The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Steve Weiner - One of the best experts on this subject based on the ideXlab platform.
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Focused ion beam-SEM 3D analysis of mineralized osteonal Bone: lamellae and cement sheath structures.
Acta biomaterialia, 2020Co-Authors: Emeline Raguin, Ron Shahar, Katya Rechav, Steve WeinerAbstract:Abstract The mineralized collagen fibril is the basic building block of Bone, and hence is the key to understanding Bone structure and function. Here we report imaging of mineralized pig Bone samples in 3D using the focused ion beam-scanning electron microscope (FIB-SEM) under conditions that reveal the 67 nm D-banding of mineralized collagen fibrils. We show that in adult pig osteons, the Lamellar Bone comprises alternating layers with either collagen fibrils predominantly aligned in one direction, and layers in which fibrils are predominantly aligned in two directions. The cement sheath contains thin layers of both these motifs, but its dominant structural component comprises a very complex layer of fibrils predominantly aligned in three or more directions. The degree of mineralization of the cement sheath is comparable to that of the osteon interior. The extent of alignment (dispersion) of the collagen fibrils in the osteonal Lamellar Bone is significantly higher than in the cement sheath. Canaliculi within the cement sheath are mainly aligned parallel to the cement sheath boundary, whereas in the Lamellar Bone they are mainly aligned perpendicular to the Lamellar boundaries. This study further characterizes the presence of two types of collagen fibril arrangements previously identified in demineralized Lamellar Bone from other species. The simple sample preparation procedure for mineralized Bone and the lower risk of introducing artifacts opens the possibility of using FIB-SEM to study more samples, to obtain automatic quantitative information on collagen fibril organization and to evaluate the degrees of mineralization all in relatively large volumes of Bone.
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the 3d structure of the collagen fibril network in human trabecular Bone relation to trabecular organization
Bone, 2015Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:article i nfo Trabecular Bone is morphologically and functionally different from compact Bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular Lamellar Bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact Lamellar Bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact Lamellar Bone display the same overall structural organiza- tion,namelythepresence oforderedanddisorderedmaterialsandthe confinementofthecanalicular networkto the disordered material. However, in trabecularBone lamellae a significant proportion of the ordered collagen fi- brilarraysisaligned with thelongaxisof the trabecula and, unlike incompact Bone, isnot related totheanatom- icalaxisofthewholefemur.Theremainingorderedcollagen fibrilsareoffsetfromtheaxisofatrabeculaeitherby about30°or70°.Interestingly,atthetissue scaleof millimeters,themostabundant anglesbetweenany two con- nectedtrabeculae —theinter-trabecularangles-centeraround30°and70°.Thisimpliesthatwithinaframework of interconnected trabeculae the same Lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular Bone to function.
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The 3D structure of the collagen fibril network in human trabecular Bone: Relation to trabecular organization
Bone, 2014Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:Trabecular Bone is morphologically and functionally different from compact Bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular Lamellar Bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact Lamellar Bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact Lamellar Bone display the same overall structural organization, namely the presence of ordered and disordered materials and the confinement of the canalicular network to the disordered material. However, in trabecular Bone lamellae a significant proportion of the ordered collagen fibril arrays is aligned with the long axis of the trabecula and, unlike in compact Bone, is not related to the anatomical axis of the whole femur. The remaining ordered collagen fibrils are offset from the axis of a trabecula either by about 30° or 70°. Interestingly, at the tissue scale of millimeters, the most abundant angles between any two connected trabeculae - the inter-trabecular angles - center around 30° and 70°. This implies that within a framework of interconnected trabeculae the same Lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular Bone to function.
