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Current Osteoporosis Reports Apr 2022Osteocytes are the conductors of bone adaptation and remodelling. Buried inside the calcified matrix, they sense mechanical cues and signal osteoclasts in case of low... (Review)
Review
PURPOSE OF REVIEW
Osteocytes are the conductors of bone adaptation and remodelling. Buried inside the calcified matrix, they sense mechanical cues and signal osteoclasts in case of low activity, and osteoblasts when stresses are high. How do osteocytes detect mechanical stress? What physical signal do they perceive? Finite element analysis is a useful tool to address these questions as it allows calculating stresses, strains and fluid flow where they cannot be measured. The purpose of this review is to evaluate the capabilities and challenges of finite element models of bone, in particular the osteocytes and load-induced activation mechanisms.
RECENT FINDINGS
High-resolution imaging and increased computational power allow ever more detailed modelling of osteocytes, either in isolation or embedded within the mineralised matrix. Over the years, homogeneous models of bone and osteocytes got replaced by heterogeneous and microstructural models, including, e.g. the lacuno-canalicular network and the cytoskeleton. The lacuno-canalicular network induces strain amplifications and the osteocyte protrusions seem to be stimulated much more than the cell body, both by strain and fluid flow. More realistic cell geometries, like minute constrictions of the canaliculi, increase this effect. Microstructural osteocyte models describe the transduction of external stimuli to the nucleus. Supracellular multiscale models (e.g. of a tunnelling osteon) allow to study differential loading of osteocytes and to distinguish between strain and fluid flow as the pivotal stimulatory cue. In the future, the finite element models may be enhanced by including chemical transport and intercellular communication between osteocytes, osteoclasts and osteoblasts.
Topics: Bone and Bones; Finite Element Analysis; Humans; Mechanotransduction, Cellular; Osteocytes; Stress, Mechanical
PubMed: 35298773
DOI: 10.1007/s11914-022-00728-9 -
Medicina (Kaunas, Lithuania) Jun 2022Background and Objectives: The gold standard for a successful prosthetic approach is the osseointegration of an implant. However, this integration can be a problem in...
Background and Objectives: The gold standard for a successful prosthetic approach is the osseointegration of an implant. However, this integration can be a problem in cases where the implant needs to be removed. Removing the implant with minimal damage to the surrounding tissues is important. Osteocytes cannot survive below −2 °C, but epithelial cells, fibroblasts, and other surrounding tissue cells can. Remodeling can be triggered by cryotherapy at temperatures that specifically affect osteocyte necrosis. In this study, we aimed to develop a method for reversing the osseointegration mechanism and for protecting the surrounding tissues by bone remodeling induced by CO2 cryotherapy. Materials and Methods: In this study, eight 2.8 mm diameter, one-piece mini implants were used in New Zealand rabbit tibias. Two control and six implants were tested in this study. After 2 months of osseointegration, a reverse torque force method was used to remove all osseointegrated implants at 5, 10, 20, and 30 Ncm. The osseointegration of the implants was proven by periotest measurements. Changes in bone tissue were examined in histological sections stained with toluidine blue after rabbit sacrifice. The number of lacunae with osteocyte, empty lacunae, and lacunae greater than 5 µm and the osteon number in a 10,000 µm2 area were calculated. Cryotherapy was applied to the test implants for 1 min, 2 min, and 5 min. Three implants were subjected to cryotherapy at −40 °C, and the other implants were subjected to cryotherapy at −80 °C. Results: Empty lacunae, filled osteocytes, lacunae >5 µm, and the osteon count around the implant applied at −40 °C were not significantly different from the control implants. The application of −40 °C for 1 min was found to cause minimal damage to the bone cells. The implants, which were applied for 1 min and 2 min, were successfully explanted on the 2nd day with the 5 Ncm reverse torque method. Test implants, which were applied cold for 5 min, were explanted on day 1. Tissue damage was detected in all test groups at −80 °C. Conclusions: The method of removing implants with cryotherapy was found to be successful in −40 °C freeze−thaw cycles applied three times for 1 min. To prove implant removal with cryotherapy, more implant trials should be conducted.
Topics: Animals; Dental Implants; Osseointegration; Rabbits; Tibia; Titanium; Torque
PubMed: 35888569
DOI: 10.3390/medicina58070849 -
Scientific Reports Nov 2022Remodelling is a fundamental biological process involved in the maintenance of bone physiology and function. We know that a range of health and lifestyle factors can...
