High-volume spine surgery center costs and resource utilization: a database study of 142,617 Medicare claims in 2019

With the advent of bundled payments in spine surgery, there is increasing emphasis on value-based care. Although there is substantial literature on economies of scale in total joint arthroplasty, there remains a paucity of literature in spine surgery. The purpose of this study was to assess the impact of hospital volume on cost, length of stay (LOS), and discharge destination after elective inpatient spine surgery procedures in a Medicare population.

The 2019 Medicare Provider Analysis and Review Limited Data Set and Centers for Medicare and Medicaid Services 2019 Impact File were used in this study. Diagnosis-related group codes were used to identify 5 spine surgery cohorts consisting of nonfusion surgery, cervical fusion, noncervical fusion, anterior-posterior fusion, and complex fusion. Elective non-Medicare Advantage patients were included (n = 142,617). Patients were grouped according to low (1-100 cases; n = 51,685 [36%]), medium (101-200 cases; n = 44,145 [31%]), and high (≥ 201 cases; n = 46,787 [33%]) hospital volume. Hospital costs were calculated using cost-to-charge ratios. Multivariate models were created to evaluate associations between hospital volume and total hospital cost, hospital LOS, and discharge destination, controlling for confounders (type of surgery, complications, demographics, comorbidities, surgical details, and hospital details).

In the univariate analysis of primary outcomes, high-volume spine centers were associated with greater cost (p < 0.001) and longer LOS (p < 0.001), and medium-volume spine centers were associated with a lower incidence of nonhome discharge (p < 0.001), compared with low-volume hospitals. However, in the multivariate analysis, increasing hospital volume was associated with decreasing cost (medium volume -$882 vs high volume -$1764, p < 0.001), decreasing LOS (medium volume -0.066 days vs high volume -0.132 days, p < 0.001), and decreasing risk of nonhome discharge (adjusted OR 0.809 [95% CI 0.783-0.836], p < 0.001 for medium volume; 0.746 [95% CI 0.721-0.772], p < 0.001 for high volume).

Increased hospital volume was independently associated with lower costs, shorter LOS, and decreased risk of nonhome discharge after elective inpatient spine surgery. High-volume centers might benefit from economies of scale and lean methodology practices that should be studied to improve value on a national level. Small and medium hospitals could be disproportionately impacted by declining Medicare reimbursements. Further study is necessary to provide fair reimbursement adjustments as bundled payments for spine surgery are introduced.