Physical characteristics affecting the tensile failure properties of compact bone

Currey, J. D.

doi:10.1016/0021-9290(90)90030-7

Cited by 191 publications

(77 citation statements)

References 6 publications

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“…Yield point was identified from linear plots of applied twisting moment (torque) versus maximum shear strain as the first point where measured strain magnitude deviated from the magnitude expected based on the initial linear slope of the curve by 200e (Currey, 1990). Strain-based safety factors in shear for the femur of D. virginiana were calculated using two slightly different approaches.…”

Section: Mechanical Properties and Safety Factorsmentioning

confidence: 99%

In vivostrains in the femur of the Virginia opossum (Didelphis virginiana) during terrestrial locomotion: testing hypotheses of evolutionary shifts in mammalian bone loading and design

Butcher

White

Hudzik

et al. 2011

Journal of Experimental Biology

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SUMMARYTerrestrial locomotion can impose substantial loads on vertebrate limbs. Previous studies have shown that limb bones from cursorial species of eutherian mammals experience high bending loads with minimal torsion, whereas the limb bones of nonavian reptiles (and amphibians) exhibit considerable torsion in addition to bending. It has been hypothesized that these differences in loading regime are related to the difference in limb posture between upright mammals and sprawling reptiles, and that the loading patterns observed in non-avian reptiles may be ancestral for tetrapod vertebrates. To evaluate whether noncursorial mammals show loading patterns more similar to those of sprawling lineages, we measured in vivo strains in the femur during terrestrial locomotion of the Virginia opossum (Didelphis virginiana), a marsupial that uses more crouched limb posture than most mammals from which bone strains have been recorded, and which belongs to a clade phylogenetically between reptiles and the eutherian mammals studied previously. The presence of substantial torsion in the femur of opossums, similar to nonavian reptiles, would suggest that this loading regime likely reflects an ancestral condition for tetrapod limb bone design. Strain recordings indicate the presence of both bending and appreciable torsion (shear strain: 419.1±212.8e) in the opossum femur, with planar strain analyses showing neutral axis orientations that placed the lateral aspect of the femur in tension at the time of peak strains. Such mediolateral bending was unexpected for a mammal running with near-parasagittal limb kinematics. Shear strains were similar in magnitude to peak compressive axial strains, with opossum femora experiencing similar bending loads but higher levels of torsion compared with most previously studied mammals. Analyses of peak femoral strains led to estimated safety factor ranges of 5.1-7.2 in bending and 5.5-7.3 in torsion, somewhat higher than typical mammalian values for bending, but approaching typical reptilian values for shear. Loading patterns of opossum limb bones therefore appear intermediate in some respects between those of eutherian mammals and non-avian reptiles, providing further support for hypotheses that high torsion and elevated limb bone safety factors may represent persistent ancestral conditions in the evolution of tetrapod limb bone loading and design.Supplementary material available online at

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Section: Mechanical Properties and Safety Factorsmentioning

confidence: 99%

In vivostrains in the femur of the Virginia opossum (Didelphis virginiana) during terrestrial locomotion: testing hypotheses of evolutionary shifts in mammalian bone loading and design

Butcher

White

Hudzik

et al. 2011

Journal of Experimental Biology

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“…inward) rotation. Yield point was identified from plots of applied twisting moment versus maximum shear strain as the first point where measured strain magnitude deviated from the magnitude expected based on the initial, linear slope of the curve by 200 microstrain (strainϫ10 -6 ) (Currey, 1990). Yield stresses in torsion (shear stress) were calculated from Eqn 3, using the value of T at the time of yield.…”

Section: Mechanical Property Tests and Safety Factor Calculationsmentioning

confidence: 99%

Femoral loading mechanics in the Virginia opossum,Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion