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three dimensional structure of human Lamellar Bone the presence of two different materials and new insights into the hierarchical organization
Bone, 2014Co-Authors: Natalie Reznikov, Ron Shahar, Steve WeinerAbstract:Abstract Lamellar Bone is the most common Bone type in humans. The predominant components of individual lamellae are plywood-like arrays of mineralized collagen fibrils aligned in different directions. Using a dual-beam electron microscope and the Serial Surface View (SSV) method we previously identified a small, but significantly different layer in rat Lamellar Bone, namely a disordered layer with collagen fibrils showing little or no preferred orientation. Here we present a 3D structural analysis of 12 SSV volumes (25 complete lamellae) from femora of 3 differently aged human individuals. We identify the ordered and disordered motifs in human Bone as in the rat, with several significant differences. The ordered motif shows two major preferred orientations, perpendicular to the long axis of the Bone, and aligned within 10–20° of the long axis, as well as fanning arrays. At a higher organizational level, arrays of ordered collagen fibrils are organized into ‘rods’ around 2 to 3 μm in diameter, and the long axes of these ‘rods’ are parallel to the Lamellar boundaries. Human Bone also contains a disordered component that envelopes the rods and fills in the spaces between them. The disordered motif is especially well-defined between adjacent layers of rods. The disordered motif and its interfibrillar substance stain heavily with osmium tetroxide and Alcian blue indicating the presence of another organic component in addition to collagen. The canalicular network is confined to the disordered material, along with voids and individual collagen fibrils, some of which are also aligned more or less perpendicular to the Lamellar boundaries. The organization of the ordered fibril arrays into rods enveloped in the continuous disordered structure was not observed in rat Lamellar Bone. We thus conclude that human Lamellar Bone is comprised of two distinct materials, an ordered material and a disordered material, and contains an additional hierarchical level of organization composed of arrays of ordered collagen fibrils, referred to as rods. This new structural information on human Lamellar Bone will improve our understanding of structure–mechanical function relations, mechanisms of mechano-sensing and the characterizations of Bone pathologies.
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three dimensional imaging of collagen fibril organization in rat circumferential Lamellar Bone using a dual beam electron microscope reveals ordered and disordered sub Lamellar structures
Bone, 2013Co-Authors: Natalie Reznikov, Rotem Almanymagal, Ron Shahar, Steve WeinerAbstract:Abstract Lamellar Bone is a major component of most mammalian skeletons. A prominent component of individual lamellae are parallel arrays of mineralized type I collagen fibrils, organized in a plywood like motif. Here we use a dual beam microscope and the serial surface view (SSV) method to investigate the three dimensional collagen organization of circumferential Lamellar Bone from rat tibiae after demineralization and osmium staining. Fast Fourier transform analysis is used to quantitatively identify the mean collagen array orientations and local collagen fibril dispersion. Based on collagen fibril array orientations and variations in fibril dispersion, we identify 3 distinct sub-Lamellar structural motifs: a plywood-like fanning sub-lamella, a unidirectional sub-lamella and a disordered sub-lamella. We also show that the disordered sub-lamella is less mineralized than the other sub-lamellae. The hubs and junctions of the canalicular network, which connect radially oriented canaliculi, are intimately associated with the disordered sub-lamella. We also note considerable variations in the proportions of these 3 sub-Lamellar structural elements among different lamellae. This new application of Serial Surface View opens the way to quantitatively compare Lamellar Bone from different sources, and to clarify the 3-dimensional structures of other Bone types, as well as other biological structural materials.
Natalie Reznikov - One of the best experts on this subject based on the ideXlab platform.
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multiscale analyses reveal native like Lamellar Bone repair and near perfect Bone contact with porous strontium loaded bioactive glass
Biomaterials, 2019Co-Authors: Helene Autefage, Natalie Reznikov, F Allen, H M Tang, Charalambos Kallepitis, Eileen Gentleman, K Nitiputri, Amy Nommeotsnomm, M D Odonnell, Claudia LangeAbstract:The efficient healing of critical-sized Bone defects using synthetic biomaterial-based strategies is promising but remains challenging as it requires the development of biomaterials that combine a 3D porous architecture and a robust biological activity. Bioactive glasses (BGs) are attractive candidates as they stimulate a biological response that favors osteogenesis and vascularization, but amorphous 3D porous BGs are difficult to produce because conventional compositions crystallize during processing. Here, we rationally designed a porous, strontium-releasing, bioactive glass-based scaffold (pSrBG) whose composition was tailored to deliver strontium and whose properties were optimized to retain an amorphous phase, induce tissue infiltration and encourage Bone formation. The hypothesis was that it would allow the repair of a critical-sized defect in an ovine model with newly-formed Bone exhibiting physiological matrix composition and structural architecture. Histological and histomorphometric analyses combined with indentation testing showed pSrBG encouraged near perfect Bone-to-material contact and the formation of well-organized Lamellar Bone. Analysis of Bone quality by a combination of Raman spectral imaging, small-angle X-ray scattering, X-ray fluorescence and focused ion beam-scanning electron microscopy demonstrated that the repaired tissue was akin to that of normal, healthy Bone, and incorporated small amounts of strontium in the newly formed Bone mineral. These data show the potential of pSrBG to induce an efficient repair of critical-sized Bone defects and establish the importance of thorough multi-scale characterization in assessing biomaterial outcomes in large animal models.
