Analysis Of Stress Distribution On Femoral Head With Changing Femoral Neck Anteversion Via 3D Finite Element Method

Purpose:As for the necrosis caused by changed femoral neck anteversion after neck fracture operation,this paper aims to study on the role of this changed anteversion in changing the femoral head's stress distribution,especially the role in causing increased stress level,to provide support for the head necrosis.Methods:(1)Use reverse engineering methods,combined with the AN SYS software to reconstruct the whole set of the femur's 2D images scanned by the 16 slice CT to femur 3D model.Then verify its biomechanical characteristic.(2)Edit program to transform the data from the lab coordinate to the femur coordinate.(3)calculate the size of the bearing area.(4)Measure the femoral neck anteversion,then reconstruct 5 models with different angles as -10,0,10,20,30degree.(5)Use the force got from hip98 as the external load to finish the FE analysis of these five different models.(6)Define three paths along the coronal plane.These paths start from the center of the head surface,and extend to the inner part of the neck,the outer part of the neck as well as the center of the neck region.Aim to find the difference of the stress between these five models under the same path.Result:With the help of reverse engineering method,this paper reconstruct the femur suface model successfully.The model and the real femur's stucture are in good coincidence.Format the data and apply it to the FE analysis sucessfully.It's more reliable. The angle of this subject is 10 degree.In single-leg standing,these five models' stress distributions have uniformly tendency,that the stress level of the inner part of the head(2.4901Mpa,2.3483Mpa,2.1951Mpa,2.3484Mpa,2.4769Mpa) is higher than that of the outer(1.6763Mpa,1.5761Mpa,1.5075Mpa,1.5739Mpa,1.6756Mpa).Besides,there are two other main areas with higher stress level,one is near the wall of the neck while the other is near the lateral side of the neck.From 10 degree to 20 degree,also from 10 degree to -10 degree,the corresponding areas's stress level become higher than the former degree. When the FNA is decreased to -10 degree or increased to 30 degree,the model has the highest stress level among these five models,respectively with 3.8907Mpa and 3.8991Mpa.Conclusion:Using 2D images with dicom3.0 standard can reconstruct the finite element model effectually.This paper successfully transform the coordinate system of the force.Among these five models,model with original angle 10 degree has the lowest stress level.With the increased deviation,the model has the higher stress level.