And yet another study has confirmed that metal-on-metal hip implants are more likely to fail compared to other types of hip replacement devices, therefore researchers are calling for the controversial medical device to be banned, after reviewing the world’s largest database on hip replacements.
The Lancet Study, being called the most comprehensive study to date, according to a Reuters report, has found that more than 500,000 patients in the U.S. and 40,000 in the U.K. have metal-on-metal hips and are at higher risk of device failure, according to the analysis.
The new study, which is published in the Lancet, shows that high early failure rates for all-metal implants are not related to a single design or manufacturer, but may be related to the entire class of devices.
“We thought it was very important to get the message across that this is not a single-brand problem,” says researcher Ashley W. Blom, MD, PhD, a professor of orthopedic surgery at the University of Bristol in the U.K.
She, along with her team, analyzed data from the National Joint Registry of England and Wales covering more than 400,000 hips replacements, including 31,171 all-metal ones, that occurred between 2003 and 2011. They found that people with metal-on-metal hip implants were twice as likely to experience early failure of their device compared to those fitted with other types of implants.
According to a report from Bloomberg News, 6.2 percent of all-metal hip implants patients need a second operation in five years. The study also found that larger metal hips failed sooner — each 1-millimeter increase in femoral head diameter corresponded to a 2 percent increase in the risk of failure. Finally, failure rates were as much as four times higher in women, who are likelier to have implants containing a larger prosthetic femoral head.
“Metal-on-metal stemmed articulations give poor implant survival compared with other options and should not be implanted,” the study authors wrote. “All patients with these bearings should be carefully monitored, particularly young women implanted with large diameter heads.”
The use of larger metal implants became popular because it was thought that they reduced the likelihood of dislocation and were highly resistant to wear, researchers led by Ashley Blom from the University of Bristol in the U.K. wrote in the study.
The study follows findings reported last month that 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, according to an investigation by the British Medical Journal and the British Broadcasting Corp.
Many medical devices didn’t undergo clinical testing like that required of drugs before they were used in patients, the BMJ and BBC said at the time. Manufacturers have replaced plastic with metal materials over the last decade to improve movement and decrease dislocation without conducting safety studies, they said.
“Policy makers need to appreciate that registry data alone are not a substitute for good pre-marketing studies, which should include testing of implants,” Art Sedrakyan, an associate professor of public health at the Weill Cornell Medical College at Cornell University in New York, wrote in an accompanying commentary. “When failures take a long time to develop, many faulty products can enter the market.”
The Lancet study is just one of many that have addressed the serious issue with the all-metal hip implants.
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