Fracture and Deformation in Trabecular Bone: Anisotropy, Hierarchy, and Scaffolds

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Left: A high resolution scan of a bovine tibia trabecular bone. Sample is imaged in a 5mm cube [Keaveny, et al., 2001]. Right: Various architectures designed and produced in Greer’s group [Montemayor, et al., 2013].

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Trabecular bone is a porous, spongy bone that is found in at the ends of long bones, inside vertebral bones, and in the core of wide flat bones such as the pelvis and the skull. It plays a critical load bearing role, and weakened or compromised trabecular bone is often to blame in age-related bone fracture. Trabecular bone has proven very difficult to study and model experimentally because of its heterogeneity, anisotropy, and multi-scale mechanics. Mean values of modulus and strength can vary by an order of magnitude within the same bone sample, and overall strength can vary by two orders of magnitude depending on age and anatomic location. Bone growth is adaptive, and trabeculae grow preferentially in the direction of highest stress, leading to bone that has highly directionally dependent strength and modulus properties. Owing to its porosity, the individual struts likely play a dominant role in the mechanical behavior at small scales (<5mm) and the properties cannot be addressed as a continuum for sample areas smaller than 5-10mm. The complexity associated with multiscale nature of trabecular bone mechanics and with the challenges on studying deformation of bone at the microscopic level, this problem has not yet prompted explosion of experimental, theoretical and computational research thrusts. We consider this problem to be a grand opportunity to pursue within the scope of ICB research. In the scope of this proposal, we will first study the architecture and anisotropy of trabecular bone and develop an understanding of the relation between trabecular architecture and mechanical properties, including modulus, strength, and fracture toughness. We will then use this knowledge – together with computational results of ARL colleagues - to design and fabricate artificial scaffolding materials that can adequately match the mechanical properties of actual trabecular bone.



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