Characteristics Of Cortical Bone Research Articles

Ultrasound Characterization of Cortical Bone Using Shannon Entropy.

Ultrasound backscattered signals encompass information on the microstructure of heterogeneous media such as cortical bone, in which pores act as scatterers and result in the scattering and multiple scattering of ultrasound waves. The objective of this study was to investigate whether Shannon entropy can be exploited to characterize cortical porosity. In the study described here, to demonstrate proof of concept, Shannon entropy was used as a quantitative ultrasound parameter to experimentally evaluate microstructural changes in samples with controlled scatterer concentrations made of a highly absorbing polydimethylsiloxane matrix (PDMS). Similar assessment was then performed using numerical simulations on cortical bone structures with varying average pore diameter (Ct.Po.Dm.), density (Ct.Po.Dn.) and porosity (Ct.Po.). The results suggest that an increase in pore diameter and porosity lead to an increase in entropy, indicating increased levels of randomness in the signals as a result of increased scattering. The entropy-versus-scatterer volume fraction in PDMS samples indicates an initial increasing trend that slows down as the scatterer concentration increases. High levels of attenuation cause the signal amplitudes and corresponding entropy values to decrease drastically. The same trend is observed when porosity of the bone samples is increased above 15%. Sensitivity of entropy to microstructural changes in highly scattering and absorbing media can potentially be exploited to diagnose and monitor osteoporosis.

Effects on Bone and Muscle upon Treadmill Interval Training in Hypogonadal Male Rats.

Testosterone deficiency in males is linked to various pathological conditions, including muscle and bone loss. This study evaluated the potential of different training modalities to counteract these losses in hypogonadal male rats. A total of 54 male Wistar rats underwent either castration (ORX, n = 18) or sham castration (n = 18), with 18 castrated rats engaging in uphill, level, or downhill interval treadmill training. Analyses were conducted at 4, 8, and 12 weeks postsurgery. Muscle force of the soleus muscle, muscle tissue samples, and bone characteristics were analyzed. No significant differences were observed in cortical bone characteristics. Castrated rats experienced decreased trabecular bone mineral density compared to sham-operated rats. However, 12 weeks of training increased trabecular bone mineral density, with no significant differences among groups. Muscle force measurements revealed decreased tetanic force in castrated rats at week 12, while uphill and downhill interval training restored force to sham group levels and led to muscle hypertrophy compared to ORX animals. Linear regression analyses showed a positive correlation between bone biomechanical characteristics and muscle force. The findings suggest that running exercise can prevent bone loss in osteoporosis, with similar bone restoration effects observed across different training modalities.

CRACK RESISTANCE CHARACTERISTICS OF MICROSTRUCTURE OF HAVERSIAN CORTICAL BONE

Background: The current research on crack propagation resistance characteristics of osteons is based on the single osteon model, which cannot reflect the interaction among osteons and the influence of material-property changes on the crack propagation. Moreover, the Haversian canal and the cement line were not included in the model, which could not reflect the influence of the true structural characteristics of the cortical bone on the microcracks. Objective: To investigate the effects of osteons, cement line and its material parameters on the stress intensity factor at the crack-tip based on theoretical formula calculation and finite element calculation. Results: The single osteon model, multi-osteon model and Haversian cortical bone model were established according to the microstructural characteristics of Haversian cortical bone. The calculation results of the first two models show that the “soft” osteon accelerates the crack propagation and the “hard” osteon hinders crack propagation, and the effect of multi-osteon model on a microcrack is significantly larger than that of single bone model. The calculation results of Haversian cortical bone model show that the stress intensity factors at both ends of the microcrack decreased when the distance from the “soft” osteon was within a certain range ([Formula: see text]). The stress intensity factor of endpoint ‘a’ in the crack-tip increases sharply when the microcrack is close to the osteon. Conclusions: The analysis results of the three models present that the microcrack propagation is affected by the material properties as well as the quantity of osteon, and the cement line is conductive to enhance the fracture toughness of the cortical bone.

