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Doctors Critical of FDA's Approach to Surveillance of Hip Implants

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Almost 16,800 adverse events associated with metal-on-metal hip implants were reported ito the FDA from 2000-2011. This number does not account for the under-reporting phenomenon whereby, it is well recognized, that consumers who take the time to report to the FDA adverse events are 10-100 times less than the total number of actual adverse events.

The reports of adverse events from metal-on-metal hip implants almost quadrupled to 682 in 2008 from the year earlier, and rose again after DePuy Orthopaedics, a division of Johnson & Johnson began recalling DePuy ASR™ hip devices in 2010. Adverse event reports in 2011 totaled 12,137 for the metal-on-metal devices, compared with 6,332 associated with other types of hip implants, according to the FDA.

J&J faces more than 6,000 lawsuits related to the hip devices in federal and state courts. The DePuy ASR hips account for 9,006, or 74 percent, of the incident reports in 2011, according to the FDA. DePuy and J&J recalled 93,000 ASR hips worldwide in 2010,.

The most-reported side effect was revision, meaning surgery to remove or replace the implant. Revisions totaled 14,131 in metal-on-metal hip implants followed by 8,704 reports of pain.

In May 2011, the FDA ordered manufacturers of metal-on-metal hip implant devices to conduct post-marketing surveillance. Joshua Rising, M.D. of the Pew Charitable Trusts and two other doctors published recently an on-line article in the New England Journal of Medicine, which criticized the FDA's approach to studying this problem. The required studies have been slow to get under way, and "methodologic issues will limit the usefulness of the information that emerges from these studies," according to Rising, et al. Moreover, according to Rising, et al. as of this week, protocols for fewer than 25% of the 104 devices covered by the FDA surveillance order had been approved. For 75% of the devices, the FDA listed the study plans as "pending" or "overdue." This is over one year after the order was issued.

More importantly, the authors argued, the FDA's requirements for the studies were 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 comparisons," Rising and colleagues wrote.

They pointed out, for example, that the FDA did not specify how the companies should measure chromium and cobalt ions in blood — a key marker of metal-on-metal implant dysfunction. The resulting variability will "introduce uncertainty into attempts to pool results," the group contended.

The authors also expressed concern that the FDA does not have authority to require post-marketing studies to extend more than 3 years, which may be inadequate to judge the performance of devices that are supposed to last 15 or more years, as is the case with metal-on-metal hip implants. One advantage to the slow start for most of the studies is that it is not too late for the FDA to require more harmonization of protocols, Rising and colleagues suggested.

They also called for the U.S. to establish comprehensive device registries — not limited to metal-on-hip implants — like those in other countries. They noted that the first warning signals about metal-on-metal devices emerged from an Australian registry. I have advocated on this blog site for the creation of a U.S. hip implant registry.

Such registries could benefit device manufacturers, Rising and colleagues contended, by reducing their costs for post-marketing surveillance and by providing better clinical feedback that, in turn, helps them develop safer and more effective products.

Next week, the FDA will hold an advisory committee meeting about metal-on-metal implants to review the existing data and future research needs.

This meeting "would be an opportune time for the FDA to address the slow start to these studies — and to signal that substantial penalties may be assessed against any manufacturer that is responsible for delays in finalizing protocols," Rising and colleagues wrote.