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Papers by Naiara Rodriguez-Florez

Age and/or skeletal diseases often lead to an increase in bone fracture risk. An understanding of... more Age and/or skeletal diseases often lead to an increase in bone fracture risk. An understanding of the fracture mechanism of bone is required for the implementation of appropriate therapies. Bone has a complex fracture behaviour comprising various toughening mechanisms at different scales. Determining the influence of micro-architecture is therefore fundamental to characterise bone toughness. This study aims to understand the influence of intracortical bone porosity in crack propagation using a two-dimensional model of the porosities of osteogenesis imperfecta murine (oim) cortical bone. Osteogenesis imperfecta is a genetic disease that results in skeletal fragility. These brittle bones have similar cortical porosity than their wild types (WT) but more numerous and more branched canals and more lacunae per unit volume [1]; thus, they provide an excellent platform to analyse the influence of porosity in crack propagation. The topology of transverse cross sections of oim and WT tibial mid-diaphysis were captured with synchrotron radiation-based computed tomography and used to create two-dimensional models that included vascular and lacunar porosity. A notch was placed in the centre of the lower edge and a displacement was applied perpendicular to the notch. Crack initiation and propagation were analysed following the Extended Finite Element Method (X-FEM Abaqus), which allows to model crack propagation along an arbitrary, solution-dependent path without the need of adaptive remeshing. The cohesive segment approach was used with maximum principal stress failure criterion for damage initiation and a single mode, energy based damage evolution law for crack propagation. The bone was considered linear elastic and homogeneous and the material properties were maintained constant for both models, to explore the influence of porosity only. Results suggest that the main crack (in green) follows the vascular canals (in red), while the contribution of lacunae (in yellow) in the crack propagation is minimal . We hypothesize that due to the difference between vascular and lacunar volume, the influence of vascular canals will be more apparent in 3D crack propagation. Our future XFEM studies will further investigate the influence of 3D micro-architecture in brittle bone in order to improve the understanding of the toughening mechanisms of bone.

Aging and skeletal diseases lead to an increase in bone fracture risk. In particular, micro-poros... more Aging and skeletal diseases lead to an increase in bone fracture risk. In particular, micro-porosity might have a profound influence on crack propagation. In osteogenesis imperfecta murine (oim) bones, which represent the moderate to severe condition of osteogenesis imperfecta in humans, a genetic mutation results in high bone fragility. Oim bones have more numerous and branched vascular canals compared to their wild type (WT) controls [1]. The objective of this study is to use the Extended Element Method (XFEM) tools provided by Abaqus (v 6.12) to characterize the role of vascular canals in mouse cortical bone during crack propagation. The topology of transverse cross sections of oim and WT tibial mid-diaphysis were captured with synchrotron radiation-based computed tomography and used to create two-dimensional models. Although XFEM allows modelling crack propagation along an arbitrary, solution-dependent path, there are some limitations when using this technique to model bone at t...

Multi-Scale Permeability of Murine Bone Measured by Nanoindentation

Poromechanics V, 2013

Journal of Bone and Mineral Research, 2014

Bone is a strong and tough material composed of apatite mineral, organic matter and water.

Journal of the Mechanical Behavior of Biomedical Materials, 2013

Nanoindentation provides the ideal framework to determine mechanical properties of bone at the ti... more Nanoindentation provides the ideal framework to determine mechanical properties of bone at the tissue scale without being affected by the size, shape, and porosity of the bone. However, the values of tissue level mechanical properties vary significantly between studies. Since the differences in the bone sample, hydration state, and test parameters complicate direct comparisons across the various studies, these discrepancies in values cannot be compared directly. The objective of the current study is to evaluate and compare mechanical properties of the same bones using a broad range of testing parameters. Wild type C56BL6 mice tibiae were embedded following different processes and tested in dry and rehydrated conditions. Spherical and Berkovich indenter probes were used, and data analysis was considered within the elasto-plastic (Oliver-Pharr), viscoelastic and visco-elastic-plastic frameworks. The mean values of plane strain modulus varied significantly depending on the hydration state, probe geometry and analysis method. Indentations in dry bone analysed using a visco-elastic-plastic approach gave values of 34 GPa. After rehydrating the same bones and indenting them with a spherical tip and utilizing a viscoelastic analysis, the mean modulus value was 4 GPa, nearly an order of magnitude smaller. Results suggest that the hydration state, probe geometry and the limitations and assumptions of each analysis method influence significantly the measured mechanical properties. This is the first time that such a systematic study has been carried out and it has been concluded that the discrepancies in the mechanical properties of bone measured by nanoindentation found in the literature should not be attributed only to the differences on the bones themselves, but also to the testing and analysis protocols.

Journal of Biomechanics, 2014

The determination of lacunar-canalicular permeability is essential for understanding local 2 flui... more The determination of lacunar-canalicular permeability is essential for understanding local 2 fluid flow in bone, which may indicate how bone senses changes in the mechanical 3 environment to regulate mechano-adaptation. The estimates of lacunar-canalicular 4 permeability found in the literature vary by up to eight orders of magnitude, and age-related 5 permeability changes have not been measured in non-osteonal mouse bone. The objective of 6 this study is to use a poroelastic approach based on nanoindentation data to characterize 7 lacunar-canalicular permeability in murine bone as a function of age. Nine wild type 8 C57BL/6 mice of different ages (2, 7 and 12 months) were used. Three tibiae from each age 9 group were embedded in epoxy resin, cut in half and indented in the longitudinal direction in 10 the mid-cortex using two spherical fluid indenter tips (R = 238 μm and 500 μm). Results