Medicare sample in a difference-in-difference framework with patients undergoing hip fracture repair serving as controls. METHODS: Among Maryland residents, there were 7147 Medicare fee-for-service patients undergoing elective major joint replacement and 1008 Medicare fee-for-service beneficiaries undergoing hip fracture repair. We used patient-level generalized linear models with a negative binomial family function and a log link function to estimate the association of the All-Payer Model with the rate of elective major joint replacement surgery. RESULTS: Under the All-Payer Model, the rate of elective major joint replacement surgery increased more than that of hip fracture repair (adjusted relative risk, 1.31
95% CI, 1.15-1.51). Compared with hospitals without affiliates in adjacent states (Maryland-only hospitals), those with affiliates (Maryland hospitals with affiliates) saw rates of elective major joint replacement grow more slowly (adjusted relative risk, 0.87
95% CI, 0.80-0.95) after the All-Payer Model. Furthermore, major joint replacement rates for Maryland residents at affiliated hospitals in adjacent states increased from 4.26 per 10,000 in the preintervention period to 5.23 per 10,000 in the postintervention period. CONCLUSIONS: Under the All-Payer Model, population-based rates of elective major joint replacement surgery increased more rapidly than did rates of hip fracture repair. Although rates of major joint replacement at Maryland hospitals with affiliates grew more slowly than for Maryland-only hospitals, rates among Maryland residents increased at the affiliates in adjacent states.