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Title: Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales

Abstract

The structure of human cortical bone evolves over multiple length-scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at nearmillimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone’s toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural-scales typically below a micron and extrinsically (i.e., during crack growth) through mechanisms (e.g., crack deflection/bridging) generated at larger structural-scales. Biological factors such as aging lead to a markedly increased fracture risk, which is often associated with an age-related loss in bone mass (bone quantity). However, we find that age-related structural changes can significantly degrade the fracture resistance (bone quality) over multiple lengthscales. Using in situ small-/wide-angle x-ray scattering/diffraction to characterize sub-micron structural changes and synchrotron x-ray computed tomography and in situ fracture-toughness measurements in the scanning electron microscope to characterize effects at micron-scales, we show how these age-related structural changes at differing size-scales degrade both the intrinsic and extrinsic toughness of bone. Specifically, we attribute the loss in toughness to increased non-enzymatic collagen cross-linking which suppresses plasticity at nanoscale dimensions and to an increased osteonal density which limits the potency of crack-bridging mechanisms at micron-scales. The link between thesemore » processes is that the increased stiffness of the cross-linked collagen requires energy to be absorbed by “plastic” deformation at higher structural levels, which occurs by the process of microcracking.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
Materials Sciences Division
OSTI Identifier:
1051788
Report Number(s):
LBNL-5180E
Journal ID: ISSN 0027-8424
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 108; Journal Issue: 35; Journal ID: ISSN 0027-8424
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; Human cortical bone; toughness; aging; plasticity; x-ray scattering; cross-linking; advanced glycation end-products

Citation Formats

Zimmermann, Elizabeth A, Schaible, Eric, Bale, Hrishikesh, Barth, Holly D, Tang, Simon Y, Reichert, Peter, Busse, Bjoern, Alliston, Tamara, Ager, III, Joel W, and Ritchie, Robert O. Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales. United States: N. p., 2011. Web. doi:10.1073/pnas.1107966108.
Zimmermann, Elizabeth A, Schaible, Eric, Bale, Hrishikesh, Barth, Holly D, Tang, Simon Y, Reichert, Peter, Busse, Bjoern, Alliston, Tamara, Ager, III, Joel W, & Ritchie, Robert O. Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales. United States. https://doi.org/10.1073/pnas.1107966108
Zimmermann, Elizabeth A, Schaible, Eric, Bale, Hrishikesh, Barth, Holly D, Tang, Simon Y, Reichert, Peter, Busse, Bjoern, Alliston, Tamara, Ager, III, Joel W, and Ritchie, Robert O. 2011. "Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales". United States. https://doi.org/10.1073/pnas.1107966108. https://www.osti.gov/servlets/purl/1051788.
@article{osti_1051788,
title = {Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales},
author = {Zimmermann, Elizabeth A and Schaible, Eric and Bale, Hrishikesh and Barth, Holly D and Tang, Simon Y and Reichert, Peter and Busse, Bjoern and Alliston, Tamara and Ager, III, Joel W and Ritchie, Robert O},
abstractNote = {The structure of human cortical bone evolves over multiple length-scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at nearmillimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone’s toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural-scales typically below a micron and extrinsically (i.e., during crack growth) through mechanisms (e.g., crack deflection/bridging) generated at larger structural-scales. Biological factors such as aging lead to a markedly increased fracture risk, which is often associated with an age-related loss in bone mass (bone quantity). However, we find that age-related structural changes can significantly degrade the fracture resistance (bone quality) over multiple lengthscales. Using in situ small-/wide-angle x-ray scattering/diffraction to characterize sub-micron structural changes and synchrotron x-ray computed tomography and in situ fracture-toughness measurements in the scanning electron microscope to characterize effects at micron-scales, we show how these age-related structural changes at differing size-scales degrade both the intrinsic and extrinsic toughness of bone. Specifically, we attribute the loss in toughness to increased non-enzymatic collagen cross-linking which suppresses plasticity at nanoscale dimensions and to an increased osteonal density which limits the potency of crack-bridging mechanisms at micron-scales. The link between these processes is that the increased stiffness of the cross-linked collagen requires energy to be absorbed by “plastic” deformation at higher structural levels, which occurs by the process of microcracking.},
doi = {10.1073/pnas.1107966108},
url = {https://www.osti.gov/biblio/1051788}, journal = {Proceedings of the National Academy of Sciences of the United States of America},
issn = {0027-8424},
number = 35,
volume = 108,
place = {United States},
year = {Wed Aug 10 00:00:00 EDT 2011},
month = {Wed Aug 10 00:00:00 EDT 2011}
}