Data reported last week in The Lancet provides “unequivocal evidence” that metal-on-metal hip devices fail more often than alternatives and that they shouldn’t be used for stemmed total hip replacements, researchers from the United Kingdom concluded.

The devices were linked to a notably higher five-year revision rate of 6.2%, compared to metal-on-polyethylene or ceramic-on-ceramic hips with five-year revision rates of 2% or lower, based on an analysis of more than 400,000 implants included in the National Joint Registry of England and Wales. Physicians from several U.K. institutions reported the results March 12.

This is not the first time that data from this registry and others have detected significantly higher failure rates for metal-on-metal hips compared to alternatives. Findings from the England and Wales registry also led to Johnson & Johnson/DePuy Inc.’s worldwide 2010 recall of its ASR and ASR XL hip resurfacing and replacement systems.

But the new analysis, focusing on total hip replacements and not resurfacing devices, is significant in part because it excludes ASR implants to remove a potential outlier effect.

“Some in the orthopedic community perceive that failing metal-on-metal prostheses is an implant-specific ASR characteristic,” the U.K. researchers note in the study. “Our analysis clearly shows that it is not.”

The team also found that failure rates for metal-on-metal implants increased with large device head sizes, an opposite result from what was expected and what was observed in the study with ceramic hips.

“We therefore recommend that metal-on-metal bearing surfaces are not used” in stemmed total hip replacements, the researchers write.

The U.K. Medicines and Healthcare products Regulatory Agency says the data does not support an outright ban on the devices.

Surgeons in the U.K. have already moved in this direction. Metal-on-metal hip implants accounted for only 5% of 2010 procedures in England and Wales, down from 10% the prior year, according to a recent registry report.

But the U.K. Medicines and Healthcare products Regulatory Agency says the data does not support an outright ban on the devices.

“We recognize that there is emerging evidence of increased revision rates associated with large head metal-on-metal hip replacements,” said Susanne Ludgate, clinical director of MHRA, in a March 13 statement. “But the clinical evidence is mixed, and this does not support their removal from the market. Metal-on-metal resurfacing hip implants enable young patients to lead pain-free, independent lives.”

The latest data come two weeks after MHRA issued a recommendation that patients with large metal-on-metal hips be monitored annually for the life of the implant, based particularly on concerns about localized adverse effects from metal toxicity. (See Also see "International News In Brief" - Medtech Insight, 5 March, 2012..)

Use of metal-on-metal hips in the U.S. remains more prevalent than in the U.K. In 2009, 35% of hips in the U.S. had metal-on-metal bearings, according to data cited in the report in The Lancet.

FDA has not adopted the same monitoring recommendations as MHRA. But the agency has responded to safety concerns with metal-on-metal hips by pursuing expanded collection of data.

“There are several differences between the U.K. and U.S. regulatory systems and some of the U.K. data may not be directly applicable to the experience in the U.S.,” FDA says on a page posted on the agency’s web site last year in response to safety concerns with the devices.

FDA scientists participated in a meta-analysis of 18 clinical studies and 29 national registries of hip implants published last November in the journal BMJ. The analysis concluded that there was very limited evidence on the comparative effectiveness of the different hip implant bearings, but no indications that metal-on-metal implants offer any advantage. (See Also see "Research In Brief" - Medtech Insight, 12 December, 2011..)

Last May, the agency ordered manufacturers of metal-on-metal hips to perform post-market surveillance studies to assess metal toxicity risks, although FDA is still working out study plans with some of the companies, according to the agency’s tracking site. (See Also see "FDA Orders Post-Market Studies On Metal-On-Metal Hips" - Medtech Insight, 16 May, 2011..)

Pre-Market Reform Impact?

The metal-on-metal hip revision rates are also being framed as a failure of the pre-market review process.

It should not have taken years on the market and hundreds of thousands of implants before the elevated failure rates were identified, argues Art Sedrakyan, director of comparative effectiveness at the Weill Cornell Medical College, in an editorial posted in The Lancet alongside the study.

“Outdated and low-threshold regulatory pathways such as the 510(k) pathway in the USA or reviews of device reliability via notified bodies in Europe have created an environment that makes regulators vulnerable to errors,” writes Sedrakyan, the lead author on the FDA hip meta-analysis published in BMJ in November and a former medical officer within FDA’s device center.

Growing controversy over the use of metal-on-metal hips, combined with the incidence of cancer tied to silicone breast implants previously marketed in Europe by the French firm Poly Implant Prosthesis Company, have led to a greater push by some in the European clinical community for the European Commission to enact stronger device oversight policies.

The EC is already planning to issue proposed regulations this spring to revise its Medical Devices Directive. Some in the medical community have pushed for a more centralized device review process in Europe to replace the highly decentralized notified-body-based system currently in place. But officials have suggested the policy reforms will focus on strengthening the notified body process, while centralizing device vigilance and surveillance efforts. (See Also see "Industry Calls For More Consistent European Oversight As EU Continues Reg Reform Process" - Medtech Insight, 5 December, 2011..)

Meanwhile, FDA is specifically reassessing its pre-market requirements for metal-on-metal hip replacements. The product type is one of more than 20 so-called pre-amendment devices that remain grandfathered into the 510(k) review process despite being technically categorized as high-risk class III devices. (See Also see "FDA Seeks PMA Requirements For More Pre-Amendment Devices" - Medtech Insight, 15 August, 2011..)

FDA’s device center has yet to issue a proposal to either reclassify the hip implants as class II and to allow the products to continue to access the 510(k) route, or to start requiring PMAs. CDRH says it aims to address the classification of every pre-amendment device, which would include metal-on-metal hips, by the end of 2012. (See Also see "CDRH In 2012: More Pilots, Guidances And Regs" - Medtech Insight, 30 January, 2012..)

Metal-On-Metal Hips Get Failing Grade In New Registry Analysis

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