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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1329-1336 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To compare the numerous modulus-density and strengthdensity relations that have been found for human trabecular bone from the proximal tibia, correlations between various measures of density were sought. Hydrated and dry apparent density, ash density, and density from quantitative computed tomography (QCT) were determined for cubic trabecular specimens taken from the proximal portion of human tibiae, and correlations between these measures were found(r 〉 0.99, P 〈.001). Orthogonal moduli and strengths of the specimens were measured mechanically, and were significantly correlated with ash density according to power relations (r ≥ 0.85, P 〈.001). The strong correlation between density from QCT and ash density indicates that these measures can be used with nearly equal precision in estimating modulus and strength of tibial trabecular bone. Equations between mechanical properties and density reported in previous studies were converted to use a common density measure and, after considering the effects of specimen size, were in general agreement with results of the present study. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 31 (1996), S. 373-378 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: To obtain information describing the postfailure behavior of human proximal tibial trabecular bone, cube specimens of bone were mechanically tested in compression beyond the point of failure. Tests were performed in the three anatomic directions, plots of stress versus strain were obtained, and measures to describe the stress-strain relations before, during, and after failure were defined. These measures included elastic modulus, strength, postfailure slope, strain during maximum stress, and first postfailure minimum stress. For each anatomic direction, analyses were performed to correlate these parameters with ash density.Each of these measures was significantly correlated with ash density at the p 〈 0.05 level for all test directions, except for postfailure slope, which was correlated in the mediolateral and superior-inferior directions, and strain during maximum stress, which was correlated only in the superior-inferior direction. The data from this study enable trilinear stress-strain relations to be estimated for proximal tibial trabecular bone of various densities, and can serve as a first step toward modeling the behavior of trabecular bone before, during, and after failure. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1055-1060 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: With the resurgence of the use of bone cement in total hip arthroplasty, a renewed interest in techniques or designs that may reduce cement fixation failure has arisen. Analysis of the stresses at the tip of the prosthesis may suggest strategies to reduce loosening. This study analyzed stresses in the cement near the tip of a femoral component as a function of cement thickness, using a three-dimensional finite element model. A section of an idealized circular femoral shaft with implanted prosthesis and cement was modeled with loading conditions representing the stance phase of gait. Increasing cement thickness from 2 to 5 mm by reducing the prosthesis diameter from 15 to 9 mm is predicted to reduce stress significantly in the cement mantle of a femoral implant. Peak tensile stresses are reduced 45%, whereas peak von Mises and shear stresses are reduced 40%. Such a reduction in stress can increase fatigue life by an order of magnitude. Peak interface tensile stresses occur on the medial side at the tip of the prosthesis in a transverse direction, indicating likelihood of failure due to debonding. The shear and tensile stresses predicted by our model greatly exceed the fatigue endurance limit values for both bulk cement and the cement-prosthesis interface, indicating the likelihood of premature fatigue failure, even allowing for considerable uncertainty. These analytical results suggest that the surgeon should adopt a strategy of selecting a prosthesis that permits a 5-mm cement mantle near the tip of the prosthesis. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 4
    Publication Date: 2010-04-06
    Print ISSN: 0031-9155
    Electronic ISSN: 1361-6560
    Topics: Biology , Medicine , Physics
    Published by Institute of Physics
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  • 5
    Publication Date: 2012-06-15
    Print ISSN: 0031-9155
    Electronic ISSN: 1361-6560
    Topics: Biology , Medicine , Physics
    Published by Institute of Physics
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  • 6
    Publication Date: 2012-10-17
    Print ISSN: 0031-9155
    Electronic ISSN: 1361-6560
    Topics: Biology , Medicine , Physics
    Published by Institute of Physics
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  • 7
    Publication Date: 2019-07-19
    Description: Elevated bone resorption is a hallmark of human spaceflight and bed rest indicating that elevated remodeling is a major factor in the etiology of space flight bone loss. In a collaborative effort between the NASA and JAXA space agencies, we are testing whether an antiresorptive drug would provide additional benefit to in-flight exercise to ameliorate bone loss and hypercalciuria during long-duration spaceflight. Measurements of bone loss include DXA, QCT, pQCT, urinary and blood biomarkers. We have completed analysis of R+1year data from 7 crewmembers treated with alendronate during flight, as well as immediate post flight (R+〈2wks) data from 6 of 10 concurrent controls without treatment. The treated astronauts used the Advanced Resistive Exercise Device (ARED) during their missions. The purpose of this report is twofold: 1) to report the results of inflight, post flight and one year post flight bone measures compared with available controls with and without the use of ARED; and 2) to discuss preliminary data on concurrent controls. The figure below compares the BMD changes in ISS crewmembers exercising with and without the current ARED protocol and the alendronate treated crewmembers also using the ARED. This shows that the use of ARED prevents about half the bone loss seen in early ISS crewmembers and that the addition of an antiresorptive provides additional benefit. Resorption markers and urinary Ca excretion are not impacted by exercise alone but are significantly reduced with antiresorptive treatment. Bone measures for treated subjects, 1 year after return from space remain at or near baseline. DXA data for the 6 concurrent controls using the ARED device are similar to DXA data shown in the figure below. QCT data for these six indicate that the integral data are consistent with the DXA data, i.e., comparing the two control groups suggests significant but incomplete improvement in maintaining BMD using the ARED protocol. Biochemical data of the concurrent control group await sample return and analysis. The preliminary conclusion is that an antiresorptive may be an effective adjunct to exercise during long-duration spaceflight.
    Keywords: Aerospace Medicine
    Type: JSC-CN-32238 , 2015 Human Research Program Investigators'' Workshop (HRP IWS 2015); Jan 13, 2015 - Jan 15, 2015; Galveston, TX; United States
    Format: application/pdf
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