人體隨著年紀增長或姿勢不良等長期不正常受力影響後，椎間盤逐漸退化造成椎間不穩定，進而壓迫到神經使病患產生疼痛感。最常見的治療方式為脊椎後方內固定器融合術，但臨床上發現由於手術端的活動喪失導致鄰近節之代償行為，可能會發生鄰近節退化問題，於是動態脊椎固定系統的觀念便延伸而出，通常進行脊椎手術時醫生只採用融合或非融合技術其中之一，但近幾年有學者提出將融合和非融合技術相結合的概念，使得混合型固定技術逐漸應用於臨床上，希望達到原有的穩定度之餘還能減少鄰近節過多的補償而產生退化。但目前少有文獻針對上述固定系統進行鄰近節補償問題之完整探討，且混用型動態固定系統因使用時間短以致臨床文獻較為不足，其治療方法大多依靠醫生臨床上應用所得出的結果進行判斷，也尚未有力學上的驗證來證明何種排列方式為最佳的固定方法，因此本研究希望能對鄰近節之變化做更進一步的探討，並試圖用力學驗證混合型固定器最佳之治療方式。
因此，本研究主要目的為使用T11-S1的脊椎模型，利用有限元素分析來評估，當脊椎L4-L5椎間盤發生輕度退化情況時植入單節剛性、半剛性及動態等不同固定系統，或雙節不同排列位置之混合型動態固定系統，在前彎、後彎、側彎及旋轉四種不同運動方向其各椎節間旋轉角度、椎間盤應力分佈及螺絲應力分佈等生物力學特性，並探討上述情況下手術節及鄰近節之變化情形進而得到最佳的之療方式。
分析結果顯示，傳統剛性固定之椎節間旋轉角度與椎間盤應力值皆小於動態固定，當手術節段之椎間旋轉角度越小即越穩定，然而當手術端越穩定鄰近節補償情形則越顯著，導致鄰近節旋轉角度及椎間盤應力增量較大，產生鄰近節退化的風險較高，且穩定度佳其螺絲應力值相對的也較高，較易發生螺絲損壞之情況；而雙節混用型動態固定使用45R-34D時，其鄰近節旋轉角度及椎間盤應力值最接近完整腰椎，且螺絲應力值偏低，因此可證實此種排列位置為較佳之治療方式。

Fusion has been the gold standard treatment for treating the disc degeneration. Many clinical studies have showed that adjacent segment degeneration was observed in patients over time. In order to overcome problems with fusion devices, dynamic stabilization systems are being used to treat disc degeneration related problems. Recently it’s began to combine fusion and non-fusion techniques in the treatment of multi-segmental Degenerative disc disease (DDD). It is hybrid dynamic stabilization designed to promote a balance of stability and adjacent segment degeneration. However, no report investigated whole spine motion and the segment adjacent to the hybrid dynamic stabilization. The purpose of this study was to investigate how different treatment methods influence the biomechanics of adjacent segment and which one is the best treatment of hybrid dynamic stabilization.
A 3-D nonlinear finite element model of the T11-S1 lumbar spine was used to evaluate biomechanics of various device including rigid rod, semi-rigid rod, Dynesys and hybrid stabilization systems inserted at level L4/L5 in comparison with intact spine. Mild disc degeneration was simulated at L4-L5 level. The loading cases of flexion, extension, lateral bending and axial rotation were simulated. Intersegmetal rotation, disc stresses and screw stresses were calculated at implant level and at the adjacent level.
Compared to an intact spine, a dynamic implant reduced inter-segmental rotation at implant level, decreased disc stresses and at implant level. With a rigid implant, these effects are more pronounced. Screw stresses were generally higher in a rigid fixator than in a dynamic implant. The rigid implant had more effect than dynamic implant at the adjacent level. With the hybrid stabilization systems, our results indicated that where the dynamic implant placed superior to the rigid fixator inserted at degenerative disc level was the better treatment.

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