Fracture toughness is dependent on bone location?A study of the femoral neck, femoral shaft, and the tibial shaft

Brown, Christopher U.; Yeni, Yener N.; Norman, Timothy L.

doi:10.1002/(sici)1097-4636(20000305)49:3<380::aid-jbm11>3.0.co;2-w

Cited by 77 publications

(55 citation statements)

References 32 publications

(51 reference statements)

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“…The decrease in the initiation toughness is consistent with the trend observed in studies that report single-value toughnesses (e.g., [22,45,46,47,48]). However, the value of R-curve measurements [10] is that is that they clearly show that not only the intrinsic resistance to fracture (as reflected by the crack-initiation toughness), but also the resistance to crack propagation (as reflected by the crack-growth toughness) decreases with age (Figs.…”

Section: Macroscopic Scale: Fracture Toughness Behaviorsupporting

confidence: 88%

“…There is now a large body of results in the literature involving determinations of the fracture toughness of cortical bone using the linear-elastic fracture mechanics (LEFM) approach. This has for the large part involved single-parameter characterization of the toughness using either the critical value of the mode I linear-elastic stress intensity, K Ic [18,19,20,21,22,23]), or the related strain-energy release rate, G c . 1 In terms of K Ic , toughness values in cortical bone range from 2 to 7 MPa√m, with the fracture toughness, in human humeri for example, typically being up to twice as high in the transverse orientation compared to the longitudinal (medial-lateral and proximal-distal)…”

Section: Macroscopic Quantificationmentioning

confidence: 99%

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Fracture, aging, and disease in bone

2006

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From a public health perspective, developing a detailed mechanistic understanding of the well-known increase in fracture risk of human bone with age is essential. This also represents a challenge from materials science and fracture mechanics viewpoints. Bone has a complex, hierarchical structure with characteristic features ranging from nanometer to macroscopic dimensions; it is therefore significantly more complex than most engineering materials. Nevertheless, by examining the micro-/nano-structural changes accompanying the process of aging using appropriate multiscale experimental methods and relating them to fracture mechanics data, it is possible to obtain a quantitative picture of how bone resists fracture. As human cortical bone exhibits rising ex vivo crack-growth resistance with crack extension, its fracture toughness must be evaluated in terms of resistance-curve (R-curve) behavior. While the crack initiation toughness declines with age, the more striking finding is that the crack-growth toughness declines even more significantly and is essentially absent in bone from donors exceeding 85 years in age. To explain such an age-induced deterioration in the toughness of bone, we evaluate its fracture properties at multiple length scales, specifically at the molecular and nano dimensions using pico-force atomic-force microscopy, nanoindentation and vibrational spectroscopies, at the microscale using electron microscopy and hard/soft x-ray computed tomography, and at the macroscale using R-curve measurements. We show that the reduction in crackgrowth toughness is associated primarily with a degradation in the degree of extrinsic toughening, in particular involving crack bridging, and that this occurs at relatively coarse size-scales in the range of tens to hundreds of micrometers. Finally, we briefly describe how specific clinical treatments, e.g., with steroid hormones to treat various inflammatory conditions, can prematurely damage bone, thereby reducing its fracture resistance, whereas regulating the level of the cytokine TGF-β can offer significant improvements in the stiffness, strength and toughness of bone, and as such may be considered as a therapeutic target to treat increased bone fragility induced by aging, drugs, and disease. *

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Section: Macroscopic Scale: Fracture Toughness Behaviorsupporting

confidence: 88%

Section: Macroscopic Quantificationmentioning

confidence: 99%

Fracture, aging, and disease in bone

2006

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“…It is also consistent with research showing significant deterioration in another material property, fracture toughness, with age. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] These measurements suggest that deteriorating material properties of bone, due to aging or disease, may play a role in bone fracture risk, in addition to the well-known factors of decreased areal bone mineral density and deterioration of microarchitecture in trabecular bone ͑i.e., loss of the structural network of the bone and/or thinning of individual struts or trabeculae͒. Instruments already exist clinically to measure these two well-known factors.…”

Section: Introductionmentioning

confidence: 99%

The bone diagnostic instrument II: Indentation distance increase

Hansma¹,

Turner²,

Drake³

et al. 2008

Review of Scientific Instruments

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The bone diagnostic instrument ͑BDI͒ is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo. Such measurements could contribute to the overall assessment of bone fragility in the future. Here, we describe an improved BDI, the Osteoprobe II™. In the Osteoprobe II™, the probe assembly, which is designed to penetrate soft tissue, consists of a reference probe ͑a 22 gauge hypodermic needle͒ and a test probe ͑a small diameter, sharpened rod͒ which slides through the inside of the reference probe. The probe assembly is inserted through the skin to rest on the bone. The distance that the test probe is indented into the bone can be measured relative to the position of the reference probe. At this stage of development, the indentation distance increase ͑IDI͒ with repeated cycling to a fixed force appears to best distinguish bone that is more easily fractured from bone that is less easily fractured. Specifically, in three model systems, in which previous mechanical testing and/or tests reported here found degraded mechanical properties such as toughness and postyield strain, the BDI found increased IDI. However, it must be emphasized that, at this time, neither the IDI nor any other mechanical measurement by any technique has been shown clinically to correlate with fracture risk. Further, we do not yet understand the mechanism responsible for determining IDI beyond noting that it is a measure of the continuing damage that results from repeated loading. As such, it is more a measure of plasticity than elasticity in the bone.

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“…Other loading configurations that induce high compressive and shear stresses and strains must also be considered in experiments to further validate the failure criteria in compression/shear. Also, further specific methods of assessing the material and fracture properties of femur are needed as these properties vary between anatomical locations [8].…”

Section: Discussionmentioning

confidence: 99%