| Objective: In this study,the CT imaging data was obtained by using a spiral CT continuous scanning.The CT imaging data was imported computer aided engineering(CAE)for image processing analysis.By this way,establishing Lenke 3 type of adult idiopathic scoliosis and 3D model of guiding target of thoracic screw channel;adding material properties according to the requirements of the finite element model,and also correcting parameters of material properties and verifying its effectiveness.The effectiveness and Scientific of pedicle screwing based on targeting of thoracic screw channel were verified by simulating pedicle screwing on 3D printing model;Simulating different surgical methods on corrected model and exploring Stress magnitude and orthopedic effect of pedicle screwing when separately using different surgical methods,thereby providing some theoretical support for exploring stress magnitude and orthopedic effect of pedicle screwing separately using different surgical methods in patients with Lenke3 type of adult idiopathic scoliosis,and finally to provide a scientific basis for its long-term effect.Method: Electing a patient,aged 28 volunteer,with Lenke 3 type of adult idiopathic scoliosis as subject of the study.Making the patient lying supine,and then Continuously scanning by using spiral CT with thickness of 0.625 mm,the scanning field range is from the upper edge of C7 to Coccyx.Subsequently,the obtained CT images were imported into Mimics16.0 reverse engineering software in Dicom format and the CT image data was built as a model.Then,the model is geometrically cleaned up and optimized,thereby the system establishes a complete scoliosis geometric model including thoracic structures and builds a guiding target of thoracic screw channel on thoracic vertebral body in the patient with Lenke 3 type of adult idiopathic scoliosis by using design module in the system;The complete geometric model is meshed by importing Ansys14.0finite element analysis software,including division of body and facial mesh grid.References to the literature assigned material properties on the real unit,establish finite element model about complete Lenke3 model of adult idiopathic scoliosis,including intervertebral discs and ligaments,etc.The intervertebral disc material properties of upper thoracic,thoracic scoliosis,lumbar scoliosis,etc divided into soft type,and rigid type and intermediate type according to right and left lateral flexion test.In accordance with orthogonal experimental design,the material parameters of finite element model were screened through intuitive analysis,thereby obtaining individual biomechanical properties of finite element model.By bothfurther simulating right and left lateral flexion test with lying supin through Optimized model and comparing with the clinical X-ray,researchers select the best combination,and extracte T1-T4,T5-T8 and L6-S1 three segments from finite element model,constraint loading for them.The results were compared with the experiments in vitro,and finally the effectiveness of the model was verified in the multiple perspectives.In optimized finite element model of Lenke 3 type of adult idiopathic scoliosis,finite element operations were simulated separately,including simulating different combinations: Case1:posterior vertebral key pedicle screw and posterior capsular rease surgery;Case2:posterior vertebral key pedicle screw and posterior capsular rease surgery as well as anterior release for thoracic scoliosis;Case3:posterior vertebral key pedicle screw and posterior capsular rease surgery and anterior release for lumbar scoliosis;Case4:posterior vertebral key pedicle screw and posterior capsular realse surgery and anterior release for thoracolumbar side convex;Case4:posterior vertebral key pedicle screwing and posterior capsular realse surgery and anterior thoracolumbar scoliosis release surgery.Exploring the effectiveness and the biomechanical characteristics of 3D orthopedics of different surgical programs in patients with Lenke3 type of adult idiopathic scoliosis.result: Researchers have established complete models of Lenke3 type of adult idiopathic scoliosis by applying finite element software,whichincludes all thoracic,lumbar,sacrum and coccyx,chest,ribs,cartilage,intervertebral disc and joint capsule,ligaments and other structures.These models consist of 440975 tetrahedron elements and 580 bar elements,a total of 441,555 elements,nodes 1,077,318.In addition,researchers have also built Screw channel guiding target models for 12 thoracic vertebraes,which include 4682 tetrahedron elements,nodes 