GAITHERSBURG, MD. — A federal advisory panel supported the approval of a stainless steel artificial cervical disk for patients with single-level cervical degenerative disk disease, provided that the manufacturer evaluates long-term efficacy and safety in a postmarketing study.
The Food and Drug Administration's Orthopedic and Rehabilitation Devices panel agreed in a 7–0 vote that the Prestige cervical disk, manufactured by Medtronic, was “approvable” but recommended further study. The device is under review for use in skeletally mature patients with cervical degenerative disk disease (DDD) at one level from C3 to C7. DDD is defined as intractable radiculopathy and/or myelopathy that produces symptomatic nerve root or spinal cord compression because of a herniated disk or osteophyte formation.
Panelists agreed that the 2-year study demonstrated the safety and efficacy of the Prestige disk for this indication, but they were concerned about the long term because recipients of the device will have expected life spans of 30–50 years after implantation.
The two-piece device is made of stainless steel, with a metal-on-metal articulation and a ball and trough mechanism, which is affixed to the vertebral body with two bone screws. The device was compared with an anterior plated fusion procedure with structural allograft in a noninferiority, prospective, randomized study of 541 patients (mean age 43–44 years). The patients had single-level cervical DDD, inadequate response to 6 weeks of conservative therapy, signs of progression or spinal cord/nerve root compression, and a neck disability index (NDI) of 30 or greater.
Based on an interim analysis of the data at 24 months after surgery in 250 patients, 80.5% of the Prestige group and 71% of the fusion (control) group met the criteria for overall success (defined as at least a 15-point improvement in the NDI score, neurological maintenance or improvement, no serious adverse event that could be associated with the device, and no second surgery failure), according to Medtronic. Furthermore, the company said, radiographic evaluations indicated that patients' motion was maintained after surgery.
About 80% of patients in both groups experienced adverse events; most occurred perioperatively and resolved over time. The rate of device-related adverse events was 3% in Prestige recipients and nearly 10% in controls, a difference due mostly to cases of pending nonunions. Fewer nonunions and spinal events occurred in the Prestige group, while rates of urogenital adverse events were lower in the fusion group. There were three deaths among fusion patients and none in the Prestige patients.
Mean NDI scores improved by about 80% (15-point improvement) in both groups at 12 and 24 months.
Panelists recommended that the Prestige disk be described as “noninferior” rather than superior to the fusion procedure, because that was what the 2-year study had demonstrated. As another condition for approval, the panel recommended that the company conduct a study in animals to examine the generation and fate of particulate debris from the device, which is a concern associated with metal-on-metal devices.
Medtronic plans to evaluate the same end points, NDI, neurological status, second procedures, and adverse events in patients at 5 years and 7 years after surgery. In response to investigators' suggestions, the device's design has been modified and larger sizes have been added, but these were not studied in the trial, according to the company.
The FDA usually follows the advice of its advisory panels. If approved, the Prestige disk would be the first artifical cervical disk to be marketed in the United States. The agency previously approved two artifical lumbar disks.