Researchers unsure how to evaluate metal ion levels in patients with metal-on-metal hip implants

 Researchers unsure how to evaluate metal ion levels in patients with metal on metal hip implantsBlood tests to measure the amount of metal ions in the blood of patients with metal-on-metal hip implants are inexpensive and provide helpful information. But they do not provide definitive information whether an artificial hip is functioning poorly and is likely to fail, new research shows.

Chromium and cobalt ion levels are generally elevated in the blood of patients with all-metal hip implants. Because the implants have been found more likely to fail than traditional hip implants, medical regulators say that patients with the devices should be monitored on a regular basis for signs of failure.

That monitoring generally includes a blood test to measure the level of chromium and cobalt in the blood. Experts are divided as to what level of metal poisoning indicates a problem requiring revision surgery to remove and replace the device.

Researchers say patients with the metal-on-metal hips generally fall into one of three categories – those with very severe symptoms, those with very few symptoms, and those who have moderate hip pain or abnormal metal ion tests. It’s easy to evaluate patients who fit into the extreme categories – those with severe symptoms require revision surgery while those with few symptoms continued to be monitored. It is the patients who fall into the “in-between” category that doctors have to decide how to treat.

Metal ion tests are inexpensive and can identify poorly functioning implants, but there have been no large studies to determine how useful the ion tests are for predicting implant failure in patients with moderate symptoms. It creates an uncomfortable place for these patients who face another major surgery to remove and replace their device, or risk more ions seeping into their bloodstream.

Cobalt and chromium in the blood cause a type of blood poisoning known as metallosis. This condition can damage DNA, which can lead to serious health problems including cancer.

Source: MedPage Today