Metal-on-metal hip replacement devices have come under significant scrutiny in recent years following the high-profile recall of the DePuy Orthopaedics ASR hip implant devices which were failing prematurely at unexpectedly high rates.
The recall which was announced in August 2010 has been followed by a number of studies which have found that the devices can shed dangerous amounts of chromium and cobalt into patient’s blood streams. This can lead to early implant failure, adverse local tissue reactions, bone and tissue loss and the development of pseudotumors and other long term health problems. Now a new study has revealed that cobalt is being seen in high levels in patients implanted with the devices.
Cobalt is known for its toxic effects on the thyroid, heart and the blood system as well as causing occupational lung disease, allergic reactions and potentially cancer.
According to the Journal of Human and Experimental Toxicology high levels of cobalt have been seen in patients implanted with metal-on-metal hip replacement devices. They have reported symptoms including noise or ringing in their ears, deafness, dizziness(vertigo), visual changes or vision loss as a result of optic atrophy, tremors and peripheral neuropathy(nerve damage on both sides) of the body. The exposure believed to be linked to cobalt-chromium alloyed orthopaedic implants, such as replacement hip devices appears to be caused by fretting and shedding of device materials.
In April 2010 the UK Medical Products and Healthcare Devices Regulatory Agency released a medical device alert recommending patients under-go a follow-up after receiving a metal-on-metal hip replacement no less than once a year for the first 5 years following surgery to determine if the devices are leading to toxicity.
About 1 million metal-on-metal hip devices have been implanted globally over the past 15 years leaving these patients at possible risk for cobalt toxicity.
Other studies have found that cobalt levels increased following implantation with an artificial hip device and during later follow up, and that the release of these metal ions is a well-documented outcome following hip arthroplasty implants, specifically metal-on-metal hip replacement devices. Levels were higher in the first 2 years following surgery and again when devices began to fail. Meanwhile, data from the NJR of England and Wales has revealed that patient outcomes following hip resurfacing arthroplasty are inferior to conventional total hip arthroplasty.