Remodelling is a fundamental biological process involved in the maintenance of bone physiology and function. We know that a range of health and lifestyle factors can impact this process in living and past societies, but there is a notable gap in bone remodelling data for populations from the Pacific Islands. We conducted the first examination of femoral cortical histology in 69 individuals from ca. 440-150 BP Taumako in Solomon Islands, a remote 'Polynesian Outlier' island in Melanesia. We tested whether bone remodelling indicators differed between age groups, and biological sex validated using ancient DNA. Bone vascular canal and osteon size, vascular porosity, and localised osteon densities, corrected by femoral robusticity indices were examined. Females had statistically significantly higher vascular porosities when compared to males, but osteon densities and ratios of canal-osteon (~ 8%) did not differ between the sexes. Our results indicate that, compared to males, localised femoral bone tissue of the Taumako females did not drastically decline with age, contrary to what is often observed in modern populations. However, our results match findings in other archaeological samples-a testament to past female bone physiology resilience, also now observed in the Pacific region.
Topics: Male; Humans; Female; Haversian System; Femur; Bone and Bones; Bone Remodeling; Melanesia
PubMed: 36344562
DOI: 10.1038/s41598-022-23171-3 -
Small (Weinheim An Der Bergstrasse,... Mar 2022Nature creates fascinating self-organized spatiotemporal patterns through the delicate control of reaction-diffusion dynamics. As the primary unit of cortical bone,...
Nature creates fascinating self-organized spatiotemporal patterns through the delicate control of reaction-diffusion dynamics. As the primary unit of cortical bone, osteon has concentric lamellar architecture, which plays a crucial role in the mechanical and physiological functions of bone. However, it remains a great challenge to fabricate the osteon-like structure in a natural self-organization way. Taking advantage of the nonequilibrium reaction in hydrogels, a simple mineralization strategy to closely mimic the formation of osteon in a mild physiological condition is developed. By constructing two reverse concentration gradients of ions from periphery to interior of cylindrical hydrogel, spatiotemporal self-organization of calcium phosphate in concentric rings is generated. It is noteworthy that minerals in different layers possess diverse contents and crystalline phases, which further guide the adhesion and spread of osteoblasts on these patterns, resembling the architecture and cytological behavior of osteon. Besides, theoretical data indicates the predominate role of ion concentrations and pH values of solution, in good accordance with experimental results. Independent of precise instruments, this lifelike method is easily obtained, cost-efficient, and effectively imitates the mineral deposition in osteon from a physiochemical view. The strategy may be expanded to develop other functional material patterns via spatiotemporal self-organization.
Topics: Bone and Bones; Haversian System; Hydrogels; Minerals; Osteoblasts
PubMed: 34921591
DOI: 10.1002/smll.202106649 -
Royal Society Open Science Aug 2022Lamellae are sheets of mineralized collagen 1-20 µm thick, extending over hundreds of µm in bone tissue, occupying bone's structural hierarchy at a level above... (Review)
Review
Lamellae are sheets of mineralized collagen 1-20 µm thick, extending over hundreds of µm in bone tissue, occupying bone's structural hierarchy at a level above collagen fibres and osteocytes, and below osteons and trabeculae. Osteons are tubular arrangements of lamellae surrounding central neurovascular canals. Lamellae in osteons are usually described as concentric cylinders based on their annular appearance in transverse section. In this review, I provide a perspective on current understanding of the relationship between geometry of the bone formation front and the shape of lamellae produced at it, reaching the conclusion that the 'closing cone' bone formation front in secondary osteonal remodelling must necessarily result in cone-shaped lamellae in the mature secondary osteon. Secondary osteons replace primary osteons through a tunnelling process of bone turnover, meaning that conical lamellae may become more common in older and damaged bone which is at greatest risk of fracture. Visualization and measurement of three-dimensional lamellar shape over hundreds of microns is needed to provide data for accurate micromechanical simulations. Treating secondary osteonal lamellae as a 'stack of cones' rather than 'nested cylinders' may have important implications for our appreciation of bone's function as a load-bearing tissue and of its behaviour in fracture.
PubMed: 35958092
DOI: 10.1098/rsos.220712 -
Biomechanics and Modeling in... Dec 2022Cortical bone is a complex hierarchical structure consisting of biological fiber composites with transversely isotropic constituents, whose microstructures deserve...
