| dc.description.abstract | The spinal surgery can be distinguished to fusion surgery and non-fusion surgery. Both of them will need pedicle screws to improve spinal stability no matter which surgery is performed. There are two different types of pedicle screws, monoaxial and polyaxial screws. Because the head of polyaxial pedicle screw can freely change its angle, it effectively reduces the difficulty when assembling the monoaxial pedicle screw. However, there are concerns about the polyaxial pedicle screw because the structure of ball-in-cup may cause slippage.
There are two parts in this study. First, the software SolidWorks and ANSYS were adopted to establish and analyze the standard ASTM F1798’s model. Experiments were performed to verify the correctness of the present finite element analysis. Second, a stabilization system was established to be a reference model by following the standard ASTM F1717. In addition, four different models were established based on the possible parameters in the clinical application, which were screw outer diameter, screw insertion depth, vertebrae angle, and angle between screw and nut. These models were imported to the software ANSYS to simulate the biomechanical behaviors in compression, flexion, lateral bending and torsion.
The results showed that the stiffness of polyaxial pedicle screw was independent of the torque which was applied to the nut. The maximum load that polyaxial pedicle screw can afford was proportional to the torque which was applied to the nut. The stiffness of models were affected by different screw outer diameter, screw insertion depth and vertebrae angle. However, different angles between screw and nut did not significantly affect the stiffness of models.
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