Papers by Keyword: Cortical Bone

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Authors: Martina Lovrenić-Jugović, Zdenko Tonković, Ante Bakić
Abstract: The present paper is concerned with an experimental research and numerical modelling of the viscoelastic-viscoplastic-damage behaviour of bovine cortical bone. A one-dimensional constitutive model is proposed to predict the experimental behaviour under creep-recovery load conditions. The material parameters are determined by fitting experimental results. The derived algorithm for the integration of the proposed constitutive model is implemented into finite element formulation. The computational algorithm shows an excellent capability to describe the tensile behaviour of bovine cortical bone for the specific mechanical conditions analyzed.
Authors: Chih Ling Lin, Han Huang, Bronwen W. Cribb, Anthony Russell
Abstract: Human bone fracture associated with osteoporosis was hypothesized to be related to the alteration of mechanical properties in bones. In this work, cortical and trabecular bones from human femoral heads were studied. Bone samples of eight female and four male patients, with ages varying from 37 to 93 years, were collected from total hip replacement surgery. Reduced modulus (Er) and hardness (H) of osteons, interstitial lamellae and trabeculae were characterized by nanoindentation. The results showed both the reduced modulus and hardness of the interstitial lamellae were significant higher than those of osteons and trabeculae. Though there was no significant difference in microstructures in the Group A (age < 60 years) and B (age > 60 years), the Group B bones demonstrated to be stiffer.
Authors: Ryoichi Suetoshi, Dorian Cretin, Shinji Ogawa, Takayoshi Nakano
Abstract: Following artificial hip joint implantation, a stress inhibition, applied to bone in the surroundings of implants, causes a structural change in bone called bone loss. To evaluate the bone mechanical characteristics, it is essential to investigate the elastic properties of cortical bone. In this article a pair of donor femora was investigated, one with an implant and the other without. Differences in Speed of Sound (SOS), a parameter reflecting elastic properties, were measured in both femora by ultrasound transmission. As a result, in almost all areas, the femur that was implanted showed significantly lower cortical SOS. Our results indicated that the change in the mechanical function of bone, due to the introduction of femoral implants, could be evaluated by the measurement of SOS.
Authors: Dong Woo Jang, Swapan Kumar Sakar, Min Sung Kim, Yong Ki Min, Ho Yeon Song, Byong Taek Lee
Abstract: The HAp-(t-ZrO2) ceramic composites with mimetic osteon microstructures were fabricated to investigate the technical feasibility of fabricating natural bone mimetics by a combination of multi-extrusion and rolling processes. The HAp and graphite powders were mixed with ethylene vinyl acetate and stearic acid using a shear mixer, and the mixture was extruded by the multi-extrusion process to create filaments. A HAp sheet was prepared by a rolling process. The HAp filaments and carbon filaments were arranged one by one on the HAp sheet, and the system was rolled to form a mimetic osteon microstructure. Burning out and sintering processes were performed for removal of the organic binder and graphite and for densification. The pore diameter and core of the mimetic osteon microstructure were approximately 50μm and 150μm, respectively. The porosity and bending strength were approximately 60% and 177MPa, respectively in the sample sintered at 1450°C.
Authors: Claudia Fleck
Abstract: Bone is a complex natural composite material built of organic and anorganic components and very well adapted to the in vivo loading conditions. The material exhibits an excellent damage resistance under static and fatigue loading conditions. This is partially due to self-healing processes, but to a great extent also to its hierarchical microstructure. The investigation of the deformation behaviour and the damage mechanisms on different length scales gives valuable insight into which level(s) of hierarchy influence the fatigue resistance in which way. In the present work, cyclic deformation tests have been performed on cortical bone specimens. On one hand, stress-strain-hysteresis measurements in different types of tests, such as constant amplitude tests, load increase tests, and combined static and cyclic tests, give information on the active damage mechanisms. For example, changes in the development of the stiffness, non-elastic strain amplitude and non-elastic mean strain as a result of different loading velocities and stress levels allow the discrimination between time and cycle dependent damage mechanisms. These results were correlated with microstructural investigations of the damage development on different hierarchical levels by light and scanning electron microscopy.
Authors: Dae Gon Woo, Han Sung Kim, Chang Yong Ko, Beob Yi Lee, Gye Rae Tack, Young Ho Kim
Abstract: In the present study, changes of morphologies and mechanical characteristics in the lumbar vertebrae of the ovariectomised (OVX) rats were investigated and analyzed by Finite Element (FE) and Rapid-Prototyped (RP) models based on micro-computed tomography (micro-CT). In previous researches, there were many studies about morphology such as bone mineral density and trabecular microstructure. However, detecting and tracking local changes were few in the trabecular and cortical bone of the lumbar vertebrae for the OVX rats. Experimental and simulated studies were used to investigate mechanical characteristics of the lumbar vertebral bones for the OVX rats. Three dimensional (3D) geometries of the models (RP and FE models), generated from in-vivo micro-CT scan data, were obtained from the 4th lumbar of the OVX rats. Three specimens (whole vertebral, trabecular and cortical bone models) were generated and analyzed in the simulated compression tests. For further verification, the experimental compression test for RP models ‘instead of real bone specimens’ was performed to indirectly validate the results of the simulated compression test for the FE models. The results were similar to those of the compression test simulated by micro-FE analysis. The present study showed the efficiency of the combined method (FE and RP techniques based on in-vivo micro-CT) as a nondestructive evaluation.
