Finite Element Analysis Of Mechanical Stability In Fixation Of Anterior Column With Posterior Hemi-transverse Fractures Of The Acetabulum By DAPSQ

Objective Using the finite element method to study biomechanical stability of anterior column with the hemi-transverse fractures of the acetabulum which fixed by dynamic anterior plate-screw system for quadrilateral area(DAPSQ) and the influence of sitting position in anterior column with the hemi-transverse fractures of the acetabulum on its biomechanical stability, in order to provide biomechanics guidance for the clinical application.Methods(1) Select a healthy male adult volunteer(excluding all kinds of pelvic lesions and deformities) who was informed consent, and using 16 row helical CT machine to do the 0.5 mm thin layer scan on his fourth lumbar vertebrae to the femur sections. Save the image date of all the pelvis layer in Dicom format and import the date to the finite element processing software Mimics10.01 to reconstruct the pelvic three-dimensional geometric model. Then, doing hexa meshing on pelvic 3D reconstruction model by using grid processing module software ICEM under the Ansys software. Using Hypermesh V10.0 software to adjust the grid quality, and loading ligament according to the anatomic structure to establish pelvic 3D hexahedral finite element model preliminarily and import the data to the finite element software ABAQUS 6.12 for the calculation analysis of pelvic stress. Next, simulating the sitting pelvic stress and make effectiveness comparison between the nephogram of simulation and literature data of vitro experiment and test model.(2) Using finite element analysis method to build the right anterior column with the hemi-transverse fractures of the acetabulum of the pelvis model, on the right side of the acetabulum fracture DAPSQ were used respectively to(A), anterior column after reconstruction of titanium plate combined lag screw(B), and double column titanium plate fixation(C). Import the established finite element model to software Abaqus6.12, comparing the condition of each fracture displacement and stress distribution under load 600 N of physiological load imitating sitting position, and analyzing the biomechanical stability of three different internal fixation methods in fixed anterior column with the hemi-transverse fractures of the acetabulum;(3) according to the verified stability of fixing the right side of the acetabulum fractures by DAPSQ, we construct three sets of internal fixation models individually: keep the contralateral pelvic ring in its integrity(A), complete for superior and inferior ramus of pubis fracture internal fixation(B) and keep the contralateral superior and inferior ramus of pubis fractures unfixed(C), in order to contract the displacement and stress distribution on the right side of the fracture between groups under load 600 N of physiological load imitating sitting position.Results(1) This study established a detailed anatomy of pelvis all three dimensional nonlinear hexahedral finite element model. This model contains 86444 finite element cell, 88388 nodes. And this model’s stress distribution under physiological load is corresponded with the experimental data and other literature model in vitro.(2) It has no significant sense in the differences of longitudinal displacement of the dome region of acetabulum between the three internal fixation models of group A,group B and group C. The lateral displacements of posterior column inner lining were(0.903±0.03),(0.930±0.045),(0.997±0.068)mm, the force on three sets of internal fixation models shows that C> B > A and the differences are significant.(3) It has no significant sense in the differences of longitudinal displacement of the dome region of acetabulum between the three internal fixation models of group a, group B and group C. The lateral displacements of posterior column inner lining were(0.903±0.034),(0.910±0.038),(1.117±0.380)mm, the force on DASPQ square area screw shows that A > B > C and the differences are significant.Conclusion(1) This research established a three-dimensional nonlinear hexahedral finite element model of the normal people body’s pelvis with high authenticity, and this model has the basic organization of the pelvic ligaments and a complete anatomical structure that make the model can generally in line with the actual circumstances of the pelvis. Through validation, the model can be applied to biomechanics research related to clinical.(2) The biomechanical stability of anterior column with posterior hemi-transverse fractures of the acetabulum fixed by DAPSQ is well.(3)The biomechanical stability of anterior column with posterior hemi-transverse fractures of the acetabulum fixed by DAPSQ is well, under the premise that the contralateral pelvic ring is stable.