Establishment Of Acetabular Fractures Fixed Digital Model And Finite Element Analysis

Part Ⅰ Establishment of finite element digital model of acetabular posterior wall fracture screws fixationObjective To explore method for establishment of a more accurate three-dimensional finite element digital model of acetabular fracture fixation.Methods The left hip of normal adults was chose to take spiral CT scanning of the pelvic. The three-dimensional acetabular geometric model was reconstructed by Mimics software, and posterior wall fracture was built. Screws were established by UG software. Then we reset the virtual surgical planning between screws and the reduction acetabulum. Their mesh was divided by3-matic and HyperMesh software, and they were given respectively the material properties. Then imported HyperMesh, and assembled to build finite element model of acetabular fracture screws fixation. In turn defined the interaction, boundary conditions and load at software Abaqus, the final calculation and post-processing. Stress and displacement results were in contrast with finite element model of the same normal acetabulum.Results we successfully established a three-dimensional finite element model of acetabular posterior wall fracture fixation. Analysis for model indicated:stress transmitted to anterior and posterior column of acetabulum along the sacroiliac joint. Stress obviously concentrated on the acetabular anterior wall, the residual posterior wall and acetabular dome edge. In displacement, anterior column and posterior column trends was respectively consistent with the normal model, but acetabular anterior wall, posterior wall and acetabular roof area has larger displacement, ala of lilum appeared low displacement area of center type.Conclusion The built three-dimensional finite element model of acetabular posterior wall fracture fixation has a higher degree of simulation, and can be used to analyze the biomechanical properties of acetabular fixation. This laid the foundation for the further evaluation of acetabular fracture surgery effects. Part II The finite element analysis of plate and screws joint fixed acetabular posterior wall fracture and screws fixation modelObjective Create three-dimensional finite element digital model of the plate and screws joint fixed acetabular posterior wall fractures, and in comparison with biomechanical properties of screw fixation model.Methods The same hip CT scan data were selected, and reconstructed3D visualization model of posterior wall acetabular fractures by the software Mimics. Shaped plate and screws were built the use of software UG. Meshed, given the material, assembled by software3-matic and HyperMesh, and then we established three-dimensional finite element model of the acetabular fracture plate and screw fixation. We researched stress distribution, screw displacement, hip displacement of simple screw fixation, and compared stress peak and displacement peak.Results In screws and plate fixation model, screws stress impenetrated the fracture fragment was mainly concentrated in the vicinity of the front and area at near fracture line, stress distribution was relatively uniform, and peak stress was10.42MPa; In screws-only model, internal fixation stress is mainly concentrated in the parts of the front and rear at near fracture line, and the peak stress was15.32MPa. The maximum stress at acetabular fracture line was2.31MPa in the screws steel fixed model, and2.62MPa in the screws-only model. In screws and plate fixation model, the direction of displacement of the internal fixation was vertical increments down, and the displacement peak was0.049mm, yet hip displacement peak was0.133mm; In screw-only model, the direction of displacement of internal fixation increased from the screw front-end to the back-end, and the displacement peak was0.055mm, yet hip displacement peak was0.139mm.Conclusion Plate and screws joint fixation was better than simply screw fixation on the biomechanical stability for posterior wall acetabular fractures; Percutaneous screw fixation is a viable surgical approach for monomer fracture fragments not crushed or embedded in the intra-articular and minimally displaced posterior wall acetabular fracture patients.