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Call for all metal hip implants to be banned

Study confirms much greater failure rate for metal-on-metal hip implants

Ingrid Torjesen

Tuesday, 13 March 2012

There has been a call for metal-on-metal (MOM) hip replacements to be banned after experts uncovered “unequivocal evidence” that the implants are failing at much higher rates than other types.

The research, published in The Lancet ten days after the Medicines and Healthcare products Regulatory Agency (MHRA) announced that patients who have received stemmed metal-on-metal (MOM) hip replacements will need annual check-ups, shows that stemmed MOM implants are failing at much higher rates than other types, expecially those with larger head sizes and those implanted in women.

The authors have called for their use to be banned. The MHRA has previously rejected calls for an outright ban on MOM hip implants, saying that their use is appropriate for some patients.

The research is based on data from the National Joint Registry of England and Wales on more than 400,000 hip replacements (of which 31,171 were MOM) undertaken between 2003 and 2011.

Researchers in Bristol tracked patients for up to seven years after surgery and found that stemmed MOM implants failed much more quickly than other types of bearing surface, such as ceramic and polythene, and had a 5-year revision rate of 6.2%. MOM implants with larger heads failed earliest; there was a 2% increase in the risk of failure for each 1mm increase in head size. By contrast, ceramic-on-ceramic implants did better with larger head sizes.

In women, failure rates for stemmed MOM implants were up to four times higher than those of other bearing surfaces, and were also higher compared with men even with the same head size.

Professor Ashley Blom from the University of Bristol said: “Metal-on-metal stemmed articulations give poor implant survival compared with other options and should not be implanted. All patients with these bearings should be carefully monitored, particularly young women implanted with large diameter heads.”

Although the use of stemmed MOM hip implants has declined in England and Wales, there are believed to be more than 40,000 people in the UK with the implants.

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