Gosnell

Butcher

Maie

et al. 2011

Journal of Experimental Biology

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SUMMARYStudies of limb bone loading in terrestrial mammals have typically found anteroposterior bending to be the primary loading regime, with torsion contributing minimally. However, previous studies have focused on large, cursorial eutherian species in which the limbs are held essentially upright. Recent in vivo strain data from the Virginia opossum (Didelphis virginiana), a marsupial that uses a crouched rather than an upright limb posture, have indicated that its femur experiences appreciable torsion during locomotion as well as strong mediolateral bending. The elevated femoral torsion and strong mediolateral bending observed in D. virginiana might result from external forces such as a medial inclination of the ground reaction force (GRF), internal forces deriving from a crouched limb posture, or a combination of these factors. To evaluate the mechanism underlying the loading regime of opossum femora, we filmed D. virginiana running over a force platform, allowing us to measure the magnitude of the GRF and its three-dimensional orientation relative to the limb, facilitating estimates of limb bone stresses. This three-dimensional analysis also allows evaluations of muscular forces, particularly those of hip adductor muscles, in the appropriate anatomical plane to a greater degree than previous two-dimensional analyses. At peak GRF and stress magnitudes, the GRF is oriented nearly vertically, inducing a strong abductor moment at the hip that is countered by adductor muscles on the medial aspect of the femur that place this surface in compression and induce mediolateral bending, corroborating and explaining loading patterns that were identified in strain analyses. The crouched orientation of the femur during stance in opossums also contributes to levels of femoral torsion as high as those seen in many reptilian taxa. Femoral safety factors were as high as those of non-avian reptiles and greater than those of upright, cursorial mammals, primarily because the load magnitudes experienced by opossums are lower than those of most mammals. Thus, the evolutionary transition from crouched to upright posture in mammalian ancestors may have been accompanied by an increase in limb bone load magnitudes.

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“…Examination of mineralized tissues across a wide range of species (including deer and whales) have associated increased tissue degree of mineralization with increased bone stiffness and strength and, in some cases, increased brittleness (the term 'brittle' is used here in an engineering sense expressing a material property, and not the likelihood of clinical fracture) [27,28]. While these studies demonstrate that tissue degree of mineralization can be biomechanically important, most do not include analyses of bone porosity and therefore cannot be used to examine the biomechanical effects of tissue degree of mineralization independent of bone volume.…”

Section: Tissue Degree Of Mineralizationmentioning

confidence: 99%

How can bone turnover modify bone strength independent of bone mass?

Hernandez¹

2008

Bone

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The amount of bone turnover in the skeleton is has been identified as a predictor of fracture risk independent of areal bone mineral density (aBMD) and is increasingly cited as an explanation for discrepancies between areal bone mineral density and fracture risk. A number of mechanisms have been proposed to explain how bone turnover influences bone biomechanics, including regulation of tissue degree of mineralization, the disconnection or fenestration of individual trabeculae by remodeling cavities, and the ability of cavities formed during the remodeling process to act as stress risers. While these mechanisms can influence bone biomechanics, they also modify bone mass. If bone turnover is to explain any of the observed discrepancies between fracture risk and areal bone mineral density, however, it must not only modify bone strength but modify bone strength in excess of what would be expected from the associated change in bone mass. This article summarizes biomechanical studies of how tissue mineralization, trabecular disconnection and the presence of remodeling cavities might have an effect on cancellous bone strength independent of bone mass. Existing data support the idea that all of these factors may have a disproportionate effect on bone stiffness and/or strength, with the exception of average tissue degree of mineralization, which is unlikely to have an effect on bone strength that is independent of aBMD. Disproportionate effects of mineral content on bone biomechanics may instead come from variation in tissue degree of mineralization at the micro-structural level. The biomechanical explanation for the relationship between bone turnover and fracture incidence remains to be determined but must be examined not in terms of bone strength but in terms of bone strength relative to bone mass.

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Physical characteristics affecting the tensile failure properties of compact bone

Cited by 191 publications

References 6 publications

In vivostrains in the femur of the Virginia opossum (Didelphis virginiana) during terrestrial locomotion: testing hypotheses of evolutionary shifts in mammalian bone loading and design

In vivostrains in the femur of the Virginia opossum (Didelphis virginiana) during terrestrial locomotion: testing hypotheses of evolutionary shifts in mammalian bone loading and design

Femoral loading mechanics in the Virginia opossum,Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion

How can bone turnover modify bone strength independent of bone mass?

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