Scanning electron microscopy of human cortical bone failure surfaces

Braidotti, P; Branca, F. P.; Stagni, Luigi

doi:10.1016/s0021-9290(96)00102-9

Cited by 59 publications

(39 citation statements)

References 17 publications

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“…Strong intramolecular bonds enhance the reinforcing nature of single collagen fibrils, and it has been thought that the ''dominant collagen fiber model'' is the basis of increased toughness in bone tissue. 41 By contrast intermolecular bonds enhance the connectivity of the network of fibers and consequently (and in accordance with well established composite theories 42 ) increase the chances of a major fatal crack starting up and propagating through the structure.…”

Section: Discussionsupporting

confidence: 64%

The role of collagen in the declining mechanical properties of aging human cortical bone

Zioupos

Currey

Hamer

1999

J. Biomed. Mater. Res.

320

153

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The importance of the mechanical role of collagen in bone is becoming increasingly more clear as evidence mounts on the detrimental effects of altered collagen on the mechanical properties of bone. We previously examined a set of mechanical properties (material stiffness, strength, and toughness) of human femoral bone (ages 35-92) and found that a gradual deterioration in these properties occurs with age. The present study examines the collagen of the same specimens and relates the collagen properties to the mechanical ones. In the collagen we measured the concentration of stable mature crosslinks, the shrinkage temperature, and the rate of contraction during isometric heating. The changes in the concentration of mature (pyridinium and deoxypyridinium) crosslinks showed no clear relationship to age nor did they correlate with the mechanical properties. The shrinkage temperature declined with age and correlated with a bone's toughness. The maximum rate of contraction was strongly correlated with three different measures of tissue toughness, but much less to stiffness and strength. Our results reinforce speculation regarding the toughening role of collagen in bone mechanics and suggest that the fragility of aging bone may be related to collagen changes.

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Section: Discussionsupporting

confidence: 64%

The role of collagen in the declining mechanical properties of aging human cortical bone

Zioupos

Currey

Hamer

1999

J. Biomed. Mater. Res.

320

153

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“…Our proposed interpretation is that the sacrificial bonds [14,15] between the collagen and mineral platelets rupture on loading, but re-form upon unloading. This interpretation extends a hypothesis [2] that the extra-cellular, non-collagenous proteins ªglueº together the collagen fibrils. Here, we extend the hypothesis with the interpretation that, facilitated by calcium ions, the sacrificial bonds exist in the ªglueº and can be reformed.…”

supporting

confidence: 84%

An Investigation of the Inelastic Deformation of Cortical Bone

2005

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Mammalian bone is a relatively tough composite consisting of aligned, compliant, collagen fibrils with attached platelets of a stiff hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) mineral phase. It is composed of two spatially distinct topologies (Fig. 1). [1] The outside consists of relatively dense, hard layer of cortical bone. The interior is cellular, referred to as cancellous or trabecular bone (Fig. 1), consisting of inter-connected struts and faces. Its open cell topology resembles that found in synthetic cellular materials, such as open-cell metallic and polymer foams. [1] Both types of bone contain collagen fibrils arranged in bundles, aligned along the longitudinal axis (Fig. 1). The mineral phase, located primarily on the outside of the collagen, is resistant to fragmentation because it consists of tiny, nano-scale platelets (Fig. 2). [2±4] Parallel to the collagen fibrils, the inelastic responses of cortical bone differ in tension and compression [1,5±10] (Fig. 3(a)). In tension, it yields, followed by (linear) hardening up to a failure strain of order 2.5 %. In compression, it also yields, but at higher stress. It strain hardens rapidly to a peak, then softens and fails at strains of about 1.5 %. Trabecular bone exhibits extensive inelastic deformation under compression ( Fig. 3(b)), often attaining strains exceeding 60 % before failure. [10] A stress peak is typical, occurring at strains of 5±10 %.Flexure tests (Fig. 4) have been designed and conducted on cortical bone with two objectives. (a) Measure the inelastic strains and parse these strains between plasticity (volume conserving permanent strain) and dilatation. (b) Deduce the hysteresis and measure changes in stiffness with permanent strain. Results and Discussion: A typical response relating the load to the axial-strain upon monotonic testing to failure is summarized on Figure 5. The corresponding stress/strain curves obtained by de-convolution [11] are plotted on Figure 6. A plot of the trends in the inelastic Poisson ratio (the ratio of the transverse to the axial inelastic strains) with inelastic strain (Fig. 7) highlights the differences in tension and compression. Such characteristics are similar to those found in other biomaterials, such as nacre, [11] and in some synthetic materials, such as oxide composites. [12] At strains beyond yield, the following features are most notable (Figs. 6±10).In tension, the material behaves as an inelastic solid with linear strain hardening (Fig. 6): tangent modulus, E H » 1 GPa. The transverse strain is negligible, signifying an inelastic Poisson ratio, m pl » 0 (Fig. 7). That is, the material dilates.In compression, the peak stress is appreciably larger than in tension, but the strain at failure is smaller (e f » 1.6 % in compression and e f » 2.4 % in tension: Fig. 6). Consequently, COMMUNICATIONS ADVANCED ENGINEERING MATERIALS 2005, 7, No. 8 Fig. 1. Schematic illustration showing the configuration of cortical and trabecular bone in a typical mammalian femur.Fig. 2. A schematic of the nano-scale organiz...

