Biomechanics of Bone / Bone Biomechanics
Behnoud Haghighi; Masoud Tahani; Gholam Reza Rouhi
Volume 5, Issue 1 , June 2011, , Pages 33-44
Abstract
Orthopedic screws are widely used devices for fixation of bone fractures. Progressive loosening of bone fixation screws, induced by stress shielding and subsequent adaptive bone remodeling, results in bone loss around the screw. A set of two-dimensional finite element models including cortical and cancellous ...
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Orthopedic screws are widely used devices for fixation of bone fractures. Progressive loosening of bone fixation screws, induced by stress shielding and subsequent adaptive bone remodeling, results in bone loss around the screw. A set of two-dimensional finite element models including cortical and cancellous bone with a functionally graded Ti-Hap screw was developed. A dimensionless set of stress-transfer parameters (STP) and strain energy density-transfer parameter (SEDTP) were developed to quantify the screw–bone load sharing. Lower STP and SEDTP values indicate weak stress and strain energy density transfer to bone which is a sign of stress shielding. The results indicated that STP and SEDTP values for FGM screw are higher than those of a fully metal screw. Moreover, reducing elastic modulus of metal fraction and increasing the volume fraction of ceramic decrease the stress shielding. For a partially graded screw (with both homogenous and FGM parts), the longer FGM part is, the greater are STP and SEDTP values. Furthermore, the results showed that decreasing compositional distribution exponent which shows composition change of FGM content from metal fraction toward ceramic fraction, increases the parameters. Results from this study are in admissible agreement with available clinical and experimental study.
Biomechanics of Bone / Bone Biomechanics
Shahab Mansourbaghaei; Majid Haghayegh; Seyed Mohammad Rajaei
Volume 3, Issue 3 , June 2009, , Pages 243-253
Abstract
An analytical method to predict the response of the inclined impact of a fluid filled elastic spherical shell having an arbitrary thickness with an elastic toroid is investigated in this paper which can be a model for analytical evaluation of blunt impact on the human head. The study is performed under ...
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An analytical method to predict the response of the inclined impact of a fluid filled elastic spherical shell having an arbitrary thickness with an elastic toroid is investigated in this paper which can be a model for analytical evaluation of blunt impact on the human head. The study is performed under a combination of Hertzian contact theory and the local effect of membrane and bending of the shell in order to state the implicit equation to determine the transmitted force. With respect to the analytical responses, it is concluded that transmitted force decreases and contact duration increases by increasing of attack angle in constant initial velocity. In addition, closed form solution is presented to obtain impact parameters including the duration, the maximum transferred load and the maximum acceleration of the shell which particularly important for the researchers. Therefore investigation of the important quantities of the impact problem with closed form solution is possible. On the other hand, limiting cases will be discussed in next step and the concluded results are validated by finite element methods to verify the response of the model. In this step, a good agreement between analytical responses and numerical results is observed that reveals the correctness of analytical equations. In the final step of this research, obtained results are compared with experimental data.
Tissue Engineering
Mohammad Haghpanahi; Mohammad Nikkhoo; Habibollah Peirovi
Volume 2, Issue 1 , June 2008, , Pages 47-56
Abstract
According to mechanobilogical studies as an infrastructure for tissue engineering researches, this paper presents a triphasic finite element modeling of intervertebral discs such a hydrated porous soft tissue. First, the governmental equations were derived on the basis of the laws of continuum mechanics. ...
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According to mechanobilogical studies as an infrastructure for tissue engineering researches, this paper presents a triphasic finite element modeling of intervertebral discs such a hydrated porous soft tissue. First, the governmental equations were derived on the basis of the laws of continuum mechanics. Then the standard Galerkin weighted residual method was used to form the finite element model. The implicit time integration schemes were applied to solve the nonlinear equations. The formulation accuracy and convergence for one dimensional case were examined with Simon's and Sun's analytical solutions and also Drost's experimental Data. It was shown that the mathematical model is in excellent agreement and has the capability to simulate the intervertebral disc response under different types of mechanical and electrochemical loading conditions. Finally, to have a short review of the capability of the model, a homogenous two dimensional version of the model was applied to simulate the response of a simple sagittal slice of the intervertebral disc.
Biomechanics of Bone / Bone Biomechanics
Mohammad Haghpanahi; Ali Gorginzadeh; Saba Sohrabi
Volume 1, Issue 2 , June 2007, , Pages 131-136
Abstract
Considering the life threatening consequences of the cervical spine injuries, the study of its biomechanical behavior has become important. The most common axis (second cervical vertebra) injury is called odontoid fracture, the majority of which is type II or dens fracture. In this study, an exact 3D ...
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Considering the life threatening consequences of the cervical spine injuries, the study of its biomechanical behavior has become important. The most common axis (second cervical vertebra) injury is called odontoid fracture, the majority of which is type II or dens fracture. In this study, an exact 3D finite element model of axis was developed and analyzed. To evaluate the stress distributions in the odontoid process during type II injuries, pressure loads were applied on the dens at locations where it is likely to come into contact with the surrounding neck construct. Results indicate stress concentration in the odontoid junction with the vertebral body, which suggests that there is a possibility of occurring type II fracture in the case of impaction of odontoid with atlas anterior arch, lateral masses and transverse ligament.
