An 18-member panel of experts was asked by the FDA to review metal-on-metal hip implants – on Thursday they said they saw little evidence to recommend surgeons continue using them. There is growing evidence that after being implanted, they are more likely to break down, exposing patients to the hazards of metallic particles exposure.

The FDA (Food and Drug Administration) had asked the Orthopaedic and Rehabilitation Devices Panel of the Medical Devices Advisory Committee to recommend guidelines for monitoring the over half-million patients in America who have undergone metal hip replacements.

Panel members recommended that all patients with metal-on-metal hip replacements should undergo annual x-rays to monitor the state of their implants – regardless of symptoms.

Some Panel member believe the labeling for metal-on-metal hip implants should warn about potentially serious side effects linked with these devices.

Originally, we were told that metal-on-metal implants were longer lasting and more reliable than the plastic or ceramic models. However, according to recent studies from the United Kingdom and some other countries, the opposite appears to be the case – they are more likely to deteriorate, leaving patients at higher risk of exposure to chromium, cobalt and other metallic substances.

Nobody went as far as suggesting that metal-on-metal implants be removed from the market. However, most of the Committee (Panel) members said they saw scant compelling evidence to make them recommend their use.

Chairman of the meeting, Dr. William Rohr, an orthopedic surgeon at Mendocino Coast District Hospital, California, said:

“I do not use metal-on-metal hips, and I can see
no reason to do so.”

For many years, surgeons happily inserted implants that were coated with plastic or ceramic ones. However, some years ago, a number of them started using metal-on-metal ones, after some studies appeared to indicate that they would last longer and reduce the risk of dislocation.

A BBC/BMJ (British Medical Journal) Newsnight investigation which was published on in February, 2012, and also broadcast on BBC Newsnight, reported that hundreds of thousands of patients around the world were suffering the consequences of failing metal hip implants – these people may have been exposed to dangerous levels of toxic metals.

Patients who receive metal-on-metal implants risk cobalt and chromium ions leaking into tissue. This can result in local reactions that damage bone and muscle, causing long-term disability in some cases. If metal ions seep into the bloodstream, which studies showed can happen, they can spread into the kidneys, lymph nodes, spleen, and liver, before exiting the body in urine. Some experts wondered whether there might be chromosome destruction, leading to genetic alterations.

Scientists in 1975 had first described in detail a link between local tissue reactions and metal ions. The BMJ/BBC investigation highlighted how manufacturers continued producing metal-on-metal implants despite increasing evidence of risk. The investigators added that regulatory authorities did not act to protect patients. (Link to article).

A month after the BBC/BMJ report, The Lancet, a British peer-reviewed medical journal published a report which called for a ban on metal-on-metal hip implants. Researchers found a failure rate of 6% in five years, compared to 1.7% for plastic implants and 2.3% for ceramic ones.

The FDA says it received 16,800 reports of problems with metal-on-metal hip implants from 2000 to 2010. Fourteen thousand had to undergo surgery to have them replaced. In most cases, the immediate problem experienced by patients was pain and inflammation caused by minute metal particles that got into the joint, causing damage to tissue and bone.

Although not proven, some experts believe long-term exposure to elevated levels of metals may lead to heart and neurological problems.

In 2008, approximately 40% of all hip implants were metal ones, in 2010 this figure dropped to 27%, and is probably around 10% at the moment. This still represents a lot of patients – over 400,000 patients undergo a hip replacement operation annually in the USA. Even though metal-on-metal implants represent a low percentage of total hip implants today, more complaints are made about them to the FDA than other types of hip replacement systems.

Now that the FDA Committee has responded and given its recommendations, will the FDA act on it? Regulators in the United Kingdom have advised that some patients with large diameter metal-on-metal hip joints should have a yearly blood test and also MRI scans. Health Canada, in May 2012, warned patients to be aware of the problems and adverse effects related to metal hip replacements.

Written by Christian Nordqvist