Uphill battle: The future of disc replacement
Click Here to Manage Email Alerts
Cervical and lumbar disc replacement have shown promising results compared with spinal fusion for the treatment of neck and lower back conditions, but sources said surgical skepticism and insurance barriers have stifled utilization rates.
Brett Freedman, MD, chair of the division of spine surgery at the Mayo Clinic, told Healio | Orthopedics Today that disc replacement is still largely underutilized.
Source: Kris E. Radcliff, MD
“There is a large swath of spine surgeons that do not use it at all,” Freedman said. “Certainly, every surgeon sees someone that is indicated for disc replacement, so there is room for growth.”
However, some spine surgeons, like Jack E. Zigler, MD, of the Texas Back Institute, said that, eventually, longer- term data and patient demand will swing the proverbial spine pendulum in favor of disc replacements.
“Cervical [disc replacement] is taking care of itself. That market is developing and will continue to,” Zigler said. “Lumbar [disc replacement] is a huge opportunity because at some point, the patient base is going to explode just like it did with cervical [disc replacement] where educated patients are going to say, ‘I do not want a fusion, I want a disc replacement.’”
Reoperation rates
One key advantage of disc replacement vs. spinal fusion is the reduction in reoperation rates, according to Freedman.
“Because nonunion can occur with fusion, and that is probably the most common reason for reoperation following a fusion procedure, there clearly is going to be a higher risk of reoperation for fusion compared to disc replacement, and that is borne out,” Freedman said.
Paul C. McAfee, MD, MBA, professor of orthopedic surgery and chief of spinal research at Georgetown University School of Medicine, said the neurological benefits of disc replacement may also decrease reoperation rates.
“There is more of an advantage in cervical disc replacement [vs. spinal fusion], and the reason is the recovery of neurologic function,” McAfee told Healio | Orthopedics Today. “But it is not so much the actual level that you are working on, it is the adjacent levels. And it has been shown in many studies that you reduce the number of reoperations at the adjacent level with a disc replacement compared to fusion.”
Preservation of motion
Disc replacements also allow patients to preserve motion, according to Freedman.
“When you preserve motion with a disc replacement, the disc above and below tend to look similar in appearance over time to how they looked at baseline,” Freedman said. “Whereas when you fuse, the disc above and below may show some progressive degenerative changes, and that is a concern.”
The preservation of motion in one disc may reduce the likelihood of wear in adjacent discs, according to Kris E. Radcliff, MD, CEO of the Spinal Disc Center.
“I tell my patients that keeping some movement in one part of their spine is good because it might help prevent wear and tear on the other parts,” Radcliff told Healio | Orthopedics Today. “In other words, if one spinal disc can still move a bit, it could reduce the chances of problems developing in the nearby discs.”
However, Joseph D. Smucker, MD, orthopedic spine surgeon at Indiana Spine Group and Healio | Orthopedics Today Editorial Board Member, said the benefits of disc replacement on adjacent segments take time to prove.
“A disc arthroplasty could prevent or even delay a future need for surgery at another operative level, and it just takes a long time to prove,” Smucker said. “As we look at our 20-year study, or as other studies have been published that now extend out 5, 10 or more years, it may be that we are going to be able to start to statistically detect that.”
Artificial disc implants
One evolution underway in the disc replacement world is the growth of artificial disc implants, according to Zigler.
“We are just scratching the surface,” Zigler told Healio | Orthopedics Today. “This is an evolving science, and we are in its infancy. At some point, there will be specific designs, specific materials built in for different levels, for men and for women.”
Radcliff said an increased knowledge base regarding each component of artificial disc implants has allowed the space to grow.
“Disc replacement is increasingly sophisticated, bolstered by enhanced sizing options and a more nuanced understanding of the interplay between size, motion and biomechanics. This evolution in technology and knowledge is transforming disc replacement into a versatile, reconstructive modality with a broadening scope of indications,” Radcliff said. “Tailoring the degree of constraint in the artificial disc to the patient’s specific pathology has become feasible, akin to the principles of ligament balancing in joint reconstruction. Our growing proficiency in determining optimal disc sizing and balancing is providing us with more refined and effective strategies in spinal surgery. This marks a significant advancement in our capability to restore spinal function with precision.”
The material of artificial disc implants has also undergone changes, and the next generation of artificial disc implants is on the way, according to Smucker.
“We are seeing novel disc replacements that include ceramics, medical-grade plastics and medical-grade plastics combined with metals such as titanium,” Smucker told Healio | Orthopedics Today. “We are looking at the overall survivorship of those arthroplasty devices in terms of wear, not only in the lab looking at multiple cycles of wear but understanding how wear and wear debris might affect the local operative level and whether or not it causes osteolysis or degeneration of the bone adjacent to it.”
Surgical skepticism
However, skepticism in the surgical community has impeded the growth and utilization of disc replacements, according to Radcliff.
