Objective To establish the three-dimensional (3D) finite element model of the knee joint including posterolateral complex (PLC), and to simulate the reconstruction biomechanical analysis in this model. Methods The knee of a 26-year-old healthy man was scanned by MRI to obtain the image data of the knee in the coronal, sagittal, and axial position. First, Mimics10.01 and Hyperworks 8.0 softwares were used to extract each slice profile data of the knee joint in a two-dimensional image data respectively and to establish 3D geometric model of bone, meniscus, articular cartilage, and ligament. Second, Unigraphics software NX 4.0 was used to establish a 3D finite element model of knee joint, which had the functions of Mesh, material properties, component connection, and contact definition. Third, displacement measurement on the model and reconstructing biomechanical analysis for PLC simulation were performed. Results The 3D finite element model of the knee joint including PLC was established successfully. Under 134 N forward force, the tibia forward displacement was 4.83 mm. PLC simulation reconstruction biomechanical analysis of the 3D finite element model of the knee joint showed that under 10 N·m varus and external rotation torque conditions, the knee varus and external rotation angles of simulation reconstruction were greater than those of the intact knee, and less than those of PLC missing. Conclusion The 3D finite element model of the knee joint including PLC can be established by the reverse engineering, and it is valid and can be used as the basis for the biomechanical properties to analog reconstruction of PLC.
A three-dimensional finite element model of premaxillary bone and anterior teeth was established with ANSYS 13.0. The anterior teeth were fixed with strong stainless labial archwire and lingual frame. In the horizontal loading experiments, a horizontal retraction force of 1.5 N was applied bilaterally to the segment through hooks at the same height between 7 and 21 mm from the incisal edge of central incisor; in vertical loading experiments, a vertical intrusion force of 1.5 N was applied at the midline of lingual frame with distance between 4 and 16 mm from the incisal edge of central incisor. After loading, solution was done and displacement and maximum principle stress were calculated. After horizontal loading, lingual displacement and stress in periodontal membrane (PDM) was most homogeneous when the traction force was 14 mm from the edge of central incisor; after vertical loading, intrusive displacement and stress in PDM were most homogeneous when the traction force was 12 mm from the incisal edge of central incisor. The results of this study suggested that the location of center of resistance (CRe) of six maxillary anterior teeth is about 14 mm gingivally and 12 mm lingually to incisal edge of central incisor. The location can provide evidence for theoretical and clinical study in orthodontics.
A geometrical model of L4-L5 lumbar segment was constructed using a three-dimensional graphics software. Four conditions of the degenerated discs, i.e. light degeneration, moderate degeneration, severe degeneration and complete excision degeneration, were simulated with loading situations using finite element method under the condition of appropriate computational accuracy. By applying a vertical load of 378.93 N on L4 vertebral plate, stress nephograms on joint isthmus under four different working conditions were obtained. The results showed that the contacted area of facet joint was influenced by the degree of intervertebral disc degeneration level, which influenced the mises stress on joint isthmus. It was proved that joint isthmus was the important pressure-proof structure of the back of lumbar vertebra, and the stress values and distribution were related to structural stiffness of the back of lumbar vertebra as well as the contact area of facet joint. The conclusion could be the theoretical reference for the analysis of spinal biomechanics and artificial disc replacement as well.
In order to evaluate the safety performance of self-expandable NiTi alloy stents systematically, the dynamic safety factor drawn up by International Organization for Standardization, was used to quantitatively reflect the safety performance of stents. Based on the constitutive model of super-elastic memory alloy material in Abaqus and uniaxial tensile test data of NiTi alloy tube, finite element method and experiments on accelerated fatigue life were carried out to simulate the self-expansion process and the shape change process under the action of high and low blood pressure for three L-type stents of Φ8×30 mm, Φ10×30 mm, Φ12×30 mm. By analyzing the changes of stress and strain of self-expanding NiTi alloy stent, the maximum stress and strain, stress concentration position, fatigue strength and possible failure modes were studied, thus the dynamic safety factor of stent was calculated. The results showed that the maximum stress and plastic strain of the stent increased with the increase of grip pressure, but the maximum stress and strain distribution area of the stent had no significant change, which were all concentrated in the inner arc between the support and the connector. The dynamic safety factors of the three stents were 1.31, 1.23 and 1.14, respectively, which indicates that the three stents have better safety and reliability, and can meet the fatigue life requirements of more than 10 years, and safety performance of the three stents decreases with the increase of stent’s original diameter.
