Construction Of Three-dimensional Finite Element Model Of The Posterior Wall Acetabular Fractures And Stress Analysis

ObjectiveTo construct 3D (three-dimensional) finite element model of the acetabulum, research how to elevate the simulation degree of digitalization mechanics model, and analyze the main factor which effect the simulation degree of cadre finite element model. Split the acetabular finite element model according to different areas fractures of posterior wall, then loading and calculate. Analyze magnitude and distribution alleosis of stress when acetabular posterior wall fractures. Explore and improve the method of performing biomechanics experiment with digitalization mechanics model.1,Construct 3D finite element model of normal acetabulum: Scan the pelvic example of human body with CT, restitution three-dimensional visible haunch bone with correlated software; investigate the method of 3D image reconstruction with plane images. Then add mechanics parameter of the acetabulum to 3D model with finite element software, and study how to elevate the method of adding parameter in order to make finite element model approximate to human body.2,Loading and stress analysis with acetabular finite element model: Split the acetabular finite element model according to different areas fractures of posterior wall, obtain the result of magnitude and distribution alleosis of stress after loading and calculating. Analyze the impact of acetabular posterior wall fractures correlate with clinic cases, introduce suggestion on healing acetabulum fractures; and investigate how to performing biomechanics experiment with digitalization finite element model instead of tradition human body materials.Methods1,Choose one fresh pelvis specimen of adult man, affirmat it is normal or not by checking it with X-ray at first; then scan it with helix CT, keep the pelvic quiescing when being scaned. Obtain series fault images of the pelvis, import the images into Mimics10.01 software and restitue 3D visible model of pelvis. Modify the model by FreeForm software and dissecte the model of haunch bone; import the 3D visible model of haunch bone(IGES format) into Ansys8.0 software. Add mechanics parameter to the haunch bone model, construct 3D finite element model of acetabulum.2,On the base of common fracture line of acetabular posterior wall fracture in clinical cases, split the acetabular 3D finite element model according to 1/3, 2/3, 3/3 areas fractures of posterior wall after simplify setting, obtain four types of acetabular posterior wall fracture model(including normal condition of acetabulum). Then loading the models in both feet standing body posture, gain stress distribution figures of the models, record stress numerus of weight bearing dome, anterior wall and posterior wall in condition of different areas posterior wall fractures.Results1,Normal 3D finite element model of acetabulumObtain 3D visible model of pelvic by restituting CT fault images with Mimics10.01; gain 3D visible model of haunch bone by splitting the pelvic model with FreeForm software. Procure normal 3D finite element model of acetabulum by adding mechanics parameter to the haunch bone model with Ansys software. The constructed 3D finite element acetabular model was divided into 69440 nodes and 45209 units.2,Stress distribution of normal and different areas posterior wall fractures acetabulumSimulate body posture of both feet standing, loading 300N on articulatio sacroiliaca surface, the direction of force was perpendicular downward. Calculating outcome showed that after 1/3,2/3,3/3 posterior wall of acetabulum fractures, stress at the weigh bearing dome increased 20%,26%,33%(compare with the condition of normal acetabulum), the perpendicular direction stress was changed obviously; stress at the anterior wall decreased 22%,30%,35%; stress at the remaining posterior wall increased 39%,47%,54%.Conclusion1,The 3D visible skeleton model and 3D finite element skeleton model could be constructed from slice section images of skeleton with Mimics10.01, FreeForm and Ansys8.0 software. The finite element model simulate morph and mechanics performance of human body reliably. It is a good method to operate vitodynamics experimentation with digitizated mechanics skeleton model. The finite element model could substitute human body partly, it has the advantages of affluence information, cheap and trustworthy repeatability.2,The posterior wall fractures alter the stress distribution of the acetabulum significantly. The fracture cause stress at the weigh beating dome increased; stress at the anterior wall decreased; stress at the remaining posterior increased. If the fracture areas reach 1/3 posterior wall, the weight loading characteristic of hip joint changed remarkably. The acetabulum must be open reduction, internal fixation and restore articular surface to maintenance stabilization.