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the 3d structure of the collagen fibril network in human trabecular Bone relation to trabecular organization
Bone, 2015Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:article i nfo Trabecular Bone is morphologically and functionally different from compact Bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular Lamellar Bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact Lamellar Bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact Lamellar Bone display the same overall structural organiza- tion,namelythepresence oforderedanddisorderedmaterialsandthe confinementofthecanalicular networkto the disordered material. However, in trabecularBone lamellae a significant proportion of the ordered collagen fi- brilarraysisaligned with thelongaxisof the trabecula and, unlike incompact Bone, isnot related totheanatom- icalaxisofthewholefemur.Theremainingorderedcollagen fibrilsareoffsetfromtheaxisofatrabeculaeitherby about30°or70°.Interestingly,atthetissue scaleof millimeters,themostabundant anglesbetweenany two con- nectedtrabeculae —theinter-trabecularangles-centeraround30°and70°.Thisimpliesthatwithinaframework of interconnected trabeculae the same Lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular Bone to function.
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The 3D structure of the collagen fibril network in human trabecular Bone: Relation to trabecular organization
Bone, 2014Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:Trabecular Bone is morphologically and functionally different from compact Bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular Lamellar Bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact Lamellar Bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact Lamellar Bone display the same overall structural organization, namely the presence of ordered and disordered materials and the confinement of the canalicular network to the disordered material. However, in trabecular Bone lamellae a significant proportion of the ordered collagen fibril arrays is aligned with the long axis of the trabecula and, unlike in compact Bone, is not related to the anatomical axis of the whole femur. The remaining ordered collagen fibrils are offset from the axis of a trabecula either by about 30° or 70°. Interestingly, at the tissue scale of millimeters, the most abundant angles between any two connected trabeculae - the inter-trabecular angles - center around 30° and 70°. This implies that within a framework of interconnected trabeculae the same Lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular Bone to function.
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three dimensional structure of human Lamellar Bone the presence of two different materials and new insights into the hierarchical organization
Bone, 2014Co-Authors: Natalie Reznikov, Ron Shahar, Steve WeinerAbstract:Abstract Lamellar Bone is the most common Bone type in humans. The predominant components of individual lamellae are plywood-like arrays of mineralized collagen fibrils aligned in different directions. Using a dual-beam electron microscope and the Serial Surface View (SSV) method we previously identified a small, but significantly different layer in rat Lamellar Bone, namely a disordered layer with collagen fibrils showing little or no preferred orientation. Here we present a 3D structural analysis of 12 SSV volumes (25 complete lamellae) from femora of 3 differently aged human individuals. We identify the ordered and disordered motifs in human Bone as in the rat, with several significant differences. The ordered motif shows two major preferred orientations, perpendicular to the long axis of the Bone, and aligned within 10–20° of the long axis, as well as fanning arrays. At a higher organizational level, arrays of ordered collagen fibrils are organized into ‘rods’ around 2 to 3 μm in diameter, and the long axes of these ‘rods’ are parallel to the Lamellar boundaries. Human Bone also contains a disordered component that envelopes the rods and fills in the spaces between them. The disordered motif is especially well-defined between adjacent layers of rods. The disordered motif and its interfibrillar substance stain heavily with osmium tetroxide and Alcian blue indicating the presence of another organic component in addition to collagen. The canalicular network is confined to the disordered material, along with voids and individual collagen fibrils, some of which are also aligned more or less perpendicular to the Lamellar boundaries. The organization of the ordered fibril arrays into rods enveloped in the continuous disordered structure was not observed in rat Lamellar Bone. We thus conclude that human Lamellar Bone is comprised of two distinct materials, an ordered material and a disordered material, and contains an additional hierarchical level of organization composed of arrays of ordered collagen fibrils, referred to as rods. This new structural information on human Lamellar Bone will improve our understanding of structure–mechanical function relations, mechanisms of mechano-sensing and the characterizations of Bone pathologies.
