Finite Element Study Of Ischemic Necrosis Of Femoral Head Based On CJFH

Objective: In this study,three-dimensional finite element analysis of the femoral head was performed by using the classification of the three-column structure in china-japan Friendship Hospital(CJFH)to simulate the modeling of the total hip joint.Digital simulation of the model was conducted in ANSYSY to obtain the stress of the femoral head in different necrotic areas and volumes,providing theoretical basis for clinical hip preservation treatment.Methods: Selection of 30 normal male youth hip CT slice,using Mimics,Geomagic studio,solidwork software carries on the preliminary modeling,extracting cortical bone of the sacrum and ilium in Mimics the cortical bone and femur cortical bone,using the threshold value division,making the pelvis and femur cancellous bone,use smooth,smooth triangles,and other functions of the model surface processing,will receive a preliminary model of import Geomagic studio,in Geomagic studio to redraw the grid,set the grid of 0.3 mm,Get relatively smooth model,to model local smoothing,rest will handle good model to another,the femur and acetabulum as key contact part,according to the three column to draw the corresponding predictions,to reverse the model processing,reverse the STP format after import solidwork,entering solidwork first to assemble model,application of origin overlap lacing,bone in solidwork parts module according to the theory of three column divided area,set up blank control volume 0% necrosis,compared with previous research using the control model,confirms the validity of the model,Then for CJFH classification of each type of femoral head total volume 5%,15%,30%,50% of the necrotic volume model,a total of 22 groups of models,each in turn into ANSYS,a set ofmodel in ANSYS according to actual hip stress distribution and the subjects of the actual weight,set up stress position,and set up the contact relationship,after dividing the grid is analyzed with mechanics,and selection of maximum stress and relative displacement as the final experiment data,the relevant conclusions.Results: Selection of 30 normal male youth hip CT slice,using Mimics,Geomagic studio,solidwork soft.According to the cloud picture and data of the displacement of the femoral head necrosis tissue displacement is larger,the displacement peak both in the necrotic tissue of weight-bearing area,different necrosis with mechanical volume distribution can be found that the dead volume is less than 15% of cases,pressure peak collapse pressure has not been achieved,when the dead volume reaches 30%,the L2 and L3 collapse risk is extremely high,L3 type with more than 50% necrosis area stress is greater than the failure stress.Volume 0% necrosis,compared with previous research using the control model,confirms the validity of the model,Then for CJFH classification of each type of femoral head total volume 5%,15%,30%,50% of the necrotic volume model,a total of 22 groups of models,each in turn into ANSYS,a set of model in ANSYS according to actual hip stress distribution and the subjects of the actual weight,set up stress position,and set up the contact relationship,after dividing the grid is analyzed with mechanics,and selection of maximum stress and relative displacement as the final experiment data,the relevant conclusions.Conclusion:(1)on the model of avascular necrosis of the upper surface of the sacrum along the Z axis 600 n load,stress nephogram of different necrotic volume get can be found that stress area are mainly concentrated in the lateral femoral head column,be located in the organization of necrosis of femoral head pressure,high displacement relative to the surrounding normal tissues slants big,necrotic tissue pressure area,the greater the percentage,the greater the relative displacement.(2)all necrotic model,maximize the displacement in the necrotic tissue,when the necrotic tissue at the lateral border column withthe middle column,the maximum stress,maximum displacement in the region of the stress area and superposition of necrotic tissue,L2 extremely lateral type with L3 full head type common displacement is larger,especially after the dead volume of more than 30%,the displacement can be more than 0.1 mm.By observing the stress cloud diagram,when the necrosis volume is below 15%,the stress peak corresponding to type L2 is the highest,but the highest value does not exceed the collapse index,and the maximum stress of type L3 is less than that of type L2,indicating that the stress concentration is mainly distributed in the lateral column and the intermediate column.When the volume of necrosis reaches 30%,the maximum stress value of L2 and L3 necrotic zones has exceeded 5.5mpa,and the stress value of L3 necrotic zones has exceeded 5.5mpa in more than 50% of the zones,at which time the risk of femoral head collapse is extremely high.