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Age-related properties at the microscale affect crack propagation in cortical bone

Gustafsson, Anna LU ; Wallin, Mathias LU and Isaksson, Hanna LU (2019) In Journal of Biomechanics 95.
Abstract

The increased risk for fracture with age is associated not only with reduced bone mass but also with impaired bone quality. At the microscale, bone quality is related to porosity, microstructural organization, accumulated microdamage and intrinsic material properties. However, the link between these characteristics and fracture behavior is still missing. Bone tissue has a complex structure and as age-related compositional and structural changes occur at all hierarchical length scales it is difficult to experimentally identify and discriminate the effect of each mechanism. The aim of this study was therefore to use computational models to analyze how microscale characteristics in terms of porosity, intrinsic toughness properties and... (More)

The increased risk for fracture with age is associated not only with reduced bone mass but also with impaired bone quality. At the microscale, bone quality is related to porosity, microstructural organization, accumulated microdamage and intrinsic material properties. However, the link between these characteristics and fracture behavior is still missing. Bone tissue has a complex structure and as age-related compositional and structural changes occur at all hierarchical length scales it is difficult to experimentally identify and discriminate the effect of each mechanism. The aim of this study was therefore to use computational models to analyze how microscale characteristics in terms of porosity, intrinsic toughness properties and microstructural organization affect the mechanical behavior of cortical bone. Tensile tests were simulated using realistic microstructural geometries based on microscopy images of human cortical bone. Crack propagation was modelled using the extended finite element method where cement lines surrounding osteons were modelled with an interface damage law to capture crack deflections along osteon boundaries. Both increased porosity and impaired material integrity resulted in straighter crack paths with cracks penetrating osteons, similar to what is seen experimentally for old cortical bone. However, only the latter predicted a more brittle failure behavior. Furthermore, the local porosity influenced the crack path more than the macroscopic porosity. In conclusion, age-related changes in cortical bone affect the crack path and the mechanical response. However, increased porosity alone was not driving damage in old bone, but instead impaired tissue integrity was required to capture brittle failure in aging bone.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Fracture energy, Microstructure, Porosity, Tensile test, XFEM
in
Journal of Biomechanics
volume
95
article number
109326
publisher
Elsevier
external identifiers
  • pmid:31526587
  • scopus:85072187838
ISSN
0021-9290
DOI
10.1016/j.jbiomech.2019.109326
language
English
LU publication?
yes
id
2ad1e6a0-a4ab-492d-beb2-971c3de3a71b
date added to LUP
2019-10-11 14:21:06
date last changed
2020-01-13 02:27:39
@article{2ad1e6a0-a4ab-492d-beb2-971c3de3a71b,
  abstract     = {<p>The increased risk for fracture with age is associated not only with reduced bone mass but also with impaired bone quality. At the microscale, bone quality is related to porosity, microstructural organization, accumulated microdamage and intrinsic material properties. However, the link between these characteristics and fracture behavior is still missing. Bone tissue has a complex structure and as age-related compositional and structural changes occur at all hierarchical length scales it is difficult to experimentally identify and discriminate the effect of each mechanism. The aim of this study was therefore to use computational models to analyze how microscale characteristics in terms of porosity, intrinsic toughness properties and microstructural organization affect the mechanical behavior of cortical bone. Tensile tests were simulated using realistic microstructural geometries based on microscopy images of human cortical bone. Crack propagation was modelled using the extended finite element method where cement lines surrounding osteons were modelled with an interface damage law to capture crack deflections along osteon boundaries. Both increased porosity and impaired material integrity resulted in straighter crack paths with cracks penetrating osteons, similar to what is seen experimentally for old cortical bone. However, only the latter predicted a more brittle failure behavior. Furthermore, the local porosity influenced the crack path more than the macroscopic porosity. In conclusion, age-related changes in cortical bone affect the crack path and the mechanical response. However, increased porosity alone was not driving damage in old bone, but instead impaired tissue integrity was required to capture brittle failure in aging bone.</p>},
  author       = {Gustafsson, Anna and Wallin, Mathias and Isaksson, Hanna},
  issn         = {0021-9290},
  language     = {eng},
  publisher    = {Elsevier},
  series       = {Journal of Biomechanics},
  title        = {Age-related properties at the microscale affect crack propagation in cortical bone},
  url          = {http://dx.doi.org/10.1016/j.jbiomech.2019.109326},
  doi          = {10.1016/j.jbiomech.2019.109326},
  volume       = {95},
  year         = {2019},
}