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Journal ArticleDOI

Mechanical properties and the hierarchical structure of bone

TL;DR: Further investigations of mechanical properties at the "materials level", in addition to the studies at the 'structural level' are needed to fill the gap in present knowledge and to achieve a complete understanding of the mechanical properties of bone.
About: This article is published in Medical Engineering & Physics.The article was published on 1998-03-01. It has received 2352 citations till now.
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Journal ArticleDOI
TL;DR: In this paper, the basic principles involved in designing hierarchical biological materials, such as cellular and composite architectures, adapative growth and as well as remodeling, are discussed, and examples that are found to utilize these strategies include wood, bone, tendon, and glass sponges.

2,274 citations

Journal ArticleDOI
TL;DR: It is shown that the nanocomposites in nature exhibit a generic mechanical structure in which the nanometer size of mineral particles is selected to ensure optimum strength and maximum tolerance of flaws (robustness) and the widely used engineering concept of stress concentration at flaws is no longer valid for nanomaterial design.
Abstract: Natural materials such as bone, tooth, and nacre are nanocomposites of proteins and minerals with superior strength. Why is the nanometer scale so important to such materials? Can we learn from this to produce superior nanomaterials in the laboratory? These questions motivate the present study where we show that the nanocomposites in nature exhibit a generic mechanical structure in which the nanometer size of mineral particles is selected to ensure optimum strength and maximum tolerance of flaws (robustness). We further show that the widely used engineering concept of stress concentration at flaws is no longer valid for nanomaterial design.

1,681 citations

Journal ArticleDOI
TL;DR: The state-of-the-art of topological design and manufacturing processes of various types of porous metals, in particular for titanium alloys, biodegradable metals and shape memory alloys are reviewed.

1,393 citations


Cites background or methods from "Mechanical properties and the hiera..."

  • ...The pore s in trabecular bone are filled with bone marrow, a nd the porosity varies between 50-90% [1, 36-38]....

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  • ...The physi cal and mechanical properties of human bone are summarized in Table 1 (values are averaged from rep ort d data) [1, 26, 34, 36-38, 42, 43]....

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  • ...It contin ues to be a major scientific challenge to fully underst and the mechanics of living bones [36-38]....

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Journal ArticleDOI
TL;DR: In this article, the authors proposed a new model to explain how intrafibrillar mineralization of collagen can be achieved during bone formation, which is based on the concept of intra-fibrilar mineralisation, which refers to the fact that growth of the mineral phase is somehow directed by the collagen matrix.
Abstract: Bone is a hierarchically structured composite material which, in addition to its obvious biological value, has been well studied by the materials engineering community because of its unique structure and mechanical properties. This article will review the existing bone literature, with emphasis on the prevailing theories regarding bone formation and structure, which lay the groundwork for proposing a new model to explain how intrafibrillar mineralization of collagen can be achieved during bone formation. Intrafibrillar refers to the fact that growth of the mineral phase is somehow directed by the collagen matrix, which leads to a nanostructured architecture consisting of uniaxially oriented nanocrystals of hydroxyapatite embedded within and roughly [0 0 1] aligned parallel to the long collagen fibril axes. Secondary (osteonal) bone, the focus of this review, is a laminated organic–inorganic composite composed primarily of collagen, hydroxyapatite, and water; but minor constituents, such as non-collagenous proteins (NCPs), are also present and are thought to play an important role in bone formation. To date, there has been no clear understanding of the role of these NCPs, although it has been generally assumed that the NCPs regulate solution crystal growth via some type of ‘epitaxial’ relationship between specific crystallographic faces and specific protein conformers. Indeed, ‘epitaxial’ relationships have been calculated; but in practice, it has not been demonstrated that intrafibrillar mineralization can be accomplished via this route. Because of the difficulty in examining biomineralization processes in vivo , the authors of this article have turned to using in vitro model systems to investigate the possible physicochemical mechanisms that may be involved in biomineralization. In the case of bone biomineral, we have now been able to duplicate the most fundamental level of bone structure, the interpenetrating nanostructured architecture, using relatively simple anionic polypeptides that mimic the polyanionic character of the NCPs. We propose that the charged polymer acts as a process-directing agent, by which the conventional solution crystallization is converted into a precursor process. This polymer-induced liquid-precursor (PILP) process generates an amorphous liquid-phase mineral precursor to hydroxyapatite which facilitates intrafibrillar mineralization of type-I collagen because the fluidic character of the amorphous precursor phase enables it to be drawn into the nanoscopic gaps and grooves of collagen fibrils by capillary action. The precursor then solidifies and crystallizes upon loss of hydration waters into the more thermodynamically stable phase, leaving the collagen fibrils embedded with nanoscopic hydroxyapatite (HA) crystals. Electron diffraction patterns of the highly mineralized collagen fibrils are nearly identical to those of natural bone, indicating that the HA crystallites are preferentially aligned with [0 0 1] orientation along the collagen fibril axes. In addition, studies of etched samples of natural bone and our mineralized collagen suggest that the long accepted “deck of cards” model of bone's nanostructured architecture is not entirely accurate. Most importantly, this in vitro model demonstrates that a highly specific, epitaxial-type interaction with NCPs is not needed to stimulate crystal nucleation and regulate crystal orientation, as has long been assumed. Instead, we propose that collagen is the primary template for crystal organization, but with the important caveat that this templating occurs only for crystals formed from an infiltrated amorphous precursor. These results suggest that the 25-year-old debate regarding bone formation via an amorphous precursor phase needs to be revisited. From a biomedical perspective, in addition to providing possible insight into the role of NCPs in bone formation, this in vitro system may pave the way toward the ultimate goal of fabricating a synthetic bone substitute that not only has a composition similar to bone, but has comparable mechanical properties and bioresorptive potential as natural bone. From a materials chemistry perspective, the non-specificity of the PILP process and capillary infiltration mechanism suggests that non-biological materials could also be fabricated into nanostructured composites using this “biomimetic” strategy.

