Intracortical porosities and marrow fibrosis are hallmarks of hyperparathyroidism and are present in bones of transgenic mice expressing constitutively active parathyroid hormone/parathyroid hormone-related protein receptors (PPR*Tg). Cortical porosity is the result of osteoclast activity; however, the etiology of marrow fibrosis is ...

Cortical bone is a viscoelastic heterogeneous medium which may be assessed with axial transmission. This work aims at evaluating the average depth investigated by the lateral wave for radial variations of material properties in relatively thick cortical bone. The equivalent contributing depth (ECD) is derived from the finite element simulation results for ...

We have previously shown that parathyroid hormone (PTH) increases cortical bone mass and mechanical strength of female rabbits after 140 days of treatment. However, cortical porosity was also shown to increase. If cortical porosity increases prior to the change in geometry, there may be a ...

Cortical bone contributes the majority of overall bone mass and bears the bulk of axial loads in the peripheral skeleton. Bone metabolic disorders often are manifested by cortical microstructural changes via osteonal remodeling and endocortical trabecularization. The goal of this study was to characterize intracortical porosity in a ...

The Haversian/Volkmann's canals make up most of the cortical porosity and ... produces higher resolutions than NMR, mCT and FESEM (~30nm) and is ideal for ...

A micromechanical multiscale model which estimates the elastic properties of cortical bone as a function of porosity and mineral content is presented. The steps of the model are divided into two main phases. In the first one, the elastic properties of the collagen fibril, collagen fiber and lamella are given. In the second phase, ...

A nuclear magnetic resonance (NMR) spin (T2) relaxation technique has been described for determining water distribution changes on turkey cortical bone tissue of simulated weightlessness (disuse) in vitro. The advantages of using NMR T2 relaxation techniques for bone water distribution are illustrated. The Carr Purcell Meiboom Gill (CPMG) T2 relaxation data can be used to ...

Large bones from many anatomical locations of the human skeleton consist of an outer shaft (cortex) surrounding a highly porous internal region (trabecular bone) whose structure is reminiscent of a disordered cubic network. Age related degradation of cortical and trabecular bone takes different forms. Trabecular bone weakens primarily by loss of connectivity of the porous ...

Large bones from many anatomical locations of the human skeleton consist of an outer shaft (cortex) surrounding a highly porous internal region (trabecular bone) whose structure is reminiscent of a disordered cubic network. Age related degradation of cortical and trabecular bone takes different forms. Trabecular bone weakens primarily by loss of connectivity of the porous ...

Parathyroid hormone (PTH [1-34]) stimulates bone formation and activates bone remodeling, resulting in increase of bone mass and strength. The effect on bone quality appears through the different mechanism from the anti-resorptive agents. The anti-resorptive agent maintains the trabecular microstructure, decreases the cortical porosity and increases the ...

Cortical defects are common and problematic in cemented revision hip arthroplasty. Extruded cement can cause thermal injury, pain, and impingement. Decreased cement pressure limits bony interdigitation and leads to loosening. Historically, surgeons have used a finger to contain cement and improve pressure, and decrease porosity, but, with large or multiple ...

The extent to which increased intracortical porosity affects the fracture properties of aging and osteoporotic bone is unknown. Here, we report the development and application of a microcomputed tomography based finite element approach that allows determining the effects of intracortical porosity on bone fracture by blocking all other age-related changes ...

Black bears (Ursus americanus) may not develop disuse osteoporosis during long periods of disuse (i.e. hibernation) because they may be able to maintain bone formation. Previously, we found that cortical bone bending strength was not compromised with age in black bears' tibias, despite annual periods of disuse. Here we showed that cortical bone tensile ...

The ultrasonic axial transmission technique, used to assess cortical shells of long bones, is investigated using numerical simulations based on a three-dimensional (3D) finite difference code. We focus our interest on the effects of 3D cortical bone geometry (curvature, cortical thickness), anisotropy, and microporosity on speed of ...

Open-pore titanium foams are produced using the so-called space holder method. The mechanical properties of titanium foams with porosities of 50-80% are studied. The stiffness and yield strength of the foams are found to encompass the property range between cancellous bone and cortical bone. The analyzed foams are found to be anisotropic due to the use of ...

