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Journal of the Mechanical Behavior of... Feb 2023The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at...
The transverse tensile strength of a naturally fallen red deer antler (Cervus Elaphus) was determined through indirect Brazilian tests using dry disc-shape specimens at quasi-static and high strain rates. Dynamic Brazilian tests were performed in a compression Split-Hopkinson Pressure Bar. Quasi-static tensile and indirect Brazilian tests were also performed along the osteon growth direction for comparison. The quasi-static transverse tensile strength ranged 31.5-44.5 MPa. The strength increased to 83 MPa on the average in the dynamic Brazilian tests, proving a rate sensitive transverse strength. The quasi-static tensile strength in the osteon growth direction was however found comparably higher, 192 MPa. A Weibull analysis indicated a higher tensile ductility in the osteon growth direction than in the transverse to the osteon growth direction. The microscopic analysis of the quasi-static Brazilian test specimens (tensile strain along the osteon growth direction) revealed a micro-cracking mechanism operating by the crack deflection/twisting at the lacunae in the concentric lamellae region and at the interface between concentric lamellae and interstitial lamellae. On the other side, the specimens in the transverse direction fractured in a more brittle manner by the separation/delamination of the concentric lamellae and pulling of the interstitial lamellae. The detected increase in the transverse strength in the high strain rate tests was further ascribed to the pull and fracture of the visco-plastic collagen fibers in the interstitial lamellae. This was also confirmed microscopically; the dynamically tested specimens exhibited flatter fracture surfaces.
Topics: Animals; Haversian System; Antlers; Brazil; Deer; Fractures, Bone
PubMed: 36610280
DOI: 10.1016/j.jmbbm.2023.105648 -
Anatomical Record (Hoboken, N.J. : 2007) Mar 2016Previous research demonstrates that the size of secondary osteons varies considerably between individuals, though what factors act in the delineation of osteon size...
Previous research demonstrates that the size of secondary osteons varies considerably between individuals, though what factors act in the delineation of osteon size remain uncertain. This study explores the influence of age, sex, percent cortical area (%Ct.Ar), percent cortical porosity (%Po.Ar), and loading environment on osteon area (On.Ar) in human ribs. The sample consisted of midshaft 6(th) ribs from 80 individuals, 6-94 years of age. T-tests demonstrated no significant differences in On.Ar between the sexes (P=0.383). Age showed a significant correlation with both %Ct.Ar and %Po.Ar, so a hierarchical regression model was used to control for the effects of age on the other variables. Results indicate that age is the most significant factor of those tested in this study (P=0.004), with %Ct.Ar playing a much smaller but still significant role (P=0.014), while %Po.Ar had no significant influence on On.Ar (P=0.443). Age demonstrates an inverse relationship with On.Ar, while %Ct.Ar has a direct relationship with On.Ar. Significant differences in On.Ar between the pleural and cutaneous cortices are attributed to variation in %Ct.Ar of each cortex. Therefore, age and %Ct.Ar account for the majority of osteon size variability in this study, although it is likely genetics play an important role as well. Understanding the biological mechanisms that act in remodeling and determine osteon size is essential for accurately addressing and interpreting histological findings, work that is invaluable in its implications for bone biology.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Child; Female; Haversian System; Humans; Male; Middle Aged; Ribs; Young Adult
PubMed: 26692499
DOI: 10.1002/ar.23305 -
Journal of Anatomy Oct 2015The primary microstructural unit of cortical bone, the secondary osteon or Haversian system, is widely assumed to have a cylindrical shape. It is generally accepted that...
