The amount of metal ions in the blood and the type of hip implant may predict premature failure of metal-on-metal hip replacements, according to a team of United Kingdom researchers.
Researchers reviewed data from 299 resurfacing procedures in 278 patients with various brands of hip implants. The patients had reported complications that were likely related to high levels of metal in their blood.
Patients were put through a blood metal ion screening protocol, ultrasound scanning, and joint aspiration to determine the level of cobalt concentration. Researchers found that blood-cobalt concentration and the type of device used were significant risk factors for device failure. Women with high cobalt blood concentration and the DePuy ASR device had the highest failure risk while patients with the BHR Smith & Nephew device had a lower risk of revision.
Typical artificial hips are made with plastic or ceramic parts and can last up to 20 years. However, in the past decade, manufacturers began making the devices with all-metal parts with expectations that they would be more durable. It didn’t take long to discover that the metal-on-metal design was flawed. The devices were failing at much faster rate than traditional implants.
Researchers also found that as the metal parts of the devices rubbed together, bits of metal debris could flake off in the joint space, causing inflammation in surrounding tissue, and pain and disability for the patient. This inflammation also led to premature failures of the implant, including device fractures and dislocations.
Doctors also discovered that these metal bits could leech into the bloodstream, causing a type of blood poisoning known as metallosis. The short-term effects of this condition include fatigue and headaches, but the long-term effects are anyone’s guess. Some researchers say metallosis damages DNA and can lead to serious health problems including cancer.