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.
In order to check the neck response and injury during motor vehicle accidents, we developed a detailed finite element model for human cervical spine C4-C6. This model consisted of cortical bone, cancellous bone, annulus, nucleus, ligaments and articular facet, and it also set up contact in the contacting parts for simulating the movement perfectly under frontal impact. This model could be used for stress and strain distribution after the frontal impact load was applied on this model. During the process of frontal impact, the most displacement simulated data were in the interval range of experimental data. The experimental results showed that this model for the human cervical spine C4-C6 simulated the movement under the frontal impact with fidelity, and reflected the impact dynamics response on the whole.
In the present study, a finite element model of L4-5 lumbar motion segment was established based on the CT images and a combination with image processing software, and the analysis of lumbar biomechanical characteristics was conducted on the proposed model according to different cases of flexion, extension, lateral bending and axial rotation. Firstly, the CT images of lumbar segment L4 to L5 from a healthy volunteer were selected for a three dimensional model establishment which was consisted of cortical bone, cancellous bone, posterior structure, annulus, nucleus pulposus, cartilage endplate, ligament and facet joint. The biomechanical analysis was then conducted according to different cases of flexion, extension, lateral bending and axial rotation. The results showed that the established finite element model of L4-5 lumbar segment was realistic and effective. The axial displacement of the proposed model was 0.23, 0.47, 0.76 and 1.02 mm, respectively under the pressure of 500, 1 000, 1 500 and 2 000 N, which was similar to the previous studies in vitro experiments and finite element analysis of other people under the same condition. The stress distribution of the lumbar spine and intervertebral disc accorded with the biomechanical properties of the lumbar spine under various conditions. The established finite element model has been proved to be effective in simulating the biomechanical properties of lumbar spine, and therefore laid a good foundation for the research of the implants of biomechanical properties of lumbar spine.
A comprehensive, geometrically accurate, nonlinear C0-T1 three-dimensional finite element (FE) model was developed for the biomechanical study of human cervical spine and related disorders. The model was developed with anatomic detail from the computed tomography (CT) images of a 46-year old female healthy volunteer, and applied the finite element model processing softwares such as MIMICS13.1, Hypermesh11.0, Abaqus 6.12-1, etc., for developing, preprocessing, calculating and analysing sequentially. The stress concentration region and the range of motion (ROM) of each vertebral level under axial rotation, flexion, extension, and lateral bending under physiologic static loadings were observed and recorded. The model was proven reliable, which was validated with the range of motion in previous published literatures. The model predicted the front and side parts of the foramen magnum and contralateral pedicle and facet was the stress concentration region under physiological loads of the upper spine and the lower spine, respectively. The development of this comprehensive, geometrically accurate, nonlinear cervical spine FE model could provide an ideal platform for theoretical biomechanical study of human cervical spine and related disorders.
The validated finite element head model (FEHM) of a 3-year-old child, a 6-year-old child and a 50th percentile adult were used to investigate the effects of head dimension and material parameters of brain tissues on the head rotational responses based on experimental design. Results showed that the effects of head dimension and directions of rotation on the head rotational responses were not significant under the same rotational loading condition, and the same results appeared in the viscoelastic material parameters of brain tissues. However, the head rotational responses were most sensitive to the shear modulus (G) of brain tissues relative to decay constant (β) and bulk modulus (K). Therefore, the selection of material parameters of brain tissues is most important to the accuracy of simulation results, especially in the study of brain injury criterion under the rotational loading conditions.
This study aims to develop and validate a three-dimensional finite element model of inferior cervical spinal segments C4-7 of a healthy volunteer, and to provide a computational platform for investigating the biomechanical mechanism of treating cervical vertebra disease with Traditional Chinese Traumotology Manipulation (TCTM). A series of computed tomography (CT) images of C4-7 segments were processed to establish the finite element model using softwares Mimics 17.0, Geromagic12.0, and Abaqus 6.13. A reference point (RP) was created on the endplate of C4 and coupled with all nodes of C4. All loads (±0.5, ±1, ±1.5 and ±2 Nm) were added to the RP for the six simulations (flexion, extension, lateral bending and axial rotation). Then, the range of motion of each segment was calculated and compared with experimental measurements of in vitro studies. On the other hand, 1 Nm moment was loaded on the model to observe the main stress regions of the model in different status. We successfully established a detail model of inferior cervical spinal segments C4-7 of a healthy volunteer with 591 459 elements and 121 446 nodes which contains the structure of the vertebra, intervertebral discs, ligaments and facet joints. The model showed an accordance result after the comparison with the in vitro studies in the six simulations. Moreover, the main stress region occurred on the model could reflect the main stress distribution of normal human cervical spine. The model is accurate and realistic which is consistent with the biomechanical properties of the cervical spine. The model can be used to explore the biomechanical mechanism of treating cervical vertebra disease with TCTM.