The primary microstructural unit of cortical bone, the secondary osteon or Haversian system, is widely assumed to have a cylindrical shape. It is generally accepted that osteons are roughly circular in cross-section and deviations from circularity have been attributed to deviations from longitudinal orientation. To our knowledge this idealized geometric relationship, which assumes osteons are perfect cylinders, has not been rigorously explored. As such, we sought to explore two research questions: (i) Does the orientation of osteons in 3D explain variation in shapes visualized in 2D? (ii) Can differences in osteon 3D orientation explain previously reported age-related differences observed in their 2D cross-sectional shape (e.g. more circular shape and decreased area with age)? To address these questions we utilized a combination of 2D histology to identify osteon shape and superimposed micro-computed tomography data to assess osteon orientation in 3D based upon the osteonal canal. Shape was assessed by the inverse of Aspect Ratio (On.AspR(-1), based on a fitted ellipse) - which ranged from 0 (infinitely elongated shape) to 1 (perfectly circular). A sample (n = 27) of human female anterior femoral cortical bone samples from across the human lifespan (20-87 years) were included in the analysis, which involved 1418 osteons. The overall mean measure of On.AspR(-1) was 0.703 (1.42 Aspect Ratio). Mean osteon orientation was 79.1° (90° being longitudinal). While we anticipated a positive relation between orientation and On.AspR(-1), we found the opposite - a weak negative correlation (with more oblique 3D osteon alignment, the 2D shape became more circular as reflected by increased On.AspR(-1)). When analysis of covariance was performed with age and orientation as covariates, the negative relation with orientation was replaced by a significant relation with age alone. This relation with age accounted for 41% of the variation of On.AspR(-1). The results revealed that osteons, on average, are not circular in cross-section and that 3D orientation cannot account for deviation from circular shape. Osteons thus are strictly speaking not cylinders, as they tend to have elliptical cross-sections. We observed that osteons did become less elliptical in cross-section with age independent of orientation - suggesting this is a real change in morphology.
Topics: Adult; Aged; Aged, 80 and over; Aging; Bone Remodeling; Female; Femur; Haversian System; Histological Techniques; Humans; Imaging, Three-Dimensional; Male; Middle Aged; X-Ray Microtomography; Young Adult
PubMed: 26249538
DOI: 10.1111/joa.12357 -
Journal of Bone and Mineral Research :... Jun 2019DMP1 (dentin matrix protein 1) is an extracellular matrix protein highly expressed in bones. Studies of Dmp1 knockout (KO) mice led to the discovery of a rare autosomal...
DMP1 (dentin matrix protein 1) is an extracellular matrix protein highly expressed in bones. Studies of Dmp1 knockout (KO) mice led to the discovery of a rare autosomal recessive form of hypophosphatemic rickets (ARHR) caused by DMP1 mutations. However, there are limitations for using this mouse model to study ARHR, including a lack of Haversian canals and osteons (that occurs only in large mammalian bones), high levels of fibroblast growth factor 23 (FGF23), and PTH, in comparison with a moderate elevation of FGF23 and unchanged PTH in human ARHR patients. To better understand this rare disease, we deleted the DMP1 gene in rabbit using CRISPR/Cas9. This rabbit model recapitulated many features of human ARHR, such as the rachitic rosary (expansion of the anterior rib ends at the costochondral junctions), moderately increased FGF23, and normal PTH levels, as well as severe defects in bone mineralization. Unexpectedly, all DMP1 KO rabbits died by postnatal week 8. They developed a severe bone microarchitecture defect: a major increase in the central canal areas of osteons, concurrent with massive accumulation of osteoid throughout all bone matrix (a defect in mineralization), suggesting a new paradigm, where rickets is caused by a combination of a defect in bone microarchitecture and a failure in mineralization. Furthermore, a study of DMP1 KO bones found accelerated chondrogenesis, whereas ARHR has commonly been thought to be involved in reduced chondrogenesis. Our findings with newly developed DMP1 KO rabbits suggest a revised understanding of the mechanism underlying ARHR. © 2019 American Society for Bone and Mineral Research.
Topics: Animals; Biomarkers; Bone Matrix; CRISPR-Cas Systems; Calcification, Physiologic; Chondrogenesis; Extracellular Matrix Proteins; Familial Hypophosphatemic Rickets; Femur; Fibroblast Growth Factor-23; Gait; Gene Deletion; Gene Knockout Techniques; Haversian System; Humans; Models, Biological; Osteogenesis; Rabbits; Tibia; X-Ray Microtomography
PubMed: 30827034
DOI: 10.1002/jbmr.3683 -
ACS Applied Materials & Interfaces May 2015Modular tissue engineering holds great potential in regenerating natural complex tissues by engineering three-dimensional modular scaffolds with predefined geometry and...
