This study was aimed to estimate the effect of different ProDisc-C arthroplasty designs after it was implanted to C5-C6 cervicalspine. Finite element (FE) model of intact C5-C6 segments including the vertebrae and disc was developed and validated. Ball-and-socket artificial disc prosthesis model (ProDisc-C, Synthes) was implanted into the validated FE model and the curvature of the ProDisc-C prosthesis was varied. All models were loaded with compressed force 74 N and the pure moment of 1.8 Nm along flexion-extension and bilateral bending and axial torsion separately. The results indicated that the variation in the curvature of ball and socket configuration would influence the range of motion in flexion/extension, while there were not apparently differences under other conditions of loads. The method increasing the curvature will solve the stress concentration of the polyethylene, but it will also bring adverse outcomes, such as facet joint force increasing and ligament tension increasing. Therefore, the design of artificial discs should be considered comprehensively to reserve the range of motion as well as to avoid the adverse problems, so as not to affect the long-term clinical results.
Extracorporeal shock wave treatment is capable of providing a non-surgical and effective treatment modality for patients suffering from osteoarthritis. The major objective of current works is to investigate how the shock wave (SW) field would change if a bony structure exists in the path of the acoustic wave. Firstly, a model of finite element method (FEM) was developed based on Comsol software in the present study. Then, high-speed photography experiments were performed to record cavitation bubbles with the presence of mimic bone. On the basis of comparing experimental with simulated results, the effectiveness of FEM model could be verified. Finally, the energy distribution during extracorporeal shock wave treatment was predicted. The results showed that the shock wave field was deflected with the presence of bony structure and varying deflection angles could be observed as the bone shifted up in the z-direction relative to shock wave geometric focus. Combining MRI/CT scans to FEM modeling is helpful for better standardizing the treatment dosage and optimizing treatment protocols in the clinic.
We developed a three-dimensional finite element model of the pelvis. According to Letournel methods, we established a pelvis model of T-shaped fracture with its three different fixation systems, i.e. double column reconstruction plates, anterior column plate combined with posterior column screws and anterior column plate combined with quadrilateral area screws. It was found that the pelvic model was effective and could be used to simulate the mechanical behavior of the pelvis. Three fixation systems had great therapeutic effect on the T-shaped fracture. All fixation systems could increase the stiffness of the model, decrease the stress concentration level and decrease the displacement difference along the fracture line. The quadrilateral area screws, which were drilled into cortical bone, could generate beneficial effect on the T-type fracture. Therefore, the third fixation system mentioned above (i.e. the anterior column plate combined with quadrilateral area screws) has the best biomechanical stability to the T-type fracture.
Based on the application of finite element analysis in spine biomechanics, the research progress of finite element method applied in lumbar spine mechanics is reviewed and the prospect is forecasted. The related works, including lumbar ontology modeling, clinical application research, and occupational injury and protection, are summarized. The main research areas of finite element method are as follows: new accurate modeling process, the optimized simulation method, diversified clinical effect evaluation, and the clinical application of artificial lumbar disc. According to the recent research progress, the application prospects of finite element method, such as automation and individuation of modeling process, evaluation and analysis of new operation methods and simulation of mechanical damage and dynamic response, are discussed. The purpose of this paper is to provide the theoretical reference and practical guidance for the clinical lumbar problems by reviewing the application of finite element method in the field of the lumbar spine biomechanics.
In order to explore the feasibility of applying magnetic detection electrical impedance tomography (MDEIT) on respiratory monitoring, aiming at the forward problem of magnetic detection electrical impedance tomography, we calculated the electric potential and current density distribution inside the imaging object by using the finite element method. We then got magnetic induction intensity outside the object at the end of exhaling and inhaling according to Biot-Savart's law. The results showed that the magnetic induction intensity at the end of inhaling was 8.875%, less than that at the end of exhaling. By the simulation results, we could understand the difference of magnetic induction intensity value surrounding the lung at the end of exhaling and inhaling due to the change of lung volume and electrical conductivity distribution better. Our research laid the foundation for the late image reconstruction and clinical disease detection.
Modified electroconvulsive therapy (MECT) and magnetic seizure therapy (MST) are effective treatments for severe major depression. MECT has better efficacy in the treatment than MST, but it has cognitive and memorial side effects while MST does not. To study the causes of these different outcomes, this study contrasted the electric filed strength and spatial distribution induced by MECT and MST in a realistic human head model. Electric field strength induced by MECT and MST are simulated by the finite element method, which was based on a realistic human head model obtained by magnetic resonance imaging. The electrode configuration of MECT is standard bifrontal stimulation configuration, and the coil configuration of MST is circular. Maps of the ratio of the electric field strength to neural activation threshold are obtained to evaluate the stimulation strength and stimulation focality in brain regions. The stimulation strength induced by MECT is stronger than MST, and the activated region is wider. MECT stimulation strength in gray matter is 17.817 times of that by MST, and MECT stimulation strength in white matter is 23.312 times of that by MST. As well, MECT stimulation strength in hippocampi is 35.162 times of that by MST. More than 99.999% of the brain volume is stimulated at suprathreshold by MECT. However, MST activated only 0.700% of the brain volume. The stimulation strength induced by MECT is stronger than MST, and the activated region is wider may be the reason that MECT has better effectiveness. Nevertheless, the stronger stimulation strength in hippocampi induced by MECT may be the reason that MECT is more likely to give rise to side effects. Based on the results of this study, it is expected that a more accurate clinical quantitative treatment scheme should be studied in the future.
