Distribution of microcrack lengths in bone in vivo and in vitro

Presbítero, Gerardo; O’Brien, Fergal J.; Lee, T.Clive; Taylor, David

doi:10.1016/j.jtbi.2012.03.027

Cited by 14 publications

(14 citation statements)

References 26 publications

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“…Bone naturally contains many internal cracks which have arrested at lengths of the order of 0.1 mm, suggesting that this is the typical separation of barriers. Other workers have measured the distances between osteon boundaries and found an average value of about 0.12 mm [42,43]. This distance corresponds to d in our model materials with barriers, for which we found L = 0.53d, so if osteons were functioning in the same way as the barrier in our model materials we would expect an L value of 0.06 mm, very close to the value found here.…”

Section: Case Study: Bonesupporting

confidence: 89%

The Theory of Critical Distances applied to multiscale toughening mechanisms

Taylor

2019

Engineering Fracture Mechanics

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The Theory of Critical Distances (TCD) is an approach used for predicting the effect of cracks and notches on fracture and fatigue behaviour. In recent years it has been successfully applied to a wide range of problems across all classes of materials. The approach relies on the identification of a material constant known as the critical distance, L, which can only be determined by fitting predictions to experimental data. It has been argued that L is related to the size of microstructural features which affect crack growth, but this argument becomes problematic in the presence of multiple toughening mechanisms operating at different scales. In the present work, this matter was approached through the use of thought experiments conducted on model microstructures. It was found that if two mechanisms operate at different length scales, then the use of the normal TCD approach is still possible, though accuracy is reduced and the value of L obtained falls between the length scales of the two mechanisms. A more sophisticated approach however can successfully identify two relevant L values and thus provide insights into the underlying mechanisms. A practical example is given: the analysis of short and long crack toughness data for bone, for which mechanisms at the hundred-micron and millimetre scales were successfully identified. Some general conclusions emerge about the effect of hierarchical toughening mechanisms: in particular it was found that the mechanisms operating at the small length scales may control the strength of the material but have relatively little effect on its toughness.

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Section: Case Study: Bonesupporting

confidence: 89%

The Theory of Critical Distances applied to multiscale toughening mechanisms

Taylor

2019

Engineering Fracture Mechanics

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“…2012). The contribution of microdamage accumulation to the reduction of fracture resistance has been evaluated in vitro by measuring changes in elastic modulus, strength, and fracture toughness (Macione et al.…”

Section: Discussionmentioning

confidence: 99%

Women with previous stress fractures show reduced bone material strength

Sosa¹,

Eriksen²

2016

Acta Orthopaedica

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Background and purpose — Bone fragility is determined by bone mass, bone architecture, and the material properties of bone. Microindentation has been introduced as a measurement method that reflects bone material properties. The pathogenesis of underlying stress fractures, in particular the role of impaired bone material properties, is still poorly understood. Based on the hypothesis that impaired bone material strength might play a role in the development of stress fractures, we used microindentation in patients with stress fractures and in controls.Patients and methods — We measured bone material strength index (BMSi) by microindentation in 30 women with previous stress fractures and in 30 normal controls. Bone mineral density by DXA and levels of the bone markers C-terminal cross-linking telopeptide of type-1 collagen (CTX) and N-terminal propeptide of type-1 procollagen (P1NP) were also determined.Results — Mean BMSi in stress fracture patients was significantly lower than in the controls (SD 72 (8.7) vs. 77 (7.2); p = 0.02). The fracture subjects also had a significantly lower mean bone mineral density (BMD) than the controls (0.9 (0.02) vs. 1.0 (0.06); p = 0.03). Bone turnover—as reflected in serum levels of the bone marker CTX—was similar in both groups, while P1NP levels were significantly higher in the women with stress fractures (55 μg/L vs. 42 μg/L; p = 0.03). There was no correlation between BMSi and BMD or bone turnover.Interpretation — BMSi was inferior in patients with previous stress fracture, but was unrelated to BMD and bone turnover. The lower values of BMSi in patients with previous stress fracture combined with a lower BMD may contribute to the increased propensity to develop stress fractures in these patients.

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“…O’Brien observed that the formation of new microcracks was initiated during an early phase of damage, which confirmed the above mentioned hypothesis. New microcracks grew up to reach a maximal length of about 100µm mainly due to cement lines acting as barriers [75], while only 6% of the native microcrack propagated. Thus, the level of damage depends on the phase of the modulus degradation curve.…”

Section: Discussionmentioning

confidence: 99%

Non Destructive Characterization of Cortical Bone Micro-Damage by Nonlinear Resonant Ultrasound Spectroscopy

et al. 2014

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The objective of the study was to evaluate the ability of a nonlinear ultrasound technique, the so-called nonlinear resonant ultrasound spectroscopy (NRUS) technique, for detecting early microdamage accumulation in cortical bone induced by four-point bending fatigue. Small parallelepiped beam-shaped human cortical bone specimens were subjected to cyclic four-point bending fatigue in several steps. The specimens were prepared to control damage localization during four-point bending fatigue cycling and to unambiguously identify resonant modes for NRUS measurements. NRUS measurements were achieved to follow the evolution of the nonlinear hysteretic elastic behavior during fatigue-induced damage. After each fatigue step, a small number of specimens was removed from the protocol and set apart to quantitatively assess the microcrack number density and length using synchrotron radiation micro-computed tomography (SR-µCT). The results showed a significant effect of damage steps on the nonlinear hysteretic elastic behavior. No significant change in the overall length of microcracks was observed in damaged regions compared to the load-free control regions. Only an increased number of shortest microcracks, those in the lowest quartile, was noticed. This was suggestive of newly formed microcracks during the early phases of damage accumulation. The variation of nonlinear hysteretic elastic behavior was significantly correlated to the variation of the density of short microcracks. Our results suggest that the nonlinear hysteretic elastic behavior is sensitive to early bone microdamage. Therefore NRUS technique can be used to monitor fatigue microdamage progression in in vitro experiments.

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Distribution of microcrack lengths in bone in vivo and in vitro

Cited by 14 publications

References 26 publications

The Theory of Critical Distances applied to multiscale toughening mechanisms

The Theory of Critical Distances applied to multiscale toughening mechanisms

Women with previous stress fractures show reduced bone material strength

Non Destructive Characterization of Cortical Bone Micro-Damage by Nonlinear Resonant Ultrasound Spectroscopy

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