Modular tissue engineering holds great potential in regenerating natural complex tissues by engineering three-dimensional modular scaffolds with predefined geometry and biological characters. In modular tissue-like construction, a scaffold with an appropriate mechanical rigidity for assembling fabrication and high biocompatibility for cell survival is the key to the successful bioconstruction. In this work, a series of composite hydrogels (GH0, GH1, GH2, and GH3) based on a combination of methacrylated gelatin (GelMA) and hydroxyapatite (HA) was exploited to enhance hydrogel mechanical rigidity and promote cell functional expression for osteon biofabrication. These composite hydrogels presented a lower swelling ratio, higher mechanical moduli, and better biocompatibility when compared to the pure GelMA hydrogel. Furthermore, on the basis of the composite hydrogel and photolithograph technology, we successfully constructed an osteon-like concentric double-ring structure in which the inner ring encapsulating human umbilical vascular endothelial cells (HUVECs) was designed to imitate blood vessel tubule while the outer ring encapsulating human osteoblast-like cells (MG63s) acts as part of bone. During the coculture period, MG63s and HUVECs exhibited not only satisfying growth status but also the enhanced genic expression of osteogenesis-related and angiogenesis-related differentiations. These results demonstrate this GelMA-HA composite hydrogel system is promising for modular tissue engineering.
Topics: Biomimetic Materials; Bone Substitutes; Cell Line; Cross-Linking Reagents; Durapatite; Equipment Design; Equipment Failure Analysis; Gelatin; Haversian System; Humans; Hydrogels; Light; Materials Testing; Methacrylates; Nanoconjugates; Osteoblasts; Osteogenesis; Tissue Engineering; Tissue Scaffolds
PubMed: 25928732
DOI: 10.1021/acsami.5b01433 -
Bone Mar 2009Birefringence variations in circularly polarized light (CPL) images of thin plane-parallel sections of cortical bone can be used to quantify regional differences in...
Birefringence variations in circularly polarized light (CPL) images of thin plane-parallel sections of cortical bone can be used to quantify regional differences in predominant collagen fiber orientation (CFO). Using CPL images of equine third metacarpals (MC3s), R.B. Martin, V.A. Gibson, S.M. Stover, J.C. Gibeling, and L.V. Griffin. (40) described six secondary osteon variants ('morphotypes') and suggested that differences in their regional prevalence affect fatigue resistance and toughness. They devised a numerical osteon morphotype score (MTS) for quantifying regional differences in osteon morphotypes. We have observed that a modification of this score could significantly improve its use for interpreting load history. We hypothesized that our modified osteon MTS would more accurately reveal differences in osteon MTSs between opposing "tension" and "compression" cortices of diaphyses of habitually bent bones. This was tested using CPL images in transverse sections of calcanei from sheep, deer, and horses, and radii from sheep and horses. Equine MC3s and sheep tibiae were examined as controls because they experience comparatively greater load complexity that, because of increased prevalence of torsion/shear, would not require regional mechanical enhancements provided by different osteon morphotypes. Predominant CFO, which can reliably reflect adaptation for a regionally prevalent strain mode, was quantified as mean gray levels from birefringence of entire images (excluding pore spaces) in anterior, posterior, medial, and lateral cortices. Results showed that, in contrast to the original scoring scheme of Martin et al., the modified scheme revealed significant anterior/posterior differences in osteon MTSs in nearly all "tension/compression" bones (p<0.0001), but not in equine MC3s (p=0.30) and sheep tibiae (p=0.35). Among habitually bent bones, sheep radii were the exception; relatively lower osteon populations and the birefringence of the primary bone contributed to this result. Correlations between osteon MTSs using the scoring scheme of Martin et al. with CFO data from all regions of each bone invariably demonstrated weak-to-moderate negative correlations. This contrasts with typically high positive correlations between modified osteon MTSs and regional CFO. These results show that the modified osteon MTS can be a strong correlate of predominant CFO and of the non-uniform strain distribution produced by habitual bending.
