Cervical Artificial Disc Replacement Outcomes at 5 to 10 Years

ISASS19 Annual Meeting Highlight

Peer Reviewed

“Cervical disc replacement is one of the most rigorously studied procedures we have in spine surgery,” Dr. Frank M. Phillips told attendees at the International Society for the Advancement of Spine Surgery’s (ISASS) 19th Annual Conference held April 3 to 5, 2019 in Anaheim, CA. Data consistently show that artificial disc replacement is safe and effective for the treatment of cervical disc degeneration with radiculopathy and/or myelopathy and demonstrates superiority over anterior cervical discectomy and fusion (ACDF) in both short-term and longer-term follow-up studies, he said.

colorful letters spell out the word data, with graphicsCervical artificial disc replacement is one of the most evidence-based treatments in spine surgery. Photo Source: 123RF.com.

Disc Replacement Shows Early Efficacy

Early two-year follow-up data on a variety of artificial disc devices show “highly significant improvements in neck and arm pain scores in both the artificial disc and ACDF groups,” explained Dr. Phillips who is Professor, Director, Section of Minimally Invasive Spine Surgery, and Director, Division of Spine Surgery, Rush University Medical Center. “

Evidence also suggests a low reoperation rate at 2 years with disc replacement, with the same trend found across various disc designs, he continued. In addition, data consistently suggest that disc replacement reduces the rate of adjacent segment degeneration.1-3 Rates of radiographic adjacent level disease in recent studies range from 10.1% to 26.7% with artificial disc replacement and from 23.1% to 44.4% with ACDF, Dr. Phillips noted.1-3

In addition, findings suggest that cervical disc replacement compares well against hip/knee replacement surgery. For example, in a study comparing cervical disc replacement to hip/knee joint replacement surgery, baseline physical function was worse in patients undergoing hip and knee replacement while mental health scores were worse in patients undergoing cervical arthroplasty.4 However, the improvement in physical component score was significantly greater following cervical disc replacement than following ACDF or hip/knee replacement.

Long-Term Disc Replacement Outcomes

Research suggests that the benefits of artificial disc replacement is maintained long term, with 7-year follow-up studies favoring artificial disc replacement over ACDF in terms of secondary surgery rates.5-8

“When we look at 7-year data from a range of disc prostheses, we consistently see an approximately one-third lower reoperation rate in favor of disc replacement versus ACDF across different designs, different centers, different authors reporting the data,” Dr. Phillips said.

In a 7-year follow-up study by Dr. Phillips and colleagues, Kaplan-Meier survivorship analysis suggests that as patients are followed out for a longer duration of time, the graphs diverge in favor of disc replacement versus ACDF. “And ultimately, to society, that difference in the graph is really what drives cost and provides value for the procedure,” Dr. Phillips said.8

Furthermore, 10-year outcomes data from a prospective, randomized study involving 128 patients who underwent total disc replacement and 104 patients who underwent ACDF found that the overall success rate was significantly higher for the disc replacement group, 81% versus 66% with ACDF (P=0.005).9 The rate of secondary surgery at adjacent levels was lower for the disc replacement group at 10 years (10% versus 16% with ACDF), but the difference did not reach statistical significance (P=0.146). A similar trend was found for Neck Disability Index (NDI) scores as well as visual analog scale (VAS) neck and arm pain, and range of motion at the disc replacement level was maintained at 10 years in the disc replacement group, Dr. Phillips said.

Differences Between US and European Outcomes Studies

Greater efficacy of cervical artificial disc replacement (C-ADR) over ACDF has been demonstrated in robust randomized controlled trials, systematic reviews, and meta-analyses involving both 1- and 2-level C-ADR performed in the United States, Dr. Phillips said.

However, a recently published European study by MacDowell et al found that 5-year outcomes from patients with cervical degenerative disc disease and radiculopathy who underwent total disc replacement did not show improved clinical or radiological outcomes after 5 years when compared with patients who underwent ACDF, Dr. Phillips explained.10

“We all need to critically look at what we’re doing, and ask why there is a difference between the European versus US experience?” Dr. Phillips said. “It is easy to blame the different outcomes on surgeon bias and industry bias, but I think that at 7 and 10 years post-operatively, those biases wash out. Is it different patient selection, different surgical technique, different levels of surgeon experience, or use of prostheses that are not on the market in the US?”

