Is the current insurance structure leading to seasonality in demand for spinal surgery? A quarterly, yearly, and insurance based analysis

Background: Elective lumbar fusion is a commonly employed procedure for degenerative lumbar spine disease. With healthcare costs rising reimbursement for procedures may be restricted by payers. Additionally, patients may undergo elective fusion once deductibles are covered, typically in the fourth quarter in a given year. The objective of this study was to analyze the trends in utilization for posterior lumbar fusion (PLF) earlier in the year (Q1-Q3) as compared to the end of the year(Q4). Variations in this proposed trend by insurance type were also studied as a primary outcome. Methods: We queried the Healthcare Cost and Utilization Project-National Inpatient Sample (HCUP-NIS) between January 1, 2012 and December 31, 2014 for patients diagnosed with lumbar disc degenerative disease (DDD). Outcomes of interest included utilization and frequency of PLF. Results: 221,466 patients hospitalized with Lumbar DDD between 2012 and 2014 were identified. Of these, 67,343(30.4 %) underwent a PLF procedure. The likelihood of lumbar fusion in patients hospitalized with DDD was significantly higher in the 4th quarter, compared to 1st quarter (OR1.13, p < 0.001). Marginal effect analysis indicated that Medicare patients were 1.0 % more likely to undergo PLF in quarter 4 compared to quarters 1−3 (p = 0.003), while privately insured patients were 2.5 % more likely to undergo PLF in quarter 4 compared to quarters 1-3(p < 0.001). Conclusion: These results indicate that utilization of PLF is higher at the end of the year relative to the beginning, especially for patients with private insurance. This may be due to deductibles that have previously been paid off, lowering out-of-pocket expenses.