Grant: Master's Award: Canada Graduate Scholarships

Currently, orthopaedic companies are embroiled in multi-billion dollar lawsuits due to failures caused by fretting corrosion in modular hip replacement prostheses. Fretting corrosion occurs when subtle relative motion (micromotion) causes abrasion between components (fretting) thus allowing surrounding fluid to degrade the material (corrosion). Modern modular hip replacement's head and neck components connect via matching taper, much like nested cones. If the head-neck taper connection isn't strong enough to resist micromotion, then fretting corrosion takes place. Modern metal-on-metal prostheses use increasingly large heads, which place a greater demand on the head-neck taper connection. The connection fails because it was designed for use with heads that are half the size of those used today. The project's goal is to strengthen the head-neck taper connection so micromotion that leads to fretting corrosion does not take place. First, Infrared Thermography will be used to measure the loading at the head-neck taper connection, without interfering with its natural behaviour. The technique measures the load in the components by detecting the heat that they generate. Using the measurements, a computer model will be developed to allow countless design simulations until the optimal geometry is determined. Finally, the optimal geometry will be made to allow direct fretting corrosion measurement and comparison to the existing geometry. Metal-on-metal bearing hip prostheses appeared to be the future of hip replacements after demonstrating remarkably low wear rates and improved joint stability. Contrarily, fretting corrosion at the head-neck taper has resulted in poor patient outcomes and large scale recall. By optimizing the head-neck taper geometry to minimize the fretting corrosion, metal-on-metal bearing hip prostheses may again become a viable treatment option, and they may fulfil the potential that accompanied their introduction.