Two-Level Cervical Artificial Disc Replacement Update

Building on 1-level data supporting the efficacy of total disc replacement for cervical disc degeneration discussed at the International Society for the Advancement of Spine Surgery (ISASS) 19th Annual Conference held April 3 to 5, 2019 in Anaheim, CA, Domagoj Coric, MD, presented current evidence on 2-level cervical disc replacement, which he said is “even more compelling.”

Cervical arthroplasty is indicated for patients with radiculopathy due to central/ paracentral disc herniation with 1- and 2-level disease. Photo Source: 123RF.com.

“For properly selected patients with 1- and 2-level central and paracentral soft disc herniation from C3-C7 with radiculopathy, cervical arthroplasty is a standard of care treatment choice with a firm evidence basis including long-term follow-up,” said Dr. Coric, who is a neurosurgeon at Carolina Neurosurgery & Spine Associates and Chief of Neurosurgery at Carolinas Medical Center in Charlotte, NC.

In fact, there is an “unprecedented volume” of Level 1 evidence from prospective, randomized studies demonstrating the safety and efficacy of single-level cervical and now 2-level artificial disc replacement, Dr. Coric told attendees.

Two devices are approved by the U.S. Food and Drug Administration (FDA) for use in two-level cervical total disc replacement: Mobi-C and Prestige LP, a two-level FDA Investigational Device Exemption (IDE) study of a third device, Simplify, was recently completed, but has not yet completed two-year follow-up necessary to submit for FDA approval.

IDE trials of two other devices—Synergy and Freedom—expect to begin this year or next, potentially for 1- and 2-level cervical artificial disc replacement.

Short-Term Trials of Two-Level Cervical Total Disc Replacement

Two-year follow-up data from a prospective, randomized, multicenter study of Mobi-C showed that the overall success rate of this device was statistically significantly superior to ACDF in 2-level surgery.¹ In addition, a statistically greater number of 2-level patients in the ACDF arm showed adjacent level radiographic degeneration.

Similarly, results of a 2-year prospective, multicenter randomized trial of Prestige LP demonstrated the superiority of this device over ACDF in overall success as well as neurological success at 24 months.²

Dr. Coric noted that while 2-year follow-up is not a sufficient duration to determine clinically significant differences in adjacent segment degeneration for reoperation rates, some longer term trials have shown statistically significant differences in these outcomes.

“Just as we suspected, what we’re seeing in 1-level disease is going to be amplified in 2-level disease,” Dr. Coric said.

Long-Term Data Support the Efficacy of Two-Level Cervical Disc Replacement

Five-year follow-up data for Mobi-C showed significantly lower levels of adjacent level degeneration radiographically with total disc replacement compared with ACDF (50.7% versus 90.5%; P<0.0001).³ In addition, the rate of adjacent level reoperation was significantly lower with total disc replacement versus ACDF (11.4% vs 3.1%; P=0.0004).

In a 7-year follow-up study of Mobi-C, “1- and 2- level cervical total disc replacement showed statistically significantly lower incidence of secondary surgery at both index and adjacent levels,” Dr. Coric told attendees.⁴ For 2-level disease, 4.4% of patients who underwent total disc replacement required adjacent level reoperation compared with 11.4% of patients who underwent ACDF (P=0.03).

Prestige LP has shown similar results with a statistically higher rate of neurological success at 7-year follow-up (92% versus 82% with ACDF) and statistically significant fewer secondary surgeries at the index level (4.2% versus 14.6%).⁵ The adjacent level reoperation rate at 7 years was lower for total disc replacement (6.5% versus 12.5%); while this difference did not reach statistical significance, the posterior probability of superiority was 94.2%, which fell just short of statistical significance, Dr. Coric explained.

Ideal Indications for Cervical Total Disc Replacement

Cervical arthroplasty is indicated for patients with radiculopathy due to central/ paracentral disc herniation with 1- and 2-level disease. Contraindications include advanced spondylosis/ osteophytic disease, osteoporosis, severe facet disease, instability, >2-level disease, and global kyphosis.

“If you look at the ideal indications for ACDF, arthroplasty and posterior cervical spine surgery (Table), there is going to be some overlap in the middle of all three,” Dr. Coric said. “But the reality is that their indications are different, and you are a better surgeon if you use all three of these operations, as opposed to just one or two of them.”

Table. Ideal Indications for Cervical Total Disc Replacement, ACDF, and Posterior Cervical Spine Surgery. ACDF, anterior cervical discectomy and fusion (ACDF); cTDR, cervical total disc replacement (cTDR) Source: Coric D. Two-level ADR: IDE Data and Beyond. Presented at: ISASS 19th Annual Conference, April 3-5, 2019, Anaheim, CA.

Disclosures
Dr. Coric disclosed the following relationships:

• Consultant/Stock/Royalties: Premia Spine, SpineWave
• Consultant/Royalties: Globus Medical,  Integrity Implants, Medtronic, Stryker
• Royalties: RTI Surgical
• Spine Advisory Board: United HealthCare