In separate announcements, the Medicines and Healthcare products Regulatory Agency (MHRA) and a group of researchers have both raised troubling new questions about the failure rates of metal-on-metal (MoM) hip implants and how regulatory authorities can best respond.
In a statement released 25 June, MHRA said it was advising surgeons to refrain from using a metal-on-metal hip implant product manufactured by Smith & Nephew after being made aware of postmarketing surveillance data showing a revision rate more than 50% above acceptable levels. The National Institute of Health and Clinical Excellence (NICE), the UK's comparative effectiveness body, has set guidance that products should not exceed a 4% revision rate over the four years following implantation. Smith & Nephew's R3 metal cup liner exhibited a 6.3% revision rate over 4 years.
"Therefore the MHRA has told surgeons to stop using the metal cup liner and to annually monitor the 281 patients who have been fitted with these cup liners so that any complications such as pain or swelling are picked up and treated early," the agency said in a statement.
MHRA also advised surgeons to extend the follow-up monitoring period to a minimum of five years for those patients implanted with the device.
Researchers Propose a New Path Forward
In a separate study released in the New England Journal of Medicines the same week, a pair of researchers from the Pew Health Group and Cornell University said there is now "compelling evidence that [metal-on-metal] hip implants fail at a higher rate than hip prostheses made of other materials."
One hip implant cited by the researchers showed a nearly 50% revision rate over the course of six years after surgery to implant the devices.
The NEJM article also criticized the current state of regulatory oversight of the devices, saying postmarketing studies of MoM hip implants are unlikely to be completed for years thanks to running disagreements between manufacturers and the US Food and Drug Administration (FDA). Of the 104 postmarketing studies of MoM hip implant products mandated by FDA, just 24 studies are actually underway at this time, said the researchers. Even after the studies are completed, the lack of study harmonization might impact the agency's ability to make cross-product comparisons, wrote the researchers.
The researchers called on FDA to require all companies conducting studies to standardize the information being collected "to the extent possible,"
"The FDA should explore ways of improving the coordination of studies conducted by multiple manufacturers to ensure that data can be pooled and cross-product comparisons can be made where appropriate," researchers Joshua Rising, Ian Reynolds and Art Sedrekyan wrote. "Coordination could be improved, in part, through creative engagement with external stakeholders. Possible models include the FDA advisory committees and efforts like the FDA-initiated International Consortium of Orthopedic Registries."
Finally, the trio called on legislators and regulators to establish "comprehensive national medical device registries" in conjunction with unique device identifiers and data standards. "Infrastructure investments would benefit all stakeholders: manufacturers could conduct less costly postmarketing trials and use the feedback for iterative device improvements; patients and clinicians would gain information on the risk-benefit profiles of devices; and the FDA would have more confidence that adverse health effects would be quickly identified."
MHRA - MHRA tells surgeons to stop using R3 metal cup liner and extends patient monitoring advice
NEJM - Delays and Difficulties in Assessing Metal-on-Metal Hip Implants