Metal-on-Metal Hip Implants Have Higher Fail Rates
Study: All-Metal Hip Replacements Fail Faster Than Other Types
March 12, 2012 -- Data from the world’s largest joint replacement registry show that troubled metal-on-metal hip implants have early failure rates that are two to four times higher than implants made with other kinds of materials.
The new study, which is published in the Lancet, shows that high early failure rates for all-metal implants are not related to a single design or manufacturer, but may be related to the entire class of devices.
“We thought it was very important to get the message across that this is not a single-brand problem,” says researcher Ashley W. Blom, MD, PhD, a professor of orthopedic surgery at the University of Bristol in the U.K.
Metal-on-metal implants are under scrutiny in both the U.K. and the U.S., though they remain on the market.
Blom, who is also a practicing orthopedic surgeon, says: “I would not implant stemmed metal-on-metal implants on my patients now with the knowledge that I have. There are other options that do better.”
Last month, the British Medicines and Healthcare Products Regulatory Agency advised patients with all-metal implants that they will need to be closely monitored for problems, getting annual exams for as long as 15 to 20 years.
Last May, the FDA ordered 21 makers of all-metal hips sold in the U.S. to conduct new safety studies.
One all-metal hip, the ASR system, was recalled by its manufacturer, DePuy, in 2010 because of high failure rates. The recall affected about 40,000 patients in the U.S. The company continues to monitor those patients and is picking up the cost of some expenses related to testing and further surgeries.
Metal Implants vs. Non-Metal
As many as one-third of patients who got hip implants in the U.S. in recent years received an all-metal replacement, in which both the ball of the joint and the socket are made from metal, typically chromium or cobalt.
When the metal parts rub together, they can release tiny particles into the blood and surrounding tissue. The particles can damage the area around the joint, causing pain and loosening of the implant, according to the FDA.
The new study, which is published in the Lancet, tracked more than 31,000 metal-on-metal replacement hips implanted in patients in the U.K. between 2003 and 2011.
The registry also includes information on more than 371,000 artificial hips made from other materials.
The study excluded the recalled ASR implants.
Compared to patients who got hips made with ceramic and plastic weight-bearing surfaces, patients who got all-metal hip replacements were significantly more likely to need revision surgery within the first few years of use.
The study shows 6.2% of all-metal implants required corrective surgery, usually to replace the implant, within five years.