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Journal of the Mechanical Behavior of... May 2024A 2D plane strain extended finite element method (XFEM) model was developed to simulate three-point bending fracture toughness tests for human bone conducted in hydrated...
A 2D plane strain extended finite element method (XFEM) model was developed to simulate three-point bending fracture toughness tests for human bone conducted in hydrated and dehydrated conditions. Bone microstructures and crack paths observed by micro-CT imaging were simulated using an XFEM damage model. Critical damage strains for the osteons, matrix, and cement lines were deduced for both hydrated and dehydrated conditions and it was found that dehydration decreases the critical damage strains by about 50%. Subsequent parametric studies using the various microstructural models were performed to understand the impact of individual critical damage strain variations on the fracture behavior. The study revealed the significant impact of the cement line critical damage strains on the crack paths and fracture toughness during the early stages of crack growth. Furthermore, a significant sensitivity of crack growth resistance and crack paths on critical strain values of the cement lines was found to exist for the hydrated environments where a small change in critical strain values of the cement lines can alter the crack path to give a significant reduction in fracture resistance. In contrast, in the dehydrated state where toughness is low, the sensitivity to changes in critical strain values of the cement lines is low. Overall, our XFEM model was able to provide new insights into how dehydration affects the micromechanisms of fracture in bone and this approach could be further extended to study the effects of aging, disease, and medical therapies on bone fracture.
Topics: Humans; Dehydration; Models, Biological; Cortical Bone; Bone and Bones; Fractures, Bone
PubMed: 38493561
DOI: 10.1016/j.jmbbm.2024.106468 -
Bone Apr 2024Chronic heavy alcohol consumption may influence the skeleton by suppressing intracortical bone remodeling which may impact the quality of bone and its mechanical...
Chronic heavy alcohol consumption may influence the skeleton by suppressing intracortical bone remodeling which may impact the quality of bone and its mechanical properties. However, this aspect has not been thoroughly assessed in either humans or animal models whose cortical bone microstructure resembles the microstructure of human cortical bone. The current study is the first to investigate the effects of chronic heavy alcohol consumption on various mechanical properties of bone in a non-human primate model with intracortical remodeling. Male rhesus macaques (5.3 years old at the initiation of treatment) were induced to drink alcohol and then given the choice to voluntarily self-administer water or ethanol (4 % w/v) for approximately 14 months, followed by three abstinence phases (lasting 34, 41, and 39-46 days) with approximately 3 months of ethanol access in between. During the initial 14 months of open-access, monkeys in the alcohol group consumed an average of 2.9 ± 0.8 g/kg/d ethanol (mean ± SD) resulting in a blood ethanol concentration of 89 ± 47 mg/dl in longitudinal samples taken at 7 h after the daily sessions began. To understand the impact of alcohol consumption on material properties, various mechanical tests were conducted on the distal tibia diaphysis of 2-5 monkeys per test group, including dynamic mechanical analysis (DMA) testing, nano-indentation, microhardness testing, compression testing, and fracture resistance curve (R-curve) testing. Additionally, compositional analyses were performed using Fourier-transform infrared (FTIR) spectroscopy. Significant differences in microhardness, compressive stress-strain response, and composition were not observed with alcohol consumption, and only minor differences were detected in hardness and elastic modulus of the matrix and osteons from nanoindentation. Furthermore, the R-curves of both groups overlapped, with similar crack initiation toughness, despite a significant decrease in crack growth toughness (p = 0.032) with alcohol consumption. However, storage modulus (p = 0.029) and loss factor (p = 0.015) from DMA testing were significantly increased in the alcohol group compared to the control group, while loss modulus remained unchanged. These results indicate that heavy alcohol consumption may have only a minor influence on the material properties and the composition of cortical bone in young adult male rhesus macaques.
Topics: Animals; Male; Macaca mulatta; Bone and Bones; Cortical Bone; Alcohol Drinking; Ethanol
PubMed: 38325648
DOI: 10.1016/j.bone.2024.117041 -
Journal of Morphology Jul 2023Bone is a dynamic tissue capable of adapting to its loading environment, allowing the skeleton to remain structurally sound throughout life. One way adaptation occurs in...
