Metal-on-metal hip replacements implanted since 2006 'more prone to failure'

Hundreds of thousands of people have hip replacements Credit: REUTERS/Daniel LeClair

New research has suggested that metal-on-metal hip replacements implanted since 2006 are more prone to failure and that when they fail they "fail in a much nastier way".

Dr David Langton, from the University Hospital of North Tees, who led the latest study said that when doctors operated on patients whose implants had failed some had found "black metal-stained tissue" around where the new joint had been put in.

He said: "We have found that they fail at a higher rate than conventional ones but they fail in a much nastier way.

"You get very high levels of chromium and cobalt around the hip and that can go into the bloodstream. There can be black metal-stained tissue."

Research findings published in the BMJ Open journal looking at the 'DePuy Pinnacle device' stated the hip replacement "has not lived up to clinical expectations" and suggested it could lead to a greater need for further surgery in patients.

A spokeswoman for DePuy stated that "there are no manufacturing problems" with their devices and questioned the validity of the Langton paper given what the company said were "significant flaws with how it was conducted".

  • Which replacement hips were looked at in the study?

The focus of the study was the 36 mm Pinnacle metal-on-metal hip which consists of a metal 'ball' which acts as the top of the thigh bone and fits inside a metal liner which acts as the replacement socket.

After studying 434 patients (243 women and 191 men), who between them had been fitted with 489 metal-on-metal hips, over a seven and a half year period researchers noted an "unacceptably high" 71 of those metal hips required surgical removal and replacement.

According to researchers implantation from 2006 onwards also carried a significantly higher risk of failure, a factor that it was suggested could be due to "an increasing tendency from this date to manufacture devices outside of their intended product specification".

  • How many people could be affected by the findings?

Data from the National Joint Registry for England and Wales for 2014 indicates that 11,871 metal on metal Pinnacle hips have been implanted.

Researchers calculated that could mean as many as 180,000 people around the world could be walking around with these hips.