幼兒半椎體所致脊柱側(cè)凸后路矯形三維有限元分析
[Abstract]:Objective: congenital scoliosis is a disease with high incidence and serious physical and mental health, especially in children with scoliosis, especially in children with scoliosis deformity, poor cardiopulmonary function, complex and serious malformation, high incidence of surgical complications and high risk of anesthesia, which has always been a difficult problem in the field of scoliosis treatment. Malformation requires early surgical correction, but it needs to minimize the effect on the growth and development of the spine. Therefore, the choice of orthopedic and vertebral fusion segments is the key factor affecting the curative effect and prognosis. In the process of orthopedics, the selection of fixed segments is mainly based on the clinical experience of doctors, and the evidence of biomechanics is insufficient. Therefore, it is easy to lead to poor correction, dissatisfaction, or postoperative complications such as spinal decompensation. Based on this, this study uses the established Congenital scol of the established children's hemivertebra. Iosis) the three-dimensional finite element model (finite element model, FEM) is used to simulate posterior hemi vertebral resection, pedicle screw fixation, and compare the biomechanical characteristics of different fixed segments, so as to provide a theoretical basis for clinical practice.
Method:
1, obtain images: 1 children with hemivertebra caused scoliosis, male, 2 years and 9 months, 12 hemivertebra, body weight 14kg, height 90cm. horizontal position, SIEMENS 64 row spiral CT from second cervical spine to sacral scan, thickness 1.25mm, interlayer space 0mm, scan range including all bone structure and intervertebral disc. Obtain Dicom format CT flat. 470 images were swept, and 148 effective parts were used in actual modeling.
2, a three-dimensional geometric model is established: the obtained Dicom format image is inverted into the reverse engineering software Mimics14.0, and the primary three-dimensional model of the thoracic vertebra, the lumbar vertebra and the intervertebral disc is generated by the mask, segmentation, and smoothness of the original image. The model's positive side view is compared with the clinical positive lateral X ray, and the size of the hemi vertebral body is measured on the model. Product, Cobb angle, etc.
3, simulated posterior orthopedic surgery: after simple treatment of the model, the 3-Matic5.1 treatment software was introduced into the simulated posterior hemivertebra resection with pedicle screw fixation. The pedicle screws were inserted before the operation, the twelve thoracic vertebrae were resected, the orthopedics was installed, the T11 and L1 intervertebral space were gradually closed, and the correction of scoliosis deformity was achieved. The orthopedic effect was satisfactory compared with the postoperative X-ray.
4, establish a three-dimensional finite element model: in 3-Matic5.1, the pedicle screws and orthopedics, vertebrae, and intervertebral discs are assembled, and the whole mesh is meshed. Then the model of congenital scoliosis is introduced into Mimics14.0 again, and the modulus of elasticity of each component of the model is set, and the related parameters such as pines ratio are obtained, and the congenital scoliosis is obtained. A convex three-dimensional finite element model.
5, the finite element analysis is carried out: the model of the scoliosis caused by the children's semi vertebral body is introduced into the finite element analysis software ANSYS13.0. The model is constrained (the bottom of the four groups of models is constrained, the displacement is limited in all directions), and the vertical downward pressure is imposed on the upper surface of the upper body (10). 0N, 200N, 300N, 400N, 500600N, the vertical upward pressure 100N, 200N, 300N, 400N, 500600N) are applied. The equivalent stress and displacement clouds of different fixed segments are obtained, and the stress and displacement changes of different fixed segments are compared.
Result:
1 a three-dimensional finite element model of scoliosis caused by children's hemivertebra was established, including the thoracic vertebra, the lumbar vertebra, and the intervertebral disc. There were 105252 units and 185849 nodes, including the thoracic vertebra model 2, the unit 31576, the node 56105, the lumbar model 2, the unit 37890, the node 67281, the disc model (nucleus pulposus + ring) 5, the unit 11577, node 21163. One.
2 the finite element model of scoliosis caused by the hemivertebra of young children vividly depicts the characteristics of the children's spine: the children's spine is wide and slightly oval; the height of the vertebral body is obviously higher than the thickness of the intervertebral disc; the vertebral foramen is more and the pore size is larger; the cancellous bone and the dense bone are mutually inclusive and difficult to define. The model is in the clinical general image, the X-ray curve of the spine curve. The volume of the chest 12 semi vertebral body is 3793mm3, the maximum length 31.27mm, the maximum height is 15.13mm, the preoperative Cobb angle is 40.2 degrees.
3 successfully completed posterior hemi vertebral resection and pedicle screw internal fixation. According to the different segments, individual groups were divided into group T_ (10) ~L_1 (3 screws on the concave and convex sides), T_ (11) ~L_1 group (2 screws in concave and convex sides), T_ (11) ~L_2 group (3 screws in concave and convex sides), and T_ (10) ~L_2 group (4 screws in concave and convex sides), and the postoperative orthopedic effect was all Reach 100%.
4 software ANSYS13.0 analysis obtained the equivalent stress (Equivalent Stress) distribution diagram, displacement cloud map and safety coefficient cloud chart under four fixed schemes. As we can see, as the loading force increases gradually (10~4N), the displacement cloud graph of the model, the base of the stress cloud graph are not changed, and the values represented by each cloud map are linearly increasing. The equivalent stress cloud chart of the four groups of fixed schemes showed that the maximum equivalent stress was mainly concentrated on the Shiumi Ne screw head and screw body, the Shiumi Ne screw and the orthopedics, the Shiumi Ne screw and Shiumi Ne junction. The displacement cloud chart of the four groups of fixed schemes showed that the maximum displacement was in the top vertebral body of each group, and the downward trend decreased in turn. Potential.
5 at the top concave side of the four groups, the vertical downward pressure 300N was applied and the vertical upward pressure was applied on the convex side. The four groups of orthopedic schemes T_ (10) ~L_1, T_ (11) ~L_1, T_ (10) ~L_2, and T_ (11) ~L_2 group were the equivalent stress of the 52.552Mpa, 59.422Mpa, and four spinal models. In the four groups of orthopedic schemes, the force of the T_ (11) ~L_1 pedicle screws was the largest, the head or tail was extended a fixed segment, and the force of the pedicle screw was reduced, such as the T_ (10) ~L_1 group, T_ (11) ~ (11). L_2 group. But a further extension of a fixed segment to the head or tail, such as the T_ (10) ~L_2 group, has no obvious effect on the force of the pedicle screw. In the safety factor cloud of the four groups of orthopedics, the image range of the minimum safety factor of the T_ (11) ~L_1 group is 4-8 times that of the other three groups, and the greater the area of the minimum safety factor, the more vulnerable to fatigue. In conclusion, T_ (10) ~L_1, T_ (11) ~L_2 two can be used as a better surgical option.
Conclusion:
1 with advanced computer aided engineering software Mimics14.0 and ANSYS13.0, a three-dimensional finite element model of scoliosis caused by children's hemivertebra can be successfully established according to the CT images of children. The model can be successfully used to simulate the posterior hemivertebra resection of the vertebral pedicle screw for three-dimensional orthopedic surgery.
2 the three-dimensional finite element model of scoliosis caused by children's hemivertebra can be analyzed and simulated under various conditions. It provides a good biomechanical theory and clinical study for the scoliosis caused by hemivertebra in children, and provides good biology for the formulation of the individualized operation scheme for scoliosis patients. The foundation of mechanics research.
【學(xué)位授予單位】:河北醫(yī)科大學(xué)
【學(xué)位級別】:碩士
【學(xué)位授予年份】:2012
【分類號】:R726.8
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