Background: Given the dramatic increase in total knee and hip replacement procedures among the US population aged 45 years and older, there is a need to compare the downstream healthcare utilization and costs between patients who undergo joint replacement and those who receive intraarticular injections as a low-cost alternative.
Objective: To compare changes in osteoarthritis (OA)-related healthcare utilization and costs for Medicare members with OA who underwent knee or hip replacement versus those receiving steroid or viscosupplementation injections.
Methods: Medicare members aged ≥45 years diagnosed with OA were identified for this retrospective longitudinal study. Data were compared for patients who underwent primary knee or hip replacement surgery between July 1, 2007, and June 30, 2012, and those receiving injection of pain-relief medication during the same period. The date of joint replacement surgery was considered the index date. For the comparison cohort, the index date was 180 days postinjection of the first intraarticular injection. Medical and pharmacy claims were examined longitudinally in 90-day increments, from 180 days preindex until 360 days postindex. Difference-in-difference analyses were conducted to compare the change in OA-related healthcare costs, postindex versus preindex, between the study cohorts. Time-to-event analyses were used to measure rates of readmissions and venous thromboembolism (VTE).
Results: The mean age was 70.7 years for patients with knee replacement, 71.7 years for those with hip replacement, and 71.1 years for those receiving pain-relief injection (P <.0001). The RxRisk-V comorbidity index scores were 4.7, 4.4, and 4.8, respectively (P <.0001). Difference-in-difference analyses indicated that decreases in OA-related costs were greater for the joint replacement cohorts (coefficient for knee replacement*time: -0.603; hip replacement*time: -0.438; P <.001 for both) than for the comparison cohort. The VTE rates were 5.6% (knee) and 5.1% (hip) postsurgery versus 1.4% (knee) and 1.3% (hip) presurgery.
Conclusion: The overall difference-in-difference results showed a greater decrease in healthcare utilization and costs for the members with joint replacement than for those receiving injection.
Keywords: difference-in-difference analysis; healthcare costs; healthcare utilization; hip replacement; intraarticular glucocorticoid injection; knee replacement; osteoarthritis; viscosupplementation.