| Summary: | 碩士 === 國立臺灣科技大學 === 醫學工程研究所 === 107 === In assessing the kinematics and dynamics of implants on the human body, methods often used include actual biomechanical experiments or finite-element method to obtain the effects of the implant; clinical experiments often accompanied by experimental design, funding, data recording and preservation, but for finite-element method, only need to construct geometric models and input various analysis parameters, you can get results close to the actual clinical experiment. Furthermore, digitized data can be recorded for multiple cases comparison or applying more investigation in detail, so finite-element method are often used in medical publications.
The common-used bone fusion surgery today has a Traditional Trajectory and a Cortical Bone Trajectory, and the performance or effect on the fixed section of the intervertebral disc and the operational adjacent section are most clinicians’ concern. However, few papers directly discuss (1) the differences between kinematics and dynamics, or (2) overestimate the diameter or length of surgical implants, and (3) even the model of finite-element method is too simple which leads to analysis bias. Therefore, this study used a complete five-segment lumbar vertebrae and sacral lumbar vertebrae model to analyze and compare the kinematics and dynamics differences between the Traditional Trajectory and the Cortical Bone Trajectory by parameterizing diameter, length and implantation trajectory of screws.
Currently, Cortical Bone Trajectory is a relatively new clinical minimally invasive surgery for the lumbar spine; therefore, many clinicians are using this surgical method gradually. However, the size of the bone screw is often limited by the size of the pedicle, so the screw with smaller diameters are used for surgical application to avoid penetrating the vertebral pedicles or vertebral body. However, most of researches indicate that bone screws with smaller diameters results in excessive stress and might break in actual use. Therefore, in this study, the pedicle screw of the cortical bone tracking will be improved, and a composite screw will be designed to achieve good performance during surgery, and it is not easy to break. Through finite-element method, we compared between the kinematics and kinetics of the pedicle screw before and after our improvement. We expect this latest style of screw can be the first choice in the future.
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