Establishment And Stress Analysis Of The Three-dimensional Finite Element Model Of The Three Internal Fixation Of Unstable Intertrochanteric Femoral Fracture

Purpose：With the increasing of the older persons, intertrochantericfemoral fracture (IFF)has become a major problem, the incidence increnceyear by year. At present surgical treatment has become the main method oftreatment of IFF. With the bio-mechanics,materical science development, avariety of internal fixation devices has emerged. Receiving the bettertreatment,it aslo bring considerable complications. The internal fixationdevices need to improved by the time. But so far, there is no internal fixationdevices resolve these issues fully. For this phenomenon, the scholars focus onhow to use different internal fixation devices to achieve a better therapeuticeffect, they often through animal experiments, the body mechanics to studythe ways and the advantages and disadvantages of the different internalfixation devices, but they can not be achieved satisfactory results, with FEAhas been used in orthopedic research, it has played an important role. FEA isnot only able to analyze the internal stress distribution and the strain state ofbone, bone-fixed devices, fixed devices but also be able to analyzequantitative. FEA has the character of persistence of repetition and changingthe quality.Comparing with the ordinary mechanical experimental, thismethods gets an objective entity experiment and has more important clinicalsignificance. This experiment is basic on the finite element modeling softwareto building the model of femur,the unstable intertrochanteric fracture,theDHS,Gamma,LCP,three internal fixation fixed fractures model. By the finiteelement analysis softwareANSYS, calculating and analysing of the model ofbone-fixed devices, proximal femoral bone,the fixed-screws to get stress andstress distribution characteristics, displacement, fracture surface stresschanging,fracture of the gap changing. In order to comparative evaluate the fixed effect of different fixation methods and to compare the DHS,theGamma, the LCP screw system of the fixed-way characteristics. Furthervalidate and research the advantages and disadvantages of the fixed unstableintertrochanteric fracture fixation from the theoretical mechanics for thetheoretical mechanics basis and guidance for clinical application.Methods：Firstly, using the Minics,Pro/Engineerr, Geomagic Studiosoftware to establish CAD model of the full adult femur,31-A2intertrochanteric fracture of the CAD model form CT scan of the adult femurdata, According to DHS, Gamma, LCP parameters, respectively building CADmodels. According to orthopedic surgical procedures required to be equipped.and establishing the the CAD model on the basis of unstable intertrochantericfractures with DHS, Gamma, and the LCP.then import them intothree-dimensional finite element analysis software ANSYS to respectivelygenerate three kinds different three-dimensional finite element analysis model.After settting of boundary conditions, material properties, simulating70KGnormal men slow walking with one foot to hip to withstand the maximumpeak value loading, analysis of the stress and stress distribution characteristicsand displacement of intact femur, the bone-the internal fixed devices model,femur proximal bone,the internal fixation screws; analysis of fracture surfacestress change, fracture of the gap changing and so on.Results：1In this study, a variety of CAD models can be realistic, objective, truerepresentation of the proximal femur, the internal fixed devices, theintertrochanteric femoral fracture with different internal fixed devices. Theywere meshed into ANSYS to generate three-dimensional finite elementanalysis model and were analyzed.2Normal intact femur stress distribution and displacement of the cloudpictures show that the forces of hip conduct form the proximal femur to thedistal,and form the pressure and tension band. The results be consistent withprevious studies, so they can be analysised.3The stress and the stress distribution and displacement values of the loaded proximal femur and internal fixed devices have a large changes compared withnormal femur.4The model of C1,C2,C3bone stress anteromedial,posteromedial,anterolateral,posterolateral of fracture section is significant difference onstatistical analysis (P <0.05). The model of C1, C2, C3fracture gapanteromedial,posteromedial,anterolateral,posterolateral of fracture sectionis significant difference on statistical analysis (P <0.05). The model of C1,C2,C3bone pressure surrounding screw top is significant difference onstatistical analysis (P <0.05)Conclusion：1On the basis of vivo femur CT data,using the Minics,Geomagic Studio, Pro/Engineerr software can successfully build a complete femur model,31-A2unstable intertrochanteric fracture model, the CAD model of DHS,Gammaand LCP, the CAD31-A2intertrochanteric fractures model were fixed byDHS,Gamma,LCP.They can be meshed and mechanics analysised byANSYS. The modeling method is accurate and saves time and effort,individually,it can be truely reflect its geometry and mechanical propertiesrealistically and objectively. These models can be used in-depth study as theoriginal model.2The DHS,Gamma,LCP fixing the31-A2intertrochanteric femur fracturehave respectively advantages and disadvantages. Theoretical mechanics fromthe overall fixed compression aspects of Gamma is better than the DHS andLCP. LCP is better than the Gamma and DHS on Anti-rotating, there is nosignificant difference between the Gamma and DHS. The Gamma and LCP,are superior to DHS on the tensile strength,there is no significant differencebetween the DHS and Gamma. Gamma can cause stress concentration of thedistal femur; DHS, LCP can cause proximal femoral stress shielding,Theeffect of proximal femoral stress shielding caused by Gamma is very small;The Gamma and DHS can produce relative sliding, in ordre to reduce thefracture gap,it aslo generate sliding compression, change the fracture surfacestress distribution. The stress of distribution is more uniform. LCP is lack of the pressure effect and relative sliding, and it is easy to produce stressconcentration.3Three dimensional finite element analysis method can be carryed outbiomechanical study of intertrochanteric femur fracture.The results is use forclinical significance, so it is a practical biomechanical research methods,it canbe used as animal mechanics, the corpse mechanics research methods usefulsupplement.