The Effect of Medicaid Expansion on Rates of Carpal Tunnel Release: An Interrupted Time Series Analysis

Background: Medicaid expansion through the Affordable Care Act (ACA) has been associated with greater access to and utilization of surgical services in underserved populations. However, its impact on use of hand surgical care is less understood. The purpose of this study was to evaluate the association between New York State adoption of the ACA and carpal tunnel release (CTR) procedural volume in Medicaid beneficiaries. Methods: The authors conducted a pooled cross-sectional analysis of patients who underwent CTR using the Healthcare Cost and Utilization Project New York State all-payer database (2010 through 2018). An interrupted time series analysis using an autoregressive integrated moving average model estimated the immediate and long-term impact of Medicaid expansion in January of 2014 on CTR procedural volume in Medicaid beneficiaries and uninsured individuals. Results: A total of 112,569 patients were included in the sample. After expansion, the authors observed an absolute increase of 6% in the share of CTR procedures provided to Medicaid beneficiaries. Policy implementation was associated with an immediate 1.81% increase (95% CI, 0.0085, 0.0277; P < 0.001) in the probability of Medicaid as the primary payer and an annual increase of 1.68% (95% CI, 0.0134, 0.0202; P < 0.001) after reform. Interrupted time series analysis found that this resulted in 4190 additional CTR procedures in Medicaid beneficiaries than predicted without expansion. Conclusions: The study results suggest that New York's adoption of the ACA was associated with an immediate and steady increase in use of outpatient CTR in Medicaid beneficiaries. Most of this increase represented newly treated patients rather than those who were previously uninsured.