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Journal of the Mechanical Behavior of... May 2021The toughening mechanism of cortical bone is closely related to its hierarchical microstructure. Osteon is the most important microstructure of cortical bone. Therefore,...
The toughening mechanism of cortical bone is closely related to its hierarchical microstructure. Osteon is the most important microstructure of cortical bone. Therefore, it is very important to study the toughening mechanism of the microstructure of osteon. There are three main kinds of cracks in cortical bone: external crack of osteon, internal radial cracks of osteon and microporous damage cracks. Numerical models for these three kinds of cracks are established by XFEM and the progressive damage approach, respectively. The multi-toughening mechanisms of microstructure of osteon are found. The cement line on the outside of osteon is its first toughening mechanism, which can make the crack deflection and improve the fracture resistance of osteon. The resistance of cement line to fracture increases with the decrease of the strength and the increase of the thickness. The second toughening mechanism is elliptical osteocyte lacunae, which can attract the crack into the elliptical lacunae and cause stress redistribution to prevent the crack propagation. The annularly elliptical lacuna structure is an optimized arrangement and shape of microstructure, which is the third toughening mechanism of osteon. This microstructure can determine the location of the crack initiation and make the microcracks propagate along the annular direction rather than penetrating into the haversian cannal to protect the integrity of the osteon. The study of these toughening mechanisms provides new ideas for the research and design of synthetic composite structures.
Topics: Cortical Bone; Finite Element Analysis; Fractures, Bone; Haversian System; Humans; Models, Biological
PubMed: 33657473
DOI: 10.1016/j.jmbbm.2021.104408 -
American Journal of Physical... Nov 2017Differentiating human from nonhuman fragmented bone is often accomplished using histological methods if the observation of gross morphology proves insufficient. Linearly...
OBJECTIVES
Differentiating human from nonhuman fragmented bone is often accomplished using histological methods if the observation of gross morphology proves insufficient. Linearly oriented primary and/or secondary osteonal systems, commonly referred to as osteon bands, are described as a strong indicator of nonhuman bone, particularly the occurrence of multiple bands. This phenomenon has been conventionally documented using two-dimensional (2D) histology, but such analyses are destructive and typically limited to a single cross-section. Progressive developments in high-resolution X-ray imaging, however, allow for the nondestructive three-dimensional (3D) visualization of bone microarchitecture. The primary objective of the current research was to visualize and document the occurrence of osteon banding in adult human cortical bone using high-resolution synchrotron radiation-based micro-Computed Tomography (SR micro-CT).
MATERIALS AND METHODS
Synchrotron radiation-based micro-CT scanning was carried out at the Canadian Light Source (CLS) national synchrotron facility. The presence or absence of osteon banding was visualized in human skeletal elements from three adult males with representative samples from all regions of the skeleton (n = 129). If present, osteon banding was described and quantified.
RESULTS
Results indicated that 23 of 129 human cortical bone specimens exhibited osteon banding, representing 18% of the sample. Linear arrangements of primary and/or secondary osteons were observed in the following skeletal elements: temporal, parietal, frontal, occipital, clavicle, mandible, femur, tibia, ulna, second metatarsal, and sacrum.
DISCUSSION
The present work represents the first 3D examination of inter-element variation in osteon banding in adult human cortical bone. Findings indicate that the presence of multiple osteon bands in a single specimen is not diagnostic of nonhuman bone. As such, osteon banding categorically should not be taken as evidence of nonhuman bone in forensic and archaeological contexts.
Topics: Adult; Anthropology, Physical; Cortical Bone; Haversian System; Humans; Male; X-Ray Microtomography
PubMed: 28832945
DOI: 10.1002/ajpa.23297 -
The Journal of Experimental Biology Jun 2020Cortical bone remodeling is an ongoing process triggered by microdamage, where osteoclasts resorb existing bone and osteoblasts deposit new bone in the form of secondary...