“Artificial disc replacement often faces skepticism within the surgical community. A contributing factor to this hesitancy is that not all surgeons are trained in disc replacement techniques. The training in this area is frequently conducted by industry professionals, especially for residents, fellows and early career surgeons,” Radcliff said. “Consequently, companies that do not have a disc replacement product tend to underemphasize or even criticize this procedure at their educational events, influencing the attitudes of surgeons over time.”
Radcliff added he and a number of his surgical colleagues are involved in designing and testing spine fusion products, such as screws, cages and biologics, which allow surgeons to have fusion products and instruments tailored to their specific preferences, enhancing outcomes in their hands. However, with a limited market for disc replacements, “few surgeons have had the opportunity to contribute to the design of these instruments and products,” according to Radcliff.
“I believe this lack of familiarity could influence a surgeon’s choice to use them, even when financial incentives are not considered,” he said. “For the advancement of disc replacement technology, it is crucial that these devices become more readily modifiable under the FDA’s 510K clearance. This would enable quicker, less cumbersome and less expensive modifications to both the instrumentation and the implants.”
Radcliff also said disc replacement surgery is more technically challenging compared with spinal fusion.
“Surgeons need to exert more effort, including extensive use of intraoperative fluoroscopy, to accurately place disc implants,” Radcliff said. “Despite the additional skill and labor required, the reimbursement for disc replacement is typically lower than for spinal fusion. This financial aspect might sway surgeons’ decisions, particularly in cases where both fusion and disc replacement are viable options. If reimbursement for disc replacement were higher, reflecting its complexity and effort, it might encourage more surgeons to adopt this technique.”
The skepticism coming from the surgeon population seems to also be regionalized, with disc replacement being underutilized and undertaught in certain regions in the United States, mainly the Northeast, Zigler said.
“In Boston, Chicago and parts of New York, there is a wasteland where almost nobody is doing or teaching lumbar disc replacement and few are doing and teaching cervical disc replacement,” Zigler said. “Although, that is getting better.”
Back pain surgery reputation
Part of this skepticism may be due to the reputation of back pain surgery, which has soured the appeal of disc replacement, according to Radcliff. Although many spine surgeons believe back pain cannot be fixed with surgery, Radcliff said spine surgeons are always operating to relieve back pain.
“Every spondylolisthesis, every deformity case has back pain,” said Radcliff. “For us to say that back pain is not a surgical target is disingenuous and incorrect. Many of us have given up on surgical treatments for back pain from degenerative disc disease, although we recognize that it is a common cause of pain and disability. The surgical literature, particularly on disc replacement, is clear that either fusion or disc replacement in properly selected patients results in improved quality of life and reduction of back pain.”
But because treatment for back pain has previously led to unfavorable monetary results for insurance companies, Zigler said, “it is hard to get [insurance companies] to change that culture and dip into the back pain arena.”
“There has been a lot of resistance from insurance companies giving us approval for [lumbar disc replacement],” Zigler said. “We have to spend a lot of time doing appeals and going back and forth with insurance companies, much more so than to get a fusion done.”
Issues with insurance
Even when disc replacement is covered by insurance companies, Zigler said the reimbursement rate is uneven compared with fusion, despite similar outcomes and better reoperation rates in favor of disc replacement.
“Even if everything is the same, just the fact that your reoperation rate is cut in half or in one-third should make you want to do that [procedure], should make patients want that operation, should make insurance companies want to pay for that operation, should make the government want to lean in that direction,” Zigler said. “We just have not seen that happening with lumbar [disc replacement], so it is one of the disappointments and conundrums of all time.”
According to Freedman, there are also insurance authorization issues that linger in the realm of disc replacement.
“Not only do you have the issue of unfair reimbursement, because it is asymmetric, but also it is harder to get a patient approved by many private pay insurers than it would be for a fusion,” Freedman said. “That needs to be resolved through continued push back by surgeons, continued peer-to-peer struggles and continued publications demonstrating noninferiority or superiority to [anterior cervical discectomy and fusion] ACDF in the cervical spine and lumbar fusion in the lumbar spine.”
He added, “As the administrative barriers, including reimbursement or authorization procedures, are lowered, the use of this technology will also increase.”
McAfee said utilization rates follow authorization rates, rather than the strength of data.
“The utilization does not necessarily follow based on the previous indications,” McAfee said. “Utilization right now is limited by insurance carriers, so it does not matter what the data show or what people think. [Insurance carriers] are limiting it because they do not know what their risk is, and they do not know how many are going to be done.”
Lumbar issues
In addition to the preconceptions about lumbar disc replacement, there is uneasiness in the surgical community about the risks associated with the procedure, according to McAfee.
“The main problem with lumbar disc replacement is in the revision case. It is a riskier operation,” McAfee said. “The iliac veins are involved, and it complicates the surgery. Revision surgery on a cervical disc replacement is no big deal at all, but in the lumbar spine it can be a challenge. You cannot get around that.”
Zigler also said there is some reluctance surrounding the comfortability of lumbar disc replacement.