Heterogeneity in mechanical properties of cortical bone for the selection and design of anatomic site-specific nanoparticle reinforced bone tissue engineering scaffold

Bone tissue has the potential to self-heal and renew, but large-scale bone abnormalities caused by infection, trauma, or any malignancy shall require intervention from external sources. To mimic the host tissue i.e., bone mechanical properties, the scaffolds for bone tissue engineering are designed. However, the host tissue mechanical properties are anatomic site-specific as per the location where a scaffold has to be implanted to facilitate tissue regeneration. This is because of the heterogeneous and hierarchical structure of bone that consists of mineral nano-particles, water, collagenous protein, etc. which makes bone a more complex material. Fabricating nano-scaffolds becomes a challenging task that can resemble the bone properties in form of biological, chemical, or mechanical. As a result, it is required to examine the change in mechanical properties of a bone throughout the site to build efficient nano-scaffolds for tissue engineering/bone regeneration. The mechanical characteristics of cortical bone were investigated at three diaphysis regions of the femoral cortical bone under tension and compression stress. The obtained mechanical properties have been compared statistically using a t-test at p < 0.05 and found a statistical difference in the mechanical properties for different diaphysis locations. The findings of this research may be helpful for the researchers working on the design of nanoparticle-based composite biomaterials to mimic the anatomic site-specific mechanical properties of bone for tissue engineering applications.

Tribological characterization of cortical bone against 316 stainless steel during dry sliding

In surgery, the friction between the cortical bone and the metal instruments cause bone cells damage, which would affect the stability of intraosseous implants. In the present work, the tribological characterization of cortical bone against 316 stainless steel during dry sliding condition was investigated by pin-on-disk tests. Finite element method was used to monitor the change of friction temperature with vibration assistance. The wear mechanism of the bone sample and the 316 stainless steel had been analyzed and discussed. The results show that the friction coefficient decrease with the increasing of load, the wear rate and the friction temperature increase. While, the friction coefficient, the wear rate and the friction temperature are increased with the increase of sliding speed, respectively. Moreover, the friction temperature with vibration assisted is lower than that in the normal friction process. Adhesive and abrasive wear behavior are the main wear mechanisms of the cortical bone against 316 stainless steel during the test. The results in this paper provide guidance for the selection of parameters during bone cutting, which has great significance for the improvement of implant stability.

Meta-Learning Analysis of Ultrasonic Guided Waves for Coated Cortical Bone Characterization.

Due to its sensitivity to geometrical and mechanical properties of waveguides, ultrasonic guided waves (UGWs) propagating in cortical bones play an important role in the early diagnosis of osteoporosis. However, as impacts of overlaid soft tissues are complex, it remains challenging to retrieve bone properties accurately. Meta-learning, i.e., learning to learn, is capable of extracting transferable features from a few data and, thus, suitable to capture potential characteristics, leading to accurate bone assessment. In this study, we investigate the feasibility to apply the multichannel identification neural network (MCINN) to estimate the thickness and bulk velocities of coated cortical bone. It minimizes the effects of soft tissue by extracting specific features of UGW, which shares the same cortical properties, while the overlaid soft tissue varies. Distinguished from most reported methods, this work moves from the hand-design inversion scheme to data-driven assessment by automatically mapping features of UGW to the space of bone properties. The MCINN was trained and validated using simulated datasets produced by the finite-difference time-domain (FDTD) method and then applied to experimental data obtained from cortical bovine bone plates overlaid with soft tissue mimics. A good match was found between experimental trajectories and theoretical dispersion curves. The results demonstrated that the proposed method was feasible to assess the thickness of coated cortical bone plates.

Experimental evaluation of cohesive laws components of mixed-mode I + II fracture characterization of cortical bone

Mixed-mode I + II fracture characterization of cortical bone tissue is addressed in this work. The mixed-mode bending test was used to impose different mode ratios. An equivalent crack length data reduction method was considered to obtain the strain energy release rate components. Crack opening and shear displacements were measured by means of digital image correlation. These quantities were then integrated to propose a direct evaluation of cohesive laws. The components of the cohesive laws for each mixed-mode loading were obtained by the uncoupled and Högberg’s methods. The later provided consistent evolution of strain energy release rate and peak stresses components in function of mode-ratio, revealing its appropriateness regarding the fracture characterization of cortical bone under mixed-mode I + II loading.

