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Objective To establish the three-dimensional finite element model of lumbar spine(L) 3-5 segments of the normal spine of 14-year-old adolescents to analyze the biomechanical changes of the lumbar spine after different degrees of lumbar foraminal plasty, and to provide reference for improvement of adolescent foraminoplasty. Methods A14-year-old female volunteer with no previous history of lumbar spine was selected to collect lumbar CT image data and we imported it into Mimics 16.0 software for modeling. ABAQUS software was used to conduct finite element model force analysis. Models M
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BACKGROUND: In recent years, the finite element analysis of lumbar biomechanics has become a hot topic. Lumbar lordosis is considered to reduce the pressure load on the lumbar intervertebral disc and protect the lumbar spine. OBJECTIVE: To study the biomechanical effects of lumbar traction on L1-L5 lumbar segments in normal physiological curvature, flexion position and maximum overextension position, and to evaluate the optimal physiological curvature of lumbar traction. METHODS: A healthy male volunteer, aged 26 years, with a height of 174 cm and a weight of 60 kg, was selected, who had no history of lumbar spine diseases. With the L3 segment as the traction site, a finite element model of the whole lumbar spine was established based on lateral radiographs of the lumbar spine at the initiation site and during the maximal overextension as photographed by a DR machine. Based on the three-dimensional finite element model of the lumbar spine, the stress values and distributions of the lumbar vertebrae, the intervertebral joints, the intervertebral discs and the anterior longitudinal ligaments of the whole lumbar spine under different physiological curvatures were calculated. The patient was fully informed of the study protocol and signed an informed consent. The study protocol was approved by the Ethics Committee of Rehabilitation Hospital Affiliated to Fujian University of Traditional Chinese Medicine. RESULTS AND CONCLUSION: (1) Under six kinds of simulated working conditions, the range of motion of L1-L2 was 9.31° for flexion and extension, 9.84° for right and left bending, and 4.43° for right and left rotation; the range of motion of L2-L3 was 10.22° for flexion and extension, 12.35° for left and right bending, and 4.57° for left and right rotation; the range of motion of L3-L4 was 11.20° for flexion and extension, 11.63° for left and right bending, and 5.32° for left and right rotation; the range of motion of L4-L5 was 13.16° for flexion and extension, 11.58° for left and right bending, and 5.05° for left and right rotation. Under the normal physiological curvature of the lumbar vertebrae, the stress value of different lumbar spine structures was much greater than the stress value of hyperextension traction. The normal curvature of the anterior longitudinal ligament was 2.47 MPa, and the curvature of hyperextension traction value was 21.20 MPa. The stress value of L3 was the highest, which was four times that of the hyperextension traction. The stress value of the intervertebral joints at L2-L3 and intervertebral disc was highest than that of any other segment of the lumbar spine. These findings indicate that the pressure of lumbar vertebrae, intervertebral joints and intervertebral discs in hyperextension position is less than that in normal physiological curvature traction, and the pressure of anterior longitudinal ligament is always within the safe range. Lumbar traction may have better clinical efficacy and definite security in hyperextension position.
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Objective To explore a faster and more precise method to establish a 3-dimensional (3 D) finite element model of maxillary in human complete unilateral cleft lip and palate. Methods The surface of the model was created using Materialists Interactive Medical Image Control System (Mimics) software to deal with Dicom standard files obtained by scanning the cranium of the patient with multi-slice helical CT. The 3D finite element model for complete unilateral cleft lip and plate in maxillary was established by Ansys software. Results A 3D finite element model of maxillary in human complete unilateral cleft lip and palate was constructed with 27 405 units and 26 876 nodes. Conclusion The combination of Mimics software, Geomagic studio software, Ansys software, and spiral CT is able to create a 3D finite element counter model, which provides a faster and more valid method to study complete unilateral cleft lip and palate.
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Objective:To establish a 3 dimensional finite element model of calcaneus and talus for analysing their stress distribution during different gait phases. Methods: CT scanning and computer image processing system were used to establish the model to simulate the situation of calcaneus and talus for 3 phases (heel strike, midstance, push off) during the gait. A finite element solver was used to calculate stress. Results: A three dimensional finite element model of calcaneus and talus was established. And the stress distribution within the bone was obtained and regions with elevated stress at 3 phases were located. The stress distributions of 3 phases were significantly different. The stress increased gradually from heel strike to push off. Conclusion:The model can be used to study biomechanics of calcaneus and talus. The regions of elevated stress of calcaneus and talus are important, which provide an insight into the factors contributing to the fractures and arthritis.
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Objective:To simulate the instantaneous distal moving trend of the maxillary first molar based on the three-dimensional finite element mode(l3-FEM)of Forsus distalizing the maxillary first molar with some visco-elastic-plastic characters and explore the favorable loading mode of molar distal movement in Forsus in order to provide biomechanical basis for clinical practice.Methods:A male patient with ClassⅡmalocclusion was selected.The 3-FEM of Forsus distalizing the maxillary first molar was built through spiral CT scanning,Mimics8.0,and Abaqus6.5 software.This study simulated instantaneous distal moving process of the maxillary first molar under three dif-ferent loading modes(loading force was 300 g,point of force was on the center of the crown's buccal surface,loading time was 1s),which included a distalizing force,a distalizing force+counterrotation moment,a distalizing force+countertipping moment+counterrotation moment.Results:When Forsus distalized the maxillary first molar,different loading modes lead to different PDL stress distributions.When the model was added by a distalizing force,the maxillary first molar would be relatively seriously inclined;when added by a distalizing force +counterrotation moment(Mt/F=9),the maxillary first molar would be relatively seriously rotated and when added by a distalizing force+ countertipping momen(tMt/F=9)+counterrotation momen(tMr/F=5),the distal surface of the PDL would bear the lightest stress,and the first molar would achieve approximate translation movement.Conclusion:When mandible is guided forward by Forsus,the maxillary first molar would achieve better molar translation effect if added certain countertipping and counterrotation moment