title: Micro CT-based multiscale elasticity of double-porous (pre-cracked) hydroxyapatite granules for regenerative medicine.
abstract: Hundred micrometers-sized porous hydroxyapatite globules have proved as a successful tissue engineering strategy for bone defects in vivo, as was shown in studies on human mandibles. These granules need to provide enough porous space for bone ingrowth, while maintaining sufficient mechanical competence (stiffness and strength) in this highly load-bearing organ. This double challenge motivates us to scrutinize more deeply the micro- and nanomechanical characteristics of such globules, as to identify possible optimization routes. Therefore, we imaged such a (pre-cracked) granule in a microCT scanner, transformed the attenuation coefficients into voxel-specific nanoporosities, from which we determined, via polycrystal micromechanics, voxel-specific (heterogeneous) elastic properties. The importance of the latter and of the presence of one to several hundred micrometers-sized cracks for realistically estimating the load-carrying behavior of the globule under a typical two-point compressive loading (as in a "splitting" test) is shown through results of large-scale Finite Element analyses, in comparison to analytical results for a sphere loaded at its poles: Use of homogeneous instead of heterogeneous elastic properties would overestimate the structure's stiffness by 5% (when employing a micromechanics-based process as to attain homogeneous properties)-the cracks, in comparison, weaken the structure by one to two orders of magnitudes.
authors.affiliation: Vienna University of Technology, Institute for Mechanics of Materials and Structures, Karlsplatz 13/202, A-1040 Vienna, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Dejaco
authors.forename: Vladimir S
authors.initials: VS
authors.lastname: Komlev
authors.forename: Jakub
authors.initials: J
authors.lastname: Jaroszewicz
authors.forename: Wojciech
authors.initials: W
authors.lastname: Swieszkowski
authors.forename: Christian
authors.initials: C
authors.lastname: Hellmich
mesh_terms: D018786:Bone Substitutes / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry*; D004548:Elasticity; D020342:Finite Element Analysis; D008422:Materials Testing; D016062:Porosity; D044968:Regenerative Medicine; D016474:Weight-Bearing; D055114:X-Ray Microtomography
chemical_list: D018786:Bone Substitutes; D017886:Durapatite