頸椎融合術補骨置入位置之生物力學探討

The Biomechanical Effects of the Positions in the Cervical Spine Bone Grafts Fusion

本研究利用電腦斷層掃瞄影像資料建立幾何外形與材料分佈較接近真實頸椎的三維有限元素模型，同時與其它頸椎實驗之分析結果相互驗證，以確認所建立模型的可靠度。並利用此頸椎模型加入骨植入物（bone graft）以取代損壞或退化的椎間盤，模擬臨床上Smith-Robinson手術過程以瞭解術後整體頸椎之生物力學的影響，同時比較骨植入物置於不同位置其力學上的差異。由研究結果顯示，骨植入物在同一椎節中分別置於不同的位置，其有骨植入物頸椎之運動範圍均較正常頸椎為小，至於骨植入物置於的位置不同，其對於不穩定椎節以及整體頸椎（C4～C6）運動範圍並無多大差異，在應力傳遞方面則置於後方的骨植入物其應力小於置於前方的骨植入物更小於在中央之骨植入物。

This study established a three-dimensional finite element cervical spine model (C4~C6). With the aid of CT images and CT numbers, this cervical spine model has a realistic approximation in the geometry and material distribution. To validate this finite element model, the range of rotation under different loading was compared with other experimental study. Bones grafts were then generated to replace the disc in order to simulate the Smith-Robinson surgical technique. The effects of bone grafts in different positions within the unstable segment were simulated. The results indicated that bone grafts at different insertion positions have minor influence on the outcome of the range of rotation. The stresses of bone grafts were much greater than the disc of intact spine, which indicated that most of the loading, was carried by the bone grafts. The peak stress of bone graft is largest, when the bone graft is inserted at the middle position, while the bone graft is at the posterior position.