Two-level Cervical Total Disc Replacement with Mobi-C® Shows Superior Efficacy to ACDF at 7 Years

Kris E. Radcliff, MD presents study results at 31st Annual Meeting of the North American Spine Society

Cervical total disc replacement (cTDR) with the Mobi-C Cervical Disc at two contiguous levels demonstrated superior overall success rates compared to anterior cervical discectomy and fusion (ACDF) through 7 years in a prospective randomized study presented by Kris E. Radcliff, MD, and colleagues.1 In addition, the Mobi-C TDR was linked to significant improvements in Neck Disability Index (NDI) scores and lower rate of subsequent surgeries at both the index and adjacent levels at 7 years, Dr. Radcliff reported at the 31st Annual Meeting of the North American Spine Society in Boston, MA.
Terms related to a medical clinical trial.There was a need to explore the long-term outcomes of cervical spine surgery at two contiguous levels. Photo Source: The Mobi-C Cervical Disc (Zimmer Biomet, Warsaw, IN—formerly LDR Spine, Austin, TX) is a cobalt chromium alloy and polyethylene mobile-bearing prosthesis that is indicated for reconstruction of the disc from C3-C7 following discectomy at one level or two contiguous levels for intractable radiculopathy in patients ages 21 to 67 years.2

“The Mobi-C Cervical Disc is the first device for cTDR to be FDA-approved for use at two contiguous levels,” said lead author Dr. Radcliff, who is Associate Professor of Orthopedic Surgery and Neurological Surgery at the Rothman Institute, Thomas Jefferson University, Philadelphia, PA. “While previous studies have described the long-term outcome of single-level cervical spine surgery, there was a need to explore the long-term outcomes of cervical spine surgery at two contiguous levels,” Dr. Radcliff said.

In Dr. Radcliff’s experience, 2-level pathology is more common than single-level disease in the cervical spine. “I often see patients who have one obviously symptomatic level and one level that is suspicious but less severe. I worry about treating only the worse level because previous studies from my colleague Dr. Alan Hilibrand have demonstrated that preoperative radiographic degeneration is a risk factor for adjacent segment disease.3 Accordingly, it is beneficial for surgeons to have the ability to treat patients with moderate or severe pathology at two levels,” Dr. Radcliff said.

Seven-Year Follow-up Study

The study involved 330 patients with symptomatic cervical degenerative disc disease at two contiguous levels who were randomized in a 2:1 ratio to TDR with Mobi-C (n=225) or ACDF (n=105). None of the patients had a history of previous cervical spine surgery.

The 7-year follow-up study was performed as part of a post-approval study protocol to report the long-term outcome of the cohort of patients included in the original FDA Investigational Device Exemption (IDE) study. The study was funded by LDR Spine (now Zimmer Biomet).

Overall Success Criteria

The FDA-defined overall treatment success criteria used in this study is as follows:

  • Improvement in NDI of at least 15/50 points in subjects with a baseline NDI score of ≥30/50 points, or a 50% improvement in subjects with a baseline NDI score of <30/50 points
  • No secondary surgical interventions at the index level
  • Absence of major complications defined as one of the following:
    • Radiographic failure
    • Neurological failure
    • Adverse event as adjudicated by the clinical events committee

The success criteria were similar to criteria that were used in all the FDA investigational device exemption studies of disc replacement. Dr. Radcliff noted, “I believe that the goal of the composite success measure was to simultaneously measure the various clinical, radiographic, neurological, and adverse events that contribute to the success of these procedures. Regarding reoperation rates, the composite success measure captures patients who underwent secondary surgery as well as those patients who had a poor outcome who chose not to undergo secondary surgery. Other estimates of secondary surgery rates from administrative databases may underestimate the latter group.”

Overall Success Rate Was Markedly Higher with cTDR

The overall success rate of cTDR at 7 years remained statistically superior to ACDF (60.8% vs 34.6%; P<0.0001).  This finding was similar to previous time points, indicating the durability of the results. (Figure 1). While both groups showed significant improvements in NDI score from baseline at all time points, patients given cTDR experienced greater improvement in NDI (Figure 2). Thus, an increased percentage of cTDR patients achieved the NDI threshold of success compared to ACDF.

Figure 1. Overall success rates of cTDR vs ACDF at two contiguous levels.Figure 1. Overall success rates of cTDR vs ACDF at two contiguous levels.

Figure 2. Secondary outcome measures of cTDR vs ACDF at various time points. Reprinted with permission from Kris E. Radcliff, MDFigure 2. Secondary outcome measures of cTDR vs ACDF at various time points. Reprinted with permission from Kris E. Radcliff, MD.Together with published follow-up data from 2-years and 5-years post surgery, the 7-year data show that the success rate is stable over time, Dr. Radcliff said.4,5

In addition, the cTDR group reported significantly lower Visual Analog Scale (VAS) Arm and Neck Pain Scores (P=0.0002 and P=0.02, respectively) as well as significantly higher Physical Component Summary of the Short-Form 12 Health Survey (P=0.0003) at all time points (Figure 2).

Patient satisfaction rates were significantly higher in the cTDR group at the following time points: 12 months (88.2% vs 75.8%), 48 months (84.6% vs 72.6%), 60 months (85.7% vs 75.0%), and 84 months (86.0% and 73.9%; P<0.05 for all comparisons).

Continue reading the study outcomes

Disclosures: Kris E. Radcliff, MD
4 Web Medical: Stock or stock Options; Unpaid consultant
ACSR: Board or committee member
Altus Spine: IP royalties; Paid consultant
DePuy, A Johnson & Johnson Company: Paid consultant; Research support; Unpaid consultant
Globus Medical: IP royalties; Paid consultant; Research support
LDR: Unpaid consultant
Medtronic: Paid consultant; Research support
NEXXT Spine: Other financial or material support
Nuvasive: Other financial or material support
Orthofix, Inc.: Paid consultant
Orthopedic Sciences, Inc: IP royalties; Paid consultant
Pacira pharmaceuticals: Research support
Paradigm Spine: Research support
Stryker: Other financial or material support

Updated on: 06/05/19
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Seven-Year cTDR Outcomes with Mobi-C® Shows Superior Efficacy to ACDF

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