ACDF in 10 years: CDR may become gold standard but 'we will always need both'

Spine

Anterior cervical discectomy and fusion is the most common surgery for treating symptoms related to a degenerative or herniated disc in the neck, but other techniques may offer more benefits to patients, depending on their spinal condition.

However, in recent years, cervical disc replacement — in which an artificial disc is inserted to maintain motion between the vertebrae — has gathered momentum and could become the standard of care for treating degenerative cervical disease, according to many surgeons.

Thirteen spine surgeons from health systems and private practices across the country discussed how ACDF and other treatment options will evolve for cervical pathology over the next decade.

Editor's note: Responses were lightly edited for style and clarity.

Question: How do you expect ACDF to develop over the next 10 years? How will it compare to other types of spinal fusion?

Venu Nemani, MD, PhD. Virginia Mason Franciscan Health (Seattle): Almost certainly, the rates of ACDF will decrease over the next 10 years as cervical disc replacement technologies continue to evolve and the indications for disc replacement are expanded. However, ACDF will always be a critical tool in the cervical spine surgeon's toolbox to deal with pathology that warrants spinal fusion (deformity, instability, etc.). Although there will continue to be innovation in interbody and biologic technology, the real change will come in more clearly understanding when our operations need to correct cervical malalignment versus just treating the neurologic problem (radiculopathy, myelopathy).

This will depend on further research to better understand what constitutes normal versus abnormal radiographic alignment in the cervical spine, how patient-reported outcomes correlate with restoration of normal cervical alignment after ACDF and the development of improved tools for surgical planning. We now have a good grasp of our alignment goals and its effect on outcomes when performing lumbar fusion, but I believe we will greatly improve our understanding of this with regard to cervical surgery over the next 10 years.

Kee Kim, MD. UC Davis Health (Sacramento, Calif.): We have witnessed tremendous advances in treating patients with cervical degenerative disc disease in the last two decades. ACDF has been an integral part of improved patient care. I have been privileged to be a part of innovations in cervical artificial disc and zero-profile cage technology. ACDF will continue to be popular compared to other types of spinal fusion, but I expect the following changes to occur over the next decade:

1. More ACDFs will be performed in the ambulatory setting.

2. More ACDFs will utilize zero-profile cages with integrated screws instead of cervical plates due to ease of use and reduction in adjacent segment disease.

3. ACDFs will decrease proportionally due to an increased use of cervical artificial discs.

4. More artificial disc surgery failures will be seen due to increased patient demand, less strict indication for its use, suboptimal surgical technique and greater awareness of periprosthetic osteolysis. Therefore, more ACDFs will be performed to revise failed artificial disc surgeries.

Praveen Mummaneni, MD. UCSF Health (San Francisco): The analysis of the cervical cases in the Quality Outcomes Database of the American Spine Registry shows that ACDF dominates over posterior fusion in the sheer number of cases done annually. This is not surprising as ACDF is very efficacious for one- and two-level disease. Currently, most posterior cervical fusions are done for patients with three or more levels of stenosis  — to avoid dysphagia from multisegmental retraction on the esophagus — and this trend is likely to continue. ACDF is likely to be done more frequently than posterior cervical fusion in the years to come. 

ACDF, unlike posterior cervical fusion, has already partially shifted to outpatient surgery for one- and two-level cases in healthy patients. However, those with comorbidities still have the ACDF done inpatient. In the future, I suspect that most ACDF cases will go to the ASC as the efficiency of the surgery centers is much better than the inefficiency with turnover that many of us experience on the inpatient side. Likely the inpatient setting will be reserved for the patients with comorbid conditions (sleep apnea, heart disease, etc.) or revision ACDF who need close observation post-op. 

Finally, in the future, hybrid constructs with ACDF and arthroplasty may increase in number. Currently, insurance approval limits these hybrid cases, but when patients have nonadjacent disc herniations, a hybrid construct where intervening normal levels are skipped makes a lot of sense.

