Finite Element Comparative Study Of Vertical And Horizontal Triangular Osteosynthesis For Denis?Sacral Fracture

Objective: To observe the difference of biomechanical stability between vertical triangular osteosynthesis and horizontal triangular osteosynthesis in Denis?sacral fracture by finite element method,and to provide biomechanical theoretical support for clinical treatment of Denis? Sacral fracture.Methods: One normal adult was selected and scanned from the third lumbar vertebra level to the pelvic outlet level(lower edge of ischial tuberosity)by three-dimensional CT.The image data were saved in the format of Digital Imaging and Communications in Medicine(Dicom).The acquired image data were imported into Mimics19.0 software for three-dimensional reconstruction and simulated surgery to establish a lumbar pelvis three-dimensional model of Denis I sacrum fracture.Internal fixation models such as iliosacral screw,tension band plate,iliolumbar fixation pins and rods were made by UG10.0 software,which were imported into Mimics software and assembled with Denis I sacrum fracture model.In Mimics and 3-matic11.0,the assembled model is pre-processed by finite element methods such as meshing and material assignment.Finally,the processed model is imported into ANSYS18.0 software to simulate the resting and standing state of the human body,restrain the acetabulum on both sides,apply a load of 500 N and 800 N on the end plate of the 5th lumbar vertebra,and analyze the stress,strain,displacement distribution and other data of Denis I sacrum fracture model.Through data analysis,the mechanical stability of vertical triangular osteosynthesis and horizontal triangular osteosynthesis are compared.Results:1.Both groups of internal fixators can reconstruct the biomechanical conduction path of pelvic fracture.When the two groups of internal fixators fix pelvic fracture,the stress of pelvis is greater around sacral ala,and the stress of sacrum ala on the healthy side is greater than that on the affected side.2.When the two groups of models are loaded at 500 N and 800 N,the stress values of the vertical triangular fixed model at 6 test points are all smaller than that of the horizontal triangular fixed model,and the average stress of the horizontal triangular fixed model is 27.5% and 28.1% higher than that of the vertical triangular fixed model respectively.The maximum stress of horizontal triangle model is 67.9% and 68.3% higher than that of vertical triangle model respectively.3.When the two groups of models are loaded at 500 N and 800 N,the maximum stress difference between the internal fixation and lumbar pelvis in the horizontal triangular osteosynthesis model is 58.4% and 58.5% higher than that in the vertical triangular osteosynthesis model.4.When the two groups of models are loaded with 500 N and 800 N,the maximum Von Mises stress of the internal fixture in the two groups of models is between 38.19~76.64 Mpa and 76.64 MPa.5.When the two groups of models are loaded at 500 N and 800 N,the maximum vertical displacement of the horizontal triangle fixed model is 28.7% and 28.4% higher than that of the vertical triangle fixed model respectively.The maximum displacement of horizontal triangle fixed model is 32.7% and 32.7% higher than that of vertical triangle fixed model respectively.6.When the two groups of models are loaded at 500 N and 800 N,the maximum strain value of the internal fixture in the horizontal triangular fixed model is 82.8% and 158.6% higher than that in the vertical triangular fixed model respectively.Conclusion: Both vertical triangular osteosynthesis and horizontal triangular osteosynthesis can effectively fix Denis type I sacrum fracture.Compared with horizontal triangular osteosynthesis,vertical triangular osteosynthesis has better mechanical stability for fracture fixation,especially limiting vertical displacement of fracture,and vertical triangular osteosynthesis has better biomechanical compatibility.