Imaging And Biomechanical Study On The Collapse Risk Of Osteonecrosis Of Femoral Head Based On Association Of Activity And Inertia Theory

Objective:1.Based on China-Japan Friendship Hospital(CJFH)femoral head necrosis typing,the volume and location distribution of the necrotic area in patients with peri-collapse and early collapse femoral head necrosis were evaluated by CT 3D reconstruction,which to a certain extent complemented the defects of CJFH typing in predicting collapse at a single image level and provided a reference for subsequent biomechanical studies to construct a3 D structural model of CJFH typing.2.Based on the theory of "dynamic-static combination" in Chinese medicine,we combined the finite element analysis(FEA)method to evaluate the three-dimensional structure of the same CJFH fraction and different CJFH fractions under different hip behavioral actions.The study investigated the biomechanical effect of the difference between CJFH typing and hip behavioral actions on the necrotic area,and guided the hip preservation treatment of ONFH,and provided reference for clinical diagnosis and treatment.Method:1.CT imaging data of patients with ARCO stage II or IIIB ONFH were reconstructed using Mimics 21.0 software,the three-column structure of the femoral head was divided according to the CJFH staging characteristics,the femoral head was divided into three subdivisions according to the three-column structure,the volume ratio of the necrotic area to the femoral head and the volume ratio of the necrotic tissue in each subdivision to the respective subdivisions were calculated for the patients included in the study,and the distribution of the necrotic area in the three-column.2.According to the inclusion and exclusion criteria,the hip tomography CT scan data of one healthy volunteer was selected,and the original 3D model of the left hip joint was extracted by Mimics 21.0 software,further preprocessed by Geomagic 2017 software,and then imported into Solidworks 2018 software in STL format based on CJFH fractionation The assembled model was finally given the same material parameters and boundary conditions for each fractal model in ANSYS 21.0 software,and after load setting,precomputational setting and mesh division,the Von Mises stresses were calculated by The Von Mises stress and maximum deformation values obtained from the analysis were used to evaluate the biomechanical effects of the load on the necrotic area and the post-necrotic femur,and to assess the risk of necrotic collapse of each fractal model.Results:1.The volume of the femoral head in the patients with ONFH included in this study was(47531.41±7794.03)mm,the volume of the necrotic area was(18456.10±7487.92)mm,the ratio of the necrotic area to the volume of the femoral head was(38.83±16.17)%,the volume of necrotic tissue in the lateral,central,and medial columns was(5782.10±(2427.09)mm,(11347.62±5115.91)mm,and(1326.38±1662.44)mm,respectively,and the volume ratio of necrotic tissue in the in the lateral,central,and medial columns was(49.49±18.57)percent,respectively(44.91±20.21)%,(14.26±18.09)%,the necrotic area of ONFH patients mostly involved the lateral column of the femoral head,followed by the central column,and the medial column part was less.2.The results of finite element analysis showed that: 1)Under the same working conditions and hip behavioral actions,the maximum deformation values of the necrotic area were all M-type < C-type < L-type,in which the deformation value of L3-type was the largest among the three hip This suggests that the risk of post-necrosis collapse is higher in patients whose necrotic area involves the lateral column than in other subtypes,especially the risk of post-necrosis collapse is highest in patients whose necrotic area penetrates the entire lateral,central,and medial cortices of the femoral head;2)The Von Mises stress cloud of the femur after necrosis shows that the Von Mises stresses of the femur are not in the femur under the three hip behavioral actions.The Von Mises stress cloud of the post-necrosis femur showed that the maximum Von Mises stress in the necrotic area was smaller than the maximum Von Mises stress in the post-necrosis femur under the three hip behavioral actions,but it was near the inner and outer edges of the femoral neck under a smaller stress load.maximum deformation.3)Comparing the deformation and Von Mises stresses in the finite element model under the same working conditions and CJFH typing,the maximum deformation values in the necrotic area were standing position < stair climbing <squatting> stair climbing > standing position.stairs > standing position.Conclusion:1.The CT 3D reconstruction method can effectively reflect the location of the necrotic area in the femoral head and the distribution of the necrotic area in each region of the three columns of the femoral head,which can compensate to a certain extent for the deficiency of the CJFH typing in assessing the characteristics of the necrotic area only at a single level.2.The risk of collapse is higher when the necrotic area involves the lateral column under the same hip behavioral maneuvers;the risk of collapse is higher when the same CJFH typing is in the squatting and stair positions compared with the standing position.and stairs were at higher risk of collapse compared to the standing position,i.e.,large-angle hip flexion is a high-risk behavior for collapse occurrence after femoral head necrosis.The implications of this study for the peri-collapse phase of femoral head necrosis are: 1)The results of finite element analysis based on CJFH staging illustrate that ensuring the integrity of the lateral column can effectively reduce the risk of post-necrotic collapse of the femoral head,and hip preservation therapy should be centered on reestablishing effective support of the lateral column.When the necrotic area involves the lateral column,the risk of post-necrotic collapse is higher,and more therapeutic interventions are needed.2)The biological properties of necrotic tissue are changed,and the strength and stiffness of the bone are reduced accordingly,so large deformation can occur under a small stress load.In daily life,high-intensity weight bearing on the affected hip should be avoided to ensure effective rest for the affected hip.It is recommended that patients should reduce their weight and avoid high-intensity movements such as standing on one foot,running and jumping,which increase the burden on the affected hip.3)The rehabilitation activities and functional exercises of patients with early stage femoral head necrosis should be carried out in an appropriate amount without increasing the risk of collapse,and it is recommended to combine motion and rest in daily life,and avoid large-angle hip flexion movements such as stairs and squatting.