Motion-preserving devices are one of the most exciting technologies being developed in spine surgery. Cervical disc arthroplasty has taken off in recent years, with long-term data continuing to impress and lumbar artificial disc replacement also gathering momentum.
Three spine surgeons discuss how motion-preserving technologies will affect their specialty in the future.
Question: How will motion-preservation technology evolve in the cervical and lumbar spine?
Brian A. Cole, MD. Englewood (N.J.) Spine Associates: I am encouraged by the clinical response of artificial disc replacement in the cervical and lumbar spine. An extensive knowledge base exists for knee and hip replacement. But unlike the hip and the knee, the spine differs in that there are two other joints to consider in the motion segment: the facet joints. I think motion preservation will progress toward including patients that are not currently candidates. Finding solutions for those patients with advanced arthritis of the facet joints will allow us to provide a "total" disc arthroplasty offering. We will also continue to find better biomaterials that function mechanically, similar to the nucleus pulposus, and mimic the motion segment mechanics of the disc.
Nitin Khanna, MD. Spine Care Specialists (Munster, Ind.): Motion-preservation surgery is shifting the spine market away from fusion and decompression surgeries. The newer technologies are able to restore motion and have gained widespread support. The new cervical disc replacements are now offered in MRI-compatible materials and can be performed on an outpatient basis. This leads to shorter recovery time, faster return to work and durable clinical results. I have continued to push the boundaries of disc replacement surgery and routinely take on selective cases with more advanced pathology. These patients have been very happy with the clinical results and typically drive the decision to maintain motion.
Lumbar disc replacement has been much more elusive, largely from the bad Charité experience. The lateral approach seems to be the most sensible and reproducible approach. Recent attempts at designing a minimally invasive lateral disc replacement have come up short and the lumbar fusion market is too lucrative for a major spine company to shift resources to develop one in house. A successful lumbar disc will likely be built by a startup in Europe and acquired by a top-five player in order to scale. We will have to continue to evolve the material science until we are able to create a biologically expanded disc from the patient's own DNA. I firmly believe that we will see this biological disc technology take hold within five years.
Todd Lanman, MD. Lanman Spinal Neurosurgery and the Advanced Disc Replacement Spinal Restoration Center (Beverly Hills, Calif.): As time goes by, we will see the continued advancement of motion-preservation surgery with more artificial discs being developed. Each will offer different capabilities with varied ranges of motion and core features. Some will have the ability to resist shear forces better than others. Some will allow for greater ranges of motion while others will allow for more compression.
As these cervical and lumbar discs continue to evolve, surgeons will have more choices. Algorithms will be developed to help these surgeons know which ones to use and in which location of the spine, depending upon the patient's anatomy and functionality. In the lumbar spine, we will see a new trial developing with a posterior artificial disc, which can be put in through the back at almost any level. The pilot studies look quite promising.
Similarly, facet joint replacement studies have been off to a soft start, but there seems to be some promise as these continue to evolve. This will replace the three points of motion in the spinal segment, discs and joints. Thus, by maintaining the vertebral body and allowing full motion, we can keep the patient's functional range of motion improved and maximized to optimize their outcomes and benefits.