Lumbar total disk replacement (TDR) with the Charité™ artificial disk did not preclude any further procedures at the index level during primary insertion, said Paul C. McAfee, MD, who led a prospective, randomized, multi-center study on the artificial disk. “Nearly one-third were revised to a new motion preserving prosthesis, and just over two-thirds were converted to fusions,” he said.

Disk doesn’t “burn any bridges”

Lumbar TDR with the Charité artificial disk does not “burn any bridges” for future procedures, Dr. McAfee told an audience gathered for the North American Spine Society’s 2007 Specialty Day presentations.

The Charité disk is the first artificial spinal disk approved by the U.S. Food and Drug Administration (FDA) to treat single-level degenerative disk disease by replacing a damaged or worn out spinal disk with an artificial one. The three-piece device is made of two metallic endplates and a moveable high-density plastic center that is designed to help align the spine and preserve its ability to move.

First report on reoperations

“Prior authors have described the anecdotal incidence of revision and reoperation following lumbar TDR,” Dr. McAfee said, “but this is the first report of the incidence and nature of these reoperations as part of a controlled, prospective, multi-center trial.”

Dr. McAfee and his colleagues conducted the FDA-regulated investigational device exemption (IDE) clinical trial at 14 centers across the United States.

A total of 688 patients meeting the inclusion and exclusion criteria were enrolled in the study. The cohort that received the Charité artificial disk included 71 patients nonrandomized as part of surgical training on the device, 205 patients randomized to surgery, and 313 patients receiving continued-access care. The control group included 99 patients randomized to receive anterior lumbar interbody fusion (ALIF) with threaded fusion cages and autograft.

The researchers performed a detailed analysis of clinical chart notes, operative notes, and adverse event reports for all patients who required another lumbar operation after the index surgery.

The findings

Of the 589 patients who received the Charité artificial disk, 52 (8.8 percent) required reoperation. That rate is not significantly different from the rate of fusion subjects who required reoperation (10.1 percent). An additional two patients from the control group required surgery for adjacent level disease.

Of the TDR patients who underwent a repeated anterior retroperitoneal approach, the prosthesis was successfully removed in 22 of 24 cases (91.7 percent). In seven of the 24 cases, the prosthesis was revised to another Charité artificial disk, usually of smaller size. The mean time to reoperation for all patients was 9 months. A total of 29 patients (4.9 percent) in the TDR group required posterior instrumentation and fusion, as did 10 patients (10.1 percent) in the control group.

High success rate at 2-yearfollow-up

“At two years or more follow-up, 93.9 percent of patients who received TDR with the Charité artificial disk had a successfully functioning prosthesis, with a mean of more than 7 degrees of flexion-extension mobility,” Dr. McAfee reported.

“Lumbar TDR with the use of the artificial disk did not preclude further procedures after primary insertion. Nearly one-third of patients were revised to a new motion-preserving prosthesis, and just over two-thirds successfully converted to ALIF and/or posterior pedicle screw arthrodesis—the original alternative procedure.”

The results of Dr. McAfee’s study have been published as a Revisability of the Charité Artificial Disc Replacement: Analysis of 688 patients enrolled in the U.S. IDE study of the Charité Artificial Disc.” Spine, 2006;31(11):1217-1226.