Osteocyte Lacunae Tissue Strain in Cortical Bone

Department of Oral Biology, University of Missouri - Kansas City, Kansas City, Missouri, United States
Journal of Biomechanics (Impact Factor: 2.75). 02/2006; 39(9):1735-43. DOI: 10.1016/j.jbiomech.2005.04.032
Source: PubMed


Current theories suggest that bone modeling and remodeling are controlled at the cellular level through signals mediated by osteocytes. However, the specific signals to which bone cells respond are still unknown. Two primary theories are: (1) osteocytes are stimulated via the mechanical deformation of the perilacunar bone matrix and (2) osteocytes are stimulated via fluid flow generated shear stresses acting on osteocyte cell processes within canaliculi. Recently, much focus has been placed on fluid flow theories since in vitro experiments have shown that bone cells are more responsive to analytically estimated levels of fluid shear stress than to direct mechanical stretching using macroscopic strain levels measured on bone in vivo. However, due to the complex microstructural organization of bone, local perilacunar bone tissue strains potentially acting on osteocytes cannot be reliably estimated from macroscopic bone strain measurements. Thus, the objective of this study was to quantify local perilacunar bone matrix strains due to macroscopically applied bone strains similar in magnitude to those that occur in vivo. Using a digital image correlation strain measurement technique, experimentally measured bone matrix strains around osteocyte lacunae resulting from macroscopic strains of approximately 2000 microstrain are significantly greater than macroscopic strain on average and can reach peak levels of over 30,000 microstrain locally. Average strain concentration factors ranged from 1.1 to 3.8, which is consistent with analytical and numerical estimates. This information should lead to a better understanding of how bone cells are affected by whole bone functional loading.


Available from: Lynda F Bonewald, Nov 26, 2014
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    • "Various studies have demonstrated the merits of using DIC to examine different bone properties. Previous studies [24] [25] have utilized DIC to analyze micro cracks in bovine cortical bone to show that the crack tip locations and osteocyte lacunae produce the highest strains. DIC has also been used for comparing local strains with nanoindentation measurements in cortical bone to show that bone microstructure and mineral content affect local strain [26]. "
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    ABSTRACT: This study investigates the use of a non-contact method known as Digital Image Correlation (DIC) to measure strains in the mouse forearm during axial compressive loading. A two camera system was adapted to analyze the medial and lateral forearm displacements simultaneously, and the derived DIC strain measurements were compared to strain gage readings from both the ulna and radius. Factors such as region-of-interest (ROI) location, lens magnification, noise, and out-of-plane motion were examined to determine their influence on the DIC strain measurements. We confirmed that our DIC system can differentiate ROI locations since it detected higher average strains in the ulna compared to the radius and detected compressive strains on medial bone surfaces vs. tensile strains on lateral bone surfaces. Interestingly, the DIC method also captured heterogeneity in surface strain fields which are not detectable by strain gage based methods. A separate analysis of the noise intrinsic to the DIC system also revealed that the noise constituted less than 4.5% of all DIC strain measurements. Furthermore, finite element (FE) simulations of the forearm showed that out-of-plane motion was not a significant factor that influenced DIC measurements. Finally, we observed that average DIC strain measurements can be up to 1.5-2 times greater than average strain gage readings on the medial bone surfaces. These findings suggest that strain experienced in the mouse forearm model by loading is better captured through DIC as opposed to strain gages, which as a result of being glued to the bone surface artificially stiffen the bone and lead to an underestimation of the strain response.
    Bone 09/2015; (Article in Press). DOI:10.1016/j.bone.2015.09.007 · 3.97 Impact Factor
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    • "The algorithm is highly effective when precise displacement between two images have to be calculated. Digital Image correlation has proven to be an extremely effective optical approach with vast applications like determining mechanical properties of human soft tissue in vivo [26], direct measurement of two-dimensional strain distributions within articular cartilage under unconfined compression [27], measuring Osteocyte lacunae tissue strain in cortical bone [28], determining local mechanical conditions within early bone callus [29] etc. DIC has been used to analyze the stresses in solder interconnects of BGA packages under thermal loading [30], [31] material characterization under thermal loading [32], dynamic testing to study deformation for flexible bodies [34], material characterization at high strain rate [35], stresses and strain in flip-chip die under thermal loading [36] etc. DIC has been applied multiple times in the past in the field of applied anthropology to assist practitioners for diagnosis [41]. DIC has been effectively used to study the mechanical properties of biological soft tissues e.g. using 2D DIC: on the human tympanic membrane [37], sheep bone callus [29], human cervical tissue [38] and recently also using 3D DIC: for the bovine cornea [39] and mouse arterial tissue [40]. "

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    • "Fig. 13 illustrates how the presence of lacunae changes locally the stress field of bone's lamellar structure; the stress concentration is vivid around both lacunae, especially at the end of their minor axes. Other researchers also reported the stress concentration in elastic fields around the osteocyte lacunae (Currey, 1962; Nicolella et al., 2006; Verbruggen et al., 2012). The FEM results obtained for the strength of bone at microscale are shown in Fig. 14 for different fibril orientation patterns. "
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    ABSTRACT: A computational multiscale model of damage mechanisms and strength of lamellar bone is presented. The analysis incorporates the hierarchical structure of bone spanning the nanoscale (mineralized collagen fibril), the sub-microscale (single lamella) and the microscale (lamellar structure) levels. Due to the presence of several constituents (collagen, hydroxyapatite minerals, and non-collagenous proteins) and the different microstructural features at each scale, various deformation and failure mechanisms occur in bone at its several levels of hierarchy. The model takes into account the dominant damage mechanisms at the above mentioned three scales and predicts the strength of bone by using a cohesive finite element method. Elastic moduli of bone at these three different scales are also obtained as part of these calculations. The obtained modeling results compare well with other theoretical and experimental data available in the literature.
    07/2013; 28C:94-110. DOI:10.1016/j.jmbbm.2013.05.025
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