While the reason for this discrepancy is not clear, Dr. Phillips emphasized that it is a finding that needs to be addressed. Dr. Phillips added that 2019 independent review conducted by Health Quality Ontario is “very telling” given that this group “has no incentive to reimburse procedures.”11

The Health Quality Ontario review found eight studies of 1-level cervical degenerative disc disease and two studies of 2-level cervical disc degeneration that satisfied the criteria of statistical non-inferiority of total disc replacement compared to ACDF on the primary outcome of 2-year overall treatment success with moderate grade of evidence.11 In 2 studies of 2-level disease, cervical artificial disc replacement was statistically superior to ACDF on overall treatment success. In addition, artificial disc replacement was superior to ACDF for recovery and return to work as well as lower rates of reoperation at the index level.

Furthermore, the group determined that cervical artificial disc replacement is likely to be cost-effective compared with ACDF for both 1-level ($11,607/quality-adjusted life-year [QALY]) and 2-level ($16,782/QALY) disc degeneration.11

Next Generation Artificial Discs

While first-generation artificial discs were designed using similar ball and socket technology used in hip and knee replacement, none of the devices truly replicate the natural disc kinematics, Dr. Phillips said. The goal of next generation designs is to create a device that has physiologic characteristics of the natural disc.

One such design is the M6-C Artificial Cervical Disc, which was approved by the U.S. Food and Drug Administration (FDA) in February 2019.12 In a prospective, concurrently controlled multicenter FDA investigational device exemption trial of the M6-C device, statistically significant improvements in NDI and VAS neck pain and shoulder/arm pain was found with the M6-C Artificial Cervical Disc versus ACDF at every time point during the 2-year follow-up period.12 Dr. Phillips said that the beneficial findings may be related to the unique design of this device.

Extended Indications: The Hybrid Concept

Findings also suggest that cervical artificial disc replacement combined with ACDF (hybrid surgery) may be effective in patients with 2-level cervical disc disease.

In a study by Shin et al, hybrid surgery was superior to 2-level ACDF in terms of improvements in NDI recovery, less post-operative neck pain, greater C2-C7 range of motion recovery, and less adjacent level motion.13 Additionally, a study by Dr. Phillips and colleagues found that cervical disc replacement to be a viable surgical option when performed adjacent to prior fusions.14

“The conclusion was that outcomes of cervical disc replacement following adjacent level ACDF were equivalent to those of primary surgeries, suggesting that prior cervical fusion need not be a contraindication to cervical disc replacement,” Dr. Phillips said.

Patient Selection is Key

Complications from total disc replacement may be related to improper patient selection, Dr. Phillips said. Contraindications include collapsed, ankylosed immobile disc; significant facet arthrosis; ossification of the posterior longitudinal ligament and/or significant spondylosis; pre-operative instability on dynamic flexion-extension images; systemic bone illness (osteoporosis, rheumatoid arthritis, metabolic bone disease); or spondylotic myelopathy (discussion of severity ongoing).

Conclusion

“Cervical disc replacement is one of the most evidence-based treatments in spine surgery,” Dr. Phillips concluded. “We have level 1 data showing that cervical disc replacement reduces adjacent segment degeneration compared to ACDF. Disc replacement is associated with a significantly lower reoperation than ACDF, with this difference becoming more pronounced as we follow these patients for longer durations.”

Disclosures
Dr. Phillips disclosed the following relationships:

  • Royalties: NuVasive, Medtronic
  • Consultant/Scientific Advisory Board: NuVasive, SI-Bone, Stryker
  • Board of Directors/Scientific Advisory Board: International Society for the Advancement of Spine Surgery, Society for Minimally Invasive Spine Surgery, TheraCell, Vital 5, EDGe Surgical, Providence Medical Technology, Vertiflex, Surgio
Updated on: 05/03/19
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Artificial Disc Replacement: Lessons Learned From IDE Trial Outcomes
Frank M. Phillips, MD
Professor of Orthopaedic Surgery
Director, Section of Minimally Invasive Spine Surgery
Director, Division of Spine Surgery
Rush University Medical Center
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