Artificial Spinal Disc Nears Approval
Experts Say More Long-Term Safety Information Needed
June 3, 2004 -- An expert panel has backed a new artificial disc implant, recommending that the FDA approve it to treat patients with degenerative disc disease in the lower spine.
The polyethylene and metal device, called Charité, would be the first permanently implantable artificial disc to come to the U.S. market if the FDA gives it the go-ahead. It has been available in Europe since 1987, where approximately 7,000 patients have received it.
Charité's advantage over existing implants is that it is designed to stay in the body permanently and perform like the body' own spinal discs. Currently available implants serve only to stabilize adjacent bones in the spine until the bones fuse together, limiting the spine's mobility.
Patients with degenerative disc disease can experience severe back pain that is usually worse when sitting or driving a car. About 30% of those patients with severe pain would be candidates for Charité disc replacement, since the company is only seeking approval for the device for single disc replacement.
Studies show a 64% success rate two years after surgery for patients who received the Charité disc implant compared to a 58% success rate for 99 patients who got an older titanium implant called the BAK cage. The FDA defined success as at least a 25% improvement in disability scores along with no major surgical complications or device failures.
"It appears the study has demonstrated the non-inferiority of the Charité," says Sergio M. de la Castillo, a reviewer in the FDA's orthopaedic devices branch.
More Data Requested
But experts approved Charité on the condition that its maker, DePuy Spine Inc., provide more information on the implant's safety in the years to come. The company has followed most patients for two years, and experts say they want data for at least five years after surgery and implant placement.
"I think we're all pretty much agreed that two years is probably not a safe period of time to follow these patients," says Maureen A. Finnegan, MD, an orthopaedic surgeon at the University of Texas Southwestern Medical Center and a member of the panel.
About three-quarters of patients who got either a Charité or a BAK implant experienced at least one adverse event including neurological damage, ongoing pain, or disc malfunction. About 12% of Charité patients experienced infection, twice the rate as patients receiving BAK. Company officials say none of the infections was device related.
FDA officials also say that 15% of Charité patients experienced "life-threatening" complications, slightly higher than the 9% rate seen in BAK patients.
That concerns some doctors, who warn that inevitable surgeries to correct failed Charité discs may be complicated and dangerous. It is unclear whether these corrective surgeries can be reliably performed on the back, or whether a malfunctioning disc will have to be removed through an incision that enters the body through the front.