Anisotropic elastic properties of human femoral cortical bone and relationships with composition and microstructure in elderly

Xiran Cai (1) , Hélène Follet (2) , Laura Peralta (1) , Marc Gardegaront (2) , Delphine Farlay (2) , Rémy Gauthier (3, 4) , Boliang Yu (4) , Evelyne Gineyts (2) , Cécile Olivier (4, 5) , Max Langer (4, 5) , Aurélien Gourrier (6) , David Mitton (3) , Françoise Peyrin (4, 5) , Quentin Grimal (1) , Pascal Laugier (1)

1 LIB - Laboratoire d'Imagerie Biomédicale [Paris]
2 LYOS - Physiopathologie, diagnostic et traitements des maladies osseuses / Pathophysiology, Diagnosis & Treatments of Bone Diseases
3 LBMC UMR T9406 - Laboratoire de Biomécanique et Mécanique des Chocs
4 Imagerie Tomographique et Radiothérapie
5 ESRF - European Synchrotron Radiation Facility
6 LIPhy - Laboratoire Interdisciplinaire de Physique [Saint Martin d’Hères]

The strong dependence between cortical bone elasticity at the millimetre-scale (mesoscale) and cortical porosity has been evidenced by previous studies. However, bone is an anisotropic composite material made by mineral, proteins and water assembled in a hierarchical structure. Whether the variations of structural and compositional properties of bone affect the different elastic coefficients at the mesoscale is not clear. Aiming to understand the relationships between bone elastic properties and compositions and microstructure, we applied state-of-the-art experimental modalities to assess these aspects of bone characteristics. All elastic coefficients (stiffness tensor of the transverse isotropic bone material), structure of the vascular pore network, collagen and mineral properties were measured in 52 specimens from the femoral diaphysis of 26 elderly donors. Statistical analyses and micromechanical modeling showed that vascular pore volume fraction and the degree of mineralization of bone are the most important determinants of cortical bone anisotropic mesoscopic elasticity. Though significant correlations were observed between collagen properties and elasticity, their effects in bone mesoscopic elasticity were minor in our data. This work also provides a unique set of data exhibiting a range of variations of compositional and microstructural cortical bone properties in the elderly and gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone. STATEMENT OF SIGNIFICANCE: This study reports the relationships between microstructure, composition and the mesoscale anisotropic elastic properties of human femoral cortical bone in elderly. For the first time, we provide data covering the complete anisotropic elastic tensor, the microstructure of cortical vascular porosity, mineral and collagen characteristics obtained from the same or adjacent samples in each donor. The results revealed that cortical vascular porosity and degree of mineralization of bone are the most important determinants of bone anisotropic stiffness at the mesoscale. The presented data gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone.

Mots clés: RESONANT ULTRASOUND SPECTROSCOPY; CORTICAL BONE; ELASTICITY; COMPOSITION; MICROSTRUCTURE

Mots clés: BIOMECANIQUE

Domaines: Biomécanique [physics.med-ph]; Sciences de l'ingénieur [physics]

Xiran Cai, Hélène Follet, Laura Peralta, Marc Gardegaront, Delphine Farlay, et al.. Anisotropic elastic properties of human femoral cortical bone and relationships with composition and microstructure in elderly. Acta Biomaterialia, 2019, 90, pp.254-266. ⟨10.1016/j.actbio.2019.03.043⟩. ⟨hal-02107625⟩