Hip replacement patients not told risks of MoM implants - BMJ


Health experts have expressed concerns that many thousands of people could be unknowingly in danger from high levels of toxic material used in 'metal on metal' (MoM) hip implants.

Hip Implant Replacement

The British Medical Journal (BMJ) acknowledges the overall success of hip replacements in modern medicine. However, the publication's editor-in-chief, Dr Fiona Godlee, said: "A combination of inadequate regulation and untrammelled commercialism has caused actual and potential harm for large numbers of patients around the world.

"They should have known about the risks, as the manufacturers and regulators did, but they were not told."

The concerns over MoM implants now threaten to outweigh the recent scandal over PIP breast surgery, despite the medical profession having first been made aware of the risks of MoM in 1975.

With MoM hip implants, ions of heavy metals such as cobalt and chromium can leak into patients' tissue, potentially damaging bone and muscle and risking long-term disability.

Further research has shown that metal ions can enter the bloodstream and spread to the liver, spleen, lymph nodes and kidneys, eventually to be excreted as urine. Concerns have also been raised over genetic damage from the ions' effect on chromosomes.

Current research suggests that manufacturers continued to produce MoM hip implants despite growing evidence of the dangers. The study has also found that regulatory bodies failed to act to protect patients.

The study further shows that in the last 10 years, manufacturers have sought to increase patient movement and prevent dislocation by enlarging the MoM's 'head' and shortening its 'stem'. However, they failed to test the devices for effectiveness and safety, or conduct post-marketing investigations into potential long-term problems.

Experts believe the design changes are probably the cause of toxic metals leaching into the body in such high volume. However, even though alarms were sounded, US and European regulators failed to spot the changes and did not warn patients and doctors of the possible risks.

Michael Carome, Deputy Director of Public Citizen's Health Research Group, said "a very large uncontrolled experiment" had exposed millions of patients to unknown risks. "We will only find out about the safety of these devices after large numbers of people have already been exposed."

Although there was evidence of high concentrations of metal in articular surface replacement (ASR) hips in 2006, the UK Medicines and Healthcare products Regulatory Agency (MHRA) took 4 more years to officially sound a safety warning and remove ASRs from the market.

The MHRA instead set up a committee of consultants and company representatives to decide outcomes for MoM hips, concluding that individuals should be notified of the risks. However, neither patients nor surgeons were issued with warnings.

Downplaying the issues, the MRHA explained that most patients with MoM implants "have well-functioning hips and are thought to be at low risk of developing serious problems."

During this period implant rates increased, with over 20,000 large-diameter MoM procedures done in England and Wales.

Nick Freemantle, Professor of Clinical Epidemiology and Biostatistics at University College London, said being in a position of such uncertainty was unacceptable. "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."

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