Poster Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Introduction: Once reserved primarily for spinal deformity, vertebral cancer, and fracture, lumbar spinal fusion has evolved into a procedure commonly used for degenerative spine pathology. We update prior epidemiological reports of the U.S. trends in rates and volume of lumbar spinal fusion by adding recent years (2016 - 2021), and by describing trends in vertebral columns fused, outpatient lumbar fusion, and associated costs.

Methods: We analyzed the Healthcare Cost and Utilization Project’s National Inpatient Sample (NIS), 2002-2021, and the Nationwide Ambulatory Surgical Sample (NASS), 2016-2021, administered by the Agency for Healthcare Research and Quality. A combination of International Classification of Disease (ICD) procedure codes and Current Procedural Terminology Codes (CPT) were used to identify lumbar fusion operations, providing a U.S. population-based representative sample of patients undergoing inpatient and outpatient lumbar fusion surgery. Adjusted annual trends in rates (per 100,000 U.S. adults, age 20+) and volumes for both inpatient and outpatient lumbar fusion were reported based on a survey-weighted Poisson regression with the U.S. Census as a denominator. We classified admissions based on Medicare definitions to describe the percent of total fusion by vertebral columns fused (anterior, posterior, combined), setting (inpatient, outpatient), and surgical indication (disc degeneration, disc herniation, stenosis, spondylolisthesis, scoliosis, other). Finally, after applying cost-to-charge ratios, we used a generalize linear regression to estimate trends in hospital costs by columns fused, adjusted for age, sex, indication, comorbidity, and inflation.

Results: Per 100,000 adults, the U.S. rate of inpatient and outpatient lumbar fusion increased from 247 in 2002 to a high of 546 in 2018, before a substantial decline through 2021, likely related to COVID-19. We observed a strong shift towards fusion among the older population. In addition, although a small percent of the total, fusion performed in the hospital outpatient setting increased sharply in 2021, with over 30,000 procedures (or 5 per 100,000), consistent with removal from Medicare’s inpatient only list. Combined anterior-posterior column fusions rapidly increased as a proportion of total fusions, from 24.8% in 2016 to 48.9% in 2021, and with a commensurate decline in single column fusions. Mean, inflation-adjusted, inpatient facility cost per case increased from $31,784 (95% CI $31,542–$32,026) in 2002 to $79,219 (95%CI $78,616-$79,822) in 2021. Mean cost for AP column fusion $86,768 (95%CI $85,839-$87,696) were significantly greater (p<0.001) than anterior column $72,136 (95%CI $70,993–$73,278) or posterior $70,023 (95%CI $69,014–$71,032) column fusions in 2021.

Discussion: Combined AP column fusions have surpassed single column lumbar fusions in the U.S., which are increasingly being performed in an older population. Limited existing evidence suggests a minimal incremental benefit in terms of improved patient outcomes for these higher cost procedures. Future research is needed to examine whether they result in improved patient-reported outcomes, reduce harm and improve value.