Finite element (FE) model of thorax with high biofidelity is one of the most important methods to investigate thoracic injury mechanism because of the absence of pediatric cadaver experiments. Based on the validated thorax finite element model, the FE models with equivalent muscles and real geometric muscles were developed respectively, and the effect of muscle biofidelity on thoracic injury was analyzed with reconstructing pediatric cadaver thorax impact experiments. The simulation results showed that the thoracic impact force, the maximum displacement and the maximum von-Mises stress of FE models with equivalent muscles were slightly greater than those from FE models with real geometric muscles, and the maximum principal strains of heart and lung were a little lower. And the correlation coefficient between cadaver corridor and FE model with real muscles was also greater than that between cadaver corridor and FE model with equivalent muscles. As a conclusion, the FE models with real geometric muscles can accurately reflect the biomechanical response of thorax during the impact.
The pediatric cadaver impact experiments were reconstructed using the validated finite element(FE) models of the 3-year-old and 6-year-old children. The effect of parameters, such as hammer size, material parameters and thorax anatomical structure characteristics, on the impact mechanical responses of 3-year-old and 6-year-old pediatric thorax was discussed by designing reasonable finite element simulation experiments. The research results showed that the variation of thorax contact peak force for 3-year-old group was far larger than that of 6-year-old group when the child was impacted by hammers with different size, which meant that 3-year-old child was more sensitive to hammer size. The mechanical properties of thoracic organs had little influence on the thorax injury because of the small difference between 3-year-old and 6-year-old child in this research. During the impact, rib deformation led to different impact location and deformation of internal organs because the 3-year-old and 6-year-old children had different geometrical anatomical structures, such as different size of internal organs. Therefore, the injury of internal organs in the two groups was obviously different. It is of great significance to develop children finite element models with high biofidelity according to its real anatomical structures.
Muscle atrophy of the residual limb after lower-limb amputation is a disadvantage of amputees' rehabilitation. To investigate the biomechanics mechanism of muscle atrophy of the residual limb, we built a finite element model of a residual limb including muscle, skeletons and main vessels based on magnetic resonance images of a trans-femoral amputee, and studied the biomechanics effects of the socket of the lower-limb prosthesis on the soft tissue and vessels in the residual limb. It was found that the descending branch of the lateral femoral circumflex artery suffered the most serious constriction due to the extrusion, while that of the deep femoral artery was comparatively light. Besides, the degree of the constriction of the descending branch of the lateral femoral circumflex vein, femoral vein and deep femoral vein decreased in turn, and that of the great saphenous vein was serious. The stress-strain in the anterior femoral muscle group were highest, while the stress concentration of the inferior muscle group was observed at the end of the thighbone, and other biomechanical indicators at the inferior region were also high. This study validated that the extrusion of the socket on the vessels could cause muscle atrophy to some degree, and provided theoretical references for learning the mechanism of muscle atrophy in residual limb and its effective preventive measures.
The decrease of corneal stiffness is the key factor leading to keratoconus, and the corneal collagen fiber stiffness and fiber dispersion are closely related to the corneal biomechanical properties. In this paper, a finite element model of human cornea based on corneal microstructure, namely collagen fiber, was established before and after laser assisted in situ keratomileusis (LASIK). By simulating the Corvis ST process and comparing with the actual clinical results, the hyperelastic constitutive parameters and corneal collagen fiber stiffness modulus of the corneal material were determined before and after refractive surgery. After LASIK, the corneal collagen fiber stiffness modulus increased significantly, and was highly correlated with central corneal thickness (CCT). The predictive relationship between the corneal collagen fiber stiffness modulus and the corresponding CCT before and after surgery was: k1 before = exp(9.14 − 0.009CCTbefore), k1 after = exp(8.82 − 0.008CCTafter). According to the results of this study, the central corneal thickness of the patient can be used to estimate the preoperative and postoperative collagen fiber stiffness modulus, and then a personalized corneal model that is more consistent with the actual situation of the patient can be established, providing a theoretical reference for more accurately predicting the safe surgical cutting amount of the cornea.