Bone is a dynamic tissue capable of adapting to its loading environment, allowing the skeleton to remain structurally sound throughout life. One way adaptation occurs in mammals is via Haversian remodeling: the site-specific, coupled resorption and formation of cortical bone that results in secondary osteons. Remodeling occurs at a baseline rate in most mammals, but it also occurs in relation to strain by repairing deleterious microdamage. Yet, not all animals with bony skeletons remodel. Among mammals, there is inconsistent or absent evidence for Haversian remodeling among monotremes, insectivores, chiropterans, cingulates, and rodents. Three possible explanations for this disparity are discussed: the capacity for Haversian remodeling, body size as a constraint, and age and lifespan as constraints. It is generally accepted, although not thoroughly documented, that rats (a common model used in bone research) do not typically exhibit Haversian remodeling. The present aim is to more specifically test the hypothesis that rats of advanced age do remodel intracortically because of the longer lifespan over which baseline remodeling could occur. Most published histological descriptions of rat bone only include young (3-6 months) rats. Excluding aged rats possibly overlooks a transition from modeling (i.e., bone growth) to Haversian remodeling as the primary mode of bone adaptation. Here, midshaft and distal femora (typical sites for remodeling in other mammals) of 24-month-old rats were examined for presence of secondary osteons. None were found, suggesting that Haversian remodeling does not occur in rats under normal physiological conditions at any age. A likely explanation is that modeling of cortical bone continues throughout most of the short rat lifespan, negating the stimulus for Haversian remodeling. Thorough sampling of key rodent taxa of varying body sizes and lifespans is key to elucidating the reasons why (i.e., body size, age/lifespan, phylogenetic factors) Haversian remodeling might not occur in all mammals.
Topics: Rats; Animals; Longevity; Haversian System; Phylogeny; Mammals; Femur
PubMed: 37313764
DOI: 10.1002/jmor.21600 -
PloS One 2024Osteocyte lacuno-canalicular network (LCN) is comprised of micrometre-sized pores and submicrometric wide channels in bone. Accumulating evidence suggests multiple...
Osteocyte lacuno-canalicular network (LCN) is comprised of micrometre-sized pores and submicrometric wide channels in bone. Accumulating evidence suggests multiple functions of this network in material transportation, mechanobiological signalling, mineral homeostasis and bone remodelling. Combining rhodamine staining and confocal laser scanning microscopy, the longitudinal cross-sections of six mouse tibiae were imaged, and the connectome of the network was quantified with a focus on the spatial heterogeneities of network density, connectivity and length of canaliculi. In-vivo loading and double calcein labelling on these tibiae allowed differentiating the newly formed bone from the pre-existing regions. The canalicular density of the murine cortical bone varied between 0.174 and 0.243 μm/μm3, and therefore is three times larger than the corresponding value for human femoral midshaft osteons. The spatial heterogeneity of the network was found distinctly more pronounced across the cortex than along the cortex. We found that in regions with a dense network, the LCN conserves its largely tree-like character, but increases the density by including shorter canaliculi. The current study on healthy mice should serve as a motivating starting point to study the connectome of genetically modified mice, including models of bone diseases and of reduced mechanoresponse.
Topics: Animals; Osteocytes; Mice; Connectome; Tibia; Mice, Inbred C57BL; Microscopy, Confocal; Humans
PubMed: 38743675
DOI: 10.1371/journal.pone.0303515 -
Journal of the Mechanical Behavior of... Feb 2024Tissue fixation is a prevalent method for bone conservation. Bone biopsies are typically fixed in formalin, dehydrated in ethanol, and infiltrated with polymethyl...
Tissue fixation is a prevalent method for bone conservation. Bone biopsies are typically fixed in formalin, dehydrated in ethanol, and infiltrated with polymethyl methacrylate (PMMA) Since some experiments can only be performed on fixed bone samples, it is essential to understand how fixation affects the measured material properties. The aim of this study was to quantify the influence of tissue fixation on the mechanical properties of cortical ovine bone at the extracellular matrix (ECM) level with state-of-the-art micromechanical techniques. A small section from the middle of the diaphysis of two ovine tibias (3.5 and 5.5 years old) was cut in the middle and polished on each side, resulting in a pair of mirrored surfaces. For each pair, one specimen underwent a fixation protocol involving immersion in formalin, dehydration with ethanol, and infiltration with PMMA. The other specimen (mirrored) was air-dried. Six osteons were selected in both pairs, which could be identified in both specimens. The influence of fixation on the mechanical properties was first analyzed using micropillar compression tests and nanoindentation in dry condition. Additionally, changes in the degree of mineralization were evaluated with Raman spectroscopy in both fixed and native bone ECM. Finally, micro tensile experiments were conducted in the 3.5-year fixed ovine bone ECM and compared to reported properties of unfixed dry ovine bone ECM. Interestingly, we found that tissue fixation does not alter the mechanical properties of ovine cortical bone ECM compared to experiments in dry state. However, animal age increases the degree of mineralization (p = 0.0159) and compressive yield stress (p = 0.041). Tissue fixation appears therefore as a valid conservation technique for investigating the mechanical properties of dehydrated bone ECM.