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three dimensional imaging of collagen fibril organization in rat circumferential Lamellar Bone using a dual beam electron microscope reveals ordered and disordered sub Lamellar structures
Bone, 2013Co-Authors: Natalie Reznikov, Rotem Almanymagal, Ron Shahar, Steve WeinerAbstract:Abstract Lamellar Bone is a major component of most mammalian skeletons. A prominent component of individual lamellae are parallel arrays of mineralized type I collagen fibrils, organized in a plywood like motif. Here we use a dual beam microscope and the serial surface view (SSV) method to investigate the three dimensional collagen organization of circumferential Lamellar Bone from rat tibiae after demineralization and osmium staining. Fast Fourier transform analysis is used to quantitatively identify the mean collagen array orientations and local collagen fibril dispersion. Based on collagen fibril array orientations and variations in fibril dispersion, we identify 3 distinct sub-Lamellar structural motifs: a plywood-like fanning sub-lamella, a unidirectional sub-lamella and a disordered sub-lamella. We also show that the disordered sub-lamella is less mineralized than the other sub-lamellae. The hubs and junctions of the canalicular network, which connect radially oriented canaliculi, are intimately associated with the disordered sub-lamella. We also note considerable variations in the proportions of these 3 sub-Lamellar structural elements among different lamellae. This new application of Serial Surface View opens the way to quantitatively compare Lamellar Bone from different sources, and to clarify the 3-dimensional structures of other Bone types, as well as other biological structural materials.
Ron Shahar - One of the best experts on this subject based on the ideXlab platform.
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Focused ion beam-SEM 3D analysis of mineralized osteonal Bone: lamellae and cement sheath structures.
Acta biomaterialia, 2020Co-Authors: Emeline Raguin, Ron Shahar, Katya Rechav, Steve WeinerAbstract:Abstract The mineralized collagen fibril is the basic building block of Bone, and hence is the key to understanding Bone structure and function. Here we report imaging of mineralized pig Bone samples in 3D using the focused ion beam-scanning electron microscope (FIB-SEM) under conditions that reveal the 67 nm D-banding of mineralized collagen fibrils. We show that in adult pig osteons, the Lamellar Bone comprises alternating layers with either collagen fibrils predominantly aligned in one direction, and layers in which fibrils are predominantly aligned in two directions. The cement sheath contains thin layers of both these motifs, but its dominant structural component comprises a very complex layer of fibrils predominantly aligned in three or more directions. The degree of mineralization of the cement sheath is comparable to that of the osteon interior. The extent of alignment (dispersion) of the collagen fibrils in the osteonal Lamellar Bone is significantly higher than in the cement sheath. Canaliculi within the cement sheath are mainly aligned parallel to the cement sheath boundary, whereas in the Lamellar Bone they are mainly aligned perpendicular to the Lamellar boundaries. This study further characterizes the presence of two types of collagen fibril arrangements previously identified in demineralized Lamellar Bone from other species. The simple sample preparation procedure for mineralized Bone and the lower risk of introducing artifacts opens the possibility of using FIB-SEM to study more samples, to obtain automatic quantitative information on collagen fibril organization and to evaluate the degrees of mineralization all in relatively large volumes of Bone.
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Structural orientation dependent sub-Lamellar Bone mechanics.
