Metal-on-Metal Hip Implant Risks Outweigh Benefits, Group Finds

A group of researchers have concluded that the potential risks associated with metal-on-metal hip implants appear to outweigh any health benefits provided by the devices, due to high revision rates linked to the newer hip replacement design and concerns about health problems from metal blood poisoning. 

The California Technology Assessment Forum (CTAF) released an assessment of the benefits and effectiveness of using metal on metal hip replacements as an alternative to total hip arthroplasty, concluding that the relatively new metal hip implants may not be worth the risk.

The assessment (PDF) is the third time the group has reviewed metal-on-metal hip implants, and the group says that some questions about the technology that were present years ago are still present today.

The CTAF listed five criteria for determining the viability of metal hip implants, including: that the technology be properly approved by a governing body; that there be scientific evidence that can be used to make conclusions on health outcomes; that the implants be shown to improve net health outcomes; that the implants be as beneficial as established alternatives; and that the improvements can be attained outside of an investigational setting. Of those requirements, metal hip implants only meet the first two, the CTAF determined.

Because of high revision rates and the risk of metallosis, a form of blood poisoning caused by cobalt and chromium particles shed by metal-on-metal implants, the group concluded that “there is clearly no evidence that the potential benefits outweigh the potential risks.”

After they were introduced, metal-on-metal hip implants quickly grew to account for about one-third of the 250,000 hip replacements performed each year in the United States. However, over the past two years, concerns have increased about a risk metal hip replacement complications, resulting in use of the implants dropping to just 5% of the artificial hip market.

Recent research suggests that as the metal hip replacement parts rub against each other, microscopic particles of cobalt and chromium may be shed into the body, which can result in metal poisoning. This may result in soft tissue damage, inflammatory reactions, bone loss, genetic damage, asceptic fibrosis, local necrosis or other problems that may lead to the need for a risky hip revision surgery.

In May 2011, the FDA requested artificial hip manufacturers to provide more data on problems with metal poisoning and metal implants.

Media attention to the metal-on-metal hip implant risks increased after a DePuy ASR hip recall was issued in August 2010. The metal-on-metal artificial hip system was removed from the market due to a high rate of failures after more than 90,000 components were sold throughout the world.

More than 1,000 people have already filed a DePuy ASR hip replacement lawsuit as a result of complications caused by the recalled system. DePuy Orthopaedics also faces a growing number of DePuy Pinnacle hip lawsuits filed as a result of problems associated with their other metal-on-metal artificial hip implant. Although a DePuy Pinnacle hip recall has not been issued, lawsuits allege that the older system features similar design defects that increase the risk of early loosening or failure.