Charité disc found more effective than lumbar fusion

Hospital stay, VAS and Oswestry scores and patient satisfaction were improved with the artificial disc.

Issue: December 2004

Total disc replacement using the Charité artificial disc was found to provide greater improvement than anterior lumbar interbody fusion using BAK cages in patients with symptomatic lumbar degenerative disc disease.

Scott Blumenthal, MD, of the Texas Back Institute in Plano, presented the results of this prospective, randomized, noninferiority study at the North American Spine Society 19th Annual Meeting in Chicago.

“The hypothesis [was] that the success rate in the Charité group will be at least as good as in the BAK group,” he said.

Investigators carried out the study at 15 centers with 304 patients randomized at 2:1 Charité disc replacement (DePuy) to fusion. Patients were aged 18 to 60 years, with symptomatic degenerative disc disease at L4-L5 or L5-S1. All patients had failed at least six months of supervised nonoperative treatment.

Optimal control group

“The BAK cage was chosen as the optimal control group, as the surgical approach and surgical morbidities were the same, and at the time, the BAK was the state of the art in FDA-approved technology,” Blumenthal said.

AP view of the implanted Charité artificial disc.

X-ray of the implanted Charité artificial disc.

COURTESY OF SCOTT BLUMENTHAL

Patients were excluded if they had noncontained disc herniation, spinal stenosis, osteoporosis or metabolic bone disease, deformities or instabilities greater than 3 mm and if they had undergone previous lumbar fusion. Data were collected preoperatively, perioperatively and at three, six, 12 and 24 months postoperatively.

The researchers measured primary outcomes using the Visual Analog Scale (VAS), which assessed pain, an Oswestry questionnaire, SF-36 and patient satisfaction. Secondary outcomes included operative time and blood loss during surgery.

“The follow-up status was quite robust, with follow-up rates of greater than 90% at all the follow-up intervals in both groups,” Blumenthal said.

The success criteria included four primary endpoints: an improvement in the Oswestry of 25% or greater from baseline to 24 months; no additional surgery at the treated level; no major complication; and the maintenance of neurologic status from baseline to 24 months. To be considered a success in either treatment arm, all four criteria needed to be satisfied, he said.

Blumenthal said that the Charité artificial disc was found to be at least equivalent in overall success to the BAK cage with an overall greater success rate, “thus proving the primary hypothesis.”

Three of the four efficacy endpoints – device failure, complications and neurologic deterioration – were found to be similar in the two groups. The Charité disc was found to be statistically superior in terms of the 25% or greater Oswestry improvement criterion.

The Charité patients also outperformed the BAK group, with statistically significant differences at six weeks, three months, six months and 12 months.

Patients receiving the Charité disc were more satisfied with the treatment, with 69% saying they would “definitely” choose the same treatment again, and another 13% saying they would “probably” choose the disc replacement. Among patients in the fusion group, the corresponding numbers were 52% and 13%, respectively.

The mean hospital stay for the Charité patients was 3.7 days vs. 4.3 days for the fusion group. Mean operative time was similar for the two groups (111 minutes for the disc replacement group and 114 minutes for the fusion group), as was the estimated blood loss (207 ml vs. 209 ml).

Charité: a good first step

The problem needs to be localized in the disc itself, and the facet joints need to be free of arthritis for the Charité disc to be most effective.

“Spine surgery, like all surgery, is slowly evolving, and I think that the Charité is a good first step,” said Hansen A. Yuan, MD, of SUNY Upstate in Syracuse, N.Y. “So will it become the standard of care? Yes, for the right indication, it should. However, if it is broadly used inappropriately, this could be a disaster.” He stressed that the problem needs to be localized in the disc itself, and the facet joints need to be free of arthritis for the Charité disc to be most effective.

Yuan is aiding in the development of several new generations of discs, including a new version that has more cushion than the current artificial discs.

“Whether it is a polyethylene ball or a metal ball, they are all hard, so they don’t yield,” he said. “So the next generation will be [facing] that. There’s no question there will be gradual evolution, hopefully into better implants,” said Yuan, who is a member of the Spine Section of the Orthopedics Today Editorial Board.

The FDA approved the Charité artificial disc in October.

For more information:

Blumenthal S, McAfee P, Guyer R, et al. Prospective randomized comparison of total disc replacement to fusion a 24-month follow up FDA-regulated study. #16. Presented at the North American Spine Society 19th Annual Meeting. Oct. 27-30, 2004. Chicago.