Finite Element Comparative Study Of Five Internal Fixation Methods In Acetabular Posterior Column Fractures

BackgroundThe acetabulum fractures is increasing as the increase of traffic accidents and high falling injury in the modern society.The anatomy of the acetabulum is deep and complicated,poor effect of conservative treatment,surgical treatment is difficult,if choose the improper treatment,the probability of postoperative complications’ rate is higher.Therefore,the treatment of acetabulum fracture is the most important.Now advocates active surgical treatment and clinical way of open reduction and internal fixation has become the preferred method for the treatment of acetabulum fracture.The acetabulum structure is comples,depending on its anatomy structure,some scholars divided the acetabulum into anterior column and posterior column,and the acetabulum fracture often involves the posterior column.The simple posterior column fracture of the acetabulum is not common clinically,always acompany with the anterior column fracture of the acetabulum,using the anterior and posterior approach during the operation to treat the acetabulum fracture will increase the patient’s trauma,no conducive to postoperative recovery.In recent years,the modified Stoppa approach as a good supplement of the traditional illac inguinal approach,is widely used,some scholars used the modified Stoppa approach to treat the anterior column fracture,in the meantime,placed the prebended plate between the lesser sciatic notch and the Iliac bone,and got the good effect.Because of the plate’s one side fixed in the illum,and the other fixed in the sciatic,and the plate is located in front of the posterior column,in order to distinguish with the conventional posterior column plate,the article named it as the medial iliac-ischial plate.But there is no biomechanical analysis and evaluation on the anterior iliac-ischial plate’s stability in the present international community.PurposeThe purpose of this paper is to establish the 3D finite element model of the pelvis and verify its effectiveness by using the computer analysis software.Furthermore,on the basis of the finite element model,it is going to build 5 models of internal fixation method including the medial iliac-ischial plate and analyze the bio-chemical characters of fixing the fracture of the acetabular posterior column by stimulating standing and sitting,thus providing basis for the clinical practice.Methods1.Select one healthy female volunteer for CT scan.Then the data will be led into Mimics15.0 software in the format of.DICOM to generate the 3D model of the pelvis.After being processed by FEM pre-processing software,it will be led to the software of finite element analysis-ANSYS to add the accessory structures of ligament,establish 3D finite element model of the pelvis and verify its effectiveness.2.The application software generates the model for the fracture of the posterior column and establishes 5 kinds of models of internal fixation.Then stress is loaded to the models,so as to analyze and evaluate the stress displacement distribution,the movement of the fracture line on the articular surface and the integral rigidity of the acetabulum and so on.3.Conduct statistical treatment with t test.If P<0.05,it means that the result has statistical difference.ResultsIn the standing position,the average displacement was(6.13±1.04)μm、(7.08±0.24)μm、(7.85±0.88)μm、(6.85±0.42)μm、(7.07±0.49)μm in the posterior iliac-ischial plate、the medial iliac-ischial plate、the anterograde tensile screw、the ischial tuerosity and the lesser sciatic notch screw;while in the sitting position,the displacement was(7.77±1.0)μm、(9.65±0.83)μm、(9.69±1.12)μm、(10.2±0.37)μm、(10.1±0.51)μm.The result between the plate fixation and screw fixation has statistical difference in standing position(P<0.05),while the result between the medial iliac-ischial plate and the screw fixations has not statistical difference in sitting position,but the mean displacement of the plate was less than the screw fixations.ConclusionThe medial iliac-ischial plate and the posterior iliac-ischial plate are more stable than the hollow screw.Therefore,they can be used in clinical practice.The specific treatment must be determined combining the practical clinical and individual conditions.