Outcomes for Single-Level Lumbar Fusion

Abstract

Study Design. Retrospective analysis of a population-based insurance claims data set. Objective. To determine the risk of repeat fusion and total costs associated with bone morphogenetic protein (BMP) use in single-level lumbar fusion for degenerative spinal disease. Summary of Background Data. The use of BMP has been proposed to reduce overall costs of spinal fusion through prevention of repeat fusion procedures. Although radiographic fusion rates associated with BMP use have been examined in clinical trials, few data exist regarding outcomes associated with BMP use in the general population. Methods. Using the MarketScan claims data set, 15,862 patients that underwent single-level lumbar fusion from 2003 to 2007 for degenerative disease were identified. Propensity scores were used to match 2372 patients who underwent fusion with BMP to patients who underwent fusion without BMP. Logistic regression models, Kaplan-Meier estimates, and Cox proportional hazards models were used to examine risk of repeat fusion, length of stay, and 30-day readmission by BMP use. Cost comparisons were evaluated with linear regression models using logarithmic transformed data. Results. At 1 year from surgery, BMP was associated with a 1.1% absolute decrease in the risk of repeat fusion (2.3% with BMP vs. 3.4% without BMP, P = 0.03) and an odds ratio for repeat fusion of 0.66 (95% confidence interval [CI] = 0.47–0.94) after multivariate adjustment. BMP was also associated with a decreased hazard ratio for long-term repeat fusion (adjusted hazards ratio = 0.74, 95% CI = 0.58–0.93). Cost analysis indicated that BMP was associated with initial increased costs for the surgical procedure (13.9% adjusted increase, 95% CI = 9.9%–17.9%) as well as total 1-year costs (10.1% adjusted increase, 95% CI = 6.2%–14.0%). Conclusion. At 1 year, BMP use was associated with a decreased risk of repeat fusion but also increased health care costs.