The data show that people who had large-diameter modular metal-on-metal implants had a 5.9 per cent chance of needing to have the implant replaced within five years, compared to a rate of 2.7 per cent among people who received the more common metal-on-plastic implant.
The data, released by the Canadian Institutes for Health Information, show that nearly three out of every four hip replacements logged into the Canadian joint replacement registry were metal-on-plastic units.
Metal-on-metal hip replacements made up only nine per cent of the procedures recorded in the registry.
Metal-on-metal units were introduced with great optimism a few years ago; the thinking was the replacement hips would be more durable and better for younger patients than the metal-on-plastic type.
But data from a number of countries have shown that hasn't been the case for a small subset of people who received the units.
Canadian orthopedic surgeons took a more conservative approach to the metal-on-metal implants and it turned out to be the way to go, says Dr. Michael Dunbar, an orthopedic surgeon from Halifax and co-chair of the joint replacement registry.
"It was the right side of the street to be on, for sure," Dunbar says.
"It was the fact of the matter that in the United States in the late 2000s almost 45 per cent of every male in the country (who got a hip replacement) got metal-on-metal. So this is why it's such a big issue in the United States."
Dunbar says the differences between the U.S. and Canadian situations underscore why it's important to gather information on joint replacements. Currently the joint replacement registry is a voluntary one, and only captures a portion of the procedures done in the country.
Two provinces — British Columbia and Ontario — are moving to make it mandatory for these procedures to be recorded in the registry. But Dunbar wishes others would follow suit.
"We have a voluntary system and until recently we've been down around 50 per cent. We think that all implants should be registered because this is important. We're spending the nation's treasure on this stuff. This is a top health-care priority in Canada," Dunbar says.
"We want to make sure we can deliver the very best product to the patients in our country. And we want to make sure that the money that we're spending ... is best spent for the most appropriate implant for the most appropriate patient."
The report is based on nearly 60,000 hip replacements done across Canada between 2003 and 2011. Data from Quebec were not included.Suggest a correction