Even though the risk of “metal on metal” (MoM) hip implants has been known and noted for decades, a joint BMJ/BBC Newsnight investigation, published on bmj.com , and broadcast on BBC Newsnight on February 28, reveals that hundreds of thousands of individuals across the world may have been exposed to dangerously high levels of toxic metals from failing hip implants.
Before hip implants were put into patients, they were not required to pass any clinical trials, similar to breast implants.
In individuals with MoM hip implants, cobalt and chromium ions can leak into the patients tissue, resulting in local reactions that damage muscle and bone, which in some patients can cause long term disability. In addition, research has demonstrated that metal ions can seep into the bloodstream, spreading to the liver, spleen, lymph nodes and kidneys, before exiting the body as urine. Concerns have also been raised regarding the destruction to chromosomes, resulting in genetic alterations.
In 1975, researchers made the first detailed description about the association between local tissue reactions and metal ions. However, the new study highlights how manufactures continued to produce MoM hip implants in light of increasing evidence of risk, as well as how the regulatory bodies did not act to protect patients.
Michael Carome, Deputy Director of Public Citizen’s Health Research Group, said:
“This is one very large uncontrolled experiment exposing millions of patients to an unknown risk. We will only find out about the safety of these devices after large numbers of people have already been exposed.”
In addition, the study demonstrates how over the last ten years, companies have changed the design of their MoM hip implants, by increasing the size of the “head” and shortening the “stem”, in an effort to increase movement and prevent dislocation. However, the companies did not conduct trials to test the effectiveness and safety of the devices, or post-marketing investigations to identify long-term problems.
According to experts, these design changes are likely to be responsible for the high levels of toxic metals seeping into the body. However, even though concerns were raised, regulators in the U.S. and Europe did not notice the changes and failed to warn patients and doctors of the potential dangers.
The FDA approved of one design change stating that the design “does not raise any new issues of safety or effectiveness.”
In 2006, there was increasing evidence regarding the high metal concentrations in individuals with articular surface replacement (ASR) hips. However, it took the UK regulator, the MHRA, another 4 years to issue an official safety alert and pull the ASR hip from the market.
Instead, the MHRA, established a committee that involved several consultants and company representatives to determine the outcome of MoM hips. As a result, they came to the conclusion that individuals should be notified about the risks, although no warning was issued to patients or surgeons.
In addition, the MRHA downplayed the issues, explaining that:
“The majority of patients implanted with MoM hip replacements have well-functioning hips and are thought to be at low risk of developing serious problems.”
Implant rates increased during this period, with more than 20,000 large diameter MoM hips implanted in England and Wales thereafter. In the United States, MoM hips are currently being marketed to orthopedic surgeons.
Nick Freemantle, Professor of Clinical Epidemiology and Biostatistics at University College London, explained:
“We shouldn’t be in this position where we don’t know and there’s so much uncertainty. The stability of a compound should have been ascertained before it was used widely in people. As yet, we don’t know the consequences of this.”
According to Dr. Fiona Godlee, BMJ Editor in Chief:
“Hip replacements are one of the great successes of modern medicine. But a combination of inadequate regulation and untrammeled commercialism has caused actual and potential harm for large numbers of patients around the world. They should have known about the risks, as the manufactures and regulators did, but they were not told.”
In an associated report, Dr. Carl Heneghan and his team, said:
“No pre-market system can ensure all devices are safe, but they can certainly make it more likely. 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.”
Written by Grace Rattue