Topics: Sheep; Animals; Tissue Fixation; Polymethyl Methacrylate; Formaldehyde; Ethanol; Extracellular Matrix
PubMed: 38128472
DOI: 10.1016/j.jmbbm.2023.106294 -
Journal of the Mechanical Behavior of... Jul 2024The present study simulates the fracture behavior of diabetic cortical bone with high levels of advanced glycation end-products (AGEs) under dynamic loading. We consider...
The present study simulates the fracture behavior of diabetic cortical bone with high levels of advanced glycation end-products (AGEs) under dynamic loading. We consider that the increased AGEs in diabetic cortical bone degrade the materials heterogeneity of cortical bone through a reduction in critical energy release rates of the microstructural features. To simulate the initiation and propagation of cracks, we implement a phase field fracture framework on 2D models of human tibia cortical microstructure. The simulations show that the mismatch between the fracture properties (e.g., critical energy release rate) of osteons and interstitial tissue due to high AGEs contents can change crack growth trajectories. The results show crack branching in the cortical microstructure under dynamic loading is affected by the mismatches related to AGEs. In addition, we observe cortical features such as osteons and cement lines can prevent multiple cracking under dynamic loading even with changing the mismatches due to high AGEs. Furthermore, under dynamic loading, some toughening mechanisms can be activated and deactivated with different AGEs contents. In conclusion, the current findings present that the combination of the loading type and materials heterogeneity of microstructural features can change the fracture response of diabetic cortical bone and its fragility.
Topics: Humans; Cortical Bone; Glycation End Products, Advanced; Weight-Bearing; Biomechanical Phenomena; Fractures, Bone; Tibia; Finite Element Analysis; Stress, Mechanical
PubMed: 38759587
DOI: 10.1016/j.jmbbm.2024.106577 -
Journal of Structural Biology Mar 2024The palette of mineralized tissues in fish is wide, and this is particularly apparent in fish dentin. While the teeth of all vertebrates except fish contain a single...
The palette of mineralized tissues in fish is wide, and this is particularly apparent in fish dentin. While the teeth of all vertebrates except fish contain a single dentinal tissue type, called orthodentin, dentin in the teeth of fish can be one of several different tissue types. The most common dentin type in fish is orthodentin. Orthodentin is characterized by several key structural features that are fundamentally different from those of bone and from those of osteodentin. Osteodentin, the second-most common dentin type in fish (based on the tiny fraction of fish species out of ∼30,000 extant fish species in which tooth structure was so far studied), is found in most Selachians (sharks and rays) as well as in several teleost species, and is structurally different from orthodentin. Here we examine the hypothesis that osteodentin is similar to anosteocytic bone tissue in terms of its micro- and nano-structure. We use Focused Ion Beam-Scanning Electron Microscopy (FIB/SEM), as well as several other high-resolution imaging techniques, to characterize the 3D architecture of the three main components of osteodentin (denteons, inter-denteonal matrix, and the transition zone between them). We show that the matrix of osteodentin, although acellular, is extremely similar to mammalian osteonal bone matrix, both in general morphology and in the three-dimensional nano-arrangement of its mineralized collagen fibrils. We also document the presence of a complex network of nano-channels, similar to such networks recently described in bone. Finally, we document the presence of strings of hyper-mineralized small 'pearls' which surround the denteonal canals, and characterize their structure.
Topics: Animals; Wolves; Tooth; Bone and Bones; Fishes; Dentin; Microscopy, Electron, Scanning
PubMed: 38224900
DOI: 10.1016/j.jsb.2024.108062 -
Journal of Anatomy Nov 2023We analyzed pedicle bone from roe bucks that had died around antler casting or shortly before or during the rutting period. Pedicles obtained around antler casting were...
