Eight surgeons discuss the future of motion preservation in the cervical and lumbar spine and how its development will affect spinal fusion.
Ask Spine Surgeons is a weekly series of questions posed to spine surgeons around the country about clinical, business and policy issues affecting spine care. We invite all spine surgeon and specialist responses.
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Note: The following responses were lightly edited for style and clarity.
Question: How do you see motion-preservation technology developing in spine?
Colin Haines, MD. Virginia Spine Institute (Reston, Va.): I firmly believe that motion-preserving spinal implants, most notably including cervical and lumbar disc replacements, will continue to grow over the next few years. Although the indications for disc replacement are more specific than spinal fusions, more than half of my cervical surgeries are disc replacements. Because the literature on cervical disc replacement is so clear, I do see more potential for growth and advancement in lumbar disc replacement. As the devices improve and data emerge on their longevity, lumbar artificial disc replacement surgery will become more common. However, I don't think it will ever eliminate spinal fusion surgery. Instability, sagittal balance mismatch and scoliosis will be better addressed with stability, which is what spinal fusions achieve. Regardless, the future brings great promise for artificial disc replacement with the continued evolution of this innovative technology.
Brent Kimball, MD. Carepoint Neurosurgery & Spine (Lone Tree, Colo.): I see motion technology in the spine advancing toward implants that allow for better postoperative imaging on MRI and CT. As disc replacement becomes more common and indications expand, the technology of the disc will grow to support not only normal physiological motion, but also varying degrees of constrained motion that can be customized not only to the patient's anatomy and spinal alignment, but also to the amount and type of motion supplied or maintained through disc arthroplasty. In the lumbar spine, indications will develop for ideal endplate angulation to support each particular spine level and coexisting spino-pelvic parameters. Available endplate shapes/sizes and possibly dome sizes will expand to support clinical demand.
Ali Mesiwala, MD. DISC Sports & Spine Center (Newport Beach, Calif.): The human body is designed for movement. The spine is the primary structure through which the nervous system delivers information to the extremities, and it allows us to stand upright and function in daily life. Motion preservation will become the standard in the future. While some patients will continue to need deformity correction and may require substantial operations resulting in rigidity of the spine, technologies are being developed that will allow us to address even these complex situations.
In the same way that disc replacements are built upon the foundation of anterior cervical and anterior lumbar surgeries for fusions, I would expect our basic fundamental surgical techniques to evolve and be adapted to new motion-preservation technologies in the future. It will be increasingly important for surgeons to remain at the forefront of technology and keep an open mind learning new surgical techniques to provide the best care for patients in the future. Patients are also realizing that outpatient surgery centers and private practice facilities may be more nimble in this regard, advancing surgical techniques well before university-based or large tertiary care systems integrate the same technologies.
Lukas Zebala, MD. NorthShore Orthopedic & Spine Institute (Chicago): Motion-preservation technology has been instrumental in changing our treatment paradigm in the cervical and lumbar spine. Cervical disc replacement has revolutionized how spine surgeons are able to provide spinal care for patients with cervical radiculopathy and myelopathy. Our literature now has 10-year follow-up outcomes on FDA-sponsored cervical disc arthroplasty implants that show excellent and durable improvement in patients' quality of life with improved neurological function and reduced pain with reduced need for secondary surgeries compared to anterior cervical discectomy and fusion. Cervical motion-preservation technology is on pace to be considered the gold standard treatment for cervical radiculopathy and myelopathy. The next step in this arena is to expand the surgical indications beyond two contiguous levels of treatment.
Jeremy Smith, MD. Hoag Orthopedic Institute (Irvine, Calif.): Motion preservation is a fundamental concept at the core of nearly all musculoskeletal treatment algorithms whether surgical or not. Technology has advanced and nearly perfected many surgical approaches to orthopaedic joints. The success has depended primarily on the complexity of the biomechanics, the stability of the surrounding bony and soft tissue envelope and the materials available with optimized wear properties. We are in the infancy of motion preservation in the spine. Cervical disc arthroplasty has proven to be as effective as arthrodesis and is becoming more commonplace. As new materials and approaches are developed, the biomechanics may more closely resemble a natural motion segment. Although results from arthrodesis yield good outcomes with regard to pain reduction and quality of life improvement, adjacent segment disease, instability and deformity plague our field. I believe that as the materials advance, so will the ability to preserve motion.
Todd Lanman, MD. Lanman Spinal Neurosurgery (Beverly Hills, Calif.): With motion preservation surgeries and treatment modalities becoming more prevalent and sought after by patients, we will see many advancements in these types of devices. Artificial discs will likely continue to develop with different types of implant polymers that will replicate normal physiologic motion and compressibility of a normal spine to maintain the originally intended anatomic motion. Titanium endplates may also mature with new types of metals that will agree with bone interface matching in a more physiologic way.
With regard to the posterior spine and arthritic facet joints, joint replacements are still under investigation. They have some promise and will certainly become sophisticated enough to provide good mobility and motion as the spine develops. In my opinion, someday we will be able to replace failed joints and discs in the spine, no matter the patient's age or activity level, in order to maintain an active and functional lifestyle.
Brian Gantwerker, MD. Craniospinal Center of Los Angeles: Motion preservation is leaping ahead and will continue to push things forward. We will see more studies looking at two to three and possibly more level disc replacement surgeries and compared head to head to cervical fusion. Payers will be forced to reckon that in many cases, arthroplasty is as good, or superior to multilevel fusion in properly selected patients. In the long run, these patients have better quality of life, less future fusions and an excellent return to life/work profile.
Richard Chua, MD, Northwest NeuroSpecialists (Tucson, Ariz.): I suspect that motion-preservation technology will continue to slowly evolve for cervical spine pathology. [There are] really good implants, instruments, techniques and long-term data currently. This has allowed more payers to allow it to be done. Hopefully more data can be published regarding hybrid indications and more than two-level indications. I doubt that the technology for the lumbar spine will ever dramatically change or increase in penetrance.