FDA scrutinizes metal hip implants
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WASHINGTON -- Metal hip replacements implanted in a half-million Americans may be failing earlier than expected, but it could be years before U.S. health regulators have a clear picture of the problem.
The Food and Drug Administration holds a two-day meeting starting Wednesday to scrutinize the safety of metal-on-metal hip implants, following years of patient reports of pain and swelling that sometimes requires the devices' removal. It is a challenging but familiar predicament for the FDA: reviewing the safety of a device that was expected to be superior, but which may actually be more dangerous than what came before.
For decades, nearly all orthopedic implants were made from plastic or ceramic. But in the past 10 years, some surgeons began to favor implants made with metal stems and sockets. Laboratory tests suggested that they would be more resistant to wear and reduce chances of dislocation.
But recent data gathered by United Kingdom surgeons appears to show just the opposite. In March, British experts at the world's largest artificial joint registry told doctors to stop using metal-on-metal hip replacements, citing an analysis showing that they have to be replaced more often than other implants.
Hip replacements are supposed to last 10 to 15 years, but more than 6 percent of patients with metal hips needed replacement after fewer than five years. That compared with just 2 percent of people who had ceramic or plastic joints. Both types of devices are prescribed for people suffering hip pain and limited movement due to arthritis or injury.
British regulators now recommend that those with implants get yearly blood tests to make sure no dangerous metals are seeping into their bodies as components rub against each other.
The FDA has not made any recommendations of its own for the estimated 500,000 U.S. patients with the devices. FDA scientists say they want to consider all available data before making their recommendations -- not just the U.K. data.
"Why look at a single registry when there's data from around the world?" William Maisel, the FDA's chief scientist for medical devices, said in an interview. "This is an opportunity for us to look at all the available information, so that we can have a thoughtful conversation about what clinical recommendations can be made."
Dr. Maisel said the FDA is working to combine data from foreign nations and the United States to determine which groups of patients and implants are most problematic. On Wednesday and Thursday, the FDA will ask an expert panel to recommend best practices for monitoring patients with the devices. Panelists will consider blood tests, medical imaging and laboratory tests.
But some U.S. orthopedic specialists say they have already reached their own conclusions about metal hips. "In my personal opinion, there is very little room, if any, for metal-on-metal implants, because the alternatives we have on the market are likely safer and as effective," said public health professor Art Sedrakyan of Weill Cornell Medical College in New York.
The FDA's deliberative approach to tackling the hip implant issue is in some ways a necessity. Unlike other countries, the United States has no national registry to track the implants' performance over time.
The FDA received 16,800 negative event reports involving metal hips between 2000 and 2011, but regulators stress that number is not very useful. Many doctors do not report problems to the FDA, and the volume of reports is influenced by news reports on safety issues.
A registry set up by Minnesota's HealthEast Care System recorded four times as many replacement surgeries for patients with metal-on-metal hips as those with other implant types. But a similar registry set up by health care provider Kaiser Permanente found no difference between the two groups.
With little definitive data on U.S. hip implants, the agency has asked manufacturers such as Johnson & Johnson, Zimmer Holdings Inc. and Biomet Inc. to conduct long-term, follow-up studies of more than 100 metal-on-metal hips on the U.S. market.
But Dr. Sedrakyan and others say it could be a decade or more before that information is available.
First Published June 26, 2012 12:00 am