Thousands of people with metal-on-metal hip implant devices could soon get some answers from the U.S. Food & Drug Administration (FDA) about the dangers they face. Tomorrow, the agency will convene a panel of outside medical experts to examine the safety record of metal-on-metal hip replacements, and recommend the best practices for monitoring patients with the devices. While hopes are high that the meeting will ultimately lead to some type of guidance for metal-on-metal hip replacement patients and their doctors, many experts fear the FDA panel could be hindered by a lack of research that adequately measures the specific safety risks associated with the implants.
Metal-on-Metal Hip Implant Safety Concerns
When metal-on-metal hip implants were first brought to market nearly a decade ago, it was thought that they would be superior to devices made from plastic or ceramic. As we’ve reported previously, most metal-on-metal hip implants sold in the U.S. were approved via the FDA’s 510(k) process, which doesn’t require human testing. According to a report from the Associated Press, lab tests indicated that metal-on-metal hip replacement devices would more resistant to wear and reduce the chances of dislocation. However, real-world experience has shown this not to be the case, as a shockingly high number of metal-on-metal hip implant patients have been stricken with severe pain, swelling and other issues that sometimes required removal of the devices.
Concerns about metal-on-metal hip implants peaked with the 2010 worldwide recall of DePuy Orthopaedics ASR hip implant devices, which were failing in about 12 percent of patients within just five years of implantation. Since then, a number of studies have pointed to significant problems with metal-on-metal hip implants. In February, the British Medical Journal warned that thousands of people with metal-on-metal hips could be at risk from potentially high levels of metallic ions released by the devices. The following month, The Lancet published a study showing that metal-on-metal implants failed at a rate of 6 percent in five years, as opposed to the 1.7 to 2.3 percent seen in their plastic or ceramic equivalents. The authors subsequently advised a ban on the devices.
An FDA report released in advance of tomorrow’s meeting does indicate that guidance from the agency is desperately needed. According to the document, data from orthopedic implant registries as well as peer-reviewed journal publications and presentations at scientific meetings have suggested increases in potential safety issues associated with metal-on-metal hips, including:
- Local complications such as pseudotumors and aseptic lymphocytic vasculitis-associated lesions
- Early device failure and the need for revision surgery
- Systemic complications from metal ion exposure
Last week, the FDA revealed that it had received 16,800 negative event reports involving metal hips between 2000 and 2011. Of those, more than 14,000 involved revision surgeries, in which a defective implant was removed.
Regulators in the U.K. and Canada have already issued guidance to help doctors and patients deal with complications from metal-on-metal hip implants. But while the FDA has asked all of the manufacturers that market metal-on-metal devices in the U.S. to conduct safety studies of their products, no recommendations have been forthcoming from the agency. That could change after tomorrow’s meeting. Among other things, the panelists will be asked to consider whether blood tests, medical imaging and laboratory tests should be considered for metal-on-metal hip implant patients.
Shortcomings of FDA Metal-on-Metal Hip Implant Review
Unfortunately, some critics of the FDA say it could be years before the agency is able to truly assess the dangers posed by metal-on-metal hip implants. Last week, researchers writing in The New England Journal of Medicine asserted that the post-market studies the agency ordered manufacturers to conduct last year will be of little use to the FDA, at least for now. Among other things, studies for fewer than one-quarter of the 104 devices covered by the FDA order have been approved. For 80 of the products, the FDA says study plans as “pending” or “overdue.” Even for those that had been approved, “it was unclear whether any studies had begun,” they wrote.
According to the article, the standards the FDA established for the studies are also excessively loose.
“One significant shortcoming is that each manufacturer is permitted to conduct its own independent study on its product or products. The resulting lack of harmonization among studies will lead to challenges in pooling the data and making cross-product comparison,” the researchers state.
Finally, the researchers voiced concern that the FDA lacks authority to require post-marketing studies to extend more than 3 years. This, they say, is likely inadequate to judge the performance of metal-on-metal hip implant devices that are supposed to last 15 years.
In its own report, the FDA acknowledged that current studies on metal-on-metal systems and their revision rates don’t adequately assess specific risks, such as dislocation, localized response by patients’ immune systems and a dangerous increase in levels of metals in patients’ bloodstreams. According to the report, many of the studies evaluated by the agency in advance of tomorrow’s meeting suffered from serious deficiencies. In some cases, for example, research was conducted at a single site by a single surgeon, or included implants not available in the U.S.
“While many studies on and resurfacing exist, the clinical literature on specific subgroups of interest and rarer outcomes is minimal,” the report said.
