Failing metal-on-metal hip replacements made by manufacturers including Johnson & Johnson (JNJ) may harm more people than leaking breast implants made in France, according to an investigation by the British Medical Journal and the British Broadcasting Corp.
Hundreds of thousands of people worldwide may have been exposed to high levels of toxic cobalt and chromium ions that can seep into tissues and destroy muscle and bone, leaving some patients with long-term disability, the BMJ and BBC said in a statement today. Studies also show that metal ions can seep into the bloodstream, spreading to the lymph nodes, spleen, liver and kidneys, they said.
J&J recalled two metal-on-metal devices in August 2010 after some patients required repeat procedures when the implants stopped functioning properly. French and German officials in December recommended that thousands of women have surgery to remove breast implants made by Poly Implants Protheses SA, after reports the products were leaking industrial silicone inside patients. The recalls have heightened scrutiny of European Union rules for medical devices that faced doubts from doctors seeking an overhaul.
“Why is it that people are afforded different levels of protection depending on whether they have a heart attack, diabetes, or a hip replacement in their old age?” said Nick Freemantle, professor of clinical epidemiology and biostatistics at University College London, in an article in the BMJ. “The methods of device regulation seem to be more from the 1950s than the 21st century.”
A spokeswoman from J&J and a Zimmer spokesman weren’t immediately available to comment.
Smith & Nephew didn’t have an immediate comment on the BMJ and BBC report today. At the request of the FDA, the first 400 patients who used the company’s Birmingham Hip Resurfacing System were followed in a study that found that 99 percent were satisfied or extremely satisfied after 10 years, Smith & Nephew said in a statement this month. The BHR hip’s metallurgy and design contribute to its success, the company said.
The hips, like other medical devices, didn’t have to undergo clinical testing like that required of drugs before they were used in patients, the BMJ and BBC said. Manufacturers have changed the design of the implants, replacing plastic with metal materials, over the last decade to improve movement and decrease dislocation, without conducting safety studies, they said. Regulators failed to identify the changes or warn doctors and patients of potential risks, according to the report.
In the U.K., 65,000 metal-on-metal implant operations have taken place since 2003, according to the Medicines and Healthcare products Regulatory Agency.
The ASR Acetabular implant from J&J’s DePuy Orthopaedics Inc. unit was removed or replaced 29 percent of the time after six years, compared with a 9.5 percent failure rate for all metal-on-metal implants, the National Joint Registry of England and Wales said in September.
The MHRA today recommended that doctors conduct annual magnetic resonance imaging scanning for the life of implants that are 36 millimeters (1.4 inches) or larger. This updates guidance issued in April 2010 that patients be monitored for at least five years after the operation.
U.K. Advice Updated
“Most patients with metal-on-metal hip replacements have well functioning hips and are at a low risk of developing any serious problems,” Susanne Ludgate, clinical director of the MHRA, said today in a statement. “We are updating our patient management and monitoring advice to surgeons and doctors because this type of hip replacement has a small risk of causing complications.”
Unlike the U.S. Food and Drug Administration’s government- run reviews for medical devices, the EU relies on a decentralized network of about 70 “notified bodies.” The closely held, mostly for-profit firms are hired by companies to check their products. The reviewers must be accredited by one of the bloc’s 27 member nations. Approval by any one of them allows companies to sell a device throughout the EU.
While the EU and U.S. require manufacturers to prove new products are safe, only the FDA mandates they also show devices are effective. That means studies for European approval are typically less in-depth than those required in the U.S, according to Carl Heneghan, a physician and director of the University of Oxford’s Centre for Evidence-Based Medicine.
“No pre-market system can ensure all devices are safe, but they can certainly make it more likely,” Heneghan said in the BMJ statement. “Creating an independent system for post- marketing analysis for implantable medical devices that is robust and increasing international coordination around device alerts and withdrawals should go some way to sorting out the current mess.”
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