Cortical bone is a complex hierarchical structure consisting of biological fiber composites with transversely isotropic constituents, whose microstructures deserve extensive study to understand the mechanism of living organisms and explore development of biomimetic materials. Based on this, we establish a three-level hierarchical structure from microscale to macroscale and propose a multiscale micromechanics model of cortical bone, which considers Haversian canal, osteonal lamellae, cement line and interstitial lamellae. In order to study the microstructural effect on the elastic behavior of hierarchical structures, the Mori-Tanaka model and locally exact homogenization theory are introduced for the homogenization of heterogeneous materials of microstructure at each level. Within sub-microscale, Haversian canal and Osteonal lamella are treated as fiber and matrix, whose homogenization is surrounded with cement line matrix in microstructure (or what we called "osteon") for the second homogenization; finally, osteon and interstitial lamella establish the meso-structure for the third homogenization, predicting the effective moduli of cortical bone. The correctness of the model in this paper is verified against the data in literature with good agreement. Finally, the dynamic viscoelastic response of cortical bones is investigated from a multiscale perspective, where the measured data are substituted into the present models to study the hydration and aging effect on bones' stiffness and viscoelasticity. It is demonstrated that the hydration is much more influential in affecting the storage and loss moduli of cortical bone than the aging effect. We also present a few numerical investigations on microstructural material and geometric parameters on the overall mechanical properties of cortical bone.
Topics: Elasticity; Biomechanical Phenomena; Haversian System; Bone and Bones; Cortical Bone; Models, Biological
PubMed: 36057052
DOI: 10.1007/s10237-022-01615-z -
American Journal of Physical... Apr 2020While double-zonal osteons (DZ) are characterized by a hyper-mineralized ring inside their lamellae, recent findings suggest that this ring is also defined by a change...
OBJECTIVES
While double-zonal osteons (DZ) are characterized by a hyper-mineralized ring inside their lamellae, recent findings suggest that this ring is also defined by a change in the collagen fibers' orientation. Collagen and minerals are essential components to the maintenance of adequate bone strength and their alteration can modify the mechanical properties of the bone tissue. Consequently, the aim of this study is to explore the effect of past loads, as estimated from cross-sectional geometric properties, on the formation of DZ osteons compared to type I (common) osteons.
MATERIALS AND METHODS
The sample consists of paired humerus and femur midshaft sections (n = 23) of Eurocanadian settlers from the historical St. Matthew cemetery, Quebec City (1771-1860). Histomorphometric variables included in this study are osteon density for DZ and type I osteons (DZD; OPD), osteon area (DZOn.Ar; On. Ar), Haversian canal area (DZH.Ar; H.Ar), and the area within the hypermineralized ring (HR. Ar). Loading history is estimated from cross-sectional properties including the following variable: cortical and total area (CA, TA), maximum and minimum second moment of area (I , I ) and polar moment of area (J).
RESULTS
When the humerus and femur of the same individuals are compared, the femur has a higher OPD, DZD, and relative DZD (DZD/OPD). DZ osteons have a smaller area and Haversian canal area compared to type I osteons. The area within the hypermineralized ring in DZ is higher than the Haversian canal area of the type I osteons. Correlations between the residual scores of the regression of histomorphometric variables and cross-sectional properties of the humerus on the femur were not significant.
DISCUSSION
Based on the analysis of the entire cross-section, the lack of correlation between variations in cross-sectional properties and remodeling combined with the significant differences between humeri and femura suggests that the creation of DZ or type I osteons in the bone tissue might be due to a bone specific response, possibly related to differences in bone tissue age that needs to be further investigated. Definitive conclusion regarding biomechanical loads still seem to be premature as regional variations associated with mechanical properties remain to be explored.
Topics: Adult; Biomechanical Phenomena; Cemeteries; Femur; Haversian System; History, 18th Century; History, 19th Century; Humans; Humerus; Middle Aged; Quebec; Young Adult
PubMed: 31675105
DOI: 10.1002/ajpa.23954 -
Journal of Maxillofacial and Oral... Jun 2022Osteomyelitis is inflammation of medullary cavities, haversian system and adjacent cortex of bone. It is devastating to patients when invasive.
BACKGROUND
Osteomyelitis is inflammation of medullary cavities, haversian system and adjacent cortex of bone. It is devastating to patients when invasive.
AIM
The purpose of this study is to retrospectively review patients diagnosed with diabetic maxillary osteomyelitis and evaluate factors relating infection & diabetes.