Demineralization characteristics of cortical bone under voltage application in phosphate-buffered saline

Demineralization characteristics of cortical bone under voltage application in phosphate-buffered saline

Analysis of Ultrasonic Guided Wave Propagation in Multilayered Bone Structure With Varying Soft-Tissue Thickness in View of Cortical Bone Characterization.

Noninvasive characterization of cortical long bones using axial transmission ultrasound is a promising diagnostic technology for osteoporotic cortical thinning assessment. However, the soft tissue-bone coupling effect remains to be a challenge and an ambiguity especially in vivo. The influence of the overlying soft tissue layer with a varying thickness on the propagation of ultrasonic guided waves in cortical bone is studied experimentally and theoretically in this article. The wave propagation is characterized based on waveform comparison, spectral density and decomposition, dispersion energy imaging, and particle displacement analysis. Good agreement between experimental observations with theoretical predictions by semi-analytical finite element simulations is observed. The sensitivity of propagation characteristics in response to the coupled tissue thickness is elucidated. As the thickness of the loading soft tissue grows, the guided wave signals exhibit greater attenuated amplitude and delayed arrival time; more complex dispersive wave patterns emerge; and the modal number and density increase. The research findings advance the fundamental comprehension of ultrasonic-guided-wave excitation and interaction in long bones and facilitate further technical development and clinical utility of quantitative guided-wave ultrasonography in routine healthcare services as a nondestructive imaging modality for cortical bone examination.

Axial Transmission: Techniques, Devices and Clinical Results.

Recent progress in quantitative ultrasound have sparked increasing interest towards the measurement of long cortical bones (e.g., radius or tibia), because their ability to sustain loading and resist fractures is known to be related to their mechanical properties at different length scales. In particular, applying guided waves for the assessment of cortical bone is inspired by widely used techniques developed earlier in the field of nondestructive testing and evaluation of different waveguide structures. This approach is based on the experimental evidence that the cortex of long bones can act as a natural waveguide for ultrasound, despite its irregular geometry, attenuation, and heterogeneous material properties. Because guided waves could yield the characterization of several bone properties (e.g., cortical thickness, anisotropic stiffness or porosity) at the mesoscopic level by fitting the dispersion characteristics of a waveguide model to the measured dispersion curves (i.e., solving an inverse problem), this method has a strong clinical potential as a tool for bone status assessment. This chapter revisits the roadmap that allowed the so-called bidirectional axial transmission technique to progress from a pure laboratory concept to a diagnostic tool of clinical interest over the second decade of the twenty-first century and discusses the current clinical challenges associated with cortical bone characterization by ultrasound guided waves.

Signal Processing Techniques Applied to Axial Transmission Ultrasound.

A new application of ultrasonography has been emerging in the bone quantitative ultrasound arena in the last twenty years: cortical bone characterization using axial transmission ultrasound (ATU). Although challenged by the complicated cortical tissue-ultrasonic wave interaction, ATU has proved to have promising potential to be a valuable diagnostic tool in the assessment of cortical bones. This chapter reviews the main landmarks of axial transmission signal processing in the past decade to provide a guide to the diversity of available techniques. In order to increase the readability of the chapter, the signal processing methods are categorized based on the experimental settings: single and multiple transmitter-receiver configuration. The review considers the key stages required for the analysis of bone guided-wave ultrasound data namely dispersion energy imaging, modal filtering, dispersion curve inversion, and measurement automation with integrated artificial intelligence concepts. Besides discussing the recent signal processing advances in the field of bone assessment by axial transmission, this communication offers developments that might be anticipated in the near future.

Deep Learning Analysis of Ultrasonic Guided Waves for Cortical Bone Characterization.

