Finite Element Analysis Of Different Lengths Sacroiliac Screws Fixation S1

Objective In this study,digital orthopedic technique and biomechanical analysis were applied to treat sacral fractures by fixing S1 with 7-degree sacroiliac joint screws through the optimal channel,providing biomechanical support for the best fixation mode and effect,and for the safety and effectiveness of screws fixation with different lengths,so as to provide reference for clinical practice.Methods A thin CT scan was performed on the pelvis of a healthy adult male volunteer,and the obtained images were stored in the Dicom data format and imported into a Software of the Materialise Mimics Innovation Suite 16.0 and reconstruction of an accurate 3D pelvic surface body model and stored in a.STL file format,leading to Imageware 12.0 software was used to perform multilayer dissection of the anterior and posterior positions of the standard sacrum to determine the optimal screw path.According to the geometric size and mechanical parameters of the tensile screws,the screws model with a diameter of 7.3mm and a length of80 mm,90mm,100 mm,110mm,120 mm,130mm and 140 mm is drawn with Solidwoks 2012software(USA).The Geomagic 2014 software will be imported for smoothing and denoising.UG Imageware 12.0 software was used to assemble pelvis and tension screws,and Ansys14.5software was imported.Tetrahedral elements were used for mesh division of sacrum and ilium to represent cancellous bone,and hexahedral mesh division was used for sacroiliac joint and pubic symphysis.The upper body gravity load(500 N)was defined,and the maximum Von Mises stress and shape variables of the pelvis and screws at the time of placement screws diameter of 7.3mm and length of 80 mm,90mm,100 mm,110mm,120 mm,130mm and140 mm were determined.The optimal length of the sacroiliac joint screws were finally determined to fix S1.Results After loading 500 N forces to the diameter and length of the inserted screws were 7.3mm and 80 mm,90mm,100 mm,110mm,120 mm,130mm and140 mm respectively.When the force value of the pelvic cortical bone was the highest,the assembled screw length was 110 mm,followed by 120 mm and 140 mm.When the stress scoreof pelvic cortical bone was the lowest,the assembled screw length was 90 mm,followed by80 mm and 100 mm,respectively.When the screw length is 140 mm,the stress is the maximum;The next screw length is 110 mm and 100 mm respectively.When the screw length is 90 mm,the stress is the least,followed by 80 mm and 120 mm respectively.When the displacement of the pelvis was minimal,the assembled screw length was 130 mm,followed by 140 mm and80mm respectively.When the length of the screw is 120 mm,the displacement of the screw is the largest,followed by 110 mm and 100 mm respectively.When the length of the screw is130 mm,the displacement is the smallest,and the length of the screw after the shift is 140 mm and 80 mm respectively.Conclusions Through the finite element analysis,the fixed peak value can be achieved with screws lengths of 110 mm and 120 mm,not as long as possible.