According to a new study, failing metal-on-metal hip implants generate toxic nano-particles that release Cobalt 2+ ions, which not only cause inflammation in surrounding tissue, but have the potential to cause long-term damage to the genetic material of cells. According to a report published by Medicalxpress.com, this “genotoxicity” could result in serious, long-term health problems, even after a defective metal-on-metal hip replacement device is removed and replaced.
The new study, published online this month in the journal Chemical Communications, is one of the first to look at the effects of nano-particles in humans. Using high resolution X-ray and electron microscopy, researchers from Imperial College London and Ohio State University attempted to determine the reasons behind chronic inflammation in tissue samples obtained from victims of failing metal-on-metal hip implants. They found that residual chromium is oxidized and Cobalt 2+ions are released as the nano-particles corrodes in the tissue, resulting in inflammation. According to the researchers, nano-particles shed from the hip implants had accumulated in white blood cells, where a corrosion process causes the cobalt to dissolve rapidly and be released into the surrounding tissue and blood stream. The less soluble chromium remains in the tissue as a solid residue.
According to Medicalxpress, studies have shown that Cobalt 2+ions are genotoxic, meaning they could potentially damage DNA and lead to further long-term medical complications.
“We were able to meet patients who had these failing implants and we could see first-hand the chronic inflammation, pain and loss of mobility they experienced,” Dr. Mary Ryan, co-author of the paper from the Department of Materials at Imperial College, said in a statement. “Even though a huge number of patients have benefited from replacement surgery, we still don’t fully understand the long-term impacts that implantable materials have on our bodies.”
The study team will next conduct research to understand why these nano-particles are corroding when most of the alloy used in metal-on-metal hip implants is corrosion resistant. They plan to use this correlative approach to explore other diseases where nanoscale materials may have an impact on human health, such as Alzheimer’s disease, Medicalxpress wrote.
As we’ve reported previously, metal-on-metal hip replacements, once believed to be more durable than other types of hip implant devices, have raised serious safety concerns ever since the August 2012 worldwide recall of DePuy Orthopaedics ASR hip implant devices. Patients have increasingly complained of pain and early implant failures, while a number of studies have pointed to significant problems with metal-on-metal hip implants. Last month, the U.S. Food & Drug Administration (FDA) revealed that it had received 16,800 negative event reports involving metal hips between 2000 and 2011. Of those, more than 14,000 involved revision surgeries, in which a defective implant was removed.
Last week, the FDA’s Orthopaedic and Rehabilitation Devices Panel recommended that metal-on-metal hip implant patients undergo regular monitoring to ensure their devices are not failing. The panel also called for new warning labels for all-metal hip implants, including warnings regarding their association with the development of pseudotumors and high levels of metal ions in patients’ blood. During their two day meeting, some experts on the FDA panel even questioned why all-metal implants would ever be used, considering their poor track record of safety.