Journal of the mechanical behavior of biomedical materials, 2015Co-Authors: Ines Jimenez-palomar, Ron Shahar, Anna Shipov, Asa H. BarberAbstract:The Lamellar unit is a critical component in defining the overall mechanical properties of Bone. In this paper, micro-beams of Bone with dimensions comparable to the Lamellar unit were fabricated using focused ion beam (FIB) microscopy and mechanically tested in bending to failure using atomic force microscopy (AFM). A variation in the mechanical properties, including elastic modulus, strength and work to fracture of the micro-beams was observed and related to the collagen fibril orientation inferred from back-scattered scanning electron microscopy (SEM) imaging. Established mechanical models were further applied to describe the relationship between collagen fibril orientation and mechanical behaviour of the Lamellar unit. Our results highlight the ability to measure mechanical properties of discrete Bone volumes directly and correlate with structural orientation of collagen fibrils.
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the 3d structure of the collagen fibril network in human trabecular Bone relation to trabecular organization
Bone, 2015Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:article i nfo Trabecular Bone is morphologically and functionally different from compact Bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular Lamellar Bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact Lamellar Bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact Lamellar Bone display the same overall structural organiza- tion,namelythepresence oforderedanddisorderedmaterialsandthe confinementofthecanalicular networkto the disordered material. However, in trabecularBone lamellae a significant proportion of the ordered collagen fi- brilarraysisaligned with thelongaxisof the trabecula and, unlike incompact Bone, isnot related totheanatom- icalaxisofthewholefemur.Theremainingorderedcollagen fibrilsareoffsetfromtheaxisofatrabeculaeitherby about30°or70°.Interestingly,atthetissue scaleof millimeters,themostabundant anglesbetweenany two con- nectedtrabeculae —theinter-trabecularangles-centeraround30°and70°.Thisimpliesthatwithinaframework of interconnected trabeculae the same Lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular Bone to function.
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The 3D structure of the collagen fibril network in human trabecular Bone: Relation to trabecular organization
Bone, 2014Co-Authors: Natalie Reznikov, Hila Chase, Ron Shahar, Vlad Brumfeld, Steve WeinerAbstract:Trabecular Bone is morphologically and functionally different from compact Bone at the tissue level, but both are composed of lamellae at the micrometer-scale level. We present a three-dimensional study of the collagenous network of human trabecular Lamellar Bone from the proximal femur using the FIB-SEM serial surface view method. The results are compared to human compact Lamellar Bone of the femoral shaft, studied by the same method. Both demineralized trabecular and compact Lamellar Bone display the same overall structural organization, namely the presence of ordered and disordered materials and the confinement of the canalicular network to the disordered material. However, in trabecular Bone lamellae a significant proportion of the ordered collagen fibril arrays is aligned with the long axis of the trabecula and, unlike in compact Bone, is not related to the anatomical axis of the whole femur. The remaining ordered collagen fibrils are offset from the axis of a trabecula either by about 30° or 70°. Interestingly, at the tissue scale of millimeters, the most abundant angles between any two connected trabeculae - the inter-trabecular angles - center around 30° and 70°. This implies that within a framework of interconnected trabeculae the same Lamellar structure will always have a significant component of the fibrils aligned with the long axes of connected trabeculae. This structural complementarity at different hierarchical levels presumably reflects an adaptation of trabecular Bone to function.
