Metal-on-plastic implants account for nearly 75% of implants used in hip replacements
July 18, 2013—How long an artificial hip implant lasts is influenced by several factors, according to a new study conducted by the Canadian Institute for Health Information (CIHI). One of these factors is the material used for the implant bearing surfaces.
CIHI’s study—based on almost 60,000 total hip replacements in Canada (excluding Quebec) reported between 2003 and 2011—looked at the effect of several factors, including the different bearing surface materials used, on the risk of patients needing to have their implants replaced early in a revision surgery (in this case, within five years of the initial replacement surgery).
Patients with a specific type of metal-on-metal hip replacement (specifically, large-diameter modular) were found to be 1.6 times more likely to require surgery within five years to replace the implant than patients who received the most common type of metal-on-plastic implant.
CIHI’s analysis found that patients with large-diameter modular metal-on-metal implants had a 5.9% chance of having an early revision surgery, compared with only a 2.7% chance for those with the most common type of metal-on-plastic implant.
The data also reveals that patients whose hips were replaced with a metal-on-metal implant were most likely to be male and younger than age 55. Studies on revisions and metal-on-metal hip implants done in other countries such as the United Kingdom and Australia have had similar findings. Though repeat surgical procedures are more common with a specific type of metal on-metal implant, these implants may still be preferable for some patients.
“Metal-on-metal hip replacement implants were generally considered to be the most suitable implants for younger, more active patients who are traditionally at higher risk of repeat surgery due to the wear and tear they place on the implant,” says Dr. Eric Bohm, an orthopedic surgeon from the Concordia Hip and Knee Institute. “Hip replacement implants are used to improve a patient’s quality of life by reducing pain and allowing increased function. The decision regarding which type to use is influenced by patient factors such as age, activity level and anatomy.”
Although the use of metal-on-metal implants has declined since its peak in 2007–2008, these implants have been linked with recent safety alerts. However, results show that they represented less than 10% of the implants used in total hip replacements. The most-used materials were metal-on-plastic (73%).
The findings matter because patients whose artificial hips need early replacement undergo a long recovery and rehabilitation period that affects their quality of life. As well, the associated health care costs of revisions are more costly than those of the initial hip replacement: patients undergoing revision typically stay in hospital an average of 17% longer than patients undergoing their initial surgery, and typical procedure costs in the hospital for revision are about 45% more than for the initial surgery (not including doctor fees and rehabilitation costs).
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