7390.The minimum difference between the finite element model established on orthogonal test and the real condition of the patient presents to the combination of A1B2C3,the results of visual analysis table show the effects of various on the difference between the results of the simulation experiment is in the order:B>C>A,in other words,the factor B is the most influential and the factor A is the minimal influential.There have no statistically significant difference between the simulation results of finite elements model that parameters are modified in lateral flexion position and the real confition of the patient.Besides,loading results of the finite element model in T1-T4 and T5-8 and L6 / S1 hree segments keep in line with experimental results in respective references.On the optimized model,designs of five surgical options(Case1-Case5)was achieved successfully.The result in Case1 shows the orthopaedic maximum stress is located at the left side of L4,the screw maximum stress value is 205.64Mpa;the result in Case2 is located at the left side of L4,the screw maximum stress value is 313.83Mpa;the result in Case3 is located at the left side of L4,the screw maximum stressvalue is 337.08Mpa;the result in Case4 is located at the left side of L4,the screw maximum stress value is 331.3 Mpa;the result in Case4 is located at the left side of L4,the screw maximum stress value is 280.48 Mpa,The five maximum values in Case1-case5 are lower than bending threshold of screw itself.The result in Case1 shows the orthopaedic minimum stress is located at the right side of T7,the screw minimum stress value is 72.12Mpa;The result in Case2 shows the orthopaedic minimum stress is located at the right side of T7,the screw minimum stress value is 83.76Mpa;The result in Case3 shows the orthopaedic minimum stress is located at the right side of T7,the screw minimum stress value is 67.20Mpa;The result in Case4 shows the orthopaedic minimum stress is located at the right side of T7,the screw minimum stress value is 63.17Mpa;the result in Case5 shows the orthopaedic minimum stress is located at the right side of T7,the screw minimum stress value is 48.82Mpa;The orthopedic rates of thoracic spine scoliosis in case1-case5 are 63.9%,59.9%,67.6%,61.5%,66.4%,respectively,rthopedic rates of lumbar scoliosis were 39.1%,32.2%,36.8%,42.9%,49.3%,respectively.The experimental results of thoracic release surgery in case 3,5 show the effectiveness of its orthopedics have no significant increase,but the stress of their respective pedicle screw structure would be significantly reduced.The results of case4?5 show its stresses in the vertebral body derotation and lumbar/thoracic screws are much better than other groups.conclusion: Researchers have established complete finite element modeles of Lenke 3 type of adult idiopathic scoliosis,which are verisimilar.Compared with patient X-ray,these models are more verisimilar in anatomy and geometry.Besides,the parameter of the modeles have optimized,corrected and verified for its effectiveness.Hereafter,researchers simulated five kinds of surgical options on the corrected model.In addition,the effectiveness of their orthopedic of the five kinds of surgical options has been measured.The screw stress was analyzed for different pedicle screw and orthopedic programs.These results show it is achievable that the effectiveness of orthopedic of key vertebral pedicle screw is the same as the effectiveness of bilateral pedicle screw.Thoracic pedicle screw stress would be reduced significantly when applying posterior key vertebral pedicle screwing and thoracic release surgery.The effect of derotation is excellent when applying key vertebral pedicle screwing and anterior thoracolumbar release surgery.In order to improve lumbar derotation and reduce stress and loading of pedicle screw for patient with Lenke3 type of adult idiopathic scoliosis,anterior thoracolumbar release surgery is optional.The screw high stress values are mainly located at the position of L4,more specifically,these high stress values is concentrated on junction of tail and shank nails,connection of spiketail and orthopedic rod,thus,the two location may be high incidence of screw breakage.These experimental results provide quantitative indicators forfinite element biomechanical study about adult idiopathic scoliosis,and subsequently provide some theoretical surpport to predict therapeutic effect of orthopedic surgery and formulate cilnical programs for patient with Lenke3 type of adult idiopathic scoliosis. |
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