We analyzed pedicle bone from roe bucks that had died around antler casting or shortly before or during the rutting period. Pedicles obtained around antler casting were highly porous and showed signs of intense osteoclastic activity that had caused the formation of an abscission line. Following the detachment of the antler plus a portion of pedicle bone, osteoclastic activity in the pedicles continued for some time, and new bone was deposited onto the separation plane of the pedicle stump, leading to partial pedicle restoration. Pedicles obtained around the rutting period were compact structures. The newly formed, often very large secondary osteons, which had filled the resorption cavities, exhibited a lower mineral density than the persisting older bone. The middle zones of the lamellar infilling frequently showed hypomineralized lamellae and enlarged osteocyte lacunae. This indicates a deficiency in mineral elements during the formation of these zones that occurred along with peak antler mineralization. We suggest that growing antlers and compacting pedicles compete for mineral elements, with the rapidly growing antlers being the more effective sinks. The competition between the two simultaneously mineralizing structures is probably more severe in Capreolus capreolus than in other cervids. This is because roe bucks regrow their antlers during late autumn and winter, a period of limited food and associated mineral supply. The pedicle is a heavily remodeled bone structure with distinct seasonal variation in porosity. Pedicle remodeling differs in several aspects from the normal bone remodeling process in the mammalian skeleton.
Topics: Animals; Antlers; Deer; Bone and Bones; Bone Resorption; Minerals
PubMed: 37278321
DOI: 10.1111/joa.13908 -
Bone Nov 2023Basic Multicellular Units (BMUs) conduct bone remodeling, a critical process of tissue turnover which, if imbalanced, can lead to disease, including osteoporosis....
Basic Multicellular Units (BMUs) conduct bone remodeling, a critical process of tissue turnover which, if imbalanced, can lead to disease, including osteoporosis. Parathyroid hormone (PTH 1-34; Teriparatide) is an osteoanabolic treatment for osteoporosis; however, it elevates the rate of intra-cortical remodeling (activation frequency) leading, at least transiently, to increased porosity. The purpose of this study was to test the hypothesis that PTH not only increases the rate at which cortical BMUs are initiated but also increases their progression (Longitudinal Erosion Rate; LER). Two groups (n = 7 each) of six-month old female New Zealand white rabbits were both administered 30 μg/kg of PTH once daily for a period of two weeks to induce remodeling. Their distal right tibiae were then imaged in vivo by in-line phase contrast micro-CT at the Canadian Light Source synchrotron. Over the following two weeks the first group (PTH) received continued daily PTH while the second withdrawal group (PTHW) was administrated 0.9 % saline. At four weeks all animals were euthanized, their distal tibiae were imaged by conventional micro-CT ex vivo and histomorphometry was performed. Matching micro-CT datasets (in vivo and ex vivo) were co-registered in 3D and LER was measured from 612 BMUs. Counter to our hypothesis, mean LER was lower (p < 0.001) in the PTH group (30.19 ± 3.01 μm/day) versus the PTHW group (37.20 ± 2.77 μm/day). Despite the difference in LER, osteonal mineral apposition rate (On.MAR) did not differ between groups indicating the anabolic effect of PTH was sustained after withdrawal. The slowing of BMU progression by PTH warrants further investigation; slowed resorption combined with elevated bone formation rate, may play an important role in how PTH enhances coupling between resorption and formation within the BMU. Finally, the prolonged anabolic response following withdrawal may have utility in terms of optimizing clinical dosing regimens.
Topics: Rabbits; Female; Animals; Parathyroid Hormone; Tibia; Bone Density; Canada; Osteoporosis; Cortical Bone
PubMed: 37574096
DOI: 10.1016/j.bone.2023.116864 -
Journal of the Mechanical Behavior of... Apr 2024Antlers are bony structures composed predominantly of primary osteons with unique mechanical properties due to their specific use by deer as weapon and shield. Antler...
Antlers are bony structures composed predominantly of primary osteons with unique mechanical properties due to their specific use by deer as weapon and shield. Antler bone fracture resistance has attracted prior scrutiny through experimental tests and theoretical models. To characterize antler mechanical properties, compression of cubes, or bending or tensioning of rectangular bars have been performed in the literature with variations in the protocols precluding comparisons of the data. Compression testing is a widely used experimental technique for determining the mechanical properties of specimens excised from cortical or cancellous regions of bone. However, the recommended geometry for compression tests is the cylinder, being more representative of the real performances of the material. The purpose of research was to report data for compressive strength and stiffness of antler cortical bone following current guidelines. Cylinders (n = 296) of dry antler cortical bone from either the main beam or the tines of Cervus elaphus, Rangifer tarandus, Cervus nippon and Damadama were tested. This study highlights the fact that compression of antler cortical bone cylinders following current guidelines is feasible but not applicable in all species. Standardization of the testing protocols could help to compare data from the literature. This study also confirms that sample localization has no effect on the mechanical properties, that sample density has a significant impact and allows enriching the knowledge of the mechanical properties of dry antler cortical bone.
Topics: Animals; Antlers; Deer; Cortical Bone; Compressive Strength; Physical Phenomena
PubMed: 38330876
DOI: 10.1016/j.jmbbm.2024.106442