Is Civilian Hospital Treatment of Lumbar Spinal Disorders Associated With Greater Odds of Fusion Procedures?

BACKGROUND: Technological advancements in spine surgical care are disproportionately slanted toward fusion-based procedures, which may influence surgeons to prefer these over other less expensive techniques. These issues may be particularly magnified within the context of integrated care delivery systems such as the Military Health System, where patients can be treated at centers with different philosophies regarding care or manner of provider reimbursement (direct care Department of Defense facilities versus the private sector) within the same network. Understanding how these factors may influence the preferential use of lumbar fusion could better inform healthcare expenditures and the cost-efficiency of spine surgical care. QUESTIONS/PURPOSES: (1) Compared with direct care models (Department of Defense facilities), does the private sector (civilian hospitals) have higher odds of performing interbody fusion versus other procedures for the surgical treatment of lumbar spine conditions? (2) For spinal conditions such as disc herniation, radiculopathy, spondylolisthesis, and spinal stenosis, are there higher odds of interbody fusion and posterolateral fusion in the private sector? METHODS: We used TRICARE healthcare claims to retrospectively compare surgical care delivery between direct and private sector care (October 2015 to September 2023). The population covered by TRICARE has previously been shown to be representative of the US demographic ages 18 to 64 years, while the unique tiered nature of the system serves as a model of care delivery that is translatable to civilian integrated hospital networks. Direct care represents a proxy for those academic medical centers with salaried reimbursement; private sector care is representative of community facilities employing fee-for-service models. We included patients 18 years and older surgically treated for a disc herniation, lumbar spinal stenosis, lumbar radiculopathy, and/or spondylolisthesis. There were minimal missing data for the factors of interest. The mean ± SD age of the cohort as a whole was 53 ± 15 years, with 82% (50,747 of 61,735) of the population male and 79% (48,966 of 61,735) White. Lumbar spinal stenosis (42% [25,942 of 61,735]) was the most common surgical indication, followed by disc herniation (30% [18,708 of 61,735]). Overall, and within each lumbar spine disorder (disc herniation, spinal stenosis, radiculopathy, and spondylolisthesis), initial bivariate comparisons were made between type of surgery (decompression, posterolateral fusion, and interbody fusion) and the environment of care using multinomial logistic regression. Adjustments were then made for patient mix using multivariable multinomial logistic regression. RESULTS: After adjusting for confounders such as age, race, gender, medical comorbidities, sponsor rank, and census region, compared with the direct care environment, lumbar surgical procedures in the private sector had higher odds of using interbody fusion (OR 1.19 [95% CI 1.13 to 1.26]; p < 0.001). For disc herniation, posterolateral fusions (OR 3.78 [95% CI 2.60 to 5.50]; p < 0.001) were performed to a greater degree in the private sector, as was also the case for radiculopathy (OR 2.62 [95% CI 1.76 to 3.89]; p < 0.001). For spinal stenosis, posterolateral fusions (OR 2.84 [2.45 to 3.29]; p < 0.001) and interbody fusions (OR 1.71 [1.56 to 1.88]; p < 0.001) were performed to a greater extent in the private sector. CONCLUSION: We found greater use of fusion-based procedures for lumbar spinal disorders, irrespective of the clinical condition, in the private sector. An increased reliance on community facilities and ambulatory care centers may disproportionately influence the use of spinal fusion. Changes in payment models and establishing centers of excellence could potentially mitigate these issues. LEVEL OF EVIDENCE: Level III, therapeutic study.