Lali Sekhon, MD, PhD. Nevada Neurosurgery (Reno): Anterior cervical fusion has been around since 1955 but every five to 10 years undergoes a change in technique, implants and materials. It's not going away. I started cervical arthroplasty in 2002 and the indications for a successful cervical arthroplasty are still tight (less than 50 percent loss of disc height, motion at treated level, no facet disease, etc.). When we wander from those initial indications, our results are less certain. Longitudinal studies on cervical arthroplasty have also shown those patients are not immune to adjacent segment disease, just less so. ACDF will still be here in 10 years.

Our understanding of stiffness and the effects on adjacent segment disease are only just starting. There is a middle ground between fused solid and totally mobile, but today that is a dimension that we can't appreciate. The concept of a "soft fusion" is something that makes no sense, but it may in the future as we discover materials and constructs less stiff than cancellous bone. ACDF is not going away. Just as the last 65 years have seen us move from dowels to allograft to PEEK to porous titanium, the continuum of change will continue and the gap between arthroplasty and current spinal fusions will blur.

Kris Radcliff, MD. Rothman Orthopaedic Institute (Philadelphia): Operative microscopes will become a dominant technology in ACDF. In addition to the usual ergonomic and practical reasons to use a microscope (lighting, assistant, etc.), the newer microscopes incorporate exoscope features and built-in endoscopes. Working on a view screen will be appealing to the next generation of surgeons who have grown up with gaming systems. Newer microscopes will also incorporate built-in navigation and physiological imaging beyond the visual spectrum including fluorescence. Surgeons will be able to see the recurrent laryngeal nerve, for example. Ultimately, the technology will make the surgery safer. 

I also expect that robotic bone resection with predefined boundaries and safe zones will become commonplace. Our colleagues in arthroplasty have already demonstrated that robotic bone removal technology standardizes surgery and improves reproducibility. Even in experienced hands, one can resect excessive bone, slip and injure the esophagus or vertebral arteries, or under-decompress particularly the foramen. Ideally, robotic guidance will lead to more efficient, safer and effective surgery and also facilitate better placement of artificial disc replacements.

My main challenge in anterior cervical surgery remains the poor bone quality of the cervical vertebral bodies. The unicortical, cancellous screws uniformly have poor purchase. Other types of spine surgery involve fixation in cortical bone with pedicle screws. We need improved screw designs and osseodensification methods to improve the fusion rate and long-term outcome.

Ciro Randazzo, MD. NorthEast Regional Surgery Center (Paramus, N.J.): The three biggest changes that I expect to come to ACDF in the near future include: movement away from ACDF to anterior cervical discectomy with disc replacement rather than fusion; migration of these cases from the hospital to the surgery center; and the use of standalone devices rather than anterior plating. Unlike other spinal surgery, I do not see a significant increase in the use of robotic surgery or navigation for anterior cervical surgery.

Harel Deutsch, MD. Rush University (Chicago): I believe artificial cervical disc replacement will replace most ACDF procedures in the future. Implants will continue to improve for artificial discs. Ten-year data has shown us that artificial disc is superior to fusion. We will still be doing some fusions, but I believe 90 percent of current ACDF surgeries will be artificial disc replacements.

Jonathan Stieber, MD. NYU Langone Health (New York City): ACDF has changed only modestly since its introduction in the 1950s. Implants have evolved to become very low profile while affording improved stability. I expect advancements in interbody implant technology and biologics will further improve the reliability of fusion and minimize the risk of pseudoarthrosis. Advanced technologies including the incorporation of hydroxyapatite and porosity will continue to evolve to enhance both on-growth and in-growth for higher fusion rates. As artificial disc replacement undergoes further study, three- and four-level arthroplasties are likely to become more commonplace. Hybrid surgeries will also find greater acceptance as the data leads to payer coverage for these procedures.

Grant Shifflett, MD. DISC Sports & Spine Center (Newport Beach, Calif.): I think the major development with ACDF over the next 10 years is simply that they won't be performed very often. But when they are performed, the technology will continue to shift away from PEEK and toward more biologically friendly materials. Radiopacity of current metallic implants is a barrier in ACDF surgery and I believe innovation will strive to overcome this, allowing surgeons to perform these surgeries with greater success. Lumbar disc replacement and other motion-preserving technologies in the lumbar spine are highly effective in many scenarios but remain inadequate in many patients with a variety of lumbar pathologies. By contrast, the overwhelming majority of patients presenting with cervical disease can be treated with motion-preserving technologies. ACDF is not going to go away entirely, but the future of this surgery is certainly imperiled by advancing technology. 

