Improving the long-term performance of modular connections in artificial joints

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Artificial joints have been used in increasing numbers since the middle of the last century to treat patients with diseased joints. Early on, mainly hip and knee joints were treated, and the devices were rarely implanted in persons younger than 60 years, as the implant survival rate was typically less than 15 years. Artificial joints have improved much in the last 50 years, and an implant survival rate of 90% or more can be expected after 15 years, in spite of the fact that they are increasingly being implanted in younger and more active patients. Improvements that were introduced in the last few years included manufacturing of artificial joints in separate pieces, such as the head, neck and stem in hip joints, and assembling them during surgery for both, primary and revision surgery. These so-called modular designs allow surgeons intra-operatively to optimally adjust the size, alignment, type of the articulation and fixation to an individual patient. Despite enormous efforts using computer modeling and elaborate near physiological testing, it appears that some of these newer primary and revision designs develop problems at their modular connections. More frequently, there is an increase in corrosion at the modular head-neck interface of hip joints, especially in hips with larger heads that can lead to tissue reactions such as the formation of cysts, pseudotumors and muscle damage. The long term goal of this research is to improve the performance of modular connections in artificial joints to achieve a reduction of revisions due to fractures and corrosion. The first study the applicant and his students will look at is the corrosion and fretting damage at head-neck tapers. The novel tests will be validated by reproducing clinical "damage" observed in a sample of retrieved artificial joints. The expected reduction of revision surgeries will increase the successful long-term performance of artificial joints benefitting the patients, and reduce the costs to health care. Training of engineering HQP in this area of expertise at the University of Manitoba and the Concordia Hip and Knee Institute will support the growth of the medical device industry in Canada.