An FDA advisory panel plans two-days of public hearings this week to examine metal-on-metal hip implant data so it can update the agency on the risks and benefits of the devices, which have come under increased scrutiny following news reports of device failure.
The agency's Orthopaedic and Rehabilitation Devices advisory panel will meet Wednesday and Thursday to discuss the current data on the safety and effectiveness of metal-on-metal hip arthroplasty systems. The FDA is seeking the panel's opinion on the relative risks and benefits of these devices based on the existing scientific literature.
Briefing documents for the meeting included an FDA review of more than 100 studies of metal-on-metal hip, studies that suggested the artificial hips may pose problems for women and for patients who received larger-sized hip implants.
Among five studies that looked at revision rates by sex, the rates ranged from 19.8% for women in one study of 545 patients, to 0% for men in another study of 185 patients (with mean follow-up times of 5 years and 3 years, respectively).
As for size differences, one study of 2,179 patients found that head sizes of greater than 32 mm were less likely to be revised for dislocation, the reviewers noted.
Artificial hip devices are used to relieve pain and restore joint function in patients with chronic hip pain or disease which is not responsive to more conservative therapy. About 400,000 hip arthroplasty procedures are performed in the U.S. annually, FDA staff noted in its briefing materials.
The advisory panel will discuss two types of hip arthroplasty systems: total hip replacement systems and hip resurfacing systems. Resurfacing systems are used in younger or more active patients who may not be suitable for traditional total hip arthroplasty.
Recently published registry date suggest that during use, tiny metal particles may wear off the devices. These particles may possibly the bloodstream, causing bone damage, tissue damage, or illnesses elsewhere in the body, such as the heart and nervous system. In addition, revision surgery rates may be higher for patients who have these implants.
In a February 2012 report, the BMJ charged that U.S and U.K. regulators were slow to inform patients and their doctors about these problems. BMJ said that the U.K.'s Medicines and Healthcare Products Regulatory Agency first became aware of problems with metal-on-metal implants in 2006, but did not issue a formal warning to physicians and patients until 2010.
FDA began informing the public about metal-on-metal hip implant risks in February 2011.
In May 2011, FDA ordered post-market surveillance studies from all companies that make these systems. But the studies have been slow to get underway and may not provide useful information to physicians and patients, physicians warned in a recent New England Journal of Medicine article.
These devices have been the subject to two significant recalls in recent years: the 2008 recall of Zimmer's Durom Acetabular Component because of inadequate instructions for use, and the 2010 recall of the DePuy ASR Total Hip due to higher-than-expected revision rates, FDA reviewers wrote.
More recently, Smith & Nephew pulled its R3 Acetabular System metal hip socket liner from the market due to higher-than-acceptable annual revision rates in patients who had this device.
The FDA advisory panel will discuss whether U.S. and outside-the-U.S. data should be considered together when looking at the safety of this device, or whether there are key differences between these data sources. The panel also will consider what other data should be gathered in existing and new hip implant registries, and what the best follow-up methods are for symptomatic and asymptomatic patients who have these implants.
Finally, the panel will discuss which patient populations are most likely to benefit from these implants, and what information should be conveyed to physicians and patients in the product labeling.
In comments submitted to FDA before the meeting, John W. Noble Jr., MD, of the Center for Orthopaedics in Lake Charles, La., who is conducting one of the FDA post-market approval studies, said that despite what he called the "mass hysteria" over metal-on-metal hip implants, "our results seem to be quite good."
"This operation appears to be at least as successful as conventional hip replacement in our hands," Noble wrote.