#141 Seven-year Results of the ProDisc-C Multi-center Randomized Clinical Trial

General Session: Cervical Motion Preservation

Presented by: J. Zigler

Author(s):

J.E. Zigler (1)
D.B. Murrey (2)
R.B. Delamarter (3)
J.M. Spivak (4)
M. Janssen (5)

(1) Texas Back Institute, Plano, TX, USA
(2) OrthoCarolina Spine Center, Charlotte, NC, USA
(3) The Spine Institute at Saint John's Health Center, Santa Monica, CA, USA
(4) Hospital for Joint Diseases Spine Center, New York, NY, USA
(5) Center for Spinal Disorders, Thornton, CO, USA

Abstract

Introduction: Cervical artificial disc replacement (C-ADR) is intended to treat symptomatic cervical degenerative disc disease (SCDD), as an alternative to cervical fusion. C-ADR maintains motion at the vertebral segment, while allowing for the decompression and relief of radicular symptoms. The purpose of this trial is to compare the safety and efficacy of C-ADR to anterior cervical discectomy and fusion (ACDF) surgery for the treatment of one-level SCDD between C3 and C7.

Methods: A prospective, randomized, controlled clinical trial was performed. Patients were enrolled and treated in accordance with the US Food and drug Administration (FDA)-approved protocol. 7 year follow-up data is presented. The study was conducted at 13 sites. A noninferiority design with a 1:1 randomization was used. Two hundred nine patients were randomized and treated (106 ACDF: 103 C-ADR). Outcome measures included: visual analog scale (VAS) pain and intensity (neck and arm), VAS satisfaction, neck disability index (NDI), neurological exam, device success, adverse event occurrence, and short form-36 (SF-36) standardized questionnaires.

Results: Demographics were similar between the two patient groups (C-ADR 42.1 years, 44.7% male; ACDF 43.5 years, 46.2% male). The most commonly treated level was C5-6 (C-ADR: 56.3%; ACDF: 57.5%). In each cohort, 54 of 66 (81.8%) of those who were alive, were 7 years post-op and agreed to participate in the long-term study were available for follow-up. Overall 54/103 (52.4%) of C-ADR patients and 54/106 (50.9%) of ACDF patients were available for follow-up. For all variables, there was significant improvement from baseline values. For all variables except secondary surgery and willingness to have the surgery again, there was no significant difference between the treatment groups. NDI at 7 years was significantly improved from baseline in both treatment groups (p=0.0001) with C-ADR 20.9 (64.2% improvement) and ACDF 22.5 +/- 21.1 (55.9% improvement). VAS satisfaction scores were similar at 7 years (p-value 0.26) with C-ADR at 86.7 and ACDF at 80.4. Secondary surgical procedures did show a difference with 6/103 (5.8%) in the C-ADR cohort compared to 17/106 (16.0%) in the ACDF group. Eight of 103 (7.2%) patients in the C-ADR cohort developed bridging bone at 7 years while 4/106 (3.8%) ACDF patients had nonunions that had not required reoperation. There was no difference in clinical outcomes of those C-ADR patients with or without bridging bone. Finally, a difference was noted in willingness to have surgery again with 100% C-ADR patients responding yes/maybe and 91.7% ACDF (p= 0.0423).

Discussion: Seven year data from this C-ADR trial shows it to be a safe and effective alternative to ACDF in the treatment of cervical DDD. C-ADR had lower rates of secondary surgery and C-ADR patients were happier with their decision to have the original surgery than ACDF patients. The rate of bridging bone in the C-ADR cohort was 8/103 but six of the eight patients came from only 2 of the 13 centers suggesting this may be related to technique or post-op protocol differences rather than device-related.