Metal-on-Metal Hip Failures Linked to Toxic Nanoparticles: Study

Another study has identified potential health risks associated with the use of metal-on-metal hip replacement systems, finding that the implants may release toxic nanoparticles. 

Researchers from Imperial College London and Ohio State University have published a new study in the Chemical Communications medical journal, finding that microscopic-sized particles of cobalt may be the cause of inflammation associated with metal-on-metal hips. The scientists warn that the cobalt ions are genotoxic and could also cause other health complications.

One of the main safety concerns with metal-on-metal hip implants is the release of metal debris caused by the joints of the implant rubbing against one another. Doctors and scientists have said that the debris causes metal blood poisoning, known as metallosis, but they have also noted that it causes inflammation and tumors in the tissue around the implant.

Searching for a way to confirm the inflammation and its causes, the researchers in this latest study used high resolution X-ray and electron microscope technology to investigate tissue samples. They found that patients who suffered inflammation after receiving an all-metal artificial hip had residual chromium which had oxidized (rusted). The rusted chromium was releasing cobalt ion nanoparticles that were causing the inflammation.

However, the researchers also expressed concern that metal-on-metal hip cobalt ion nanoparticles may be doing more damage than just causing inflamed tissue. Previous studies have shown cobalt ions to be genotoxic; meaning they can cause damage to human DNA. This can lead to cancer and other health complications.

High Rates of Failure

The most common result of metal-on-metal hip replacement metal debris is revision surgery, where patients have to undergo having the implant surgically removed and usually replaced. This can lead to permanent injury, mobility problems and chronic pain. The researchers estimate that about 7,500 patients in the United Kingdom alone have had revision surgery on metal-on-metal hip implants that needed to be replaced.

It was a British registry of hip implants which first noted a problem with the DePuy ASR line of metal-on-metal hips, which were reporting a failure rate of up to 13%. This lead to an August 2010 DePuy ASR metal hip recall which affected 93,000 units worldwide.

A recent FDA advisory committee convened to look at metal-on-metal hip safety resulted in recommendations that all patients who have a metal hip implant get imaging tests done every year to make sure the implant isn’t failing. If they have pain or swelling, the committee recommended they get an annual blood test for metal blood poisoning.

Metal-on-Metal Hip Lawsuits

Thousands of individuals throughout the United States have already filed a DePuy ASR hip lawsuit against Johnson & Johnson and their DePuy subsidiary, alleging that the manufacturers failed to adequately research the design of their metal-on-metal hip implant or warn about the risk of metal-on-metal hip poisoning.

In addition, hundreds of individuals are currently pursuing a DePuy Pinnacle lawsuit, after experiencing problems with the older metal-on-metal hip implant, which has also been linked to a high number of failures.

Similar product liability lawsuits have also been filed over problems with Wright Conserve metal hips, BioMet M2A-Magnum metal hips and other metal-on-metal hip replacements manufactured by other companies.

In May 2011, the FDA asked device manufacturers to obtain more information about the level at which the metal particles shed by hip replacements becomes dangerous, how much metal they actually shed and what the potential side effects of metallosis are. But critics of metal hip replacement systems note that those results may not be available for another decade.