This study investigated the relative contributions of pore size and pore density (number of pores per mm2) to porosity in the midshaft of the human femur. Cross-sections were obtained from 168 individuals from a modern Australian population (mostly Anglo-Celtic). The study group comprised 73 females and 95 males, aged from 20 to 97 years. Microradiographs were made of ...

Sintered Ti6Al4V powder compacts potentially to be used in implant applications were prepared using commercially available spherical and angular powders (100-200 mum) within the porosity range of 34-54%. Cylindrical green powder compacts were cold compacted at various pressures and then sintered at 1200 degrees C for 2 h. The final percent porosity and ...

�837. Davidson, S.R.H., James, D.F., 2000. Measurement of thermal conductivity of bovine cortical bone. Med. Eng's personal copy Spectral analysis and connectivity of porous microstructures in bone Kenneth M. Golden �, N: Bone Sea ice Porosity Percolation Spectral reconstruction a b s t r a c t Cancellous bone is a porous

Recently, the mesoscale of cortical bone has been given particular attention in association with novel experimental techniques such as nanoindentation, micro-computed X-ray tomography and quantitative scanning acoustic microscopy (SAM). A need has emerged for reliable mathematical models to interpret the related microscopic and mesoscopic data in terms of effective elastic ...

The aim of this study was to evaluate the influence of microstructural parameters, such as porosity and osteon dimensions, on strength. Therefore, the predictive value of bone mineral density (BMD) measured by quantitative computed tomography (QCT) for intracortical porosity and other microstructural parameters, as well as for strength of ...

A systematic investigation into solid-state foaming of commercial purity titanium (CP-Ti) is presented. Transformation superplasticity (TSP), which relies on the biasing of internal mismatch strains present during the phase transformation due to density differences in the two phases, was found to be active during foaming, where the deviatoric biasing stress was provided by the internal pore ...

Cortical development depends upon tightly controlled cell fate and cell survival decisions that generate a functional neuronal population, but the coordination of these two processes is poorly understood. Here we show that conditional removal of a key apical complex protein, Pals1, causes premature withdrawal from the cell cycle, inducing excessive generation of early-born ...

Background and AimsAerenchyma formation is thought to be one of the important morphological adaptations to hypoxic stress. Although sponge gourd is an annual vegetable upland crop, in response to flooding the hypocotyl and newly formed adventitious roots create aerenchyma that is neither schizogenous nor lysigenous, but is produced by radial elongation of cortical cells. The ...

Quantitative cortical micro-architectural endpoints are important for understanding structure-function relations in the context of fracture risk and therapeutic efficacy. This technique study details new image-processing methods to automatically segment and directly quantify cortical density, geometry, and micro-architecture from HR-pQCT images of the ...

Treatment with parathyroid hormone 1-84 (PTH) or teriparatide increases osteonal remodeling and decreases bone mineral density (BMD) at cortical (Ct) bone sites but may also increase bone size. Decreases in BMD and increases in size exert opposing effects on bone strength. In adult ovariectomized (OVX) rhesus monkeys, we assessed the effects of daily PTH treatment (5, 10 or 25 ...

In many species, including humans, disuse causes an imbalance in bone remodeling that leads to increased bone porosity as a result of increased bone resorption and decreased bone formation. However, black bears (Ursus americanus) may not develop disuse osteopenia, to the extent that other animals do, during long periods of disuse (i.e. hibernation) because they maintain ...

Accurate clinical interpretation of the sound velocity derived from axial transmission devices requires a detailed understanding of the propa-gation phenomena involved and of the bone factors that have an impact on measurements. In the low-megahertz range, ultrasonic propagation in cortical bone depends on anisotropic elastic tissue properties, porosity, ...

This study examines the impact of voxel size on 3D micro-CT analysis of human cortical bone porosity. The study is based on computed microtomography scans of 10 human anterior femoral midshaft specimens acquired at 5, 10, and 15 microm voxel sizes. Artificial voxel sizes (10, 20, and 40 microm) were generated from the smallest scan voxel size (5 microm) in ...

Disuse (i.e. inactivity) causes bone loss, and a recovery period that is 2�3 times longer than the inactive period is usually required to recover lost bone. However, black bears experience annual disuse (hibernation) and remobilization periods that are approximately equal in length, yet bears maintain or increase cortical bone material properties and whole bone mechanical ...