| Osteonecrosis of femoral head(ONFH)refers to the progressive disease that causes blood vessel damage,osteonecrosis,aseptic inflammation,and severe hip joint pain and function limitation due to various reasons.Finally,it is necessary to restore the function of the hip joint through artificial joint replacement surgery to ensure quality of life.For young and middle-aged patients with ONFH,because of the service life of the artificial joint and the problems of high difficulty,high risk and many complications in the revision of hip joint,hip salvage surgery has a clear practical significance.For the hip preservation treatment of type CJFH-L2 femoral head necrosis,Sugioka showed through clinical practice and postoperative evaluation that rotational osteotomy through the intertrochanteric femur can replace the necrotic part of the weight-bearing area with the normal femoral head to prevent the femoral head from continuing to collapse.After that,the hip preservation surgery has been continuously innovated and improved,such as the rotational osteotomy at the base of the femoral neck through the surgical dislocation approach,which has achieved better results.Sugioka used cancellous bone screws for fixation during the operation,but occasionally the fixation was unstable.Femoral neck system(FNS)is a new type of fixation device for the treatment of femoral neck fractures in recent years,with the characteristics of stable fixation and less damage.There is still a lack of systematic investigation and retrospective study on the efficacy evaluation of FNS in rotational osteotomy for ONFH in the early stage of collapse.How to implant the traditional cannulated screw,whether to choose the femoral neck internal fixation system as the fixation device,the new femoral neck internal fixation system with different implantation positions and the different rotation angles during osteotomy have great significance for the functional recovery of patients after operation.In view of the above problems,this study explored the biomechanical characteristics of rotational osteotomy with different fixation methods for the treatment of femoral head necrosis through finite element analysis,providing theoretical basis for clinical practice.The whole study is divided into the following four parts:Part Ⅰ: Finite element analysis of the treatment of femoral head necrosis by rotational osteotomy with FNS and cannulated screwsObjective: The purpose of this study was to analyze the biomechanical characteristics of rotating osteotomy with a novel femoral neck system for CJFH-L2 femoral head necrosis by using a three-dimensional finite element analysis method.Methods: A healthy volunteer was selected for CT scanning of the full length of femur,and the CT data were imported into Mimics 21.0,a medical reconstruction software,to obtain a rough three-dimensional model of femur.The model was imported into the graphics processing software Geomagic 2013 in STL format to construct the structures of cortical bone,cancellous bone and necrotic area,and the model was repaired and imported into the engineering modeling software Solidworks 2017,and the rotational osteotomy of the base of the femoral neck was simulated by the segmentation command.The osteotomy model was created with 90° forward rotation and 180° backward rotation.According to the actual used FNS and the size of hollow screws,the three-dimensional model was established,and the FNS fixing group and 3 hollow screws fixing group were established by a new assembly.Finally,finite element analysis software ANSYS Workbench 19.0 was used to perform material assignment,mesh division,applied mechanics and equation calculation,analyze the stress distribution and displacement of proximal femoral osteotomy,internal fixation device,necrotic area and femur in the model,and summarize the biomechanical characteristics.Results: In the 90° anterior rotation and 180° posterior rotation models,the stress of proximal femur and necrotic zone and the displacement of proximal femur,internal fixation models,necrotic zone and femur in the FNS group were smaller than those in the cannulated screws group.Compared with the cannulated screws group,the stress peak values of the proximal femur and necrotic zone were significantly reduced in the FNS group,with 47.45% and 13.64% reduction in the proximal femur,44.96% and 35.52% reduction in the necrotic zone.Conclusion: Compared with cannulated screws,FNS provided better biomechanical stability regardless of 90° forward rotation or 180° backward rotation after osteotomy.Part Ⅱ: Finite element analysis of rotational osteotomy with cannulated screws fixed in different directions for the treatment of femoral head necrosisObjective: The purpose of this study was to compare the biomechanical characteristics of the treatment of CJFH type L2 femoral head necrosis by rotating osteotomy with 180 ° posterior rotation using cannulated screws with different directions as internal fixation devices by finite element analysis.Methods: Using the structural model of cortical bone,cancellous bone and necrotic area of the femur obtained in the first part,in the software Solidworks 2017,the rotational osteotomy at the base of the femoral neck was simulated by the segmentation command,and the osteotomy model with a backward rotation of 180 ° was created.Four groups of models were created according to the possibility of clinical cannulated screw implantation,which were: group A model(three cannulated screw parallel fixation group);Group B