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  • 1
    Electronic Resource
    Electronic Resource
    Shear Stress Distribution in the Trabeculae of Human Vertebral Bone (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 1194-1199 
    Details
    ISSN: 1573-9686
    Keywords: Cancellous bone ; stress ; strain ; strength ; adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The statistical distribution of von Mises stress in the trabeculae of human vertebral cancellous bone was estimated using large-scale finite element models. The goal was to test the hypothesis that average trabecular von Mises stress is correlated to the maximum trabecular level von Mises stress. The hypothesis was proposed to explain the close experimental correlation between apparent strength and stiffness of human cancellous bone tissue. A three-parameter Weibull function described the probability distribution of the estimated von Mises stress (r2) 〉 0.99 for each of 23 cases). The mean von Mises stress was linearly related to the standard deviation (r2=0.63) supporting the hypothesis that average and maximum magnitude stress would be correlated. The coefficient of variation (COV) of the von Mises stress was nonlinearly related to apparent compressive strength, apparent stiffness, and bone volume fraction (adjusted r2=0.66, 0.56, 0.54, respectively) by a saturating exponential function [COV=A+B exp(−x/C)]. The COV of the stress was higher for low volume fraction tissue (〈0.12) consistent with the weakness of low volume fraction tissue and suggesting that stress variation is better controlled in higher volume fraction tissue. We propose that the average stress and standard deviation of the stress are both controlled by bone remodeling in response to applied loading. © 2000 Biomedical Engineering Society. PAC00: 8719Rr
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.1318928
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of Fatiguing Exercise on Longitudinal Bone Strain as Related to Stress Fracture in Humans (1998)
    Springer
    Annals of biomedical engineering 26 (1998), S. 660-665 
    Details
    ISSN: 1573-9686
    Keywords: Stress fracture ; Bone strain ; Fatigue ; Aging ; Exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Muscular fatigue in the training athlete or military recruit has been hypothesized to cause increased bone strain that may contribute to the development of a stress fracture. Under normal circumstances, muscles exert a protective effect by contracting to reduce bending strains on cortical bone surfaces. In vivo strain studies in dogs show that muscle fatigue following strenuous exercise elevates bone strain and changes strain distribution. However, a similar experiment has yet to be performed in humans. The purpose of this work was to test the hypothesis in humans that strenuous fatiguing exercise causes an elevation in bone strain. It was also hypothesized that this elevation is greater in younger people than in older people due to the decline in muscle strength and endurance that normally occurs with age. To test these hypotheses, strain in the tibiae of seven human volunteers was measured during walking before and after a period of fatiguing exercise. Neither hypothesis was sustained. Post-hoc analysis of the strain data suggests that strain rate increases after fatigue with a greater increase in younger as opposed to older persons. Although not conclusive, this suggests that it is strain rate, rather than strain magnitude, that may be causal for stress fracture. © 1998 Biomedical Engineering Society. PAC98: 8745Dr, 8745Bp, 0180+b
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1114/1.103
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  • 3
    Electronic Resource
    Electronic Resource
    Digital volume correlation: Three-dimensional strain mapping using X-ray tomography (1999)
    Springer
    Experimental mechanics 39 (1999), S. 217-226 
    Details
    ISSN: 1741-2765
    Keywords: Strain measurement ; X-ray tomography ; image correlation ; trabecular bone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A three-dimensional extension of two-dimensional digital image correlation has been developed. The technique uses digital image volumes generated through high-resolution X-ray tomography of samples with microarchitectural detail, such as the trabecular bone tissue found within the skeleton. Image texture within the material is used for displacement field measurement by subvolume tracking. Strain fields are calculated from the displacement fields by gradient estimation techniques. Estimates of measurement precision were developed through correlation of repeat unloaded data sets for a simple sum-of-squares displacement-only correlation formulation. Displacement vector component errors were normally distributed, with a standard deviation of 0.035 voxels (1.22 μm). Strain tensor component errors were also normally distributed, with a standard deviation of approximately 0.0003. The method was applied to two samples taken from the thigh bone near the knee. Strains were effectively measured in both the elastic and postyield regimes of material behavior, and the spatial patterns showed clear relationships to the sample microarchitectures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02323555
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  • 4
    Electronic Resource
    Electronic Resource
    A unifying principle relating stress to trabecular bone morphology (1986)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 4 (1986), S. 304-317 
    Details
    ISSN: 0736-0266
    Keywords: Cancellous bone ; Remodeling ; Apparent density ; Trajectory hypothesis ; Wolff's law ; Optimal material ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The relationships between cancellous bone apparent density, trabecular orientation, and stress are developed and a mathematical theory describing these relationships is proposed. The bone is assumed to be a self-optimizing material. Using a continuum model, sufficient conditions are developed which ensure that, for a given stress encountered during normal activity, the theory will predict both trabecular orientation and apparent density. Using two special approaches, one based on optimizing strain energy density (stiffness) and the other on optimizing strength, the relationship between apparent density and stress is derived. This is the first time that a single theory has been advanced to predict both the orientation and apparent density of cancellous bone.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100040307
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of ingrowth, geometry, and material on stress transfer under porous-coated hip surface replacements (1988)
    Hoboken, NJ [u.a.] : Wiley-Blackwell
    Journal of Orthopaedic Research 6 (1988), S. 425-433 
    Details
    ISSN: 0736-0266
    Keywords: Surface replacement ; Prosthesis design ; Finite elements ; Stress shielding ; Porous ingrowth ; Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Three different interface geometries for porous ingrowth surface replacements of the hip were examined using two-dimensional linear and non-linear contact finite element analyses. The results indicate that incorporation of a nearly flat prosthesis interface between the surface replacement and the underlying cancellous bone may reduce stress shielding and improve stress transfer from the component. For all designs analyzed, the bone stress shielding was insensitive to component material stiffness when the elastic modulus was 〉30 MPa. The use of titanium instead of cobalt-chrome (Co-Cr) as the prosthesis material therefore had a negligible effect on stress shielding.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jor.1100060314
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    Paper (German National Licenses)
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