A new study funded by the National Joint Registry of England and Wales and published this month in the British medical journal The Lancet calls on surgeons to stop using metal-on-metal hip implants completely, saying that evidence shows patients who receive the implants are much more likely to need revision surgery to have the implants repaired or replaced.
The study’s authors analyzed data from the National Joint Registry of more than 400,000 hip replacements made from 2003 to 2011. While the vast majority of those surgeries involved traditional implants made of plastic or ceramic, more than 31,000 patients received metal-on-metal implants. Of those patients, six percent experienced device failure and other problems within five years, requiring them to undergo further corrective surgeries. The rate of failure for all-metal device was found to be about three times higher than implants made of plastic or ceramic.
Many of the British patients with failed metal hips received metal articular surface replacement (ASR) implants made by DePuy Orthopaedics, which the company recalled in August 2010 after data from the same British registry revealed higher than expected rates of failure. That analysis, which specifically looked at DePuy ASR implants, found 13 percent of DePuy’s ASR XL Acetabular system and 12 percent of its ASR Hip Resurfacing System failed within five years. Traditionally, hip implants are supposed to last about 10-15 years.
But hip failure is just the beginning of the problem for some patients fitted with a DePuy ASR implant. Metal particles released into the tissue by the implant’s metal parts has been blamed for destroying bone and muscle and causing a number of injuries related to metallosis, including damaging the lymph nodes, spleen, liver, and kidneys. Concerns over the metal implants have become so heightened that Britain’s Medicines and Healthcare Products Regulatory Agency advises patients with all-metal hips to undergo a yearly blood test to check the levels of cobalt and chromium in their blood. Those with potentially toxic levels of the metals in their blood should undergo regular MRIs to check for systemic damage, the agency recommends.
Dr. Ashley Blom, head of orthopedic research at the University of Bristol and one of the study’s authors, stressed that most people with metal hip replacements don’t need to have them removed. But for people who haven’t yet undergone hip replacement surgery, so many reliable alternatives exist that metal implants are not worth the risk.
According to the Associated Press, Dr. Blom says “the new analysis suggests the problem applies to all metal-on-metal hips, not just one brand.”
Some researchers fear other types of metal implant devices may cause widespread injury.
“I wouldn’t be surprised if this was just the beginning of the storm,” Art Sedrakyan, an associate professor of public health at Weill Cornell Medical College in New York, who authored an accompanying commentary in Lancet, told the AP. “A lot of products have been allowed onto the market without clinical evidence they work.”