model(one cannulated screw was rotated downward 5 ° to fix group);Group C model(one cannulated screw was rotated downward 10 ° to fix group);Group D model(1 cannulated screw rotated downward 10 °,1 cannulated screw rotated downward 5 °,3 cannulated screws were not fixed in parallel group).Finally,finite element analysis software ANSYS Workbench 19.0 was used to perform material assignment,mesh division,applied mechanics and equation calculation,analyze the stress distribution and displacement of proximal femoral osteotomy,internal fixation device,necrotic area and femur in the model,and summarize the biomechanical characteristics.Results: In the 180 ° posterior rotation model,the stress in the femoral necrosis area and the displacement of the proximal femoral osteotomy,internal fixation device,necrosis area and femur in Group A were smaller than those in the other three groups.The peak stress of necrotic area in group A was significantly lower than that in group D,and the peak stress decreased by 47.53%.Conclusion: In the 180 ° posterior rotation model,compared with the other three groups,the three cannulated screws parallel to each other can achieve better mechanical support effect in rotational osteotomy.Part Ⅲ: Finite element analysis of the treatment of femoral head necrosis with rotational osteotomy fixed by FNS at different implantation positionsObjective: The purpose is to compare the biomechanical characteristics of the FNS with different heights as the internal fixation device applied to the treatment of CJFH type L2 femoral head necrosis by rotating osteotomy with 90 ° forward rotation and 180 ° backward rotation,respectively.Methods: Using the structural model of cortical bone,cancellous bone and necrotic area of the femur obtained in the first part,in the software Solidworks 2017,the rotational osteotomy at the base of the femoral neck was simulated by the segmentation command,and the osteotomy model with 90 ° forward rotation and 180 ° backward rotation was created.The femoral neck internal fixation system was respectively implanted into the osteotomy model from top to bottom by simulating different implantation heights.The implantation height was 1 mm apart.A total of 9 groups of models were created by rotating 90 ° forward and 16 groups of osteotomy models were created by rotating 180 ° backward.Finally,finite element analysis software ANSYS Workbench 19.0 was used to perform material assignment,mesh division,applied mechanics and equation calculation, analyze the stress distribution and displacement of proximal femoral osteotomy,internal fixation device,necrotic area and femur in the model,and summarize the biomechanical characteristics.Results: In the 90 ° forward rotation model,the stress of the proximal femoral osteotomy and the displacement of the proximal femoral osteotomy,internal fixation device,necrosis area and femur in the FNS decreased by 9 mm were less than those in the other 8 groups.In the 180 ° posterior rotation model,the stress of proximal femoral osteotomy and internal fixation device and the displacement of proximal femoral osteotomy,internal fixation device,necrotic area and femur in the FNS decreased by 15 mm were relatively small.Conclusion: In the models of 90 ° forward rotation and 180 ° backward rotation,FNS can provide better biomechanical stability when the implantation position is close to the femoral calcar.Part Ⅳ: Finite element analysis of FNS-fixed rotational osteotomy with different rotation angles for the treatment of femoral head necrosisObjective: The purpose is to compare the biomechanical characteristics of rotational osteotomy with different rotation angles of proximal osteotomy in the treatment of CJFH type L2 femoral head necrosis.Methods: Using the structural model of cortical bone,cancellous bone and necrotic area of the femur obtained in the first part,in the software Solidworks 2017,the rotational osteotomy at the base of the femoral neck was simulated by the segmentation command,and the proximal osteotomy block was rotated at different angles,respectively creating a forward rotation of 30 °,a forward rotation of 60 °,a forward rotation of 90 °,a forward rotation of 120 °,a backward rotation of 30 °,a backward rotation of 60 °,a backward rotation of 90 °,a backward rotation of 120 ° There are 10 groups of 150 ° backward rotation and 180 ° backward rotation.Then the FNS model was implanted into 10 groups of models with different rotation angles for the treatment of osteonecrosis of the femoral head,and the establishment of the model was completed.Finally,finite element analysis software ANSYS Workbench 19.0 was used to perform material assignment,mesh division,applied mechanics and equation calculation,analyze the stress distribution and displacement of proximal femoral osteotomy,internal fixation device,necrotic area and femur in the model,and summarize the biomechanical characteristics.Results: In the model of 150 ° backward rotation and 180 ° backward rotation,the stress peak value of osteotomy and necrosis area of proximal femur is smaller than that of other groups.In the model of 60 ° backward rotation and 90 ° backward rotation,the displacement of proximal femoral osteotomy,internal fixation device,necrosis area and femur were smaller than that of other groups.Conclusion: During the operation of rotational osteotomy,the femoral head necrosis area should be moved out of the acetabular load-bearing area of the hip joint as far as possible to ensure better biomechanical stability. |
