Canadian regulators have issued a new alert for patients who have been implanted with metal-on-metal hip devices, advising them to watch for certain signs that could indicate the implants are failing.
Prompted by growing concerns over the safety of hip implant devices made of all-metal components, Health Canada says that patients who have received such implants should “be on the lookout for pain the groin, hip or leg, swelling at or near the hip joint, or onset of a limp or change in walking ability or limited range of motion,” according to The Canadian Press.
Much of the concern about metal-on-metal hip implants has been generated by the recall of DePuy’s two ASR hip implant systems, the XL Acetabular System and the Hip Resurfacing System, in August 2010. DePuy recalled the devices after clinical data showed the devices were prone to fail prematurely at a rate of 12-13 percent within five years.
The devices are also widely blamed for a number of serious health problems related to excessive levels of cobalt and chromium in the blood. Health Canada and other health authorities believe these problems could be caused when friction between the implants’ metal parts casts metallic particles into the blood and tissue, sometimes causing significant local damage and systemic illness.
According to Health Canada, 10 percent of Canadians who have undergone hip-replacement surgery have received a metal-on-metal hip. People who are most likely to be adversely affected by the devices are women, physically active patients, severely overweight patients, and those who have received all-metal hip implants in both hip joints.
Health Canada also instructs Canadian health care providers on how to manage patients who have received an all-metal hip implant. The agency recommends that doctors perform blood and other tests on patients who may be exhibiting signs of trouble with their all-metal hip implants.
Because medical researchers don’t yet understand why elevated levels of chromium and cobalt in the blood affect people differently, Health Canada cautions doctors that the test results could be subjective and open to interpretation.
Patients who received a metal-on-metal hip implant should be checked by the doctor annually for five years, Health Canada advises. After that, patients should be checked on a schedule that conforms to established practices in their area, the agency said, unless they are at a high risk for developing problems. In that case, the patients should be followed more closely.