Mouse/rat knee static loading test apparatus
Rose, Thomas Joseph.
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Osteoarthritis (OA) involves mechanically-related cartilage deterioration and affects millions worldwide. To date no effective treatments for OA exist and to expedite the solution process rodent models that mimic human disease are used before attempting to apply to human models. Rodent models of osteoarthritis involve mechanical destabilization of the knee joint which likely changes the contact pressure distribution. However, no methods currently exist for measuring the contact pressure distribution in mouse or rat knees. Therefore, the objective was to develop a method to measure the contact pressure distribution within a mouse knee. This research designed and tested an apparatus to apply loads to mouse knees based on measurements of young mouse knees and mature rat knees. Applied loads were used to explore measureable pressure zone shifts within the knee for varying flexion angles. Measurements of the tibia plateau were used to estimate contact area for an expected pressure range. Based on this preliminary information, a machine was designed to incorporate 6 degrees of freedom that allows the application of compressive loading while allowing the knee as natural of movement as possible. To apply the load a mechanical system was devised to both measure and apply joint loading. Several iterations of both of these systems were considered and the final product was created for testing. Several hurdles were overcome during testing, which included creating a method to interface the biological knee to the mechanical system, developing a technique to measure the pressure distribution of extremely small areas, and the requirement for accurate calibration of both the load application and measurement. It is assumed that the results will be the first pressure distribution measurements in the murine knee. Extension of these results may yield valuable insight into the mechanical environment of rodent osteoarthritis models.