Artificial Disc Replacement: Lessons Learned From IDE Trial Outcomes

ISASS19 Annual Meeting Highlight

Peer Reviewed

When artificial disc replacement first emerged in the early 2000s, concerns were raised that this surgical approach would lead to “stretched” indications, poor outcomes, higher perioperative complications, and the need for anterior revision surgery with the potential for significant morbidity and mortality, Jack E. Zigler, MD, FACS, FAAOS, explained at a disc replacement symposium during the International Society for the Advancement of Spine Surgery (ISASS) 19th Annual Conference held April 3 to 5, 2019 in Anaheim, CA. Twenty years later, these concerns are no longer relevant as there is robust and reproducible data from Investigational Device Exemption (IDE) trials supporting the efficacy and safety of both cervical and lumbar disc replacement, Dr. Zigler told attendees.

side view of an artificial disc implanted in the spineThere is robust and reproducible data from IDE trials that support the efficacy and safety of cervical and lumbar disc replacement. Photo Source: 123RF.com.

Indications for Artificial Disc Replacement

“The indications for disc replacement are different for lumbar arthroplasty, which is really for discogenic mechanical back pain, and cervical arthroplasty, which is really for neurologic decompression for radiculopathy or focal mild myelopathy,” said Dr. Zigler, who is an Orthopedic Spine Surgeon and Co-Director of the Center for Disc Replacement at Texas Back Institute in Plano, Texas. “Thus, there are different indications for similar looking devices.”

However, there is no evidence to suggest that there has been an expansion in indication for use of artificial disc replacement or that there has been a spike in total number of patients undergoing anterior lumbar or cervical surgery, Dr. Zigler told attendees. “In other words, patients who are getting arthroplasty are those who would have otherwise received fusions.”

Insurance coverage for cervical total disc replacement is widely accepted—with 90% to 95% of insured Americans now having access to cervical arthroplasty, Dr. Zigler said. Rates of coverage for lumbar total disc replacement have increased markedly in recent years to just over 60% for 1-level procedures, he continued.

Perioperative Complications of Total Disc Replacement

Perioperative reporting and post-market surveillance mandated by the FDA have allowed for collection of data regarding intra-operative and immediate post-operative issues with up to 5 years of surveillance for lumbar total disc replacement and 7 to 10 years for cervical total disc replacement.

“Very strong data has been published repeatedly showing that the perioperative morbidity of lumbar arthroplasty is no worse, and in fact is better, than anterior lumbar interbody fusion (ALIF),” Dr. Zigler noted. Likewise, “the perioperative morbidity of cervical arthroplasty is no worse, and in fact is better, than anterior cervical discectomy and fusion (ACDF).”

Reoperation Rates Favor Artificial Disc Replacement Over Fusion

In addition, data on revision surgery for cervical and lumbar total disc replacement do not show an increased reoperation rate compared with fusion.

“In four papers with level 1 prospective, multicenter, randomized studies with 7-year follow-up data we can see that the secondary surgical rates for cervical arthroplasty are two to threefold less than that for ACDF,” Dr. Zigler said.1-4

The lumbar total disc replacement revision rates for the first 1,000 cases performed using the ProDisc-L device was 0.3%, and for the cases performed by the first 1,300 surgeons trained between 2006 and 2013 was <1% (unpublished industry data). In addition, data presented by Dr. Zigler and colleagues at ISASS18 on consecutive patients (n=1,707) undergoing arthroplasty at Texas Back Institute since 2000 showed that 17 patients (1%) required anterior revision. All of these revision surgeries were performed without loss of limb or life, Dr. Zigler said.5

Outcomes Data Confirm Efficacy and Safety of Total Disc Replacement Surgery

“Lumbar and cervical total disc replacement outcomes have exceeded expectations with long-term published data,” Dr. Zigler told ISASS19 attendees. “The number of published studies on arthroplasty have exploded over the last 10 years. This has allowed the level of evidence on spine arthroplasty to increase from level 1b based on prospective randomized, multicenter studies, to level 1a based on meta-analysis of randomized controlled trials subjecting a larger database to different scrutiny.”

For example, a meta-analysis of three artificial cervical disc trials involving approximately 1,200 patients with 2-year follow-up data found that patients who underwent arthroplasty had a greater neurologic success rate and a lower reoperation rate than those who underwent ACDF, Dr. Zigler explained.6 In a more recently published meta-analysis by the Chinese Orthopaedic Association, researchers analyzed data from 21 randomized controlled trials involving more than 4,200 patients followed for up to 10 years. The findings validated a statistically significantly lower reoperation rate with cervical disc arthroplasty versus ACDF.7

In addition, a meta-analysis by Dr. Zigler and colleagues of 5-year outcomes from four lumbar total disc replacement trials showed a 48% relative reduction in the risk of reoperations compared with fusion (P=0.001).8 Patients who underwent lumbar arthroplasty were 9% more likely to achieve Oswestry Disability Index (ODI) success compared with those who underwent fusion (P=0.05). Furthermore, patient satisfaction scores were significantly greater with lumbar arthroplasty than with fusion (P=0.009). The long-term findings of this study showing improved clinical and safety benefits with total disc replacement at 5 years have important implications on the health care and economic burden associated with symptomatic lumbar degenerative disc disease, according to Dr. Zigler.

Furthermore, in a 5-year follow-up study of the progression of adjacent-level degeneration after lumbar total disc replacement by Dr. Zigler and colleagues, a progressive decline in the rate of adjacent segment disease was found for each additional degree of motion at the total disc replacement level.9 Additionally, preliminary data from an ongoing analysis of arthroplasty versus fusion by Dr. Zigler and colleagues shows that the greater benefit of arthroplasty on ODI and visual analog scale outcomes remains after 10 years of follow-up.

Conclusions on Cervical and Lumbar Disc Replacements

“In 2019, there is very robust and reproducible level 1 data that lumbar arthroplasty outcomes are as good as fusion outcomes and are even superior on some measures,” Dr. Zigler concluded. “We have strong published data showing that adjacent lumbar degeneration occurs only one-third as frequently above artificial disc replacement than with fusion. Additionally, cost studies consistently show that lumbar arthroplasty is less expensive for hospitals and insurers than spinal fusion.”

Similarly, level 1 data from cervical artificial disc replacement studies show that this surgical technique reduces or delays adjacent segment degeneration and has a significantly lower reoperation rate compared with ACDF, Dr. Zigler said. “There is no data suggesting that cervical artificial disc replacement is inferior to ACDF based on clinical outcomes, complications, or reoperations at 5 or 7 years post-operatively,” he said.

In addition, recently published meta-analyses have increased the evidence on spine arthroplasty to level 1a, again showing that previous concerns regarding the safety and efficacy of disc replacement have not been borne out, Dr. Zigler concluded.

Disclosures
Dr. Zigler is a paid consultant for Aesculap/B.Braun, Centinel Spine, Medtronic, Nocimed, Orthofix, Inc., Simplify Medical, and Vertera Spine. He is on the editorial or governing board of Coluna/Columna and the Journal of ISASS, is a Board or Committee member of ISASS, has received IP royalties from K2M and Zimmer Biomet, and has received stock or stock options from Safe Orthopedics.

Updated on: 05/03/19
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Cervical Disc Arthroplasty Found More Cost-Effective Than Anterior Cervical Discectomy for Disc Herniation
Jack E. Zigler, MD, FACS, FAAOS
Orthopaedic Spine Surgeon
Texas Back Institute
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