Three-dimensional Finite Element Analysis The Effect Of Femoral Anterior Cortical Notch On The Supracondylar Stress After Total Knee Arthroplasty

Objective: This study is based on the 2D image data of CT and laser scanning,we used the virtual construction of femoral replacement model of knee joint by software.and The models of different depth of femoral anterior cortical notching were constructed by the computer assisted surgery after primary total knee arthroplasty.Finite element analysis is used to explore the maximum equivalent stress changes in the supracondylar section of the anterior femoral condyle under the different notch depths.Finally we will find The "safe depth" of the notch to guide clinical work,To provide biomechanical evidence for the correlation between the cortical notch of the femur and the fracture of the upper part of the condyle after total knee arthroplasty.Methods: 1?A healthy young male was selected and scanned with spiral CT of lower extremity to obtain 2D image data.To simulate the femur model of normal adults,The data were processed in Mimics ? Geomagic ? Solidworks.Using the posterior cruciate ligament femoral prosthesis of Link company in Germany,the object prosthesis was scanned by laser,and the point cloud data of the prosthesis was processed by geomagic software,then imported into solidworks,and the femur was subjected to virtual osteotomy and assembly.Three-dimensional model of knee joint femur replacement was obtained.2?On the basis of the femoral replacement model,the different notch depths were created by simulation,and the stress cloud map of the anterior femoral condyle was obtained by introducing the Finite element ansys software,to analyze the supracondylar stress of the anterior femoral condyle.The changes of maximum equivalent stress in different experimental groups and control groups were compared.Results: 1 ? The 3D finite element model of knee arthroplasty is proved to be effective and reasonable compared with the traditional biomechanical experimental results and the results of retrospective clinical studies.2?The maximum equivalent stress of the supracondylar is directly related to the notch depth,which has significant statistical significance(p < 0.05),and the local stress concentration is more significant with the increase of the notch depth.However,the notch length has no statistical significance for the maximum equivalent stress of supracondyle in this study(p > 0.05).3?We found that when the notch depth is at the junction of cortical bone and cancellous bone,the stress concentration mutation can occur,and when the cancellous bone is completely exposed,the local maximum equivalent stress will be superimposed.Conclusion: 1?When the thickness of cortical bone at the distal notch of the femur is more than 3 mm,the depth of the notch should be avoided more than 3 mm in order to reduce the possibility of supracondylar fracture.2?When the thickness of cortical bone at the distal notch of the femur is less than 3mm,the depth of the notch should be avoided beyond the junction of the cortical bone and cancellous bone.This reduces the likelihood of supracondylar fractures.