1,299 citations


Cites background from "Mechanical properties and the hiera..."

  • ...This article will not discuss bone’s mechanical properties, for which there are many excellent reviews [1–9] as well as recent contributions [10–17]; but instead it will focus on the unique structure that confers these properties, and to the materials chemistry underlying its formation....

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Journal ArticleDOI
TL;DR: The results suggest that the newly developed NHAP/polymer composite scaffolds may serve as an excellent 3D substrate for cell attachment and migration in bone tissue engineering.

1,200 citations


Cites background from "Mechanical properties and the hiera..."

  • ...The nanometer size of the inorganic component (mainly bone-like apatite) in natural bone is considered to be important for the mechanical properties of the bone [22]....

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References
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Journal ArticleDOI
TL;DR: These power relationships, which were shown to hold for all bone in the skeleton, allow meaningful predictions of bone tissue strength and stiffness based on in vivo density measurements.
Abstract: Compression tests of human and bovine trabecular bone specimens with and without marrow in situ were conducted at strain rates of from 0.001 to 10.0 per second. A porous platen above the specimens allowed the escape of marrow during testing. The presence of marrow increased the strength, modulus, and energy absorption of specimens only at the highest strain rate of 10.0 per second. This enhancement of material properties at the highest strain rate was due primarily to the restricted viscous flow of marrow through the platen rather than the flow through the pores of the trabecular bone. In specimens without marrow, the strength was proportional to the square of the apparent density and the modulus was proportional to the cube of the apparent density. Both strength and modulus were approximately proportional to the strain rate raised to the 0.06 power. These power relationships, which were shown to hold for all bone in the skeleton, allow meaningful predictions of bone tissue strength and stiffness based on in vivo density measurements.

1,977 citations


"Mechanical properties and the hiera..." refers background in this paper

  • ...Although both types of bone (cortical and cancellous) are most easily distinguished by their degree of porosity or density [9,10], true differentiation comes from histological evaluation of the tissue’s microstructure....

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  • ...[9] Carter DR, Hayes W....

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  • ...Some workers [9,13,14] consider cortical and cancellous bone to be a single morphological material which can be characterized by a highly variable porosity or apparent density (mass/total volume, including pores)....

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Journal ArticleDOI
TL;DR: The results suggest that when considered mechanically, cortical and trabecular bone are not the same material.

1,109 citations


"Mechanical properties and the hiera..." refers background or result in this paper

  • ...However, many investigators produced values for the elastic modulus of individual trabeculae, single osteons, and a thin cortical shell that were considerably less than that for whole bone [5,17,18]....

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  • ...This led the authors [17] to conclude that the materials of the two bones were intrinsically different....

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  • ...However, in spite of recent reports [5,15,17,18], there remains some controversy regarding the value of the elastic modulus of single trabeculae (Table 1)....

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  • ...Others [5,15–17] consider these two types to consist of two different materials....

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  • ...[17] showed that the relationship derived from these data, between elastic moduli and density in cancellous bone material, could not be extrapolated from similar data from tests on cortical bone material and its density....

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Journal ArticleDOI
TL;DR: The results of this previous study are applied to cancellous bone in an attempt to further understand its mechanical behaviour and the results agree reasonably well with experimental data available in the literature.

867 citations

Journal ArticleDOI
TL;DR: An experimental investigation was undertaken to measure the intrinsic elastic properties of several of the microstructural components of human vertebral trabecular bone and tibial cortical bone by the nanoindentation method, and differences in the measured moduli are statistically significant.

867 citations


"Mechanical properties and the hiera..." refers background in this paper

  • ...The possible causes include: (i) the influence of microstructural defects such as cement lines and voids (Haversian and Volkmann canals, lacuna, osteocytes, canaliculi) on the measured displacements; (ii) uncertainties in specimen geometry, which are often exacerbated at small scales; and (iii) problems in properly seating and aligning small bending specimens in small test fixtures [6]....

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  • ...Recently, the Young’s modulus of osteon lamellar bone measured by nanoindentation was approximately 22 GPa (dry specimen, submicrostructure property [6]) close to that for the macrostructure....

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  • ...[6] Rho JY, Tsui TY, Pharr GM....

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