Hydraulic Strengthening Affects the Stiffness and Strength of Cortical Bone

Liebschner, Michael A. K.; Keller, Tony S.

doi:10.1007/s10439-005-8960-0

Cited by 28 publications

(23 citation statements)

References 45 publications

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“…The larger viscoelasticity in wet bones compared to dry bones was also reported in human tibia [57] and bovine cortical bone [58]. Also, pore water present in wet bone, but not dry, contributes to hydraulic stiffening of bone as suggested by fluid flow constitutive models of cortical bone [59]. In an analytical model of cortical bone, loss of creep upon partial dehydration was attributed to the loss of bound water residing between mineral crystals, which facilitated ductile sliding (and thereby energy dissipation) between mineral crystals [60].…”

Section: Effect Of Thermal Dehydration On the Mechanical Properties Omentioning

confidence: 75%

The Role of Water Compartments in the Material Properties of Cortical Bone

2015

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Comprising ~20% of the volume, water is a key determinant of the mechanical behavior of cortical bone. It essentially exists in 2 general compartments: within pores and bound to the matrix. The amount of pore water – residing in vascular-lacunar-canalicular space – primarily reflects intracortical porosity (i.e., open spaces within the matrix largely due to Haversian canals and resorption sites), and as such, is inversely proportional to most mechanical properties of bone. Movement of water according to pressure gradients generated during dynamic loading likely confers hydraulic stiffening to the bone as well. Nonetheless, bound water is a primary contributor to mechanical behavior of bone in that it is responsible for giving collagen the ability to confer ductility or plasticity to bone (i.e., allows deformation to continue once permanent damage begins to form in the matrix) and decreases with age along with fracture resistance. Thus, dehydration by air-drying or by solvents with less hydrogen bonding capacity causes bone to become brittle, but interestingly, it also increases stiffness and strength across the hierarchical levels of organization. Despite the importance of matrix hydration to fracture resistance, little is known about why bound water decreases with age in hydrated human bone. Using 1H nuclear magnetic resonance (NMR), both bound and pore water concentrations in bone can be measured ex vivo because the proton relaxation times differ between the two water compartments giving rise to two distinct signals. There are also emerging techniques to measure bound and pore water in vivo with magnetic resonance imaging (MRI). NMR/MRI-derived bound water concentration is positively correlated with both strength and toughness of hydrated bone, and may become a useful clinical marker of fracture risk.

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Section: Effect Of Thermal Dehydration On the Mechanical Properties Omentioning

confidence: 75%

The Role of Water Compartments in the Material Properties of Cortical Bone

2015

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“…While, at present, this model is strictly phenomenological, some physically based models that show similar trends are available in the literature. For example, Liebschner & Keller [5] present a rate-dependent strength model for cortical bone based on the hydraulic strengthening (HS) hypothesis. The predicted range of behaviour is similar to that which can be obtained from a Maxwell element incorporating a nonlinear damper.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Hopkinson bar techniques for the intermediate strain rate testing of bovine cortical bone

Cloete

Paul

Ismail

2014

Phil. Trans. R. Soc. A.

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Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant strain rates have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate strain rate (ISR) range (i.e. 1–100 s −1 ), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the strain rate sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour.

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“…Previous researchers have utilized poroelastic finite-element simulations and calculated that relaxation times associated with fluid flow in the Haversian canals is also on the order of microseconds [23,24]. Furthermore, Liebschner and Keller have demonstrated that a shear-thickening fluid within a linear elastic solid structure mimicking that of cortical bone can lead to significant increases in apparent Young's modulus at rates of up to 10 3 s À1 [25]. These results agree closely with the predictions of our own model, suggesting that the higher-rate viscoelastic branch is potentially capturing a hydraulic stiffening effect.…”

Section: Discussionmentioning

confidence: 99%