Ultrasonic guided waves (UGWs) propagating in the long cortical bone can be measured via the axial transmission method. The characterization of long cortical bone using UGW is a multiparameter inverse problem. The optimal solution of the inverse problem often includes a complex solving process. Deep neural networks (DNNs) are essentially powerful multiparameter predictors based on universal approximation theorem, which are suitable for solving parameter predictions in the inverse problem by constructing the mapping relationship between UGW and cortical bone material parameters. In this study, we investigate the feasibility of applying the multichannel crossed convolutional neural network (MCC-CNN) to simultaneously estimate cortical thickness and bulk velocities (longitudinal and transverse). Unlike the multiparameter estimation in most previous studies, the technique mentioned in this work avoids solving a multiparameter optimization problem directly. The finite-difference time-domain (FDTD) method is performed to obtain the simulated UGW array signals for training the MCC-CNN. The network that is exclusively trained on simulated data sets can predict cortical parameters from the experimental UGW data. The proposed method is confirmed by using FDTD simulation signals and experimental data obtained from four bone-mimicking plates and from ten ex vivo bovine cortical bones. The estimated root-mean-squared error (RMSE) in the simulated test data for the longitudinal bulk velocity ( VL ), transverse bulk velocity ( VT ), and cortical thickness (Th) is 97 m/s, 53 m/s, and 0.089 mm, respectively. The predicted RMSE in the bone-mimicking phantom experiments for VL|| , VT|| , and Th is 120 m/s, 80 m/s, and 0.14 mm, respectively. The experimental dispersion trajectories are matched with the theoretical dispersion curves calculated by the predicted parameters in ex vivo bovine cortical bone experiments. Our proposed method demonstrates a feasible approach for the accurate evaluation of long cortical bones based on UGW.

OpenMandible: An open-source framework for highly realistic numerical modelling of lower mandible physiology

ObjectiveComputer modeling of lower mandible physiology remains challenging because prescribing realistic material characteristics and boundary conditions from medical scans requires advanced equipment and skill sets. The objective of this study is to provide a framework that could reduce simplifications made and inconsistency (in terms of geometry, materials, and boundary conditions) among further studies on the topic. MethodsThe OpenMandible framework offers: 1) the first publicly available multiscale model of the mandible developed by combining cone beam computerized tomography (CBCT) and μCT imaging modalities, and 2) a C++ software tool for the generation of simulation-ready models (tet4 and hex8 elements). In addition to the application of conventional (Neumann and Dirichlet) boundary conditions, OpenMandible introduces a novel geodesic wave propagation - based approach for incorporating orthotropic micromechanical characteristics of cortical bone, and a unique algorithm for modeling muscles as uniformly directed vectors. The base intact model includes the mandible (spongy and compact bone), 14 teeth (comprising dentin, enamel, periodontal ligament, and pulp), simplified temporomandibular joints, and masticatory muscles (masseter, temporalis, medial, and lateral pterygoid). ResultsThe complete source code, executables, showcases, and sample data are freely available on the public repository: https://github.com/ArsoVukicevic/OpenMandible. It has been demonstrated that by slightly editing the baseline model, one can study different “virtual” treatments or diseases, including tooth restoration, placement of implants, mandible bone degradation, and others. SignificanceOpenMandible eases the community to undertake a broad range of studies on the topic, while increasing their consistency and reproducibility. At the same time, the needs for dedicated equipment and skills for developing realistic simulation models are significantly reduced.

A new approach for quantifying localized bone loss by measuring void spaces.

The application of high resolution peripheral quantitative computed tomography (HR-pQCT) for the study of bone health has provided valuable insight into the role bone microarchitecture has in determining bone strength and fracture risk. However, conventional density and morphological parameters struggle to distinguish whether localized bone loss is present, visible as heterogeneous deterioration in the trabecular network. This is because current HR-pQCT parameters quantify a global average of properties in the cortical or trabecular compartment. This study proposes a new metric we term "void space" that segments volumes of localized deterioration in the trabecular bone network from HR-pQCT scans and quantifies void space as the void space to total volume ratio (VS/TV, %). A simple and fully automated protocol for segmenting and quantifying void space in HR-pQCT scans is presented, along with the assessment of accuracy, precision, and cross-calibration between generations of HR-pQCT systems. Finally, prevalence of void space and the association with standard HR-pQCT parameters is demonstrated using a large population-based cohort (n=1236). Void space detection was found to be highly reproducible (accuracy >95%, least significant change <1.76% VS/TV) and correlation between scanner generations was strong (R2=0.87), although the first generation system struggled to identify small voids. Assessment of void space prevalence in the population-based cohort revealed that void spaces were more common in females than males, prevalence increased with age, and void spaces were typically systemic (occurring at both scan sites rather than only one). A comparison of group-wise differences between participants with and without void space demonstrated that individuals with void spaces had significantly worse trabecular properties for both sexes and at both scan sites. Specifically, the median trabecular bone mineral density, bone volume fraction, and trabecular number were below the 25th percentile of the population, while trabecular separation and inhomogeneity were above the 75th percentile of the population in participants with void spaces. Cortical bone characteristics did not differ between participants with and without void spaces. When the void space region was excluded from morphological analysis so that only the remaining "functional bone" was considered, trabecular properties of participants with void spaces were greatly improved, especially for those who were the greatest outliers. Void space is an intuitive morphological parameter that captures localized deterioration in the trabecular bone network, and has the potential to provide valuable insight into the assessment of bone fragility.

