AANS Neurosurgeon | Volume 28, Number 3, 2019

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The Science of Spine Surgery

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The development of and greater appreciation of the importance of high-quality clinical research has driven substantial evolution of thought in spine surgery over the last twenty years. Evidence based medicine (EBM) has played an increased role on the development of clinical practice guidelines, payor policy development and the introduction of new technologies. 

Revolutionary Mistakes

In the late 1990’s, cylindrical cages were introduced as interbody implants for use to treat low back pain secondary to degenerative disc disease. These devices were revolutionary in their ease of implantation and their purported capacity to treat a population of patients notoriously unresponsive to traditional therapies. These devices were brought to market and popularized based on very low-quality data consisting of case series published by the developers of the devices and their paid consultants

Around the same time, the use of methylprednisolone as a treatment for acute spinal cord injury was advocated universally and became a de facto “standard of care” based on a set of randomized trials from a single research group.2 While the published results were technically positive, contemporary and retrospective analysis both called into question the importance and overall impact of the drug on patient outcome.3 At the present time, the use of interbody cages to treat axial low back pain and the use of methylprednisolone to treat spinal cord injury have both fallen out of favor. 

These examples illustrate rapidly adopted technologies subsequently discarded with understanding the importance of high-quality evidence

Lessons Learned

The important question is “how did these things become adopted so quickly?” as opposed to “why did they fail to live up to their promise?” What were we (the surgical spine community) thinking when we accepted biased, low-quality evidence as a basis for invasive procedures performed on healthy patients with a disease process known to be extremely difficult to treat? Subsequent non-industry sponsored case series showed significantly worse results than the initial reports.4 How many patients suffered severe consequences or went through unnecessary surgery before we came to our senses? In the case of methylprednisolone, there really has not been a lot of new data presented. Why did we initially ignore the substantial methodological flaws in the original studies and why did it take decades to acknowledge the limitations of the evidence3,5?

The answers to these questions are complicated. Certainly, financial, political and personal biases played a substantial role in the initial enthusiasm for these treatment strategies. The fact that the spine community was relatively naive with regard to the interpretation of evidence played an important and enabling role. Beginning in the mid to late 1990’s, the leadership of AANS/CNS Section on Disorders of the Spine and Peripheral Nerves (the section), recognized the need for a more sophisticated and in-depth analysis of new and existing therapies and technologies. The sections’ guidelines committee was born and was tasked with bringing the principles of Evidence Based Medicine (EBM) to the world of spine surgery. The initial charge was cervical spinal cord injury and subsequent topics have included in depth reviews of:

As the section moved forward with this initiative its’ processes were popularized and embraced by other neurosurgical specialties as well as the North American Spine Society (NASS), which has published a complementary series of spine guidelines written from a multidisciplinary perspective on:

Into the Future: Real Science of Practice

The silver lining that resulted from too rapid adoption of technology included at least three major advances:

1. Education of spine surgeons regarding the importance of clinical trial design and the limits of evidence provided by our literature.

2. In-depth training of a cadre of young leaders in the principles of EBM that were taken back to working committees and academic programs.

3. Increasing sophistication of the spine community’s understanding of the role that bias plays in the design, execution and interpretation of clinical trials.

It has become clear that while a randomized trial represents the potentially ideal design for answering therapeutic questions, such trials remain at substantial risk for bias and need to be interpreted with caution prior to the introduction of new technologies.14 

Having witnessed the growth in sophistication of the spine surgeon consumer base I remain optimistic about the continued participation of spine surgeons in the development, interpretation and application of new science to guide the future of our specialty.

References

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1. Kuslich, S. D., Danielson, G., Dowdle, J. D., Sherman, J., Fredrickson, B., Yuan, H., & Griffith, S. L. (2000). Four-Year Follow-up Results of Lumbar Spine Arthrodesis Using the Bagby and Kuslich Lumbar Fusion Cage. Spine, 25(20), 2656-2662.

2. Bracken, M. B., Shepard, M. J., Holford, T. R., Leo-Summers, L., Aldrich, E. F., Fazl, M., . . . Young, W. (1998). Methylprednisolone or tirilazad mesylate administration after acute spinal cord injury: 1-year follow up. Journal of Neurosurgery, 89(5), 699-706.

3. Hurlbert, R. J., Hadley, M. N., Walters, B. C., Aarabi, B., Dhall, S. S., Gelb, D. E., . . . Theodore, N. (2015). Pharmacological Therapy for Acute Spinal Cord Injury. Neurosurgery, 76.

4. Button, G., Gupta, M., Barrett, C., Cammack, P., & Benson, D. (2005). Three- to six-year follow-up of stand-alone BAK cages implanted by a single surgeon. The Spine Journal, 5(2), 155-160.

5. Hadley, M.N., Walters, B.C., Grabb, P.A., Oyesiku, N.M., Przybylski, G.J., Resnick, D.K., Ryken, C., & Mielke, D.H. (2002). Guidelines for the management of acute cervical spine and spinal cord injuries. Clinical Neurosurgery, 49, 407-98.

6. Resnick, D. K., Choudhri, T. F., Dailey, A. T., Groff, M. W., Khoo, L., Matz, P. G., . . . Hadley, M. N. (2005). Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 1: Introduction and methodology. Journal of Neurosurgery: Spine, 2(6), 637-638.

7. Resnick, D. K. (2006). Evidence-based guidelines for the performance of lumbar fusion. Clinical Neurosurgery, 53, 279-284.

8. Matz, P. G., Holly, L. T., Mummaneni, P. V., Anderson, P. A., Groff, M. W., Heary, R. F., . . . Resnick, D. K. (2009). Anterior cervical surgery for the treatment of cervical degenerative myelopathy. Journal of Neurosurgery: Spine, 11(2), 170-173.

9. Kaiser, M. G., Eck, J. C., Groff, M. W., Watters, W. C., Dailey, A. T., Resnick, D. K., . . . Ghogawala, Z. (2014). Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 1: Introduction and methodology. Journal of Neurosurgery: Spine, 21(1), 2-6.

10. Kreiner, D. S., Hwang, S. W., Easa, J. E., Resnick, D. K., Baisden, J. L., Bess, S., . . . Toton, J. F. (2014). An evidence-based clinical guideline for the diagnosis and treatment of lumbar disc herniation with radiculopathy. The Spine Journal, 14(1), 180-191.

11. Bono, C. M., Ghiselli, G., Gilbert, T. J., Kreiner, D. S., Reitman, C., Summers, J. T., . . . Lamer, T. (2011). An evidence-based clinical guideline for the diagnosis and treatment of cervical radiculopathy from degenerative disorders. The Spine Journal, 11(1), 64-72.

12. Watters, W. C., Bono, C. M., Gilbert, T. J., Kreiner, D. S., Mazanec, D. J., Shaffer, W. O., . . . Toton, J. F. (2009). An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spondylolisthesis. The Spine Journal, 9(7), 609-614.

13. Watters, W. C., Baisden, J., Gilbert, T. J., Kreiner, S., Resnick, D. K., Bono, C. M., . . . Toton, J. F. (2008). Degenerative lumbar spinal stenosis: An evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis. The Spine Journal, 8(2), 305-310.

14. Resnick, D. K. (2019). Show me the evidence: Dealing with bias in the medical literature. The Spine Journal, 19(1), 2-7.

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