Cortical bone remodeling is an ongoing process triggered by microdamage, where osteoclasts resorb existing bone and osteoblasts deposit new bone in the form of secondary osteons (Haversian systems). Previous studies revealed regional variance in Haversian systems structure and possibly material, between opposite cortices of the same bone. As bone mechanical properties depend on tissue structure and material, it is predicted that bone mechanical properties will vary in accordance with structural and material regional heterogeneity. To test this hypothesis, we analysed the structure, mineral content and compressive stiffness of secondary bone from the cranial and caudal cortices of the white-tailed deer proximal humerus. We found significantly larger Haversian systems and canals in the cranial cortex but no significant difference in mineral content between the two cortices. Accordingly, we found no difference in compressive stiffness between the two cortices and thus our working hypothesis was rejected. As the deer humerus is curved and thus likely subjected to bending during habitual locomotion, we expect that similar to other curved long bones, the cranial cortex of the deer humerus is likely subjected primarily to tensile strains and the caudal cortex is subject primarily to compressive strains. Consequently, our results suggest that strain magnitude (larger in compression) and sign (compression versus tension) affect the osteoclasts and osteoblasts differently in the basic multicellular unit. Our results further suggest that osteoclasts are inhibited in regions of high compressive strains (creating smaller Haversian systems) while the osteoid deposition and mineralization by osteoblasts is not affected by strain magnitude and sign.
Topics: Animals; Bone Remodeling; Deer; Haversian System; Humerus; Skull
PubMed: 32366689
DOI: 10.1242/jeb.225482 -
Journal of Forensic Sciences Jul 2020Aging adult skeletal material is a crucial component of building the biological profile of unknown skeletal remains, but many macro- and microscopic methods have...
Aging adult skeletal material is a crucial component of building the biological profile of unknown skeletal remains, but many macro- and microscopic methods have challenges regarding accuracy, precision, and replicability. This study developed a volumetric method to visualize and quantify histological remodeling events in three dimensions, using a two-dimensional serialized approach that applied circular polarizing microscopy and geographic information systems protocols. This approach was designed as a tool to extend current histological aging methodologies. Three serial transverse sections were obtained from a human femoral midshaft. A total sample size of 6847 complete osteons from the three sections was identified; 1229 osteons connected between all sections. The volume of all connected osteons was interpolated using ArcGIS area calculations and truncated cone geometric functions. Each section was divided into octants, and two random samples of 100 and of 30 connected osteons from each octant were generated. Osteon volume was compared between the octants for each random sample using ANOVA. Results indicated that the medial aspect had relative uniformity in osteon volume, whereas the lateral aspect showed high variability. The anterolateral-lateral octant had significantly smaller osteon volume, whereas the posterior-posterolateral octant had significantly larger osteon volume. Results also indicated that a minimum of 100 osteons is statistically more robust and more representative of normal osteon distribution and volume; the use of 30 osteons is insufficient. This research has demonstrated that osteon volume can be interpolated using spatial geometry and GIS applications and may be a tool to incorporate into adult age-at-death estimation techniques.
Topics: Age Determination by Skeleton; Bone Remodeling; Femur; Forensic Anthropology; Geographic Information Systems; Haversian System; Humans; Image Processing, Computer-Assisted; Microscopy
PubMed: 32092159
DOI: 10.1111/1556-4029.14305 -
BioEssays : News and Reviews in... Aug 2021Osteons are cylindrical structures of bone created by matrix resorbing osteoclasts, followed by osteoblasts that deposit new bone. Osteons align with the principal...