As a representative part of the oral system and masticatory robot system, the modeling method of the dental model is an important factor influencing the accuracy of the multi-body dynamic model. Taking the right first molars of the masticatory robot as the research object, an equivalent model, point-contact higher kinematic pair composed of v-shaped surface and sphere surface, was proposed. Firstly, the finite element method was used to analyze the occlusal dynamics of the original model in three static contact cases (intrusive contact, centric occlusion, and extrusive contact) and one dynamic chewing case, and the expected bite force was obtained. Secondly, the Hertz contact model was adopted to establish the analytical expression of the bite force of the equivalent model in three static contact cases. The normal vectors and contact stiffness in the expression were designed according to the expected bite force. Finally, the bite force performance of the equivalent model in three static contact cases and one dynamic chewing case was evaluated. The results showed that the equivalent model could achieve the equivalent bite force of 8 expected items in the static contact cases. Meanwhile, the bite force in the early and late stages of the dynamic chewing case coincides well with the original model. In the middle stage, a certain degree of impact is introduced, but it can be weakened by subsequent trajectory planning. The equivalent modeling scheme of the dental model proposed in this paper further improves the accuracy of the dynamic model of the multi-body system. It provides a new idea for the dynamic modeling of other complex human contacts.
The dynamic analysis of the implantation process of a new vena cava filter was carried out by finite element analysis method to reveal the influence of the angle, length, width and thickness of the filter rod on its mechanical properties and the inner wall of the blood vessel. The results showed that the high-stress and high-strain areas of the filter were mainly concentrated in the connection between the filter rod and the filter wire. With the increase of the angle of the filter rod, the maximum equivalent stress and the maximum elastic strain on the filter wall decreased, while the maximum equivalent stress on the vascular wall increased. With the increase of the length of the filter rod, the maximum equivalent stress and strain peak of the filter wall increased, but the maximum equivalent stress of the vessel wall decreased. With the increase of the width and thickness of the filter rod, the maximum equivalent stress of the filter wall, the maximum elastic strain and the maximum equivalent stress of the vessel wall all showed an upward trend. The static safety factor of all filter models was greater than 1, and the structure after implantation was safe and reliable. The results of this study are expected to provide a theoretical basis for the structural optimization and deformation mechanism of the new type vena cava filter.
Lower extremity movement is a complex and large range of limb movement. Arterial stents implanted in lower extremity are prone to complex mechanical deformation, so the stent is required to have high comprehensive mechanical properties. In order to evaluate the mechanical property of different stents, in this paper, finite element method was used to simulate and compare the mechanical properties of six nitinol stents (Absolute Pro, Complete SE, Lifestent, Protégé EverFlex, Pulsar-35 and New) under different deformation modes, such as radial compression, axial compression/tension, bending and torsion, and the radial support performance of the stents was verified by experiments. The results showed that the comprehensive performance of New stent was better than other stents. Among which the radial support performance was higher than Absolute Pro and Pulsar-35 stent, the axial support performance was better than Complete SE, Lifestent and Protégé EverFlex stent, the flexibility was superior to Protégé Everflex stent, and the torsion performance was better than Complete SE, Lifestent and Protégé Everflex stent. The TTR2 type radial support force tester was used to test the radial support performance of 6 types, and the finite element analysis results were verified. The mechanical properties of the stent are closely related to the structural size. The result provides a reference for choosing a suitable stent according to the needs of the diseased location in clinical applications.
This study aims to overcome the shortcomings such as low efficiency, high cost and difficult to carry out multi-parameter research, which limited the optimization of infusion bag configuration and manufacture technique by experiment method. We put forward a fluid cavity based finite element method, and it could be used to simulate the stress distribution and deformation process of infusion bag under external load. In this paper, numerical models of infusion bag with different sizes was built, and the fluid-solid coupling deformation process was calculated using the fluid cavity method in software ABAQUS subject to the same boundary conditions with the burst test. The peeling strength which was obtained from the peeling adhesion test was used as failure criterion. The calculated resultant force which makes the computed peeling stress reach the peeling strength was compared with experiment data, and the stress distribution was analyzed compared with the rupture process of burst test. The results showed that considering the errors caused by the difference of weak welding and eccentric load, the flow cavity based finite element method can accurately model the stress distribution and deformation process of infusion bag. It could be useful for the optimization of multi chamber infusion bag configuration and manufacture technique, leading to cost reduction and study efficiency improvement.