On the back of two-year data comparing the M6-C cervical disc with anterior cervical discectomy and fusion published in The Spine Journal, eight surgeons discuss the future of total disc replacement in spine:
Question: How do you see disc replacement developing in the next five to 10 years?
Brian Cole, MD. Englewood (N.J.) Spine Associates: I think cervical disc replacement is becoming the standard of care for treating degenerative cervical disease now. In my own practice, I perform many more replacement surgeries than fusions. This is primarily because of the outstanding clinical results in terms of pain relief, return to function and patient satisfaction. Today we wouldn't think about fusing a knee or hip, so why are we fusing spines that aren't unstable?
Adam Shimer, MD. UVA Health (Charlottesville, Va.): There will undoubtedly be an increase in use of cervical disc arthroplasty relative to ACDF over the next five to 10 years. With that said, this shift will be evolutionary as opposed to the historical revolutionary explosion of low-friction hip and knee arthroplasty. Hip and knee fusions are pretty terrible whereas ACDF is a darned good procedure. I believe three key facts limit rapid, widespread transition to cervical disc replacement:
1. ACDF is a good surgery with predictable outcomes and a long proven track record.
2. There is more to 'think about' when choosing to do CDR. Just look at the FDA IDE inclusion criteria: DEXA scans, motion evaluation, no prior anterior or posterior surgery, no facet arthropathy.
3. The unknown as to what happens to CDRs 10, 20, 30 years down the line. These are being used in younger patients and we just do not know the longevity of these devices.
With increased use of CDR over the next five to 10 years we will see papers about not only the positive outcomes, but also more reports of complications and limitations.
Frank Phillips, MD. Midwest Orthopaedics at Rush: I have been fortunate to have been close to this field for over a decade and participate in numerous cervical TDR FDA IDE studies. Cervical TDR is arguably one of the best studied procedures in spine care with numerous level 1 studies supporting its effectiveness in appropriately selected patients. We are seeing compelling data favoring their outcomes over ACDF with long-term (10 year) follow-up with first generation design prosthesis, and now excellent data with second generation TDR designs that more closely mimic natural disc kinematics.
In addition, a number of FDA IDE studies with novel disc designs for both one- and two-level indications are starting up. Given the quality of the evidence, most payers are now routinely covering cervical TDR which favorably impacts clinical adoption. As younger surgeons are increasingly exposed to TDR in their training, I would anticipate this becoming an integral part of their treatment algorithms for cervical radiculopathy and myelopathy. I expect that all major spine manufacturers will participate in this space, likely by acquisitions of approved TDR prostheses from smaller companies. Although many indications for cervical fusion remain, with the confluence of events outlined, I anticipate cervical TDR continuing to grow over the next five to 10 years.
Todd Lanman, MD. Lanman Spinal Neurosurgery (Beverly Hills, Calif.): Spine arthroplasty or artificial disc replacement will expand in its usage dramatically over the next 10 years compared to fusion. Nine artificial cervical discs have been FDA approved. Three have already been retired from use as newer devices are continually being developed and tested. There are currently three clinical trials beginning shortly for new types of artificial discs for the neck and low back.
Artificial disc replacements will become routinely used, superseding fusion as the standard of care over the next five to 10 years. The parallel is quite similar to that which was seen in the past with severe arthritic and degenerative hips and knees, where these were routinely being fused.
Now, no one would even contemplate having their knees or hips fused. They would opt for an artificial hip or knee replacement. In fact, artificial discs for the spine offer even better long-term data demonstrating they will not fail for likely over 70 years. These implants, if placed properly by an experienced spine surgeon, provide excellent relief of cervical or neck pain, arm pain, and low back pain and leg pain in the lumbar region. They maintain mobility and motion of the spine, which is an imperative component to maintaining an active, functional lifestyle.
Adam Bruggeman, MD. Texas Spine Care Center (San Antonio) and CMO of MpowerHealth (Addison, Texas): The future of disc replacement will depend on studies looking at more commonly performed surgeries, such as those on patients with prior fusions at other levels and those with multiple levels that need to be performed. Over the next five to 10 years, I see further adoption of disc replacement as well as additional studies looking at more common situations seen in day-to-day practices. I also anticipate implant designs will adjust for these evolving indications to include multiple options to address stability as well as endplate variations.
Brian Gantwerker, MD. Craniospinal Center of Los Angeles: We are coming to a time when cervical arthroplasty will become as prevalent and reproducible as knee and hip replacements. Disc replacement has become a legitimate alternative to cervical fusion and, in many cases, is a better choice. Although the exact 'special sauce' of semi-constrained, constrained, keel, no-keel remains to be elucidated, many patients have and will continue to benefit from motion-preservation surgery.
There are many different choices in the arthroplasty market; most coming from big box spinal instrumentation companies. There are some smaller, boutique companies and the competition fostered will undoubtedly make the tech increasingly reliable and less expensive. Since most insurance companies will remunerate for this legitimate approach to treating cervical neck pain and radiculopathy/myelopathy, it will become a more accessible alternative to fusion. In the next five to 10 years, I predict about 50 percent to 60 percent of anterior cervical surgeries will be arthroplasty.
Multilevel surgeries will also become more prevalent, amongst surgeries. There will be a demand in the U.S. for reliable outcomes data in two- and three-level arthroplasty. Some surgeons are already performing them, and are reporting some outcomes, but I still think reliable data will more fully support the practice.
Lastly, the hybrid construct, an often-overlooked and sidelined technique, combining both fusion and arthroplasty in the same patient at different levels, will also become more frequent. This is an excellent way to treat levels that are different time points in degenerative progression. There is already a growing body of peer-reviewed research, and it would be beneficial for additional studies to be done to flesh out its roles in cervical spine surgery. It is the surgeon's mandate to reduce pain and suffering. Cervical disc replacement reduces future operations, decreases opioid use and sometimes is a more effective surgery, especially in the young. In the future, arthroplasty technologies will match and perhaps surpass the reliable successes seen in other forms of joint replacement.
Lali Sekhon, MD, PhD. Reno (Nev.) Orthopedic Center: I think cervical arthroplasty will continue to grow. I've been involved with cervical arthroplasty since 2000 and the original indications still stand: soft disc herniation, one to two levels with less than 50 percent loss of disc height for concordant radiculopathy or myelopathy, in the absence of facet disease. Correction of deformity, it's place in the aging population (average age in most [investigational device exemptions] was early 40s), use for severe spondylotic disease are still issues. There will always be a place for spinal fusion. Material choices for fusion may fill the gap between arthroplasty so that different stiffness implants can be used. With the plethora of devices available, it's not so much which device is used (they all work in the forgiving cervical spine), it's patient selection. Lumbar arthroplasty may be revisited by lateral approaches.
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.