Effects of Microstructure Characteristics of Cortical Bone on its Microcrack Propagation

Scanning electron microscope (SEM) was used to observe and analyze the microstructure of the cross section of cortical bone. The observation results illustrated that the cortical bone is composed of cylindrical osteons and interstitial bone between osteons, and the osteon are unevenly distributed. Based on the microstructure characteristics of cortical bone, three types of cortical bone mesoscopic analysis models were established. Then, the extended finite element method (X-FEM) was used to simulate the microcrack propagation process in bone. The simulate results show that the crack initiation strain of the two-phase model is 19.1% larger than that of the single-phase model, and the three-phase model is 57.8% larger than that of the two-phase model, which demonstrated that the osteons and cement line can significantly enhance the crack initiation strain of bone. In addition, under the same boundary conditions, the model with cement line can effectively change the propagation path of microcrack and prevent the propagation of crack. Therefore, the cement lines in cortical bone can effectively increase the fracture resistance of bone and enhance the fracture toughness of cortical bone.

3d Solid Modeling and Pre-Static Finite Element Modeling of Intact Human Tibia

This paper presents a standard solid model for human tibia, accounting for the material characteristics of cortical bone, cancellous bone and bone marrow. A CT scan of a cadaveric human tibia was used as the basis of developed model. A total of 201 CT scan slices of the tibia were taken with the distances between the scans varying along the length of the bone with a higher density at the proximal and distal ends, as those were the regions of interest. The data was imported into MIMICS (Materialise), and the&#x0D; threshold method was used to differentiate between the cortical bone region, cancellous bone region, and the bone marrow cavity. The solid model used to generate the FE model is constructed based on CT scan data of an actual cadaveric human tibia. The geometric information is retrieved and edited in (MIMICS). The surfaces defining the cortical bone, the proximal and distal epiphyseal cancellous bone and medullar cavity regions are converted into NURBS surfaces using (GEOMAGIC STUDIO).

Short-term antidepressant treatment has long-lasting effects, and reverses stress-induced decreases in bone features in rats

Antidepressants are among the most-prescribed class of drugs in the world and though weight gain is a common outcome of antidepressant treatment, that effect is not well understood. We employed an animal model comprised of 2 weeks of chronic restraint stress with antidepressant treatment, followed by diet-induced obesity. We showed that short-term antidepressant treatment had long-lasting effects, not only leading to weight gain, but also enhancing trabecular and cortical bone features in rats; therefore, weight gain in this model was different from that of the classic diet-induced obesity. Late in the post-restraint recovery period, antidepressant-treated animals were significantly heavier and had better bone features than saline-treated controls, when assessed in the distal femoral metaphysis. The propensity to gain weight might have influenced the rate of catch-up growth and bone allometry, as heavier animals treated with fluoxetine also had enhanced bone features when compared to non-stressed animals. Therefore, short-term antidepressant treatment ameliorated the long-term effects of stress on body growth and bone. Growth and bone structural features were associated with leptin levels, and the interaction between leptin levels and antidepressant was significant for bone mineral content, suggesting that short-term antidepressants in the context of long-term diet-induced obesity modified the role of leptin in bone formation. To our knowledge this is the first study reporting that short-term antidepressant treatment has long-lasting effects in restoring the effects of chronic stress in body weight and bone formation. Our findings may be relevant to the understanding and treatment of osteoporosis, a condition of increasing prevalence due to the aging population.

