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" Fluid flow, matrix strain and loading frequency as interdependent control parameters in skeletal adaptation "
Y.-X. Qin
C. T. C. Rubin, Fu-Pen
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Latin Dissertation
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English
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| Record Number
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1113341
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TLpq304398733
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| Main Entry
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C. T. C. Rubin, Fu-Pen
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Y.-X. Qin
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| Title & Author
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Fluid flow, matrix strain and loading frequency as interdependent control parameters in skeletal adaptation\ Y.-X. QinC. T. C. Rubin, Fu-Pen
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| College
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State University of New York at Stony Brook
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| Date
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1997
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| student score
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1997
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| Degree
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Ph.D.
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| Page No
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206
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| Abstract
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Bone's ability to respond relatively high frequencies of mechanical stimuli is indicative as to how bone cells sense the signal for adaptation. This frequency sensitivity data extends beyond identifying the factor that stimulates bone formation. The most active inhibitor of bony ingrowth is the shear strain and stress generated at the bone-implant interface. While specific mechanical parameters, i.e., normal strains and strain gradients, may mildly encourage the bony ingrowth, shear actively inhibits it. To maximally stimulate bony ingrowth, implant design must promote specific stresses or strains and their gradients, while minimizing shear stress or strain at the bone-implant interface. The ability of bone tissue to differentiate shear and normal strain conditions was evaluated by monitoring the adaptive response of axial and torsional loading conditions in a turkey ulna model. Of three distinct regimens (disuse, axial and torsional loads), only disuse caused a significant change in gross areal properties as compared to controls (12% loss of bone), suggesting both axial and torsional loading conditions were suitable substitutes for functional signals normally responsible for bone homeostasis. However, the intracortical response was strongly dependent on the manner in which the bone was loaded. It appears that bone tissue can readily differentiate between distinct components of the strain environment, with strain per se necessary to retain coupled formation and resorption, shear strain (achieving this goal by maintaining the status quo, while axial strain elevates intracortical turnover, but retains coupling. The interdependent role of loading frequency, cycle number and intensity was investigated by quantifying the bone remodeling response to a relatively high frequency (30 Hz) loading regimen. The applied strain distributions were correlated to site-specific surface modeling/remodeling and intracortical porosity under long duration loading, following disuse plus 18,000 of applied loading cycles with peak normal strain of 700 usd\mu\varepsilon,usd and disuse plus 108,000 applied loading cycles induced at 100 usd\mu\varepsilon.usd While new bone was found in the low cycle, high strain magnitude group, the sites correlated poorly with the distribution of induced strain. However, a strong correlation was observed between the preservation of bone mass and longitudinal normal strain (R = 0.91) in the high cycle, low strain magnitude group. These results indicate that mechanical loading can hold anti-resorptive potential, even at levels less than 100 usd\mu\varepsilon,usd should a sufficient number of strain cycles be applied. Considering the interdependent role of strain magnitude, shear and normal strain components, strain gradient and loading frequency, a likely candidate involved in the adaptive process may be the intracortical fluid pressure and resultant fluid flow which arises in the cortical bone matrix by the time-varying mechanical strain, which may serve as a critical signal to regulate cell activity. This hypothesis is supported by experiments which evaluate whole bone fluid pressure and its gradient in a porous media model incorporated with in vivo streaming potential measurements. (Abstract shortened by UMI.)
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Applied sciences
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Biological sciences
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Biomedical research
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Biophysics
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bone
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Mechanical engineering
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