METHODOLOGY
Case records of patients diagnosed with diabetic maxillary osteomyelitis were studied. Patient's demographic data, predisposing factors, etiology, clinical features, culture sensitivity reports, microbiology, treatment and complications were studied. Diabetic status was confirmed by glycosylated hemoglobin (HbA1c) test. Duration of diabetes and anti-diabetic medication adherence was also studied.
RESULTS
There were 28 patients diagnosed with diabetic maxillary osteomyelitis, (23-male; 5-female). Majority of the patients (60.7%) belonged to fourth & fifth decades. Twenty (71.4%) patients had poorly controlled diabetes (HbA1c > 8%). All patients reported with random blood sugar > 200 mg/dl. Thirteen patients (46.4%) were diagnosed for diabetes on admission and 11 patients (39.3%) had poor anti-diabetic medication adherence. Predominant etiology was odontogenic infection (50%). Cases of bacterial osteomyelitis (50%) were more frequent than those of fungal osteomyelitis (32.1%). Recurrence was observed in three cases.
CONCLUSION
Non-cognizance about diabetes mellitus can prove devastating for maxillofacial region and may prove fatal for the patient.
PubMed: 35712438
DOI: 10.1007/s12663-020-01371-6 -
Proceedings of the Institution of... Mar 2022This paper comprehensively reviews the various experimental and numerical techniques, which were considered to determine the fracture characteristics of the cortical... (Review)
Review
This paper comprehensively reviews the various experimental and numerical techniques, which were considered to determine the fracture characteristics of the cortical bone. This study also provides some recommendations along with the critical review, which would be beneficial for future research of fracture analysis of cortical bone. Cortical bone fractures due to sports activities, climbing, running, and engagement in transport or industrial accidents. Individuals having different diseases are also at high risk of cortical bone fracture. It has been observed that osteon orientation influences cortical bone fracture toughness and fracture mechanisms. Apart from this, recent studies indicate that fracture parameters of cortical bone also depend on many factors such as age, sex, temperature, osteoporosis, orientation, location, loading condition, strain rate, and storage facility, etc. The cortical bone regains its fracture toughness due to various toughening mechanisms. Owing to these factors, several experimental, clinical, and numerical investigations have been carried out to determine the fracture parameters of the cortical bone. Cortical bone is the dense outer surface of the bone and contributes to 80%-82% of the skeleton mass. Cortical bone experiences load far exceeding body weight due to muscle contraction and the dynamics of motion. It is very important to know the fracture pattern, direction of fracture, location of the fracture, and toughening mechanism of cortical bone. A basic understanding of the different factors that affect the fracture parameters and fracture mechanisms of the cortical bone is necessary to prevent the failure and fracture of cortical bone. This review has summarized the advancement considered in the various experimental techniques and numerical methods to get complete information about the fracture mechanisms of cortical bone.
Topics: Biomechanical Phenomena; Bone and Bones; Cortical Bone; Fractures, Bone; Humans; Osteoporosis
PubMed: 35001738
DOI: 10.1177/09544119211070347 -
Frontiers in Endocrinology 2020Bone possesses a highly complex hierarchical structure comprised of mineral (~45% by volume), organic matrix (~35%) and water (~20%). Water exists in bone in two forms:... (Review)
Review
Bone possesses a highly complex hierarchical structure comprised of mineral (~45% by volume), organic matrix (~35%) and water (~20%). Water exists in bone in two forms: as bound water (BW), which is bound to bone mineral and organic matrix, or as pore water (PW), which resides in Haversian canals as well as in lacunae and canaliculi. Magnetic resonance (MR) imaging has been increasingly used for assessment of cortical and trabecular bone. However, bone appears as a signal void on conventional MR sequences because of its short T2. Ultrashort echo time (UTE) sequences with echo times (TEs) 100-1,000 times shorter than those of conventional sequences allow direct imaging of BW and PW in bone. A series of quantitative UTE MRI techniques has been developed for bone evaluation. UTE and adiabatic inversion recovery prepared UTE (IR-UTE) sequences have been developed to quantify BW and PW. UTE magnetization transfer (UTE-MT) sequences have been developed to quantify collagen backbone protons, and UTE quantitative susceptibility mapping (UTE-QSM) sequences have been developed to assess bone mineral.
Topics: Animals; Bone Density; Cortical Bone; Echo-Planar Imaging; Humans; Magnetic Resonance Imaging; Time Factors; Water; X-Ray Microtomography
PubMed: 33071975
DOI: 10.3389/fendo.2020.567417