| Objective: To establish a finite element model of adolescent idiopathic scoliosis by finite element analysis,to design a surgical scheme for correction and internal fixation with different types of pedicle screws,and to analyze the orthopedic rate of different types of pedicle screws after operation.The unrotation rate of the top vertebra,the screw-rod system and the stress of the vertebral body,in order to provide reference for better orthopedic effect and provide guidance for the selection of operation plan in clinic.Methods: A 13-year-old female adolescent idiopathic scoliosis was scanned with 64-row spiral CT.The obtained image was engraved into the CD in Dicom format.The obtained image was imported into the Mimics20 software to get the preliminary bone model.After smooth polishing and other operations by the Geomagic2012 software,the intervertebral disc model was obtained by using the Solidworks2014 software,and then the soft tissue was added and the material attributes were assigned by Ansys Workbench software.Finally,the finite element model of adolescent idiopathic scoliosis was obtained.After the piecewise loading verification on the constructed model,it is confirmed that the constructed model is effective and can be used for surgical simulation.To simulate the whole segment,multi-axial pedicle screws and single plane pedicle screws were used to obtain the finite element model after correction,and the relevant parameters,screw-rod system stress and vertebral body stress were collected.Results: The main results are as follows:(1)The finite element model of adolescent idiopathic scoliosis was established successfully.There are 548022 nodes and 2641667 cells in total.(2)The segmented loading verification of the model proves that the model is effective and can be applied to surgical simulation.(3)The orthopedic rate of multiaxial pedicle screw group was67.04%,that of single plane pedicle screw group was 67.86%,that of multiaxial pedicle screw group was 15.14%,and that of single plane pedicle screw group was 19.76%.(4)The maximum stress of screw-rod system in multiaxial pedicle screw group and single plane pedicle screw group appeared on the right side of T7 vertebral body,which were 270.26 MPa and 263.19 MPa,respectively.(5)The maximum stress of multiaxial pedicle screw group and single plane pedicle screw group appeared in T6 vertebra,which were 163.68 MPa and 163.59 MPa,respectively.Conclusions: The main results are as follows:(1)A highly simulated and visual adolescent idiopathic scoliosis model can be established by using the finite element method,and the researchers can simulate the operation on the model and plan before operation,which is of guiding significance to the clinic.(2)For the first time,the finite element model was used to simulate the application of different types of pedicle screws in AIS orthopedic surgery,and the conclusions are as follows:(1)The derotation effect of single plane pedicle screws is significantly stronger than that of multiaxial pedicle screws,which can effectively prevent the progression of deformities.(2)Both single plane pedicle screw and multiaxial pedicle screw can well correct the coronal deformity of AIS patients,but there is no significant difference in orthopedic rate.(3)The overall stress of the convex pedicle screw was greater than that of the concave pedicle screw in both surgical options.The stress values and stress trends of the screw system and vertebral body were similar after orthosis for single plane/multi-axis pedicle screws and multi-axis pedicle screws,indicating that the single plane/multi-axis pedicle method is safer than the traditional surgical method. |
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