Survivorship Analysis of the Charité Artificial Disc: Review of 1,938 Patients

[Justin]

The Spine Journal
Volume 7, Issue 5, Supplement 1, September-October 2007, Pages 81S-82S
Proceedings of the 22nd Annual Meeting of the North American Spine Society

Survivorship Analysis of the Charité Artificial Disc: Review of 1,938 Patients from Eight Leading International Spine Centers

Bryan W. Cunningham MSc1, George Demuth MSc2, Paul C. McAfee MD3, Matthew Scott-Young MD4, Kj Yoon MD5, Scott Blumenthal MD6, Richard D. Guyer MD6, Fred Geisler MD7, John Regan MD8, Bart Conix MD9, Robert Hes MD9, Luiz Pimenta MD10, Roberto Diaz MD11, Ira L. Fedder MD12 and P. Justin Tortolani MD13

1St. Joseph Medical Center, Towson, MD, USA
2NC, USA
3St. Joseph Hospital, Towson, MD, USA
4Southport, Queensland, Australia
5seoul, South Korea
6Texas Back Institute, Plano, TX, USA
7Chicago, IL, USA
8Beverly Hills, CA, USA
9AZ middleheim hospital, Antwerpen, Belgium
10Sao Paolo, Brazil
11Sao Paulo, Brazil
12Spine and Scoliosis Center, Towson, MD, USA
13MD, USA

PURPOSE: The current investigation reviews data from 1,938 Charité Artificial Disc patients at eight international spine centers and examines the incidence of surgical revision at the index and adjacent levels.

STUDY DESIGN/SETTING: Patients from eight leading international spine centers were evaluated in this study.

PATIENT SAMPLE: A total of 1,938 patients served as the basis for this study.

OUTCOME MEASURES: Surgical revision, reoperation or implant at the index and adjacent levels.

METHODS: A total of 1,938 patients were included in this analysis. 305 patients from the United States were all single level reconstructions and included those randomized in the Charité Food and Drug Administration Investigational Device Exemption and continued access studies. 1,633 patients from Australia, Korea, Belgium and Brazil all received single or multilevel Charité Disc implantations (two to four levels). Survival of the prosthesis was defined as absence of implant revision and re-operation at the index level, including removal of the prosthesis. Any incidence of surgical re-intervention at the adjacent level(s) was also compared to ALIF controls (n=58). Patient populations were divided into five groups -United States, Australia, Korea, Belgium, and Brazil - and tabulated in terms of total patient number, reoperative rate, mean overall follow-up, and mean follow-up at revision. For each group, Kaplan-Meier estimates were provided for the time to revision. For individual sites and the overall plot of subjects, the 95% lower two-sided bound was used as obtained from Peto's adjusted standard error. Patients were further grouped into postoperative time intervals of less than or greater than 2 years follow-up. A likelihood ratio chi-square test was performed on each subset to determine whether an association existed between clinical failure and the number of months to follow-up.

RESULTS: Mean follow up was 23 months. The 5-year predicted survivorship for the Charité Artificial Disc (without revision, reoperation, or removal) ranged from 91.6% (Brazil) to 96.2% (Korea), with an average of 93.1%. This compares with 80.1% for ALIF with BAK cages. The lower confidence limit for Charité Artificial Disc survival was 87.7%, and the lower confidence limit for lumbar fusion was 51.5%, which is highly significant (p=0.0034). The predicted five-year survivorship for the adjacent levels in Charité cases averaged 95.6%, with 19/1938 cases requiring surgical reintervention. This compares with 89.0% survivorship for ALIF with BAK cages at the same time interval, which was significantly different (p=0.035). The likelihood ratio test suggests that a statistically significant association exists with clinical failure occurring early postoperatively if it occurs (p=0.020).

CONCLUSIONS: This investigation is the first international, long-term survivorship analysis conducted on the Charité Artificial Disc. The 5-year predicted survivorship for the Charité, based on patient return to the operating room, is 93.1%. Moreover, the frequency of surgical reintervention and revision at the index level following Charité Artificial Disc reconstruction is significantly greater within the first 2-year postoperative interval than at 2 to 8 years postoperatively.

FDA DEVICE/DRUG STATUS: Charité Artificial Disc: Approved for this indication.

Copyright © 2007 Elsevier Inc. All rights reserved.