title: Computational and experimental methodology for site-matched investigations of the influence of mineral mass fraction and collagen orientation on the axial indentation modulus of lamellar bone.
abstract: Relationships between mineralization, collagen orientation and indentation modulus were investigated in bone structural units from the mid-shaft of human femora using a site-matched design. Mineral mass fraction, collagen fibril angle and indentation moduli were measured in registered anatomical sites using backscattered electron imaging, polarized light microscopy and nano-indentation, respectively. Theoretical indentation moduli were calculated with a homogenization model from the quantified mineral densities and mean collagen fibril orientations. The average indentation moduli predicted based on local mineralization and collagen fibers arrangement were not significantly different from the average measured experimentally with nanoindentation (p=0.9). Surprisingly, no substantial correlation of the measured indentation moduli with tissue mineralization and/or collagen fiber arrangement was found. Nano-porosity, micro-damage, collagen cross-links, non-collagenous proteins or other parameters affect the indentation measurements. Additional testing/simulation methods need to be considered to properly understand the variability of indentation moduli, beyond the mineralization and collagen arrangement in bone structural units.
authors.affiliation: Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gusshausstrasse 27-29, A-1040 Vienna, Austria; Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands. Electronic address: e.m.spiesz@tue.nl.
authors.forename: Ewa M
authors.initials: EM
authors.lastname: Spiesz
authors.forename: Andreas G
authors.initials: AG
authors.lastname: Reisinger
authors.forename: Werner
authors.initials: W
authors.lastname: Kaminsky
authors.forename: Paul
authors.initials: P
authors.lastname: Roschger
authors.forename: Dieter H
authors.initials: DH
authors.lastname: Pahr
authors.forename: Philippe K
authors.initials: PK
authors.lastname: Zysset
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D015519:Bone Density; D003094:Collagen / Q000378:metabolism*; D005260:Female; D005269:Femur / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D008422:Materials Testing; D055595:Mechanical Phenomena; D008954:Models, Biological
chemical_list: D003094:Collagen
keywords: Collagen fibril orientation; Homogenization; Mineralization; Nanoindentation; Quantitative polarized light microscopy (qPLM); Site-matching