“Not every spine surgeon is comfortable with an anterior lumbar workplace,” Zigler said. “We are not used to working around and repairing the big vessels. That means you have to coordinate your time with an access surgeon, and sometimes it means splitting your fee with an access surgeon.”
Indications, FDA approval
The difficulty in defining the appropriate indications for disc replacements has been another barrier to utilization, according to Smucker.
“Disc arthroplasty in the neck and low back implies that the only pathologic process in the neck or low back is the disc, and that might not be the only issue for the patient,” Smucker said. “An ideal indication for disc arthroplasty is a patient who has disc concerns without significant arthritic or degenerative change in the joints. But unfortunately, many of our patients have all of those concerns rather than just discogenic concerns on presentation, which makes a fusion more attractive for that patient than a disc arthroplasty.”
McAfee also said the slow pace of the review process of the FDA for novel disc replacement designs and devices has been another roadblock for disc replacement. He said it could take up to 10 years to receive approval from the FDA, by which time the device is outdated and in need of improvements that cannot be complete without an investigational device exemption study.
“It is tough when you do all this work, and your device is 10 years out of date the first day it becomes approved. But you cannot get around that until the FDA loosens up a little bit,” McAfee said.
Robotics, navigation
Another hurdle to the use of disc replacements is the lack of robotics and navigational apparatus, according to Radcliff.
“It is surprising that we continue to depend on fluoroscopy, especially for 3D axial plane orientation, where even a slight rotation can significantly impact kinematics,” said Radcliff. “The absence of a navigational or robotic solution for motion preservation in this context is equally perplexing. Considering the remarkable enhancements robotics has brought to the precision and accuracy in hip and knee replacements, its application in spinal procedures is notably overdue.”
Despite the frustrations regarding the lack of navigational solutions, McAfee said improvements are being made.
“There is no excuse for not putting these devices in perfectly,” McAfee said. “You should be able to get them within a millimeter. You should be able to get it perfect. It is all because of navigation and robotics, and we are improving on that every few months.”
Future of disc replacement
Surgeons should begin to consider patients as disc replacement candidates at presentation and discuss the option with patients to bring the procedure to the forefront, according to Radcliff.
“As a spine surgeon, I view surgery as a team activity, but the rarity of disc replacement procedures poses a challenge since many team members may be unfamiliar with it,” Radcliff said. “This extends to the broader community, including pain management physicians, physical therapists, chiropractors, primary care physicians, attorneys and patients, who are often not well-informed about the advantages of disc replacement. When patients seek a disc replacement, there may not be enough familiarity in their support network to endorse the decision confidently. The key to altering community perception and our own biases lies in increasing the utilization of disc replacement and consistently demonstrating good outcomes. Now, when I evaluate a patient, I consider them a candidate for disc or facet replacement until there is evidence to suggest otherwise.”
Another way to bring disc replacement to the forefront is by identifying novel uses of the devices based on long-term data.
“Historically, [disc replacement devices were] for more straight-forward clinical indications, one- or maybe two-level treatment of discogenic cervical disease,” Smucker said. “We are now looking at whether, both clinically and biomechanically, disc arthroplasty has favorable outcomes over the long-term to someone who has had a prior fusion or in a patient with more than two-levels of disc pathology.”
He added, “While some of those indications were considered to be esoteric, these are now becoming more commonplace as these devices and an understanding of their use matures.”
As long as the surgical community continues to produce reliable data, Freedman said he is optimistic about the future of disc replacement.
“Industry and surgeons partnering with industry need to work together to optimize the implants and surgical technique, so we get reliable outcomes that rival those of our hip and knee arthroplasty colleagues,” Freedman said. “The future is bright for disc arthroplasty.”
- References:
- Park CK, et al. Asian Spine J. 2018;doi:10.4184/asj.2018.12.1.178.
- Phillips FM, et al. Spine (Phila Pa 1976). 2015;doi:10.1097/BRS.0000000000000869.
- Radcliff KE, et al. J Neurosurg Spine. 2016;doi:10.3171/2015.12.SPINE15824.
- Radcliff KE, et al. Spine (Phila Pa 1976). 2015;doi:10.1097/BRS.0000000000000822.
- Wahood W, et al. World Neurosurg. 2020;doi:10.1016/j.wneu.2019.10.032.
- For more information:
- Brett Freedman, MD, of the Mayo Clinic, can be reached at madson.rhoda@mayoclinic.edu.
- Paul C. McAfee, MD, MBA, of Georgetown University School of Medicine, can be reached at mack8132@gmail.com.
- Kris E. Radcliff, MD, of the Spinal Disc Center, can be reached at radcliffk@gmail.com.
- Joseph D. Smucker, MD, of the Indiana Spine Group, can be reached at jsmucker@indianaspinegroup.com.
- Jack E. Zigler, MD, of the Texas Back Institute, can be reached at jzigler@texasback.com.
Click here to read the Point/Counter to this Cover Story.
Collapse
Read more about
Click Here to Manage Email Alerts