Tens of thousands of British patients with metal hip replacements may be at risk of being poisoned by them.

An investigation by The Sunday Telegraph showed that more than 30,000 British patients have had the metal-on-metal hip replacements—a metal ball that fits into a metal cup implanted into the pelvis.

Problems reportedly occur when friction between the ball and cup causes tiny metal filings to break off, which can seep into the bloodstream and cause inflammation, destroying muscle and bone.

Advisers to Britain's Medicines and Healthcare products Regulatory Agency (MHRA) claim the devices could be causing "systemic toxicity"—effectively poisoning the body.

"On the evidence currently available, the majority of patients implanted with metal-on-metal hip replacements are at low risk of developing any serious problems," an MHRA spokesperson said. "We are continuing to closely monitor all evidence. This needs more analysis before any conclusions can be drawn and further advice given."

The spokesperson added, "We have already taken prompt action to investigate safety concerns and have provided advice on patient management to relevant health care professionals."

The metal-on-metal devices were introduced in the 1990s, when they were seen as offering better mobility than other materials.

They were withdrawn from the UK market in 2010, but a study by the British Hip Society found that they had much higher failure rates than first thought. Up to half of the implants fitted by a company called DePuy failed within the first six years.

With legal action pending for more than 1,000 people who claim they suffered as a result of the devices, lawyers say some six-figure payouts are likely.

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