| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 100 === The Spine is an important structure of the human body for supporting body weight and movement, from top to bottom, it can be divided into 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 5 sacral vertebrae and coccyx. The facet joints, which lie between upper and lower vertebrae, are located at both left and right sides of the posterior arch of the vertebra and can be used to resist torque and shear force. When the vertebrae or the facet joints suffered from congenital defects or injuries, it may lead to the separation of upper and lower adjacent vertebrae. When both sides of the posterior arch of the vertebra fractured, it is well known as” spondylolysis “ and usually causes patients to reduce their activities. If the injured vertebra subjected to gravity load to slide forward, it is called “spondylolisthesis”, usually occurring at L5-S1 level, and accompanies with the diseases of disc degeneration.
This study used MSC.Patran as the pre-processing tool and ABAQUS as finite element program solver to analyze the slippage between the fifth lumbar vertebra L5 and the sacrum S1 with the lumbosacral angle 40 degrees under three cases: spondylolysis, grade 1 and grade 2 of spondylolisthesis. The ways to treat the above cases were uses of the internal fixation systems, 2 or 3 segments, PEEK or titanium material of the cage, and both L4-S1 and L5-S1 levels were analyzed and discussed. The cage was inserted at L5-S1 level and four movements like extension, flexion, lateral bending and axial rotation were considered. This study explored the maximum von Mises stress, strain energy density, distributing among the intervertebral discs, screws and vertebral cage, and relative rotation angle of the endplates, and hoped that this investigation would provide more accurate treatment of spinal diseases.
This study established an finite element model of the lumbosacral spine by a series of processing steps as follows: getting the DICOM images from the CT scan, handling by the medical image processing software 3D-Doctor to obtain a smooth surface STL format profile, trimming model on the geometry, setting material properties, boundary conditions and the loads in MSC.Patran, and then creating an executable finite element model, and finally, putting this model into ABAQUS for solving.
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