title: Pore network microarchitecture influences human cortical bone elasticity during growth and aging.
abstract: Cortical porosity is a major determinant of bone strength. Haversian and Volkmann׳s canals are׳seen' as pores in 2D cross-section but fashion a dynamic network of interconnected channels in 3D, a quantifiable footprint of intracortical remodeling. Given the changes in bone remodeling across life, we hypothesized that the 3D microarchitecture of the cortical pore network influences its stiffness during growth and ageing. Cubes of cortical bone of 2 mm side-length were harvested in the distal 1/3 of the fibula in 13 growing children (mean age±SD: 13±4 yrs) and 16 adults (age: 75±13 yrs). The cubes were imaged using desktop micro-CT (8.14µm isotropic voxel size). Pores were segmented as a solid to assess pore volume fraction, number, diameter, separation, connectivity and structure model index. Elastic coefficients were derived from measurements of ultrasonic bulk compression and shear wave velocities and apparent mass density. The pore volume fraction did not significantly differ between children and adults but originates from different microarchitectural patterns. Compared to children, adults had 42% (p=0.033) higher pore number that were more connected (Connective Density: +205%, p=0.001) with a 18% (p=0.007) lower pore separation. After accounting for the contribution of pore volume fraction, axial elasticity in traction-compression mode was significantly correlated with better connectivity in growing children and with pore separation among adults. The changes in intracortical remodeling across life alter the distribution, size and connectedness of the channels from which cortical void fraction originates. These alterations in pore network microarchitecture participate in changes in compressive and shear mechanical behavior, partly in a porosity-independent manner. The assessment of pore volume fraction (i.e., porosity) provides only a limited understanding of the role of cortical void volume fraction in its mechanical properties.
authors.affiliation: Laboratoire Vibrations Acoustique, INSA Lyon, Campus LyonTech la Doua, 69621 Villeurbanne Cedex, France; INSERM UMR 1033, Université de Lyon, 69372 Lyon Cedex 08, France. Electronic address: yohannbala@gmail.com.
authors.forename: Yohann
authors.initials: Y
authors.lastname: Bala
authors.affiliation: Aix-Marseille University, CNRS, ISM UMR 7287, 13009 Marseille, France; APHM, Institute for Locomotion, Sainte-Marguerite Hospital, 13009 Marseille, France.
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Lefèvre
authors.affiliation: INSERM UMR 1033, Université de Lyon, 69372 Lyon Cedex 08, France.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Roux
authors.affiliation: Aix-Marseille University, CNRS, ISM UMR 7287, 13009 Marseille, France; APHM, Institute for Locomotion, Sainte-Marguerite Hospital, 13009 Marseille, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Baron
authors.affiliation: Laboratory of Mechanics and Acoustics, UPR CNRS 7051, Aix-Marseille University, Centrale Marseille, 13009 Marseille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Lasaygues
authors.affiliation: Aix-Marseille University, CNRS, ISM UMR 7287, 13009 Marseille, France; APHM, Institute for Locomotion, Sainte-Marguerite Hospital, 13009 Marseille, France.
authors.forename: Martine
authors.initials: M
authors.lastname: Pithioux
authors.affiliation: Laboratoire Vibrations Acoustique, INSA Lyon, Campus LyonTech la Doua, 69621 Villeurbanne Cedex, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Kaftandjian
authors.affiliation: INSERM UMR 1033, Université de Lyon, 69372 Lyon Cedex 08, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Follet
mesh_terms: D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D002648:Child; D000071538:Cortical Bone / Q000254:growth & development* / Q000502:physiology*; D004548:Elasticity; D006801:Humans; D008875:Middle Aged; D016062:Porosity; D055114:X-Ray Microtomography
keywords: Aging; Bone microarchitecture; Bone microstructure; Cortical porosity; Growth