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More checks urged on metal hip replacements

Surgeons are being urged to carry out more regular checks on patients with certain kinds of metal hip replacement, as a joint investigation by the BMJ and the BBC raises new concerns over the implants
By
WebMD UK Health News
Medically Reviewed by Dr Keith David Barnard
hip xray

28th February 2012 - Hundreds of thousands of people around the world may have been exposed to dangerously high levels of toxic metals and high revision rates from failing hip implants, according to an investigation.

The British Medical Journal (BMJ) and BBC Newsnight say it may affect more people than the recent scandal over PIP breast implants.

On the same day, the Medicines and Healthcare products Regulatory Agency (MHRA) has urged surgeons to carry out more frequent checks on a certain type of metal-on-metal hip replacement.

Cobalt-chrome alloy

The joint investigation by the BMJ and BBC focuses on a whole class of hip implants. These are known as metal-on-metal replacements because the head at the top of the femur (thigh bone) and the lining of the cup it fits into that is attached to the pelvis are made of cobalt-chrome alloy rather than ceramic or polyethylene. 

There are models of metal-on-metal implants for both total hip replacement and hip resurfacing. Hip resurfacing systems use metal to replace the surface of both joints, preserving the head of the femur. 

Conventional total hip replacement requires complete removal of the femoral head with the prosthesis secured into the upper part of the femoral shaft. Hip resurfacing was introduced in 1997 and was targeted at young active patients who needed a hip that would last a whole lifetime.

Health risks

The report says that cobalt and chromium ions can seep into the tissues of patients with these metal-on-metal hip implants, causing local reactions that destroy muscle and bone, causing the implants to fail, and often leaving patients with long term disability.

It says studies have also shown that metal ions can leach into the bloodstream, spreading to the lymph nodes, spleen, liver and kidneys, before leaving the body in the urine. There are also concerns about damage to chromosomes in the tissues around the hip joint, leading to genetic changes and possibly cancers.

It is thought that up to 60,000 people in England and Wales have been fitted with the all-metal implants since 2003, around 40,000 of them made by DePuy International Ltd. In 2010, DePuy recalled its ASR range because of an abnormally high failure rate - in some cases as high as 50% over six years. The MHRA, which only recently sought to reassure patients about the safety of metal-on-metal implants, admitted that an unknown number of patients never received the recall notice.

Regulatory failures

The report says that health risks associated with metal-on-metal implants have been known about since the mid-1970s, but that manufacturers remained silent about the problem, while regulatory bodies have failed to protect patients.

It blames the regulatory system in which hip implants, like breast implants, did not have to pass any clinical trials before they were put into patients.

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