Metal-on-Metal Hip Implants Endangering Thousands, Thanks to Lax Regulation in U.S. and Abroad

A report published in the British Medical Journal (BMJ) is raising troubling questions about way regulators in the U.S. and abroad responded to mounting evidence of the health risks posed by metal-on-metal hip implants. According to the investigative report, which was a collaborative effort between the BMJ and BBC Newsnight, hundreds of thousands of people around the world may have been exposed to dangerously high levels of toxic metals from failing metal-on-metal hip implants, thanks to an inadequate response by medical device regulators, including the U.S. Food & Drug Administration (FDA).

This blog has long reported on the dangers posed by metal-on-metal hip implants. It is believed that the devices can shed microscopic metal shards into the surrounding tissue, causing local reactions that destroy muscle and bone, and long term disability. Studies have also shown that metal ions can leach into the bloodstream, spreading and poisoning organs throughout the body. Most recently, preliminary findings from a study conducted by researchers at the University of Bristol in the U.K. indicated that patients fitted with all-metal hip implants may be at risk of experiencing genetic changes to the cells of the bladder, a possible precursor to cancer, and possibly bladder cancer itself.

Metal-on-metal hip implants include DePuy Orthopaedics’ ASR Hip Resurfacing System and the ASR Acetabular Hip Implant System, which were recalled in 2010 because of an unusually high premature failure rate. According to the BMJ report, years before the ASR hip implant devices were recalled, evidence was mounting about high metal concentrations in patients fitted with those devices. According to the article, DePuy itself appears to have been aware of one significant problem associated with the ASR hip implants known as genotoxicity, a condition where the metal ions shed from the devices altered the DNA of the cells, thereby causing cancer or mutation. The report quotes a DePuy memo from 2005 regarding the ASR hip implant devices:

“In addition to inducing potential changes in immune function, there has been concern for some time that wear debris may be carcinogenic. The mechanism is not known and only 24 local malignancies have been reported in patients with joint replacements. Also worrying is the possibility of distant effects. One study suggested a threefold risk of lymphoma and leukemia 10 years after joint replacement.

Yet DePuy continued to aggressively market metal-on-metal hips, and never mentioned the memo’s concerns in any of its promotional materials for the devices. In fact, in 2006 the company’s sales teams were equipped with a paper entitled, “Setting the record straight on metal hypersensitivity,” written by one of DePuy’s prosthesis designers, Los Angeles orthopedic surgeon Thomas Schmalzried, to counter emerging concerns on the topic.

Prior to the August 2010 DePuy hip implant recall, the U.K.’s Medicines and Healthcare Regulatory Authority’s (MHRA) only response to the growing crisis was to appoint a committee that included company representatives and several consultants to decide the fate of metal on metal hips. The committee concluded that patients should be told about the risks, but no alert was issued to surgeons or patients. The MRHA also downplayed the problems, stating: “The majority of patients implanted with MoM (metal-on-metal) hip replacements have well-functioning hips and are thought to be at low risk of developing serious problems,” according to the BMJ report.

The U.S. FDA did not fare much better, according to the article. As we’ve reported previously, the agency allowed the ASR Acetabular Hip Implant System to be cleared through its 510(k) protocols, which do not require any human testing, because it was purportedly similar in design to a device already on the market. According to the BMJ, other all-metal hips made by various manufacturers, including Zimmer and Stryker, were also cleared this way. The FDA started to clear metal-on-metal devices with larger heads for market use in 1998 and by the end of 2010 had approved 175 implants through the 510(k) route.

The ASR Hip Resurfacing System, however, was never cleared by the FDA. It was ineligible for 510(k) process because hip resurfacing was a new procedure, and therefore had to undergo clinical trials. In 2009, the FDA declined to approve that device after DePuy’s human studies indicated there was problem with early failure of the implant. It stands to reason that had the FDA required human studies for the all-metal hip implants it has approved via the 510(k) process, the complications now being attributed to the devices would have been spotted earlier.

The ASR isn’t the only metal-on-metal hip implant to raise red flags in recent years. According to the BMJ report, data showing raised metal ions in people with a metal-on-metal version of DePuy’s Pinnacle hip implant have been available in the medical literature since 2008. Yet DePuy promoted the Pinnacle as “an alternative for the majority of patients” when the ASR implants were recalled globally. According to the article, unhealthy levels of metal ions have been recorded in around 20% of patients with a metal-on-metal hip implant, including the all-metal Pinnacle device. A study published in May 2011 indicated that other metal-on-metal hip implants, including Zimmer’s Durom Cup and Smith and Nephew’s Birmingham total hip replacement, had similar problems, the report said.

Apparently, regulators in both the U.S. and Europe also missed the fact that companies have changed the design of their metal hips over the last decade (making the “head” larger and part of the “stem” shorter) in a bid to prevent dislocation and increase movement. New trials were never conducted to evaluate the safety and effectiveness of the modified designs, and there have never been post-marketing studies to detect any long-term problems. However, according to the BMJ, some experts believe these changes are responsible for the release of high levels of toxic metals into the body.

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