Charité disc recommended for approval

The device would be the first artificial spinal implant approved in the United States.

Issue: July 2004

GAITHERSBURG, Md. — The Orthopaedic and Rehabilitation Devices Panel has unanimously recommended FDA approval of the Charité Artificial Disc.

The Charité Artificial Disc (DePuy Spine Inc.), intended for spinal arthroplasty in patients with single-level lumbar degenerative disc disease from L4-S1, has been used in Europe since 1987. The panel recommended its approval with conditions.

“We don’t know all the issues related to the cause of back pain. [The Charité Artificial Disc] is an empirical measure to try to solve that problem,” said panel member John Kirkpatrick, MD, University of Alabama School of Medicine, Birmingham.

“The motion, as approved, was a reasonable compromise of the need for long-term follow-up for both safety and effectiveness measures with the potential benefit to patients and the sponsor’s desire to place it quickly on the market,” Kirkpatrick said.

Conditions for approval

The Charité Artificial Disc for degenerative disc disease is made of two metal endplates and a polyethylene core that mimics the motion and function of a normal disc. It is the first artificial disc to be reviewed by the panel and recommended for FDA approval.

COURTESY OF DEPUY SPINE INC.

According to information on the FDA Web site, the first condition the panel recommended for the Charité disc was that a postmarket study of all patients enrolled in the investigational device exemption (IDE) study (including continued access patients) should be followed until the last-enrolled continued access patient reaches the two-year time point. The follow-up data from all these subjects should be provided to FDA.

Additionally, all patients who are treated with the Charité Artificial Disc should have access to documentation describing the specific components of their implant, including associated lot numbers, as well as a telephone number to be used for the reporting of any adverse events.

A postmarket in vitro study should be done to further assess wear debris. Wear debris testing should be conducted using a combination of flexion/extension and lateral bending motions (without axial rotation) to determine if this combination would produce a different wear profile.

Finally, the FDA should consider requiring that surgeons receive training on how to implant the device.

The panel also recommended that the FDA and DePuy Spine Inc. discuss the following possible conditions to come to a mutually agreeable course of action. The discussion between the two should be to consider whether each item, if determined to be relevant and reasonable given the study protocol, should be addressed pre- or postmarket:

Provide mobility testing data or complete references.
Provide an adequate rationale for “normal biomechanics” including demonstration that facet joint strains/stresses are comparable to the control group patients.
Provide an adequate rationale for not testing the biological response to submicron particles of ultra high molecular weight polyethylene.
Clarify the neurological grading scale and how statistics were applied to this measure.
Stratify results by indication group, particularly for patients with facet joint changes noted in preoperative assessments, for both the investigational and control groups.
Consider IDE patients with range of motion ranging from 0º to 5º at two years as failures, and reevaluate the data.
Consider if axial imaging can be done to compare facet degeneration at the index level at two years and preoperatively.
Provide radiographic evaluation of adjacent segment degeneration for the preoperative and two-year time points, as well as through the follow-up period described in the first condition.

An innovation

“This device represents a significant innovation in our strategy to treat a very challenging clinical problem,” said Choll W. Kim, MD, PhD, University of California, San Diego. Kim served as a consultant for the panel.

“[DePuy Spine Inc.] has done an excellent job in obtaining both preclinical and randomized controlled clinical trials. We all appreciate that the key question of implant longevity cannot be answered. Luckily, we do have some data from the European experience that helps us feel more comfortable with the fact that this is likely an efficacious and safe procedure comparable with what exists today,” Kim said during the FDA meeting.

William R. Christianson, vice president of clinical and regulatory affairs for DePuy Spine Inc., said that the premarket approval conditions were reasonable.

“We are very pleased with the results of the panel review. The panel was thorough in their analysis, and their recommendations represent reasonable considerations. In fact, surgeon training and follow-on clinical and biomechanical studies were already in progress. We’re working on the answers now and we are continuing to move forward efficiently. We do not expect significant delays in the potential approval timeframe,” he told Orthopedics Today.