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.
An unequal loss of peripheral vision may happen with high sustaining multi-axis acceleration, leading to a great potential flight safety hazard. In the present research, finite element method was used to study the mechanism of unequal loss of peripheral vision. Firstly, a 3D geometric model of skull was developed based on the adult computer tomography (CT) images. The model of double eyes was created by mirroring with the previous right eye model. Then, the double-eye model was matched to the skull model, and fat was filled between eyeballs and skull. Acceleration loads of head-to-foot (Gz), right-to-left (Gy), chest-to-back (Gx) and multi-axis directions were applied to the current model to simulate dynamic response of retina by explicit dynamics solution. The results showed that the relative strain of double eyes was 25.7% under multi-axis acceleration load. Moreover, the strain distributions showed a significant difference among acceleration loaded in different directions. It indicated that a finite element model of double eyes was an effective means to study the mechanism of an unequal loss of peripheral vision at sustaining high multi-axis acceleration.
We developed a three-dimensional finite element model of the shoulder glenohumeral joint after shoulder arthroplasty including humerus shaft, scapular, scapular cartilage and eight muscles, while each of the muscles was simulated with 50 spring elements. To reduce the element number and improve the analytical precision, we used mixed tetrahedral and hexahedral elements in the model. We then used the model to calculate the biomechanics of the shoulder glenohumeral joint after hemiarthroplasty during humeral external rotation. Results showed that the maximum joint reaction force was 374.72 N and the maximum contact stress was 6.573 MPa together with the contact areas at 40° external rotation. These might be one of the reasons for prosthetic disarticulation, and would provide theoretical bases to prosthetic design.
The purpose of this study is to analyze the biomechanics of ankle cartilage and ligaments during a typical Tai Chi movement–Brush Knee and Twist Step (BKTS). The kinematic and kinetic data were acquired in one experienced male Tai Chi practitioner while performing BKTS and in normal walking. The measured parameters were used as loading and boundary conditions for further finite element analysis. This study showed that the contact stress of the ankle joint during BKTS was generally less than that during walking. However, the maximum tensile force of the anterior talofibular ligament, the calcaneofibular ligament and the posterior talofibular ligament during BKTS was 130 N, 169 N and 89 N, respectively, while it was only 57 N, 119 N and 48 N during walking. Therefore, patients with arthritis of the ankle can properly practice Tai Chi. Practitioners with sprained lateral ligaments of the ankle joint were suggested to properly reduce the ankle movement range during BKTS.
Based on the surgical model using transforaminal lumbar interbody fusion (TLIF) to treat lumbar spondylolisthesis, this paper presents the investigations of the biomechanical characteristics of cage and pedicle screw in lumbar spinal fusion implant fixed system under different combinations with finite element method. Firstly, combining the CT images with finite element pretreatment software, we established three dimensional nonlinear finite element model of human lumbar L4-L5 segmental slight slippage and implant under different fixed combinations. We then made a comparison analysis between the biomechanical characteristics of lumbar motion range, stress distribution of cage and pedicle screw under six status of each model which were flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation. The results showed that the motion ranges of this model under different operations were reduced above 84% compared with those of the intact model, and the stability of the former was improved significantly. The stress values of cage and pedicle screw were relatively larger when they were fixed by single fusion device additional unilateral pedicle screw, but there was no statistically significant difference. The above research results would provide reference and confirmation for further biomechanics research of TLIF extracorporal specimens, and finally provide biomechanical basis for the feasibility of unilateral internal fixed diagonal intervertebral fusion TLIF surgery.
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.