多軸向椎弓根螺釘於不同設計參數下之生物力學影響

江富萱(Fu-Xuan Jiang)

指導教授 ： 黃俊仁

國立中央大學/工學院/機械工程學系/碩士(2015年)

摘要

脊椎手術主要可分為骨融合術和非骨融合術，而無論是何種方式，均必須利用椎弓根螺釘提高脊椎穩定度。而椎弓根螺釘可分為單軸向和多軸向兩種，多軸向椎弓根螺釘因為其螺釘頭部的角度可以自由改變，有效改善單軸向椎弓根螺釘在安裝上時的困難，但其球結構可能會產生滑脫的缺點，也成為多數人疑慮的一項議題。
　　本文分為兩大部分，第一部分利用軟體SolidWorks根據規範ASTM F1798建立出多軸向椎弓根螺釘模型，匯入軟體ANSYS進行有限元素分析，接著利用相同方法進行實驗，驗證有限元素分析之正確性。第二部分同樣利用軟體SolidWorks根據規範ASTM F1717建立出多軸向椎弓根螺釘穩定系統當作基準模型，並根據臨床應用上可能會產生的參數，繪製出四種不同參數模型，分別為不同螺釘外徑、不同螺釘鎖入深度、不同椎骨間角度、不同螺釘與螺帽間角度，並將不同參數模型均匯入軟體ANSYS，模擬前彎、後仰、側彎、扭轉四種不同運動方式之生物力學行為。
　　結果發現多軸向螺釘之勁度和施加於螺帽上的扭矩無關，而能承受的最大負載和施加的扭矩成正比。另外，不同螺釘外徑、不同螺釘鎖入深度、不同椎骨間角度均會改變模型的勁度，而不同螺釘與螺帽間角度對勁度無造成明顯改變。

關鍵字

多軸向椎弓根螺釘 ； 有限元素法 ； 勁度

並列摘要

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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