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The Spine Blog

Sunday, February 24, 2019

Increasing rates of lumbar fusion surgery

The rates of medical procedures have been studied extensively, though the "appropriate rate" of most procedures remains unknown. However, changes in procedure rates can be illuminating and can reflect changes in medical knowledge that affects practice patterns, change in the prevalence of the underlying disease, change in demand for the procedure among patients, and changes in physician reimbursement. To better understand the rate of elective lumbar fusion over time, Dr. Martin and colleagues from Utah analyzed the National Inpatient Sample administrative billing database from 2004-2015. They excluded fusions that extended outside of the lumbar region and those performed for non-elective indications (i.e. trauma, tumor, or infection). After applying their exclusion criteria, they identified over 2 million elective lumbar fusion admissions. Overall, the absolute number of lumbar fusions increased by approximately 60%, and the age- and gender-adjusted rate increased by 32% over the time frame under study. The steepest increase occurred from approximately 2008-10, with rates essentially flat from 2010-2015. After stratifying by age, there was minimal change in the rate of fusion for those under 65 years old, while the rate increased by 73% for those over 65 from 2004-2015. The authors used a validated algorithm to classify the diagnosis for each case as either spondylolisthesis, scoliosis, disk herniation, spinal stenosis, or degenerative disk disease. Approximately 45% of patients had a diagnosis of spondylolisthesis and 12% were diagnosed with scoliosis, both of which are widely accepted indications for fusion. The remaining 43% underwent fusion for spinal stenosis, disk herniation, and degenerative disk disease, diagnoses for which fusion is frequently not indicated. Total hospital costs reached approximately $10 billion in 2004.

This paper did a nice job documenting elective lumbar fusion rates in the United States over a decade. While the overall rate increased modestly over time, there was a major increase in the rate of fusion for elderly patients over 65. The cause of the increased rate in this population is likely multifactorial. It could be related to surgeons being more willing to offer surgery to this more medically fragile group given improvements in anesthesia and post-operative medical care. Additionally, older patients' expectations may have changed over time, and they may have become more enthusiastic to undergo surgery in an effort to preserve function. Another interesting finding is that the rates of fusion for spondylolisthesis and scoliosis have increased, while the rates for diagnoses with more dubious indications have fallen. Whether this is due to an actual change in practice or simply reflects a change in coding patterns cannot be determined from this study. This paper has all of the limitations of large administrative database studies, namely that there were few clinical details available, and the diagnoses were based on billing codes, which could have been inaccurate. Another limitation is that the denominator of patients with the condition for which surgery was being performed was unknown, so the rates were based on age- and sex-adjusted population numbers. It would have been helpful for the authors to have included data on discectomy and laminectomy without fusion to see how those rates have changed alongside the fusion data. Previous studies have suggested that has been no increase in laminectomy rates while fusion rates were increasing. Overall, the data suggest that surgeons may be operating more frequently for evidence-based indications. An alternative, more cynical explanation is that surgeons have simply changed their coding in order to avoid payment problems with insurance companies.

Please read Dr. Martin's paper on this topic in the March 1 issue. What do you think about how frequently lumbar fusion is performed in the United States? Let us know by leaving a comment on The Spine Blog.

Adam Pearson, MD, MS

Associate Web Editor