QUANTIFYING THE REGIONAL VARIATIONS IN THE MECHANICAL PROPERTIES OF CANCELLOUS BONE OF THE TIBIA USING INDENTATION TESTING AND CT IMAGING

Abstract

<p>Finite element (FE) models are a fast and cost-effective way to evaluate stress behavior in bone under various loading conditions. However, accurate material property assignment is required when developing the model. Bone is an inhomogeneous material as there is much variation in the distribution of its mechanical properties. However, there has been limited investigation into the extent of regional variations in the cancellous bone of the proximal tibia. Dynamic FE models simplify bone as a homogeneous material, which may affect their accuracy. However, density-modulus relationships have been successful in assigning accurate material properties in the development of static FE models. There are many such equations in the literature and the most appropriate densitymodulus relationship for cancellous bone of the proximal tibia has yet to be determined. In the first study of this thesis, indentation testing was performed on four slices, each consisting of nine regions, from five cadaveric tibiae. The modulus and yield strength were found to vary regionally, where the bone closest to the joint and in the medial condyle were strongest, and the intercondylar region the weakest. These areas of strength can serve as improved sites of attachment to ensure the long-term success of orthopaedic devices. It also suggests that regional variations in cancellous bone need to be considered in the development of subject-specific FE models. In the second study, density-modulus relationships developed for cancellous bone of the tibia were evaluated for their ability to predict mechanical properties. Computed tomography (CT) was used to determine bone density, which was used in three equations from the literature to compare predicted modulus to experimental elastic modulus. It was</p>