FINITE ELEMENT MODELLING OF BONE TISSUE USING ANSYS 16.0-Develop a 3d model of bone.

OBJECTIVES:
 Prediction of bone behavior under different working load
 Study of bone response under fatigue loading
 Identifying and describing the structure and functions of the two types of bone tissue
 classifying bones according to their shapes or their relative proportion of the two types of bone tissues
Bones make good fossils. While the soft tissue of a once living organism will decay and fall away over time, bone tissue will, under the right conditions, undergo a process of mineralization, effectively turning the bone to stone.
LITERATURE REVIEW
M.Doblare et al. Bone tissue has very interesting structural properties. This is essentially due to composite structure of bone, composed by hydroxyapalite, collagen, small amounts of proteoglycans, noncollagenous proteins and water. Inorganic components are mainly responsible for the compression strength and stiffness, while organic components provide the corresponding tension properties.
From microscopic point of view, bone tissue is said to be non-homogenous, porous and anisotropic. We usually discuss about two types of bone tissue. First one is trabecular or cancellous bone with 50-95% porosity and it is found in cuboidal bones, flat bones and at the ends of the long bones. Second type is cortical or compact bone with 5-10% porosity and different types of pores. Vascular porosity is the largest (50 um diameter), formed by the Haversian canals (aligned with the long axis of the bone) and Volkmanns’s canals (transverse canals connecting Haversian canals) with calipers and nerves. Cortical bone consists of cylindrical structures known as osteons or Haversian systems, with a diameter of about 200 um forced by cylindrical lamellae surrounding the Haversian canal.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4686238/# Sabet FA, Raeisi Najafi A, Hamed E, Jasiuk I.InterfaceFocus.2016Feb6;6(1):20150055.doi:10.1098/rsfs.2015.0055
The hierarchical structure of bone significantly contributes to high stiffness, strength, toughness and energy absorption, light weight and other remarkable mechanical properties of bone. There are two main types of bone: cortical (compact or dense) and trabecular (cancellous or spongy). The cortical bone forms a dense, hard outer shell that mostly contributes to bone stiffness and strength. The porous trabecular bone fills interior spaces or ends of long bones and is mainly responsible for energy absorption and load distribution in the body. Bone also serves as a reservoir of minerals such as calcium and phosphorus.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3805534/# Bone damage removal and callus formation in response to fatigue loading are essential to prevent fractures. Periostin (Postn) is a matricellular protein that mediates adaptive response of cortical bone to loading. Whether and how periostin influences damage and the injury response to fatigue remains unknown. We investigated the skeletal response of Postn -/- and Postn +/+ mice after fatigue stimulus by axial compression of their tibia. In Postn +/+ mice, cracks number and surface (CsNb, CsS) increased 1h after fatigue, with a decrease in strength compared to non-fatigued tibia. At 15 days, CsNb had started to decline, while CtTV and CtBV increased in fatigued vs non-fatigued tibia, reflecting a woven bone response that was present in 75% of the fatigued bones. Cortical porosity and remodelling also prominently increased in the fatigued tibia of Postn +/+ mice. At 30 days, paralleling a continuous removal of cortical damage, strength of the fatigued tibia was similar to the non-fatigue tibia. In Postn -/- mice, cracks were detectable even in the absence of
fatigue, while the amount of collagen crosslinks and tissue hardness was decreased compared to Postn +/+. Fatigue significantly increased CsNb and CsS in Postn -/-, but was not associated with changes in CtTV and CtBV, as only 16% of the fatigued bones formed some woven bone. Cortical porosity and remodelling did not increase either after fatigue in Postn -/- , and the level of damage remained high even after 30 days. As a result, strength remained compromised in Postn -/- mice. Contrary to Postn +/+ , which osteocytic lacunae showed a change in the degree of anisotropy (DA) after fatigue, Postn-/- showed no DA change. Hence periostin appears to influence bone materials properties, damage accumulation and repair, including local modeling/remodeling processes in response to fatigue. These observations suggest that the level of periostin expression could influence the propensity to fatigue fractures.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4524611/# One of the major challenges that developing organs face is scaling, that is, the adjustment of physical proportions during the massive increase in size. Bone superstructures are projections that typically serve for tendon and ligament insertion or articulation. Therefore, superstructure position along the bone is crucial for musculoskeletal functionality. As bones are rigid structures that elongate only from their ends, it is unclear how superstructure positions are regulated during growth to end up in the right locations. Here, by analyzing a massive database of micro-CT images of developing mouse long bones, we show that all superstructures maintain their relative positions throughout development. It has been suggested that during development, superstructures are continuously reconstructed and relocated along the shaft, a process known as drift. However, our analysis reveals that most superstructures did not drift at all, implying the involvement of another mechanism. Indeed, we identify a novel mechanism for bone scaling, whereby each bone exhibits a specific and unique balance between the growth rates from its two ends, which accurately maintains the relative position of its superstructures. The three-dimensional (3D) morphology of bones is fundamental to the ability of an organism to move, feed, and protect itself. Yet, we know little about the mechanisms that regulate bone shaping during development. Most bones develop by endochondral ossification, a process whereby an anlage of cartilage roughly in the shape of the future bone is formed and then gradually replaced by mineralized tissue [5].
