Biomechanical Analyses and Experimental Test of the Vertebral Body Cage
| Autor: | Wen-Hsien Hsu, 許文賢 |
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| Rok vydání: | 2009 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 97 The Vertebral Body cages (VBCs) have been used to treat vertebral bodies with different maladies such as osteomyelitis, severe compression fracture, metastases, tumor, or infection. However, a vertebral body replacement commonly experiences graft fracture, loosening, and collapse in a short period after an orthopaedic surgery especially for the osteoporotic bone. The interface between the implant and vertebral body is an important topic. Therefore, the purposes of this study were to analyze the subsidence and loosening by using a FEM-based Taguchi method and mechanical tests and to investigate the effects of various factors to find the robust design of the vertebral body cage interface. In this study, three kinds of topics would be discussed including the comparative study of the commercially VBC designs, the pullout strength of the VBC, and the subsidence of the VBC. Firstly, the analytical model, which based on a 37-year-old man with no clinical or roentgenological abnormalities, was obtained by computed tomography (CT) scanning. Three-dimensional finite element models of the lumbar spine were created with a vertebral body replacement at L3, and a paired internal fixation device between L2 and L4 was also inserted. The subsidence of both Stryker VBC and Titanium mesh cage (TMC) was performed and compared. The results showed that Stryker VBC was superior to TMC. Secondly, the pullout strength of the VBCs would be evaluated by the Taguchi method and the finite element analysis. Six design variables of the VBCs were considered. Two kinds of fusion situations were discussed including the model with bone fusion and that without bone fusion. The results revealed that the optimum factor level settings in the situation without bone fusion was, which correspond to the pyramidal spike type, a spike height of 2 mm,a spike diameter of 2.2 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 10 mm. In addition, the optimum factor level settings in the situation with bone fusion was, which correspond to the conical spike type, a spike height of 2 mm, a spike diameter of 2.2 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 20 mm. In the correlation study, the results of the finite element models were closely related to that of the mechanical tests with a high correlation coefficient of 0.802. Thirdly, the subsidence of the VBCs was analyzed by using the same method. The results showed that the optimum factor level settings in the situation without bone fusion was, which correspond to the pyramidal spike type, a spike height of 2 mm,a spike diameter of 1.4 mm, an oblique geometry, 11 rows per 28 mm, and an inner diameter of 10 mm. In the correlation study, a high correlation coefficient of 0.847 between the finite element models and the mechanical tests was found. The optimum design of the VBC was, if both the pullout strength and the subsidence were considered simultaneously. In the conclusions, the FEM-based Taguchi method could decrease the effort and time needed to analyze the spike factors of the VBC, and the mechanical tests might provide useful evidence to prove the applicability of the finite element models. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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