由於近年來人口老化的趨勢越來越嚴重，而這種趨勢將導致許多人可能患有跟年齡相關的骨科疾病，其中以骨質疏鬆症為最常見，而在患有骨質疏鬆症的病患，通常發生骨折的機率相當的高，而且在治療時都會使椎弓根螺絲的咬合能力大幅的降低，同時也提高鬆脫的風險性。近年來已經有研究提出一種新型的椎體成型術(Vertebroplasty)，為使用中空椎弓根螺絲結合骨水泥固定椎體，以達到增加椎弓根螺絲咬合能力的效果，而椎弓根螺絲原本在脊椎內固定器中就是屬於較易發生破壞的元件，所以若是使用中空型的椎弓根螺絲將會增加椎弓根螺絲破壞的可能性。目前為止，尚未有人探討這種中空型椎弓根螺絲的強度。本文將以有限元素分析方式，探討中空型椎弓根螺絲之彎曲強度與骨咬合強度進行模擬分析。
以市售繪圖軟體SolidWork 2008建立彎曲強度模型與骨咬合強度模型，而模型繪製完成後，匯入市售有限元素分析軟體ANSYS Workbench 11進行有限元素分析，其在彎曲強度的部份，探討三種不同類型的椎弓根螺絲(實心椎弓根螺絲、中空型椎弓根螺絲以及中空型椎弓根螺絲鎖入銷)，並且分析圓錐型與圓柱型這兩種不同類型的椎弓根螺絲；而在骨咬合強度的部份，則是分析骨水泥在不同位置之最大拉出強度，並且也探討了圓錐型與圓柱型椎弓根螺絲，而在圓錐型椎弓根螺絲，考慮了有無骨壓縮效應，將進行參數化分析以及靈敏度分析。
從分析結果中發現，在於彎曲強度模型中，中空圓錐型椎弓根螺絲相較於中空圓柱型椎弓根螺絲有較佳的抗彎曲強度，且中空圓柱型椎弓根螺絲鎖入銷相較於中空圓柱型螺絲，有顯著的提高螺絲的抗彎曲強度；在於骨咬合強度模型中，發現骨水泥越靠近螺絲近端處，其會有較佳的拉出強度，並且在考慮骨壓縮效應之模型會優於未考慮骨壓縮效應之模型。而本研究所建立的數值模型，可以有效的預測中空型椎弓根螺絲之彎曲強度與骨咬合強度，且這些模型在於產品的開發與設計上能夠減少時間與人力。

The tendency of population aging has become more and more serious in recent years. This tendency will lead many people to suffer from orthopedic diseases such as osteoporosis. Anchoring pedicle screws on osteoporotic spine is a challenge work, especially in patients with very low bone mineral density (BMD). Cannulated pedicle screws with injection of bone cement might be useful method to improve their bone holding power. However, the biomechanical performance of cannulated pedicle screws for the bone holding power was unclear. In addition, the pedicle screws are the weakest part of the spinal implants. Unfortunately, screw failure would become more serious when cannulated pedicle screws were used. Thus, the purpose of this study was to investigate the bending strength and bone holding power of cannulated pedicle screws with different screw designs using finite element methods.
Two types of the finite element models, which consisted of the bending strength models and the bone holding power models, were constructed and analyzed using SolidWorks and ANSYS Workbench. For the bending strength models, three types of screw structures (solid pedicle screws, cannulated pedicle screws, and cannulated pedicle screws with pin) and two types of screw threads (conical design and cylindrical design) were discussed. For the bone holding power models, conical pedicle screws and cylindrical pedicle screws with bone cement were analyzed. The best location of bone cement for different pedicle screw designs was also discussed. In the discussion of conical pedicle screws, whether there is the effect of bone compaction is discussed to do parameterized analysis and sensitivity analysis.
For the results of the bending strength models, the bending strength of the conical cannulated pedicle screws was significantly superior to that of the cylindrical cannulated pedicle screws. In addition, the cylindrical cannulated pedicle screw with pin could greatly improve their bending strength as compared with the cylindrical cannulated pedicle screw alone. For the results of the bone holding power models, the best bone cement distribution was very close to the proximal site of pedicle screws and the model with bone compaction is better than the model without bone compaction. This result was compatible with the past study. Therefore, the numerical models created in this study can be used to predict the bending strength and the bone holding power of the cannulated pedicle screws with injection of bone cement. These models can also decrease the time and effort for improving commercial products or developing a new design.

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