Understanding Geospatial Trends in Lumbar Fusion Incidence and Technique in Medicare Populations

Study Design. Retrospective study with epidemiologic analysis of public Medicare data. Objective. This study seeks to utilize geospatial analysis to identify distinct trends in lumbar fusion incidence and techniques in Medicare populations. Summary of Background Data. With an aging population and new technologies, lumbar fusion is an increasingly common procedure. There is controversy, however, regarding which indications and techniques achieve optimal outcomes, leading to significant intersurgeon variation and potential national disparities in care. Materials and Methods. Medicare billing datasets were supplemented with Census Bureau socioeconomic data from 2013 to 2020. These databases listed lumbar fusions billed to Medicare by location, specialty, and technique. Hotspots and coldspots of lumbar fusion incidence and technique choice were identified with county-level analysis and compared with Mann-Whitney U. A linear regression of fusion incidence and a logistic regression of lumbar fusion hotspots/coldspots were also calculated. Results. Between 2013 and 2020, 624,850 lumbar fusions were billed to Medicare. Lumbar fusion hotspots performed fusions at nearly five times the incidence of coldspots (101.6-21.1 fusions per 100,000 Medicare members) and were located in the Midwest, Colorado, and Virginia while coldspots were in California, Florida, Wisconsin, and the Northeast. Posterior and posterolateral fusion were the most favored techniques, with hotspots in the Northeast. Combined posterior and posterolateral fusion and posterior interbody fusion was the second most favored technique, predominantly in Illinois, Missouri, Arkansas, and Colorado. Conclusions. The geographic distribution of lumbar fusions correlates with variations in residency training, fellowship, and specialty. The geospatial patterning in both utilization and technique reflects a lack of consensus in the application of lumbar fusion. The strong variance in utilization is a potentially worrying finding that could suggest that the nonstandardization of lumbar fusion indication has led to both overtreatment and undertreatment across the nation. Level of Evidence. Level 3 - retrospective.