MEDICAL regulators have launched an investigation into the safety of metal hip replacements amid fears that thousands of British patients are at risk of being poisoned by the implants.

The Medicines And Healthcare Products Regulatory Agency said it had taken “prompt action” over the safety concerns, but said the majority of people with the devices were at “low risk of developing any serious problems”.

Last year, The Press revealed that scores of people around the country were being represented by York law firm Pryers, after claiming their hip replacements had left them with intense pain, swelling and difficulty walking.

An investigation has now found more than 30,000 British patients have received the “metal-on-metal” hip replacements and they are feared to be more dangerous than previously thought.

Problems occur with such devices when friction between the metal ball and cup causes tiny metal filings to break off and potentially get into the blood. These fragments can also cause a soft tissue reaction, destroying muscle and bone.

The Sunday Telegraph yesterday reported that there were growing concerns that the implants could also cause “systemic toxicity” in the body, prompting the MHRA to start drawing up new advice for those fitted with them.

In September 2010, DePuy International Limited, a subsidiary of Johnson & Johnson, announced it was urgently recalling two types of its ASR metal hip replacement implants.

It came after data from the National Joint Registry of England And Wales found “failure rates” of 13 per cent for the ASR XL Acetabular system and 12 per cent for the ASR Hip Resurfacing System. However, a report by the British Hip Society seen by the Sunday Telegraph said failure rates of the Acetabular system could actually be as high as 50 per cent six years after surgery.