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A Meta-Analysis of Comparative Outcomes Following Cervical Arthroplasty or Anterior Cervical Fusion: Results From 4 Prospective Multicenter Randomized Clinical Trials and Up to 1226 Patients

McAfee, Paul C. MD, MBA*; Reah, Chris PhD; Gilder, Kye PhD; Eisermann, Lukas MS; Cunningham, Bryan MSc*

doi: 10.1097/BRS.0b013e31823da169
Cervical Spine

Study Design. Meta-analysis of 4 prospective randomized controlled Food and Drug Administration (FDA) Investigational Device Exemption (IDE) clinical trials.

Objective. To maximize the information available from 4 IDE studies by analyzing the combined outcomes of cervical arthroplasty versus fusion at 24-month follow-up.

Summary of Background Data. To date, 4 randomized clinical trials have been completed in the United States under FDA IDE protocols to study cervical arthroplasty. Each trial reported arthroplasty to be at least as successful as fusion controls based on noninferiority trial designs. However, sample sizes in any given trial may not be sufficient to demonstrate superiority of treatment effect. Meta-analysis enables pooling of results from comparable trials, which may lead to more precise and statistically significant estimates of treatment effect.

Methods. Four cervical arthroplasty randomized clinical trials with comparable enrollment criteria and outcome measures were conducted independently by 3 separate sponsors to study the following devices: Bryan, Prestige, ProDisc-C, and PCM cervical disc replacements. A total of 1608 patients were treated across 98 investigative sites. Data were available for 1352 treated patients, of which 1226 were evaluable at 24 months. Assessments included clinical success definitions based on neck disability index, maintenance or improvement of neurological status, subsequent surgery or intervention at the index level (survivorship), and a composite score comprising these as well as serious device-related adverse events. Trial endpoint comparisons were made at 24 months postoperatively. For each endpoint, a random-effects meta-analysis was performed to compare the success rates of cervical arthroplasty with anterior cervical discectomy and fusion (ACDF). Also, supportive frequentist and Bayesian analyses were performed.

Results. The pooled primary overall success results indicated a statistically significant treatment effect favoring arthroplasty compared with ACDF. Overall success was achieved by 77.6% of the arthroplasty patients and by 70.8% of the ACDF patients (pooled odds ratio [OR]: 0.699, 95% confidence interval [CI]: 0.539–0.908, P = 0.007). The results of the individual subcomponent meta-analyses, all of which favored arthroplasty, were neck disability index success (OR: 0.786, 95% CI: 0.589–1.050, P = 0.103), neurological status (OR: 0.552, 95% CI: 0.364–0.835, P = 0.005), and survivorship (OR: 0.510, 95% CI: 0.275–0.946, P = 0.033). Only the survivorship endpoint suggested low heterogeneity.

Conclusion. These findings suggest that cervical arthroplasty is superior to ACDF in overall success, neurological success, and survivorship outcomes at 24 months postoperatively.

Meta-analysis of 4 completed US Investigational Device Exemption trials of cervical arthroplasty versus instrumented discectomy and fusion shows superiority of cervical arthroplasty in the treatment of symptomatic single-level cervical degenerative conditions with respect to overall clinical success, neurological success, and survivorship outcomes at 24 months postoperatively.

*Spine and Scoliosis Center, St. Joseph's Hospital, Baltimore, MD; and

NuVasive, Inc., San Diego, CA.

Address correspondence and reprint requests to Paul C. McAfee, MD, MBA, Spine and Scoliosis Center, St. Joseph's Hospital, O'Dea Medical Bldg #104, 7505 Osler Dr, Towson, MD 21204; E-mail:

Acknowledgment date: January 11, 2011. First revision date: September 17, 2011. Acceptance date: September 28, 2011.

The device(s)/drug(s) that is/are the subject of this manuscript is/are being evaluated as part of an ongoing FDA-approved investigational protocol (IDE) or corresponding national protocol for anterior cervical discectomy and fusion.

Corporate/industry funds were received to support this work.

One or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., honoraria, gifts, consultancies, royalties, stocks, stock options, decision-making position.

© 2012 Lippincott Williams & Wilkins, Inc.