Pseudarthrosis Found in Half of Patients With PEEK Implants for Anterior Cervical Discectomy and Fusion

Peer Reviewed

Use of polyetheretherketone (PEEK) cages for anterior cervical discectomy and fusion (ACDF) was linked to a fivefold increased incidence of pseudarthrosis compared with use of allograft materials, and a nearly twofold increase in the rate of subsequent revision surgery for pseudarthrosis, according to findings from a retrospective study presented at the AANS/CNS Joint Section on Disorders of the Spine and Peripheral Nerves Annual Meeting held March 14-17 in Orlando, FL.

“There is no doubt in my mind that PEEK cages do not heal as well as structural allografts,” said senior author Khoi D. Than, MD, Assistant Professor, Department of Neurological Surgery, Oregon Health & Science University, Portland, OR. “My interest in this area began during my first few years of practice, during which I performed approximately 10 anterior cervical revision surgeries involving removal of PEEK cages placed by other surgeons that did not heal.”
Computer imagery of a patient with a PEEK interbody deviceExample of a patient with a PEEK interbody device who was found to have pseudarthrosis 1 year after surgery.The retrospective chart review included 127 consecutive adult patients who underwent a one-level ACDF at a single tertiary care center and had one-year radiographic follow-up data available (ie, x-ray or computed tomography image). Fifty-six of the patients received smooth PEEK implants and the other 71 patients received cadaveric structural allograft implants. Most PEEK cages were filled with non-structural allograft with demineralized bone matrix (47/56), and the remainder were filled with local autograft (9/56).

No significant difference in baseline age, sex, body mass index, or prevalence of tobacco use was found between the two groups. The primary outcome measure was the rate of pseudarthrosis, defined as lack of solid bony growth across the disc space.

Pseudarthrosis Rate at Follow-up
Radiographic evidence of pseudarthrosis at follow-up was found in 51% patients (29/56) with PEEK implants compared to 10% of patients (7/71) patients with structural allograft (P≤0.001, odds ratio [OR], 9.82). In addition, 7 patients with PEEK implants (24%) required a revision surgery for pseudarthrosis compared to 1 patient (14%) with structural allograft (P=0.01, OR 10.00). No statistically significant difference was found in pseudarthrosis rate between a PEEK implant with or without a plate (P=0.171).

Limitations of the study include the retrospective design, surgeries performed by multiple surgeons making standardization of findings difficult, and lack of objective clinical data, Dr. Than and colleagues noted. In addition, there was a lack of uniformity of physical graft placement, type of structural allograft utilized (although the vast majority were composite), and materials used to pack the PEEK cages (although the vast majority were packed with allograft and demineralized bone matrix), according to the researchers.

Reimbursement Implications
“In an age where cost effectiveness and quality measures are being increasingly utilized to drive reimbursement, surgeons should account for these results when deciding among the many graft choices available for ACDF,” the researchers concluded.

The reimbursement rate for implantation of PEEK devices per surgical level is markedly higher than those for structural allograft (6.7 vs 1.8 relative value units), according to Dr. Than.1 In addition, surgeons can bill for each PEEK cage implanted in multilevel cases but can bill for structural allograft only once per surgery regardless of levels instrumented, Dr. Than said.

COMMENTARY
Jeffrey C. Wang, MD
Chief, Orthopaedic Spine Service
Co-Director USC Spine Center
Professor of Orthopaedic Surgery and Neurosurgery USC Spine Center
Los Angeles, CA

The use of allograft is likely becoming or has become a “gold-standard” for ACDF, much like the use of autograft in the past. The introduction of PEEK cages was interesting because many early case series showed similar results with use of these devices compared with allograft. This study shows a higher non-union rate and a greater need for revision surgery with the use of PEEK cages in the study population. We need future studies like this one with even longer follow-up in order to determine if there is a benefit to using the cages over what has become the standard of care. If more studies with longer follow-up show this trend, this could allow for a best-practices situation where surgeons may preferentially choose allograft over the PEEK cages.

I am always looking for the best materials for my own patients, as I want them to achieve the best outcomes. When doing a fusion, I do believe that attaining a solid fusion that is healed is likely associated with a better outcome. It is not always associated with a good outcome, and certainly there are many patients who do not heal their fusion, but still do very well. However, I am always looking at the “biology” and the potential for healing for each of my patients.

There are some patients who are likely to have a high rate of healing and would likely heal at a high rate regardless of whether allograft or a PEEK cage is used. However, there are many patients who have risk factors that would likely lead to a decreased chance of healing, and these are the cases in which the surgeon needs to consider what is best for the individual patient. If there is a patient who is at higher risk, then I would probably want to use the option that has the highest chance of healing. However, we need more studies like this to help us determine which is the best approach. I am using mostly structural allografts but have used PEEK cages in situations where I need a longer graft or to allow for more correction with an expandable cage. For a single-level fusion, as in this study, I think the surgeon is going to choose the option that allows for the highest healing rate, is easy to use, and saves time. We need these studies to help us make this decision.

There are many questions in my mind. For example, were all the cages the same cage and comparable? We need more details, and we need to make sure we are comparing apples to apples and oranges to oranges.

Disclosures
Dr. Than is a consultant for Bioventus.

Dr. Wang disclosed the following:
Royalties: Biomet, Seaspine, Amedica, Synthes
Investments/Options: Bone Biologics, Expanding Ortho, PearlDiver, Fziomed, Electrocore, Surgitech
Board of Directors: North American Spine Society, AO Foundation, Cervical Spine Research Society
Editorial Boards: Spine, The Spine Journal, Clinical Spine Surgery, Global Spine Journal
Fellowship Funding (paid to institution): AO Foundation

Updated on: 07/02/18
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Mesenchymal Stem Cell Allograft and ACDF Study Outcomes
Khoi D. Than, MD
Assistant Professor
Department of Neurological Surgery
Oregon Health & Science University
Portland, OR
Jeffrey C. Wang, MD
Chief, Orthopaedic Spine Service
Co-Director USC Spine Center
Professor of Orthopaedic Surgery and Neurosurgery USC Spine Center
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