| Summary: | 碩士 === 國立成功大學 === 生物醫學工程學系 === 101 === Pedicle screw instrumentation has been frequently used for reconstruction, fixation, correction and coupling decompression. For osteoporotic cancellous bone, conventional pedicle screw shows inability to provide enough screw-bone interface strength resulting in loosening or failure complications. A novel bone cement anchoraged thoracolumbar pedicle screw was design to enhance fixation strength for osteoporotic spine and simplify traditional spinal surgery procedures that includes using bone cement. The design of bone cement anchoraged thoracolumbar pedicle screw introduces one central hole and three side-grooves for bone cement to pass through the interior of the screw to inject into the spinal column. However, these design features may also significantly decrease the structural strength of the pedicle screw, which may result in pedicle screw failure after implantation.
The goal of this research is to study the mechanical properties of the Cement Anchoraged pedicle screw, understand how different design features affects its mechanical performance. Also, a Medtronic manufactured pedicle screw was selected as compare group to evaluate the Cement Anchoraged pedicle screws safety level. The research is carried out by creating different failure mods by a bending test and compare relative mechanical strength under the same failure condition. The failure mods are Static setscrew failure, Static Neck failure, Dynamic Neck failure and Dynamic side groove failure. These are common or possible failure conditions on a pedicle screw. The bending test was conducted under the guidance of American Society for Testing and Materials (ASTM) testing standard F2193.
The specific aims are as follows: (1) Design and manufacture the Cement Anchoraged pedicle screws with different features; (2) Conduct Static bending test to create setscrew failure; (3) Conduct Static bending test to create Neck failure; (4) Conduct Dynamic bending test to create Neck failure; (5) Conduct Dynamic bending test to create side groove failure.
The Results shows the re-designed Cement Anchoraged pedicle screw can withstand greater maximum bending forces in all kinds of failure mode conducted compared to the original version, proofing the design modification works to increase mechanical strength. It also achieves higher load durability than the compare group, which can be considered a safe product for use.
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