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three dimensional structure of human Lamellar Bone the presence of two different materials and new insights into the hierarchical organization
Bone, 2014Co-Authors: Natalie Reznikov, Ron Shahar, Steve WeinerAbstract:Abstract Lamellar Bone is the most common Bone type in humans. The predominant components of individual lamellae are plywood-like arrays of mineralized collagen fibrils aligned in different directions. Using a dual-beam electron microscope and the Serial Surface View (SSV) method we previously identified a small, but significantly different layer in rat Lamellar Bone, namely a disordered layer with collagen fibrils showing little or no preferred orientation. Here we present a 3D structural analysis of 12 SSV volumes (25 complete lamellae) from femora of 3 differently aged human individuals. We identify the ordered and disordered motifs in human Bone as in the rat, with several significant differences. The ordered motif shows two major preferred orientations, perpendicular to the long axis of the Bone, and aligned within 10–20° of the long axis, as well as fanning arrays. At a higher organizational level, arrays of ordered collagen fibrils are organized into ‘rods’ around 2 to 3 μm in diameter, and the long axes of these ‘rods’ are parallel to the Lamellar boundaries. Human Bone also contains a disordered component that envelopes the rods and fills in the spaces between them. The disordered motif is especially well-defined between adjacent layers of rods. The disordered motif and its interfibrillar substance stain heavily with osmium tetroxide and Alcian blue indicating the presence of another organic component in addition to collagen. The canalicular network is confined to the disordered material, along with voids and individual collagen fibrils, some of which are also aligned more or less perpendicular to the Lamellar boundaries. The organization of the ordered fibril arrays into rods enveloped in the continuous disordered structure was not observed in rat Lamellar Bone. We thus conclude that human Lamellar Bone is comprised of two distinct materials, an ordered material and a disordered material, and contains an additional hierarchical level of organization composed of arrays of ordered collagen fibrils, referred to as rods. This new structural information on human Lamellar Bone will improve our understanding of structure–mechanical function relations, mechanisms of mechano-sensing and the characterizations of Bone pathologies.
F. Javier Fuenmayor - One of the best experts on this subject based on the ideXlab platform.
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Explicit expressions for the estimation of the elastic constants of Lamellar Bone as a function of the volumetric mineral content using a multi-scale approach
Biomechanics and Modeling in Mechanobiology, 2018Co-Authors: Ana Vercher-martínez, Eugenio Giner, Ricardo Belda, Abdelmalik Aigoun, F. Javier FuenmayorAbstract:In this work, explicit expressions to estimate all the transversely isotropic elastic constants of Lamellar Bone as a function of the volumetric Bone mineral density (BMD) are provided. The methodology presented is based on the direct homogenization procedure using the finite element method, the continuum approach based on the Hill bounds, the least-square method and the mean field technique. Firstly, a detailed description of the volumetric content of the different components of Bone is provided. The parameters defined in this step are related to the volumetric BMD considering that Bone mineralization process occurs at the smallest scale length of the Bone tissue. Then, a thorough description provides the details of the numerical models and the assumptions adopted to estimate the elastic behaviour of the forward scale lengths. The results highlight the noticeable influence of the BMD on the elastic modulus of Lamellar Bone. Power law regressions fit the Young’s moduli, shear stiffness moduli and Poisson ratios. In addition, the explicit expressions obtained are applied to the estimation of the elastic constants of cortical Bone. At this scale length, a representative unit cell of cortical Bone is analysed including the fibril orientation pattern given by Wagermaier et al. (Biointerphases 1:1–5, 2006 ) and the BMD distributions observed by Granke et al. (PLoS One 8:e58043, 2012 ) for the osteon. Results confirm that fibril orientation arrangement governs the anisotropic behaviour of cortical Bone instead of the BMD distribution. The novel explicit expressions obtained in this work can be used for improving the accuracy of Bone fracture risk assessment.
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Influence of the mineral staggering on the elastic properties of the mineralized collagen fibril in Lamellar Bone.
Journal of the mechanical behavior of biomedical materials, 2014Co-Authors: Ana Vercher-martínez, Eugenio Giner, Camila Arango, F. Javier FuenmayorAbstract:In this work, a three-dimensional finite element model of the staggered distribution of the mineral within the mineralized collagen fibril has been developed to characterize the Lamellar Bone elastic behavior at the sub-micro length scale. Minerals have been assumed to be embedded in a collagen matrix, and different degrees of mineralization have been considered allowing the growth of platelet-shaped minerals both in the axial and the transverse directions of the fibril, through the variation of the lateral space between platelets. We provide numerical values and trends for all the elastic constants of the mineralized collagen fibril as a function of the volume fraction of mineral. In our results, we verify the high influence of the mineral overlapping on the mechanical response of the fibril and we highlight that the lateral distance between crystals is relevant to the mechanical behavior of the fibril and not only the mineral overlapping in the axial direction.
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Homogenized stiffness matrices for mineralized collagen fibrils and Lamellar Bone using unit cell finite element models.