There is a firm evidence basis for ACDF to be safely performed in outpatient facilities, and there will be continued economic pressure to make the procedure competitive in that setting. The anterior plate and interbody spacer procedure will continue to be simplified, such as individual sterile wrapping with construct pricing and standalone spacers with intrinsic fixation. ACDF will be challenged in this milieu by cervical disc replacement, which will continue to make inroads in the younger, more active population with one- and two-level disease. Furthermore, in the next decade, the indications for cervical disc replacement will likely expand to include hybrid cervical disc replacement/fusion and three-level indications. There will be continued evolution and sophistication of disc replacement devices, and ACDF will adapt by becoming even more streamlined, cost-effective and efficient.

Conversely, ACDF will retain primacy in the inpatient setting. These indications include trauma, tumor, infection and deformity. In the inpatient setting, ACDF will need to adapt to an older population with significant comorbidities including osteo-penia/-porosis, multilevel disease and deformity. ACDF plates will allow for straightforward load sharing and simplified application techniques. Interbody spacers will continue to evolve with fusion-friendly materials, such as 3D-printed metals and multiple lordotic options. Finally, common sense and evidence basis will ultimately prevail and certain insurers will no longer classify interbody spacers — which have been used safely and effectively for the past two decades — as "investigational." Ultimately, ACDF is here to stay.

Brian Gantwerker, MD. The Craniospinal Center of Los Angeles: I think ACDF's future in the next decade is stable overall. Like many arrows in the quiver of spine surgery, it will always have a place in the armamentarium of spine surgeons.  

Especially in the setting of infection and disc-disruptive trauma, fusion remains the gold standard. In many cases of degenerative disease, where the patient's facet joints no longer function, anterior cervical fusion is usually the best treatment.

I think now that most payers have relented and are paying for artificial disc replacement and patients are doing very well from them, we will see it more widespread. Artificial disc replacement instrumentation will continue to improve as new models are released and longer-term data is revealed on which bear out as superior. And now that many surgeons have had more experience in patient selection and postoperative management, it will be much more widespread. I do hope that fusion does not fall completely out of favor as it is an important bail-out in the case of a failed arthroplasty. In short, we will always need both.

Domagoj Coric, MD. Carolina Neurosurgery & Spine Associates (Charlotte, N.C.): ACDF will continue to be a workhorse procedure over the next 10 years. The two biggest factors affecting the development of ACDF will be the continued movement of the procedure to the ASC setting and the increasing adoption of cervical total disc replacement. These factors will bifurcate the development of ACDF into an outpatient procedure as well as a complex, inpatient procedure.

Thomas Loftus, MD. Austin (Texas) Neurosurgical Institute: The ACDF procedure has achieved excellent outcomes for many years. While I expect nuanced improvements in instrumentation and biologics over the next 10 years, I do not foresee major changes in how the procedure is performed. I expect its acceptance as mostly an outpatient procedure will continue to grow and there will be a more widened application of its use in the outpatient setting for three-and four-level procedures also. While there is some growth in cervical artificial disc replacement application, I still expect ACDF to play a major role in treatment of cervical spine disorders. Compared to other spinal fusion procedures, I expect ACDF to continue to be considered one of the most highly successful procedures in our armamentarium.

Issada Thongtrangan, MD. Microspine (Scottsdale, Ariz.): I anticipate that there will be more movement toward cervical disc replacement including multilevel or hybrid cases. Many data have shown the noninferiority outcomes of cervical disc replacement compared to ACDF and even superiority outcomes in multilevel diseases. I think surgeons will do less traditional ACDF using anterior cervical plates and move toward the standalone device that can restore the lordotic alignment with excellent fixation and can be done efficiently in the ASC setting. As far as endoscopic cervical spine surgery, I think there will be less adoption of endoscopic anterior cervical procedures compared to endoscopic posterior cervical procedures due to the intraoperative risks with the anterior approach.

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