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“…In the case of microtensile experiments, bone samples were dry, which is known to significantly affect the elastic modulus and the stiffness of the tissue (Hengsberger et al, 2002;Rho and Pharr, 1999). Nevertheless, bone failure behaviour has been reported to be governed by the same mechanisms in both dry and wet samples (Braidotti et al, 2000a;Braidotti et al, 1997a). In more detail, despite the differences in energy absorption and ductility, both conditions exhibit fibre/matrix debonding and delamination-like failure.…”

Section: Discussionmentioning

confidence: 95%

“…Bone is a hierarchical composite material composed of mineralized type I collagen fibrils immersed into a matrix of noncollagenous proteins (NCPs) (Braidotti et al, 2000b;Braidotti et al, 1997b). Several studies on the structure-function relationships of bone on different hierarchical levels, show that age-and disease-related increased fragility cannot be solely attributed to bone mass loss (Hui et al, 1988;Kanis et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Load-bearing in cortical bone microstructure: Selective stiffening and heterogeneous strain distribution at the lamellar level

Katsamenis

Chong

Andriotis

et al. 2013

Journal of the Mechanical Behavior of Biomedical Materials

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An improved understanding of bone mechanics is vital in the development of evaluation strategies for patients at risk of bone fracture. The current evaluation approach based on bone mineral density (BMD) measurements lacks sensitivity, and it has become clear that as well as bone mass, bone quality should also be evaluated.The latter includes, among other parameters, the bone matrix material properties, which in turn depend on the hierarchical structural features that make up bone as well as their composition. Optimal load transfer, energy dissipation and toughening mechanisms have, to some extent, been uncovered in bone. Yet, the origin of these properties and their dependence upon the hierarchical structure and composition of bone are largely unknown. Here we investigate load transfer in the osteonal and subosteonal levels and the mechanical behaviour of osteonal lamellae and interlamellar areas during loading. Using cantilever-based nanoindentation, in situ microtensile testing during atomic force microscopy (AFM) and digital image correlation (DIC), we report evidence for a previously unknown mechanism. This mechanism transfers load and movement in a manner analogous to the engineered "elastomeric bearing pads" used in large engineering structures. ȝ-RAMAN microscopy investigations 2 showed compositional differences between lamellae and interlamellar areas. The latter have lower collagen content but an increased concentration of noncollagenous proteins (NCPs). Hence, NCPs enriched areas on the microscale might be similarly important for bone failure as on the nanoscale. Finally, we managed to capture stable crack propagation within the interlamellar areas in a time-lapsed fashion, proving their significant contribution towards fracture toughness.

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Scanning electron microscopy of human cortical bone failure surfaces

Cited by 59 publications

References 17 publications

The role of collagen in the declining mechanical properties of aging human cortical bone

The role of collagen in the declining mechanical properties of aging human cortical bone

An Investigation of the Inelastic Deformation of Cortical Bone

Load-bearing in cortical bone microstructure: Selective stiffening and heterogeneous strain distribution at the lamellar level

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