ELASTIC PROPERTIES OF CANCELLOUS BONE

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The long range objective of the proposed research is to map the elastic properties of the entire femur and tibia as a function of anatomical site. In previous work by the author, the elastic properties of the cortical portion of these were measured. To date, there exists no technique that can be used to obtain accurate values of the elastic properties from small specimens of cancellous bone. Hence, a large portion of the proposed work will be to develop such a technique. Having accurate values of the elastic properties as a function of position is a necessary prerequisite to the mechanical analysis of these load bearing bones; particularly in finite element analyses where accurate values of the elastic moduli, shear moduli, and Poisson's ratios are crucial to the design of improved hip and knee prosthetics. The specific aims of the proposed research are the develop an ultrasonic technique that can be used to measure the elastic properties of small specimens of cancellous bone. The proposed methodology is 1) to measure ultrasonic wave velocities over a range of frequencies from 50 kHz to 3 MHz, 2) to relate the velocities to elastic properties by appropriate continuum theories, 3) to measure material density, bulk density, and bone mineral content of the ultrasonic specimens, 4) to measure the elastic properties by mechanical methods on adjacent specimens, and 5) to correlate the ultrasonically measured elastic properties with the densities, mineral content, and mechanically measured elastic properties to evaluate the validity of the ultrasonic technique. Once the ultrasonic technique is developed, the elastic properties of the cancellous and cortical portions of both the femur and tibia will be mapped as a function of anatomical site.