Biomechanics and modeling in mechanobiology, 2013Co-Authors: A. Vercher, Eugenio Giner, Camila Arango, J. E. Tarancón, F. Javier FuenmayorAbstract:Mineralized collagen fibrils have been usually analyzed like a two-phase composite material where crystals are considered as platelets that constitute the reinforcement phase. Different models have been used to describe the elastic behavior of the material. In this work, it is shown that when Halpin–Tsai equations are applied to estimate elastic constants from typical constituent properties, not all crystal dimensions yield a model that satisfy thermodynamic restrictions. We provide the ranges of platelet dimensions that lead to positive definite stiffness matrices. On the other hand, a finite element model of a mineralized collagen fibril unit cell under periodic boundary conditions is analyzed. By applying six canonical load cases, homogenized stiffness matrices are numerically calculated. Results show a monoclinic behavior of the mineralized collagen fibril. In addition, a 5-layer Lamellar structure is also considered where crystals rotate in adjacent layers of a lamella. The stiffness matrix of each layer is calculated applying Lekhnitskii transformations, and a new finite element model under periodic boundary conditions is analyzed to calculate the homogenized 3D anisotropic stiffness matrix of a unit cell of Lamellar Bone. Results are compared with the rule-of-mixtures showing in general good agreement.
Ana Vercher-martínez - One of the best experts on this subject based on the ideXlab platform.
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Explicit expressions for the estimation of the elastic constants of Lamellar Bone as a function of the volumetric mineral content using a multi-scale approach
Biomechanics and Modeling in Mechanobiology, 2018Co-Authors: Ana Vercher-martínez, Eugenio Giner, Ricardo Belda, Abdelmalik Aigoun, F. Javier FuenmayorAbstract:In this work, explicit expressions to estimate all the transversely isotropic elastic constants of Lamellar Bone as a function of the volumetric Bone mineral density (BMD) are provided. The methodology presented is based on the direct homogenization procedure using the finite element method, the continuum approach based on the Hill bounds, the least-square method and the mean field technique. Firstly, a detailed description of the volumetric content of the different components of Bone is provided. The parameters defined in this step are related to the volumetric BMD considering that Bone mineralization process occurs at the smallest scale length of the Bone tissue. Then, a thorough description provides the details of the numerical models and the assumptions adopted to estimate the elastic behaviour of the forward scale lengths. The results highlight the noticeable influence of the BMD on the elastic modulus of Lamellar Bone. Power law regressions fit the Young’s moduli, shear stiffness moduli and Poisson ratios. In addition, the explicit expressions obtained are applied to the estimation of the elastic constants of cortical Bone. At this scale length, a representative unit cell of cortical Bone is analysed including the fibril orientation pattern given by Wagermaier et al. (Biointerphases 1:1–5, 2006 ) and the BMD distributions observed by Granke et al. (PLoS One 8:e58043, 2012 ) for the osteon. Results confirm that fibril orientation arrangement governs the anisotropic behaviour of cortical Bone instead of the BMD distribution. The novel explicit expressions obtained in this work can be used for improving the accuracy of Bone fracture risk assessment.
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Influence of the mineral staggering on the elastic properties of the mineralized collagen fibril in Lamellar Bone.
Journal of the mechanical behavior of biomedical materials, 2014Co-Authors: Ana Vercher-martínez, Eugenio Giner, Camila Arango, F. Javier FuenmayorAbstract:In this work, a three-dimensional finite element model of the staggered distribution of the mineral within the mineralized collagen fibril has been developed to characterize the Lamellar Bone elastic behavior at the sub-micro length scale. Minerals have been assumed to be embedded in a collagen matrix, and different degrees of mineralization have been considered allowing the growth of platelet-shaped minerals both in the axial and the transverse directions of the fibril, through the variation of the lateral space between platelets. We provide numerical values and trends for all the elastic constants of the mineralized collagen fibril as a function of the volume fraction of mineral. In our results, we verify the high influence of the mineral overlapping on the mechanical response of the fibril and we highlight that the lateral distance between crystals is relevant to the mechanical behavior of the fibril and not only the mineral overlapping in the axial direction.