Osteons are cylindrical structures of bone created by matrix resorbing osteoclasts, followed by osteoblasts that deposit new bone. Osteons align with the principal loading direction and it is thought that the osteoclasts are directed by osteocytes, the mechanosensitive cells that reside inside the bone matrix. These osteocytes are presumably controlled by interstitial fluid flow, induced by the physiological loading of bones. Here I consider the stimulation of osteocytes while the osteon is closed by osteoblasts. In a conceptual finite element model, bone is considered a poro-elastic material and subjected to locomotion-induced loading conditions. It appears that the magnitude of flow is constant along the closing cone, while shear strain rate in the bone matrix diminishes linearly with the deposition of bone. This suggests that shear strain rate, rather than fluid flow, is the physical cue that controls osteocytes and bone deposition in newly formed osteons.
Topics: Bone and Bones; Haversian System; Osteoblasts; Osteoclasts; Osteocytes
PubMed: 34111316
DOI: 10.1002/bies.202000327 -
Journal of Biomechanics 2006The interfacial strength of secondary osteons from the diaphysis of the Thoroughbred equine third metacarpal was evaluated using the fiber pushout test. The pushout was...
The interfacial strength of secondary osteons from the diaphysis of the Thoroughbred equine third metacarpal was evaluated using the fiber pushout test. The pushout was performed on 300-500 microm sections of 4x4x15 mm bone blocks machined from four anatomic regions of the cortex. Pushout strength was evaluated from proximal to distal location within the diaphysis on four osteon types classified under polarized light on adjacent histologic sections from each block. The shear strength of the interfaces were estimated from shear lag theory. Differences were found in the interfacial strength of osteons based on appearance under polarized light with bright field having the highest interfacial strength (40.3 MPa). The lowest strength was found in the dark field osteons (22.8 MPa). The dorsal region had the highest shear strength and toughness compared to all other regions. The cement line and interlamellar interfaces are similar in strength, but exhibit regional dependence--specifically, the palmar region strength is less (17.5 MPa) than the osteon interlamellar interfaces (30.4 MPa) and osteon type dependent (alternating significantly weaker than other types). Histomorphometry revealed significant regional differences (p<0.0001) in osteon area fraction among the four osteon types as well as differences in the osteon diameter (p=0.01), with dorsal regions having larger osteons (170 microm) than the palmar region (151 microm). Fatigue life and fracture toughness of Haversian bone are reported in the literature to be regionally dependent and are known to be associated with osteon pullout--an osteon interfacial phenomenon. Therefore, the results presented in this study are important to further the understanding of the mechanisms of fragility and damage accumulation in cortical bone.
Topics: Animals; Haversian System; Horses; Microscopy, Electron, Scanning; Models, Biological; Stress, Mechanical; Tensile Strength
PubMed: 16019009
DOI: 10.1016/j.jbiomech.2005.05.006 -
Bone Sep 2008Osteon diameter is generally smaller in bone regions that experience larger strains. A mechanism relating osteon diameter to strain is as yet unknown. We propose that...
Osteon diameter is generally smaller in bone regions that experience larger strains. A mechanism relating osteon diameter to strain is as yet unknown. We propose that strain-induced osteocyte signals inhibit osteoclastic bone resorption. This mechanism was previously shown to produce load-aligned osteons in computer simulations. Now we find that it also predicts smaller osteon diameter for higher loads. Additionally, we find that our model predicts osteon development with two cutting cones, one moving up and one moving down the loading axis. Such 'double-ended osteons' were reported in literature as a common type of osteon development. Further, we find that a steep gradient in strain magnitude can result in an osteonal tunnel with continuous resorption along the less strained side, which corresponds to 'drifting osteons' reported in literature.
Topics: Animals; Biochemistry; Biomechanical Phenomena; Bone Remodeling; Bone and Bones; Compressive Strength; Computer Simulation; Haversian System; Humans; Models, Statistical; Osteoblasts; Osteoclasts; Osteocytes; Stress, Mechanical; Tensile Strength
PubMed: 18619937
DOI: 10.1016/j.bone.2008.05.015 -
Cells, Tissues, Organs 2010Pattern of osteonal classification referred to collagen fiber orientation in a human fibula was studied. Along the length of the whole bone, serial 100-microm parallel...
