在臨床上有許多不同型態的植入物被用於治療各種腰椎的病變，對於評估其使用效果，目前文獻中常用的方法是生物力學實驗與數值模擬，其中有限元素法已廣泛被用於評估植入物對腰椎組織的運動學與力學影響。本研究建立一完整的腰椎有限元素分析平台，包括健康與退化病變的幾何模型。對於文獻中常見的不同控制法，使用健康狀態以及植入單節靜態固定器的退化腰椎模型，比較其分析的結果差異，根據比較的結果而選用效率最佳的控制法，用於研究調整動態混合固定器之剛性，對應於不同椎間盤退化等級的結果，希望了解不同的退化等級應配合的剛性大小，並對此建立一平衡區間之觀念，給予未來植入物設計與臨床手術使用參考。對於計算效率而言，本研究提出的DCM在分析時所花的時間比RCM快十七倍，且與其他控制法的結果沒有明顯差異，所以選擇DCM作為非線性腰椎生物力學分析的控制方法。本研究的結果也顯示，使用動靜態混用固定器確實能保護過渡節椎間盤適度，但由於受到固定器的限制，鄰近節問題仍然存在。本研究提出的妥協區間概念，在保護過渡節椎間盤與鄰近節的補償之間應該取得平衡，且應依照不同的固定器設計與椎間盤的退化等級，在手術植入動靜態混用固定器時選用相對應的動態固定器剛性。 There have been many types of implants used to treat various diseases related to lumbosacral instability and deformity. Prior to their clinical use, the in vivo behaviors of the implants can be evaluated by means of biomechanical experiment and numerical simulation. In the field of lumbosacral biomechanics, the finite-element method has been used to evaluate implant-induced effects on the kinematic and mechanical responses at the fixed and adjacent segments. This study first developed intact and degenerative models of the five-segment lumbosacral column. After validation, the intact model served as the comparison baseline and the degenerative model was instrumented with a transpedicular fixation to calculate the load-controlled method (LCM) and ROM-controlled method (RCM) results. Subsequently, a displacement-controlled method (DCM) was proposed by using the nodal displacements of the intact model to guide the vertebral motion of the instrumented model. By using the most efficient controlled method, the current study aimed to investigate the biomechanical effects of fixator stiffness and disc degeneration on the transition and adjacent segments. The degeneration grade of the discs and cord stiffness of the dynamic fixator were varied to investigate the trade-off of the junctional problem at the adjacent segments and motion preservation at the transition segments. The findings of the current study are to provide insight into the device- and surgery-related factors associated with better outcomes of the hybrid fixation. For computational efficiency, the calculation time of the DCM model was seventeen times faster than that of the RCM models. The comparable results and efficient calculation make the DCM the improved strategy for executing the lumbosacral nonlinear analysis. This study also showed that the hybrid fixator can serve as both a motion-preserver and a load-shield for the transition segment. However, the kinematic and mechanical constraints due to the hybrid fixation were inevitably compensated to the adjacent segments. Consequently, the hybrid fixator protected the transition segment but potentially deteriorated the adjacent segments. This study presented the trade-off concept that the protection of the transition segment and the deterioration of the adjacent segments should be balanced. The trade-off stiffness of the flexible cord provides improved rigidity and flexibility of the hybrid fixation and depends on both fixator design and disc degeneration.
