The Study Of Traumatic Femoroacetabular Impingement Induced By Tile-type-B2Pelvic Fractures Through Computerized Simulation And Image Measurement

Objective To explore the genesis and development mechanism of traumatic femoroacetabular impingement induced by Tile-type-B2pelvic fractures. To interpret the interrelationship between the level of rotational displacement of pelvic fractures and the range of motion of hip joint as traumatic femoroacetabular impingement happened.Methods (1) The stage of establishing a3-D digital model:we need to establish the3D digital models of pelvic ring and hip joint based on CT section image with Mimics software to simulate pelvic fractures and the movement of hip joint. The process to establish the3D digital model of pelvic ring and hip joint include data acquisition, data saving and transmission technology, threshold values setup, image edit and3-D calculation.(2) The stage of computer simulation and image measurement:the procedure of this stage involved that:to set up the center of rotation of hip joint and acetabulum based on the feature of hip joint movement and the type of Tile B2fracture of pelvic; to simulate concentric movement of hip joint and Tile B2fracture of pelvic; to measure the distance from the junction of the femoral neck and head to posterior edge of acetabulum; to take statistic analysis using SPSS software.(3) The stage of validating the clinical measurement:we need to validate the result reciprocity between computer simulation and the clinical measurement on CT section image. The procedure involved that:to set up the center of rotation of pelvic fracture; to simulate pelvic fracture; to process measurement on CT section image; and to take statistic analysis using SPSS software.Results (1) We established the3D digital models of pelvic and hip joint that fit for simulation of movement of hip joint and pelvic fractures. The model of femur comprised8884triangles and4472points. The volume of the model was164838mm3, and the surface area19853mm2.The model of Ilium comprised40366triangles and20245points. The volume of the model was314552mm3, and surface area59035mm2.(2) The dynamic process simulation of movement of hip showed that the movement of normal hip is a curvilinear motion. The curve slope gradually decreases as the hip joint extended. The motion curves were down as a whole when acetabulum internal rotation induced by pelvic fractures. The static simulation showed that the DFPA was correlated linearly with the angle of acetabulum internal rotation.(3) The paired-samples T test showed that:there were no difference between test group and control group (t=-1.983, P=0.067). The sensitivity of the new measuring method was 80.95percent.Conclusion (1) A Verisimilar3D digital models of pelvic ring and hip joint were established easily. The Mimics software is a kind of powerful simulation software that can be used to simulate the movement of hip joint and the fracture of pelvic, and can be used to reversely show the CT images when simulation was progressed, and the imaging measurement can be performed simultaneously.(2) We can draw conclusions through computerized simulation and image measurement that acetabulum internal rotation induced by pelvic fractures may cause the femoral head was covered excessively by acetabulum, as can become one of risk factors of femoroacetabular impingement. The traumatic femoroacetabular impingement wasn’t relevant only to the angle of acetabulum internal rotation, but to the range of motion of hip. The angle of acetabulum internal rotation and the range of motion of hip are to some extent in inverse proportion when FAI happened.(3) We can also confirm that there was no statistically difference between the new method and actual conditions, and the new method is the difference value of the suffered ones and normal ones in pelvic. The method has a high sensitivity, and can exactly reflect the acetabulum rotation after pelvic fractures, but it should be paid attention to the standardization of operation and indications when we apply it.