| ObjectiveTo study and compare the stress distribution and changes of acetabular dysplasia which with different CE angle decrease by the method of finite element analasis (FEA). To analyse the relationship between stress chang of acetabular dysplasia and osteoarthritis(OA). To illuminate the mechanism of OA relating to acetabular dysplasia and the disorder's arising and development. To simulate CE angle of different degree acetabular dysplasia and to do the loading experiment on the FEA model. Then to discuss the compensative-ability scope of body according to CE angle. To analyze the pathogenesis mechanism of this type of OA,with which we can provide biomechanics guidance to the prevention and treatment of this kind of OA. MethodsTwo abnormal hips and one normal hip of volunteers were obtained. Six total pelvic X-ray photographs were obtained by taking them in two different conditions which direct the volunteers stand strightly with double feet (DFS)or with single foot(SFS). After the images operated by the computer,we artificially divided these models into handreds of elements and nodes according to FEA principles. For example,in the condition of normal hip which with CE angle 35?, on DFS phrase, the model was divided into 899 elements(Es) including 1029 nodes(Ns). On SFS phrase , the model was divided into 896 Es including 1028 Ns. In the condition of abnormal hip which with CE angle 20 ?, on DFS phrase, the model was divided into 894 Es including 1024 Ns. On SFS phrase , the model was divided into 893 Es including 1026 Ns. In the condition of abnormal hip which with CE angle 2?, on DFS phrase, the model was divided into 882 Es including 1014 Ns. On SFS phrase , the model was divided into 886 Es including 1020 Ns. Then ,we used the computer software(Super-sap93) to create six plain FEA models. The loading of body weight in normal condition was calculated. When loading on the models ,the condition of two kinds of postures was imitated such as on DFS phrase or on SFS phrase. The stress loading state and distrbution especially shear stress,compress stress and Von mises stress were calculated by the computer. Then,the relation between acetabular dysplasia and OA was gotten by analyzing. A probable compensative ability scope of CE angle was introductively provided by simulating CE angle decrease and giving the same loading on the models.ResultsOn the DFS phrase,with the CE angle's decrease,the compress stress at Z axis significantly concentrated on the lateral-superior edge(p<0.01), at the same time, the draw stress on the inferior edge of capsule significantly increased compared with normal hip(p<0.01). On the SFS phrase,the compress stress and the shear stress on the lateral-superior edge of acetabular increased gradually. With CE angle's decreasing ,the draw stress of hip capsule increased gradually at Y axis. With the increase of stress, the change of phrase and the decrease of CE angle,the compress stress increasingly concentrated on the lateral-superior cartilage of the acetabulais Meanwhile ,the loading area on the head of femur moved inwardly and the stress concentrated on the interior-suprior part of the head. With valgus muscle's working,Von mises stress,shear stress and compress stress significantly increased(p<0.01). In simulating test ,when the CE angle was minorized to -10 ,the draw stress of valgus muscle of a 60kg-weight patient could balance the dislocation stress at Y axis,moreover,a calculation was gotten that the compensative ability scope of this acetabular dysplasia patient was between CE angle-10 to CEangle20 according to the degree of acetabular dysplasia. Conclusion1. On DFS phrase,with CE angle's decrease,vulgas muscle's begining to work,the compress stress increasingly concentrates on the lateral-suprior part of acetabular,the draw stress of capsule occurs and significantly increases.the loading area moves inwardty,the shear stress and Von mises stress increase significantly.2. On SFS phrase ,with CE angle's decrease ,the bone and cartilage of acetabular get more... |
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