Authors: Adel A. Abdel-Wahab, Vadim V. Silberschmidt
Abstract: Bone is the principal structural component of a skeleton: it assists the load-bearing framework of a living body. Structural integrity of this component is important; understanding of its mechanical behaviour up to failure is necessary for prevention and diagnostic of trauma. Bone fractures occur in both low-energy trauma, such as falls and sports injury, and high-energy trauma, such as car crash and cycling accidents. By developing adequate numerical models to predict and describe the deformation and fracture behaviour up to fracture of a cortical bone tissue, a detailed study of reasons for, and ways to prevent or treatment methods of, bone fracture could be implemented. This study deals with both experimental analysis and numerical simulations of this tissue and its response to impact dynamic loading. Two areas are covered: Izod tests for quantifying a bone’s behaviour under impact loading, and a 3D finite-element model simulating these tests. In the first part, properties of cortical bone tissue were investigated under impact loading condition. In the second part, a 3D numerical model for the Izod test was developed using the Abaqus/Explicit finite-element software. Bone has time-dependent properties – viscoelastic – that were assigned to the specimen to simulate the short term event, impact. The developed numerical model was capable of capturing the behaviour of the hammer-specimen interaction correctly. A good agreement between the experimental and numerical data was found.
Authors: Chuan Shao Wu, Fu Tsai Chiang, Jui Pin Hung
Abstract: This study was aimed at investigating the effect of the bone compositions on the fracture toughness of bovine cortical bone. A series of the SENB bovine cortical bone specimens were tested to assess the fracture toughness. Dual energy X-ray absorptiometry (DEXA) was applied to determine the mineral content of each bovine cortical specimen and hence the porosity and bone mineral fraction were measured. Current results indicate that the mean value fracture toughness is 9.37 MNm3/2. Moreover, the fracture toughness was found to be significantly correlated with the apparent wet bone density and porosity of bone structure. No apparent correlations are found among clinical BMD and mechanical properties, implying that the BMD is an invalid indicator of the bone properties. Additionally, the tested data were fitted to the relationship, based on power law model, that the fracture toughness increase as a power (1.526) of increasing volume fraction and as a power of increasing bone mineral fraction (0.8195). These data indicate that small changes in the amount or density of compact bone tissue exert a more pronounced influence on fracture property.
Authors: Alexandru Mircea Nicolau, Elisabeta Vasilescu, Vlad Gabriel Vasilescu, Marian Iulian Neacsu
Abstract: This paper presents some results of the experimental investigations that were aimed at assessing the primary stability of orthodontic mini-implant anchorage by measuring the tensile force with a special device adapted for traction in the axial direction and at a 45 degree angle, taking as variables bone characteristics (thickness and cortical bone density, thickness and density of the medulla). We used samples (pork ribs) whose characteristics were measured at computer tomography with a specialized software, in which there have been inserted orthodontic mini-implants with spherical head, round thread having different characteristics of shape and dimensions of the thread (length diameter, pitch). Experiments have provided information on the relationship between bone characteristics of samples and maximum traction force in the axial direction and at 45degree angle, as well as mini-implant primary stability.
Authors: Liang Wen, Zi Han Zhao, Jin Bang Song, De Dong Yu, Ming Chen, Steve G.F. Shen
Abstract: Cutting force and temperature are the two chief factors affecting bone rehabilitation during bone cutting in many orthopedic surgeries. To reveal new knowledge of thermal and force when milling cortical bone, slotting experiments were carried on high-speed milling platform. Cutting force and temperature were measured during the milling process. The effects of cutting inputs on cutting thermal and force were researched in detail. The results showed that: feed rate and spindle speed had a great impact on the milling temperature, while the milling force was mainly influenced by spindle speed. A feed rate of 1.0-1.4 mm/s is recommended to obtain preferable milling force and temperature, and a larger feed rate of 1.2-1.4 mm/s is advised to use with a lower spindle speed (8000-20000 r/min), while a smaller feed rate of 1.0-1.2 mm/s should be chosen when spindle speed was between 20000-40000 r/min. Feeding parallel to the growth direction of the cortical bone can significantly reduce the milling temperature, but there was no obvious change in milling force. The lowest cutting temperature obtained during the experiment was around 50 °C without coolant, which was acceptable for orthopedic surgeries.
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