Pattern of osteonal classification referred to collagen fiber orientation in a human fibula was studied. Along the length of the whole bone, serial 100-microm parallel cross sections were obtained and analyzed by circularly polarized light microscopy. The distribution of 3 different kinds of osteons (transversal, alternated and longitudinal-hooped) depending on their collagen fiber orientation were analyzed to determine the effect of length, anatomical quadrant and cortical thickness. Referring to length, the 3 types of osteons appeared with approximately the same relative frequency, but when the symmetry of the fibula was considered and the length was expressed as distance from the bone mid-section, the alternated osteons are predominant in the mid-section. On the contrary, moving toward the epiphyses, the balance is inverted, and transversal together with longitudinal-hooped types become more frequent than the alternated type. Osteonal pattern distribution was not significantly affected by the anatomical quadrant of each section or by the thickness of the cortex. This observation seems to confirm that along the fibula shaft the orientation of collagen fibers within the osteons is consistent with the loading conditions which the bone undergoes.
Topics: Aged; Biomechanical Phenomena; Collagen; Diaphyses; Epiphyses; Female; Fibula; Haversian System; Humans; Microscopy, Polarization; Stress, Mechanical
PubMed: 19776542
DOI: 10.1159/000240045 -
Cells, Tissues, Organs 1999Drifting osteons were followed longitudinally through the cortex of human and baboon long bones using serial sections. Direction of transverse drift was recorded at...
Drifting osteons were followed longitudinally through the cortex of human and baboon long bones using serial sections. Direction of transverse drift was recorded at different cross-sectional levels of the same systems, and maximum angular change in drift direction was measured for each system. Most drifting osteons exhibit: (1) substantial ( approximately 90 degrees ) variation in the direction of transverse drift along their longitudinal axes, (2) intermittent regions of concentric (type I) morphology, and (3) change in drift direction over time, evident at single cross-sectional levels. Additionally, 3-dimensional reconstruction reveals that the basic multicellular units (BMUs) responsible for creating drifting osteons are morphologically distinct from the cutting-cone-closing-cone model BMUs that produce other types of osteons. The stimulus involved in the activation and guidance of drifting BMUs is unclear, but it is likely that the complex strain environment experienced by long bone cortices exerts a significant influence on their morphology.
Topics: Adolescent; Animals; Bone Remodeling; Child; Female; Fibula; Haversian System; Humans; Leg; Male; Metatarsal Bones; Papio
PubMed: 10436327
DOI: 10.1159/000016659 -
Journal of Forensic Sciences Mar 2016Many histological methods in forensic anthropology utilize combinations of traditional histomorphometric parameters which may not accurately describe the morphology of...
Many histological methods in forensic anthropology utilize combinations of traditional histomorphometric parameters which may not accurately describe the morphology of microstructural features. Here, we report the novel application of a geometric morphometric method suitable when considering structures without anatomically homologous landmarks for the quantification of complete secondary osteon size and morphology. The method is tested for its suitability in the measurement of intact secondary osteons using osteons digitized from transverse femoral diaphyseal sections prepared from two human individuals. The results of methodological testing demonstrate the efficacy of the technique when applied to intact secondary osteons. In providing accurate characterization of micromorphology within the robust mathematical framework of geometric morphometrics, this method may surpass traditional histomorphometric variables currently employed in forensic research and practice. A preliminary study of the intersectional histomorphometric variation within the femoral diaphysis is made using this geometric histomorphometric method to demonstrate its potential.
Topics: Aged, 80 and over; Anatomic Landmarks; Bone Remodeling; Diaphyses; Female; Femur; Forensic Anthropology; Fourier Analysis; Haversian System; Humans; Image Processing, Computer-Assisted; Mathematical Concepts; Microscopy
PubMed: 26478136
DOI: 10.1111/1556-4029.12966