Topics: Adaptation, Physiological; Animals; Calcaneus; Deer; Haversian System; Horses; Metacarpal Bones; Microscopy, Polarization; Radius; Sheep; Stress, Mechanical; Weight-Bearing
PubMed: 19049911
DOI: 10.1016/j.bone.2008.10.053 -
Journal of Anatomy Jun 2019Bone can adapt to its habitual load history at various levels of its hierarchical structural and material organization. However, it is unclear how strongly a bone's...
Collagen fiber orientation pattern, osteon morphology and distribution, and presence of laminar histology do not distinguish torsion from bending in bat and pigeon wing bones.
Bone can adapt to its habitual load history at various levels of its hierarchical structural and material organization. However, it is unclear how strongly a bone's structural characteristics (e.g. cross-sectional shape) are linked to microstructural characteristics (e.g. distributions of osteons and their vascular canals) or ultrastructural characteristics [e.g. patterns of predominant collagen fiber orientation (CFO)]. We compared the cross-sectional geometry, microstructure and ultrastructure of pigeon (Columba livia domestica) humeri, and third metacarpals (B3M) and humeri of a large bat (Pteropus poliocephalus). The pigeon humerus is habitually torsionally loaded, and has unremodeled ('primary') bone with vessels (secondary osteons are absent) and high 'laminarity' because a large majority of these vessels course circularly with respect to the bone's external surface. In vivo data show that the bat humerus is also habitually torsionally loaded; this contrasts with habitual single-plane bending of the B3M, where in vivo data show that it oscillates back and forth in the same direction. In contrast to pigeon humeri where laminar bone is present, the primary tissue of these bat bones is largely avascular, but secondary osteons are present and are usually in the deeper cortex. Nevertheless, the load history of humeri of both species is prevalent/predominant torsion, producing diffusely distributed shear stresses throughout the cross-section. We tested the hypothesis that despite microstructural/osteonal differences in these pigeon and bat bones, they will have similar characteristics at the ultrastructural level that adapt each bone for its load history. We postulate that predominant CFO is this characteristic. However, even though data reported in prior studies of bones of non-flying mammals suggest that CFO would show regional variations in accordance with the habitual 'tension regions' and 'compression regions' in the direction of unidirectional habitual bending, we hypothesized that alternating directions of bending within the same plane would obviate these regional/site-specific adaptations in the B3M. Similarly, but for other reasons, we did not expect regional variations in CFO in the habitually torsionally loaded bat and pigeon humeri because uniformly oblique-to-transverse CFO is the adaptation expected for the diffusely distributed shear stresses produced by torsion/multidirectional loads. We analyzed transverse sections from mid-diaphyses of adult bones for CFO, secondary osteon characteristics (size, shape and population density), cortical thickness in quadrants of the cortex, and additional measures of cross-sectional geometry, including the degree of circular shape that can help distinguish habitual torsion from bending. Results showed the expected lack of regional CFO differences in quasi-circular shaped, and torsionally loaded, pigeon and bat humeri. As expected, the B3M also lacked CFO variations between the opposing cortices along the plane of bending, and the quasi-elliptical cross-sectional shape and regional microstructural/osteonal variations expected for bending were not found. These findings in the B3M show that uniformity in CFO does not always reflect habitual torsional loads. Osteon morphology and distribution, and presence of laminar histology also do not distinguish torsion from bending in these bat and pigeon wing bones.
Topics: Adaptation, Physiological; Animals; Biomechanical Phenomena; Chiroptera; Collagen; Columbidae; Haversian System; Stress, Mechanical; Wings, Animal
PubMed: 30924933
DOI: 10.1111/joa.12981 -
Journal of the Mechanical Behavior of... Sep 2014In this work, we present two strategies for the numerical modelling of microcracks and damage within an osteon. A numerical model of a single osteon under compressive...
