Metal-on-metal hip implants since 2006 may be more likely to fail: study

Tens of thousands of people worldwide who had metal-on-metal hip replacements may need further surgery because of the high failure rate of the devices, British researchers say.

The researchers focused on the DePuy Pinnacle device. It has a metal ball that serves as the top of the thigh bone and sits inside a metal liner that acts as a replacement socket.

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Writing in Thursday's BMJ Open, Dr. David Langton of University Hospital of North Tees in Stockton, U.K., and his co-authors reviewed the progress of 243 women and 191 men who had 489 metal-on-metal Pinnacle hip replacements in northern England andcombined the patient data with national registry data.

The patients were monitored for an average of 7.5 years after surgery.

In total, 71 hips needed to be surgically removed and replaced.

"This device was found to have an unacceptably high revision rate," researchers said.

By combining the high failure rate and extrapolating from the company's sales records, the team learned 180,000 patients globally have had the implant. These people might be a risk for early revisions, they said.

Use of metal-on-metal hips has gone down over the past five years.

Implants from 2006 on showed higher risk of revision compared with those manufactured before 2006, which the researchers speculate could be due to manufacturing variations between batches.

MindyTinsley, aspokeswoman forDepuy,said there were no manufacturing problems as the studysuggests. Measurements taken at the company's U.K.manufacturing facility showed all liners were within specification.

"We question the validity of the Langton paper given significant flaws with how it was conducted, the limited data reported, and the clear conflicts of interest of some of its authors. The paper is also inconsistent with the results of many peer-reviewed studies that were conducted with more scientific rigour and transparency," she said in an emailed statement.

In the study, wear rates of the metal surfaces retrieved from patients was generally low.

One of the limitations of the research is that not all patientsattended the followup clinics. Those who didn't were assumed to have no symptoms.

There was no specific grants for the research. Some of the authors areretained asexperts for plaintiffsin ongoing litigation about metal-on-metal implants.