title: Nanoindentation analysis of the micromechanical anisotropy in mouse cortical bone.
abstract: Studies investigating micromechanical properties in mouse cortical bone often solely focus on the mechanical behaviour along the long axis of the bone. Therefore, data on the anisotropy of mouse cortical bone is scarce. The aim of this study is the first-time evaluation of the anisotropy ratio between the longitudinal and transverse directions of reduced modulus and hardness in mouse femurs by using the nanoindentation technique. For this purpose, nine 22-week-old mice (C57BL/6) were sacrificed and all femurs extracted. A total of 648 indentations were performed with a Berkovich tip in the proximal (P), central (C) and distal (D) regions of the femoral shaft in the longitudinal and transverse directions. Higher values for reduced modulus are obtained for indentations in the longitudinal direction, with anisotropy ratios of 1.72 ± 0.40 (P), 1.75 ± 0.69 (C) and 1.34 ± 0.30 (D). Hardness is also higher in the longitudinal direction, with anisotropic ratios of 1.35 ± 0.27 (P), 1.35 ± 0.47 (C) and 1.17 ± 0.19 (D). We observed a significant anisotropy in the micromechanical properties of the mouse femur, but the correlation for reduced modulus and hardness between the two directions is low (r2< 0.3) and not significant. Therefore, we highly recommend performing independent indentation testing in both the longitudinal and transverse directions when knowledge of the tissue mechanical behaviour along multiple directions is required.
authors.affiliation: Institute for Biomechanics , ETH Zürich , Zürich , Switzerland.
authors.forename: Michele
authors.identifier: 0000-0002-7746-0123
authors.initials: M
authors.lastname: Casanova
authors.affiliation: Institute for Biomechanics , ETH Zürich , Zürich , Switzerland.
authors.forename: Anna
authors.initials: A
authors.lastname: Balmelli
authors.affiliation: Complex Materials, Department of Materials , ETH Zürich , Zürich , Switzerland.
authors.forename: Davide
authors.initials: D
authors.lastname: Carnelli
authors.affiliation: Laboratory for Nanometallurgy, Department of Materials , ETH Zürich , Zürich , Switzerland.
authors.forename: Diana
authors.initials: D
authors.lastname: Courty
authors.affiliation: Institute for Biomechanics, ETH Zürich, Zürich, Switzerland; Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK.
authors.forename: Philipp
authors.identifier: 0000-0001-7499-3576
authors.initials: P
authors.lastname: Schneider
authors.affiliation: Institute for Biomechanics , ETH Zürich , Zürich , Switzerland.
authors.forename: Ralph
authors.initials: R
authors.lastname: Müller
keywords: hardness; mechanical anisotropy; mouse cortical bone; nanoindentation; reduced modulus