Modeling And Biomechanical Comprehensive Analysis Of Bone Structure

Acetabular fracture is a kind of serious bone and joint injury caused by high-energyviolence, and transverse acetabular fracture is the common kind among them. Fixationdevices that use a fixed three-dimensional anatomy of the fracture sites were reset, so thatfaster growth of the healing fracture site. In recent years, scholars of the acetabular fracturehad been more in-depth research carried out. Biomechanical acetabulum pelvis is widely usedby many scholars to study issues related to the mechanical properties of the pelvis.Supported by National Young Scientists Fund, the differences between different internalfixations for transverse acetabular fracture are studied, with methods of the biomechanicsexperiment and the finite element analysis, including the construction of finite element modelbefore and after the operation, research on the materials anisotropy of pelvis bones, boundaryconditions, pelvic muscle forces, the analysis of different fixations and so on.Firstly, Based on various physiological parameters of the pelvis, designed the pelvisspecial fixtures and the mechanical properties muscle simulator. This device is suitable forvarious sizes of specimens, can strictly guarantee the pelvis standing posture, no damage tothe pelvic structure and to the bone and can ensure the normal mechanical pathways pelviswithout increasing the excess load. Muscle simulator simulation to achieve the mechanicalproperties of muscles, by increasing the device make the experimental conditions more closerto the true physiological state of the pelvis.Secondly, Using the jig we designed, we did biomechanical experiments according tothe requirements of the doctors and patients extent of exposed injury and make three differentgroups in different fixation modes. The mechanical properties and stability were compared.The three groups were: posterior column long plate and posterior column short plate; posterior column plate and posterior column long plate and anterior column lag screw;double-column screw and double columns plate. Meanwhile, compare the three kinds oftwo-column fixed methods.Thirdly, the three-dimensional finite element pelvic model is constructed based on thedates of a patient and two cadavers through some processes, such as segmentations, repairs,smoothing and so on. Then after operating on the pelvic, adding the models of plates andscrews with true size, transforming the place position coordinate, the model after operation isgenerated.Forthly, With the QCT method, the mechanics parameter with256grades can becalculated according to the bone density. Simulate20muscle forces at the beginning of paces,analysis and validate the size, direction, position, and loading in effect of every muscle, andset the tighten force between the pelvis and screws, element types, material properties ofscrews and plates, fix supports, loads and so on.Finally, compare the stabilities of different fixations with finite element models,including four groups, A: long single posterior column plate, short single posterior columnplate, B: long single posterior column plate, long single posterior column plate and anteriorcolumn lag screw, long single posterior column plate and posterior column lag screw, C:anterior column lag screw and posterior column lag screw, good pelvis model, D: long singleposterior column plate, anterior column plate and posterior column plate. The differencesbetween different fixations are analyzed under the situation of standing and sitting, providingreferences for clinicians.The Conclusions are as follow:Firstly, By the verification experiment confirmed that the fixture does not impact themechanical transmission on the pelvis. Pelvic jig can fully meet the test requirements.Posterior column long plate is better than posterior column short plate which the short platewith a unstable fracture line displacement over3mm; posterior column long plate and anteriorcolumn lag screw is better than the posterior column plate alone; double-column screw isbetter than double columns plate. But no significant difference were founded among the double column fixation methods; anterior column screw plate fixation was superior to theposterior column of the posterior column plate.Secondly, The mechanical indexes we interested in are as follows, the maximaldisplacement, the maximum equivalent stress and the maximum stress around the fractureline. Through the compare of these indexes, we found the biomechanical propertiesdifferences of the two groups of fixation methods. The first group is including the posteriorcolumn long plate(NPL) and the posterior column short plate(NPS) fixations. The secondgroup is composed of the following three double-column fixation methods, thedouble-column lag screws(SSG), the anterior column lag screw and posterior plate(SPG)fixation and the double-column plates(PPG) methods. All these analyses are during thedouble-leg stand position. conclusion:NPL is much better than NPS. SSG is better than SPG,while SPG is better than PPG.