RESEARCH METHODOLOGY INTRODUCTION Biomechanics is the application of mechanical principles on living organisms. By applying the laws and concepts of physics, biomechanical mechanisms and structures can be simulated and studied. Finite Element Method (FEM) is widely accepted as a power tool for biomechanics modeling. Irregular geometry, complex microstructure of biological tissues and loading situations are specific problems of the FEM in biomechanics and are still difficult to model. Straight beam theory is proposed to calculate stress distributions in the femur due to the body weight and some muscles force given some major simplifying assumptions on the muscles and the joint reactions. FE model would be advantageous in complementing experimental works And in overcoming the inherent limitations associated with experimental studies which can provide only limited amount of information. Although some of these methods were found to provide enough automation, intrinsic accuracy, robustness and generality to be used in clinical applications. Hard tissues are rigid organs that form part of the endoskeleton of vertebrates. Bone tissue is a type of dense connective hard tissue. Bones is composed of inorganic salts impregnated in a matrix of collagen fibers, proteins and minerals. They maintain the shape of body and to assist in force transmission during movement. Long bones are characterized by a shaft, the diaphysis that is much longer than it is wide. The femur bone is the most proximal bone of the leg in vertebrates capable of walking or jumping. In human anatomy, the femur is the longest and largest bone but strongest under compression only. The femur at its bottom portion meshes with the tibia bone to create the knee joint. At its top end, the femur meshes with the acetabulum to create the hip joint. The femur is responsible for bearing the largest percentage of body weight during normal weight-bearing activities. The aim of this study is to create a model of human femur bone in CATIA software . This model was analyzed in FEM package ANSYS 16.0. This paper aims to construct a complete three-dimensional Femur bone from CT scan data. The CATIA software is used to create 3D models and smooth the surface of the domain. The Finite element method is applied to find the stress distribution and deformation on different implant materials at different load conditions . STEPS FOR MODELLING AND ANALYSIS OF A FEMUR BONE: 1. Design Considerations For FE analysis of femur bone, firstly the three dimensional model of femur was developed. In early studies either a frozen bone, a wet bone, synthetic bone or a bone with apparent density was analyzed but here, geometrical data of real proximal human femur bone in the form of CT scan image format of 17 years old male, whose weight is 75 Kg is obtained from CT scan is used. Digital Imaging and Communications in Medicine (DICOM) contains binary data elements. CT scan data in the form of DICOM consist of two-dimensional gray scaled images of a human male. The Hounsfield Unit corresponding to each element are averaged and converted into gray values and then to material properties of bone. CT images are a pixel map of the linear X-ray attenuation coefficient of tissue.

1. Meshing 3. Material Assignment 4. Description Of Model 5. Area Selection For Applying Constrains 6. Boundary Conditions 7. Area Selection For Applying Pressure 8. Analysis Of Structural Steel For different loads 9. Results and Coclusion
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