In this work, we present two strategies for the numerical modelling of microcracks and damage within an osteon. A numerical model of a single osteon under compressive diametral load is developed, including lamellae organized concentrically around the haversian canal and the presence of lacunae. Elastic properties have been estimated from micromechanical models that consider the mineralized collagen fibrils reinforced with hydroxyapatite crystals and the dominating orientation of the fibrils in each lamella. Microcracks are simulated through the node release technique, enabling propagation along the lamellae interfaces by application of failure criteria initially conceived for composite materials, in particular the Brewer and Lagacé criterion for delamination. A second approach is also presented, which is based on the progressive degradation of the stiffness at the element level as the damage increases. Both strategies are discussed, showing a good agreement with experimental evidence reported by other authors. It is concluded that interlaminar shear stresses are the main cause of failure of an osteon under compressive diametral load.
Topics: Adolescent; Adult; Biomechanical Phenomena; Collagen; Compressive Strength; Elasticity; Finite Element Analysis; Haversian System; Humans; Mechanical Phenomena; Minerals; Young Adult
PubMed: 24907671
DOI: 10.1016/j.jmbbm.2014.05.006 -
Calcified Tissue Research Jul 1975Analysis of partial cross sections of 101 human tibiae indicated that osteon remodeling in the outer cortex is affected by age. The frequency of resorption spaces...
Analysis of partial cross sections of 101 human tibiae indicated that osteon remodeling in the outer cortex is affected by age. The frequency of resorption spaces remained constant throughout life suggesting no loss of osteoclast function with age. However, the frequency of both forming osteons and osteons which were structurally complete but not completely mineralized increased with age. This suggests that protein matrix synthesis by osteoblasts slows with age and that initial mineralization, possibly mediated by osteroblasts, and final mineralization, possibly mediated by osteocytes, becomes increasingly deficient with increasing age. The frequency of osteons which have dense (sclerotic) inner lamellae decreases with age. This supports a hypothesis that such lamellae are functional, perhaps representing a specialized, labile, mineral phase and that osteons having this feature become less frequent as part of the general degenerative changes associated with aging.
Topics: Aging; Bone Resorption; Calcification, Physiologic; Haversian System; Humans; Statistics as Topic; Tibia
PubMed: 1148890
DOI: 10.1007/BF02546224 -
American Journal of Physical... Dec 2006Variation in the size of structures within mature cortical bone is relevant to our understanding of apparent differences between human samples, and it is relevant to the...
Variation in the size of structures within mature cortical bone is relevant to our understanding of apparent differences between human samples, and it is relevant to the development of histologically based age-estimation methods. It was proposed that variation may reflect effects of physical activity, through biomechanical and/or metabolic mechanisms. If these factors are local, femoral osteon area (On.Ar) should be more histologically variable than On.Ar in ribs. Ribs should show a higher variation in Haversian canal area (H.Ar) if they are sites of more remodeling activity and hence of arrested refilling of secondary osteons at time of death. This study compares On.Ar and H.Ar of secondary osteons from femora (15) and ribs (29) from 44 Holocene (Later Stone Age) foragers from South Africa (M = 19, F = 25) to values from paired femora and ribs from historic samples (Spitalfields and St. Thomas, 20 pairs from each). Fixed-effects analysis of variance demonstrates rib On.Ar to be significantly smaller than femur, but with no sex or age effects. The femur-to-rib On.Ar ratio is lower for the Holocene foragers than for the two modern samples because of relatively large rib On.Ar. Femora and ribs from the same skeleton normally show femoral On.Ar larger than rib On.Ar (37/44 pairs). Mean femoral values of On.Ar are more diverse than rib On.Ar values, but within-sample coefficients of variation are similar. Values for H.Ar are highly variable and do not reflect anatomical site, age, sex, or population effects. The patterning of osteon size does not appear to be linked to physical activity or to different rates of metabolic activity within the skeleton, at least not in a straightforward way.
Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aging; Anthropometry; Female; Femur; Haversian System; Humans; Male; Middle Aged; Osteocytes; Paleontology; Ribs; Sex Characteristics
PubMed: 16685724
DOI: 10.1002/ajpa.20454