Metal Hip Replacements Made after 2006 Prone to High Failure RateMay 13, 2016
Researchers are studying the long-term performance of metal-on-metal hip implants, specifically the most commonly used device worldwide, the 36 mm Pinnacle manufactured after the year 2006. The metal hip implant is a device with a metal ball that sits atop the thigh bone (femoral head), fits inside a metal liner and acts as a replacement socket, BMJ Open reports.
A study was conducted in the United Kingdom with 243 women and 191 men, with 489 Pinnacle hip replacements where the researchers combined data from north England with data from the national registry. Patients were monitored for an average of 7.5 years, post-surgery, and 71 of these hips had to be surgically removed and replaced. "This device was found to have an unacceptably high revision rate," said researchers.
Only 5 out of 43 hips (12 percent) made before 2006 failed to meet the manufacturer's product specification. After 2006, more than 36 percent (43 out of 118) failed to comply, reports BMJ Open.
The research further revealed in over 40 percent of cases, the taper surface was defective. The taper surface is the inside of the femoral head that is attached to the femoral stem or the part that anchors the implant in the thigh bone. This defect was associated with excessive metal particle release which may lead to metallosis, or metal poisoning. Symptoms of metallosis are bone and tissue death, implant failure, and severe pain, according to Drugwatch.
Metal hips implanted into women were more likely to fail, but researchers point out that twice as many women as men had bilateral hip replacements. Therefore, when findings were analyzed according to sex and liner thickness, thinner liners had the greater failure rate, BMJ Open reports.
Data from the National Joint Registry for England and Wales for 2014 show that 11,871 metal-on-metal Pinnacle hips have been implanted, suggesting to researchers that 180,000 people around the world are now walking around with these devices. The researchers suggest these patients may be at risk for early revision surgery.