Members of FDA’s Orthopedic and Rehabilitation Devices Advisory Panel recently explained they see little value in most patients receiving metal-on-metal replacement hips. The panel was asked to discuss the current status of such replacement hips in light of increasing reports of patients having problems with them.
FDA has not talked about a recall of the devices and the panelists stopped short of calling for one. But most panelists said there were few, if any, cases where they would recommend implanting the devices. “I do not use metal-on-metal hips, and I can see no reason to do so,” said committee chair William Rohr.
Recent data gathered from foreign registries show the devices fail at a higher rate than older implants. That information comes on top of nearly 17,000 reports to FDA of problems with the implants, which sometimes require invasive surgery to replace them. Experts say that the pain and inflammation reported by patients is usually caused by tiny metal particles that seep into the joint, damaging the surrounding tissue and bone. The long-term effects of elevated metal levels in the bloodstream are not clear, though some studies have suggested links to neurological and heart problems.
Agency staff told the committee that patients complaining of pain and other symptoms should get regular x-rays and blood testing for metal levels. However, panelists reportedly noted problems with the accuracy of blood tests and the difficulties of interpreting the results. There are no standard diagnostic kits for sale that test for chromium and other metals. For patients who are not experiencing pain, panelists said annual x-rays would be sufficient to monitor their implants.
FDA scientists say the studies will help “fill in the blanks” on a number of scientific questions, including the long-term effects of metal particles. But public health advocates said it could take a decade before that information is available.
Writing in the New England Journal of Medicine, Joshua Rising of the Pew Charitable Trusts and colleagues said that “there is now compelling evidence that these implants fail at a higher rate than hip prostheses made of other materials; indeed, one type of metal-on-metal hip has a failure rate of nearly 50% at six years.”
Critics, including an independent panel of experts at the Institute of Medicine, reportedly have expressed concern that metal-on-metal implants may have been approved too quickly under FDA’s “fast-track” program for medical devices.
Responding to concerns, in May 2011 FDA ordered manufacturers to carry out post-marketing studies, tracking the safety of the implants in recipients. But in the New England Journal article, Rising reported that most of these studies have yet to begin and their first results will take years to arrive.
Metal-on-metal devices have already been recalled twice. In 2008, Zimmer’s Durom Acetabular Component, was recalled because instructions were not clear. And in 2010, a DePuy Orthopaedics device was recalled because more patients than expected had to have new surgeries, according to FDA. Earlier this month, a device called the Smith & Nephew R3 Acetabular System was taken off the market because the company said it was “not satisfied with the clinical results of this component.”
“Keeping these metal-on-metal hips on the market for the next five to 10 years while research is conducted is not ethical,” said Diana Zuckerman, president of the National Research Center for Women & Families, during a public comment session at the meeting. “If the companies want to sell metal-on-metal hips, they should be required to prove their safety first.”