Assessment of cortical bone material distribution in medial column of proximal humerus with computed tomography

Objective: To evaluate the cortical bone characteristics in the medial column of proximal humerus. Methods: A total of one hundred and three healthy adults who underwent shoulder computed tomography scanning in Tianjing Hospital were included in this study.The subjects were divided into three groups according to the age: group A (20-39 years), group B (40-59 years), and group C (>60 years). Cortical bone mapping (CBM) was used to analyze ordinary clinical CT scans using Stradwin 5.2 software.Colors thickness maps were created for each proximal humerus.The region of interest (ROI) 1-6 were set at three levels of the lateral and medial column of proximal humerus.Cortical thickness (CTh), cortical mass surface density (CMSD), and endocortical trabecular bone mineral density (ECTD) were assessed in the three slices in proximal metaphysis.The impact of age, gender to the cortical bone indices of medial column of proximal humerus were investigated with relative analysis.Cortical indices of the lateral and medial column were compared with independent samples t test. Results: In ROI 2 and 3, men had higher cortical bone values than women, and significant differences in ECTD and CMSD were found in ROI 2, 3 and ROI 2 (t=2.100, 2.238, 2.530, all P<0.05). The lineal regression analysis showed that all cortical indices in ROI 1-3 decreased significantly with age for both women and men (r(2)=0.042-0.248, all P<0.05). In group A-C, the medial columns had higher CTh and CMSD values than lateral sides in plane 1, although significant differences were found only in group A (t=3.696, 3.749, both P<0.05). The highest CTh, CMSD and ECTD of the medial compact bone was detected in ROI 1, followed by ROI 2 and 3 in group A (F=5.867, 6.776, 19.062, all P<0.05). The medial columns had approximately equivalent cortica indices values in ROI 1-3 in group B and C. Conclusion: It indicated that significant regional variation in all cortical parameters exists in the medial column of proximal humerus, and the indices are influenced by gender and age.

Inverse characterization of radius bone using low-frequency ultrasonic guided waves

The success of the cortical bone characterization using the axial transmission is highly dependent on the inversion model used to match experimental data with the true bone properties. Simplified models such as plate or cylinder are typically used in the literature. In our previous work, a more elaborate model based on a bone-like geometry built using semi-analytical finite element (SAFE) method was introduced. The model was successfully implemented in an inverse characterization routine using laboratory-controlled measurements on bone phantoms. Thus, the aim of this work is to apply the proposed inverse scheme on the characterization of ex-vivo radius samples. In order to do so, five radiuses were taken from donors aged between 53 and 88 years old and tested using typical axial transmission configuration. Ultrasonic guided wave modes were excited at low-frequency (100-400 kHz) using a piezoelectric transducer and measured using a laser interferometer at the middle of the diaphysis. The measured velocities were systematically compared to velocities obtained with the SAFE model in order to predict the cortical bone properties. For each sample, four parameters were estimated: (1) Young’s modulus; (2) density; (3) thickness; and (4) outer diameter. The results showed a notable correlation of the thickness and outer diameter with respect to the μCT images of the samples, while a less significant correlation was observed for the Young’s modulus and density with respect to the gray level of the μCT images.

Regional variations of cortical bone in the humeral head region: A preliminary study.

Incidence of proximal humeral fractures dramatically increased over the last decade due to demographic changes. The goal of this study was to analyze regional characteristics of cortical bone in the humeral head region using cortical bone mapping (CBM) technique. The proximal humerus of 103 healthy volunteers was imaged by clinical computed tomography (CT) scans. Three groups of volunteers were identified according to age: group A (20-39years), group B (40-59years), and group C (>60years). CBM was applied to create color 3D thickness maps for each proximal humerus. Cortical parameters, including the cortical thickness (CTh), cortical mass surface density (CM), and the endocortical trabecular density (ECTD) were measured over humeral head region after nine regions of interest (ROI) were defined. Cortical bone structure of the humeral head region varied dramatically in cross-section independent of age, with significant cortical thinning at the posterior wall. Particularly, notable cortical thinning was also found in the distal end of lateral wall at 60years of age or older. The degree of regional variability of cortical properties within lateral wall tended to diminish with age. Substantial regional variations in cortical bone structure at humeral head region were observed quantitatively in this study. These morphologic data provided useful information on clinical medicine such as surgical fixation.