Ban urged by experts on ‘high failure’ hip implants

New figures covering more than 400,000 hip replacements found metal-on-metal implants needed further surgery more often than other types and that failure rates were higher in women.

The findings come weeks after the Medicines and Healthcare products Regulatory Agency (MHRA) issued new guidance on the implants, saying almost 50,000 patients in the UK will need annual blood or MRI checks.

Tiny metal ions are thought to break off from the implants and leak into the blood, with fears this causes muscle and bone damage and neurological problems.

Today’s research, published in The Lancet medical journal and based on the National Joint Registry of England and Wales, found metal-on-metal implants failed much more quickly than other types of implant, with a five-year revision rate of 6.2 per cent. This compared with 2.3 per cent for ceramic-on-ceramic implants and 1.7 per cent for metal-on-plastic types.

Failure was related to the head size of the implant, with larger heads failing more quickly.

The analysis included more than 31,000 metal-on-metal implants. It looked at patients given implants between 2003 and 2011 and tracked for up to seven years after surgery.

The results showed stark differences between the implants depending on type and head size and confirm previous findings on failure rates.

In women, failure rates for metal-on-metal were up to four times higher than for other types and were also higher compared with men even with the same head size.

At seven years after surgery, some revision rates were as high as 10 per cent.

The experts concluded the length of survival of metal-on-metal implants was “poor” compared with other options and they “should not be implanted”.

“All patients with these bearings should be carefully monitored, particularly young women implanted with large diameter heads,” they added.

The authors said they agreed with current MHRA advice but surgeons should seek to use other implants.

Alison Smith, a statistician in orthopaedic surgery at Bristol University, added: “We think there are better alternatives so we don’t see a reason to use stemmed metal-on-metal implants any longer.”

Around 65,000 people in the UK have received metal-on-metal hip implants since 2003, of which 49,000 are affected by the MHRA’s guidance because the joint head is 36mm or greater.

Hip replacements are mostly used for patients with osteoarthritis, where there is substantial wear and tear on the hip joint.

Use of metal-on-metal implants has declined in England and Wales, but data suggest they are still used extensively in the US.

Susanne Ludgate, clinical director of the MHRA, said: “We recognise that there is emerging evidence of increased revision rates associated with large head metal-on-metal hip replacements.

“But the clinical evidence is mixed and this does not support their removal from the market. Metal-on-metal resurfacing hip implants enable young patients to lead pain free, independent lives.”

The MHRA was continuing to closely monitor all evidence about the implants, she added.