Fretting-Corrosion Apparatus With Low Magnitude Micro-Motion (<15 Μm) for Hip Implants

• Demi Ibrahim
• Rajeshwari Meenakshi
• Diana Gutierrez
• Elizabeth Brott

Previous research has demonstrated that wear and corrosion occur at implant interfaces. This wear and corrosion causes failure in the implant performance and survivorship. The metal ion release that occurs due to the tribocorrosion process results in local and systemic adverse reactions, which include metal toxicity that can affect various organs and cause a multitude of symptoms, inflammatory responses around the implant, and more. In order to minimize the impact on the individual patient and society, it is absolutely imperative that this metal ion release is reduced as much as possible. In particular, the hip modular junction interfaces between the femoral head and femoral stem of a hip implant are greatly affected by wear and corrosion. To create a solution to this problem it is necessary to simulate the fretting processes at this modular junction. This simulation should be able to achieve very low micromotion, within a range of 5μm-15μm, that tribocorrosion systems currently in use cannot achieve. This is because the fretting-corrosion between the neck-head interface of a hip implant encompasses two contacting surfaces that are subjected to a small displacement of 5μm-15μm under variable load. The main objective of this project is to develop a miniature fretting apparatus with very low micro-motion that can monitor the corrosion and electrochemical response of implant materials under a specific load. The current fretting apparatus design includes a stepper motor actuator with an optical encoder that actuates a linear stage with a resolution of 0.1μm, a frame that can apply 15kg of load between the two metals, a load cell to measure the tangential force, and an electrochemical cell with a double wall chamber to monitor the electrochemical response and keep the electrolyte at a desired temperature.