Essay On Spongy Bone Remodeling Theory

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2.1 A semi-mechanistic bone remodeling theory As opposed to soft biological tissues, which can experience both appositional and interstitial growth, hard biological tissue can experience just appositional growth because of the nonexpendable nature of the bone matrix [16, 17, 2829]. The proposed regulatory process of spongy bone remodeling, as proposed by Huiskes et al. [1920], can be seen in Fig. 1. Bone remodeling is depicted as a coupled process of bone resorption and bone formation on the bone free surface. Osteoclasts are assumed to resorb bone stochastically, and osteocytes are suggested to act as SED rate sensing cells, and play a role in the regulation of bone remodeling. It is assumed that osteocytes locally sense the SED rate…show more content…
This two-dimensional model was a square domain of 1.52×1.52 mm2 and was divided into 38×38 rectangular four-node elements. Relative (or apparent) bone density (m) per element is considered to vary between 0.01 (no bone, just bone marrow), and 1.0 (no void, fully solid mineralized bone) (see Fig. 2). In this study, the criterion of m for separating bone matrix from bone marrow in the configuration was assumed to be 0.4. In order to apply external loads to our 2D computer model, the perimeter of the square domain was assumed to be surrounded by a band. The thickness of the band was one element, equal to 40 µm. This band did not participate in the bone remodeling process, and the load was applied at the edge of the bone model. In order to minimize the effect of stress shielding caused by continuous band corners, no external load was imposed on the corner of the band (see Fig. 2), and the material properties of the band were the same as those of a fully mineralized trabecular bone tissue, which were given a Young 's modulus of 5GPa and a Poisson ratio of 0.3. The structure was loaded by a sinusoidal stress, cycling between 0 and 2MPa, and at frequency of 1Hz [1920]. The semi-mechanistic bone remodelling theory assumed that the stimulus sensed by osteocytes is the maximal SED-rate during one loading cycle. It has been shown that the maximum SED-rate can be substituted by the SED value for some static load [3132]. Hence, the bone remodeling process can be evaluated by static finite element analysis. In this study, the SED value was calculated using a substitute static stress of 4MPa

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