造成脊椎傷害的原因可能為年齡增長的老化現象、長期姿勢不良或是受到外部力量所導致，以上原因將使得椎間盤受損而造成椎間不穩定，甚至壓迫周圍神經使病患產生疼痛感，因此後方椎間融合術為較常見的治療方式。但臨床上的術後追蹤觀察期發現，由於手術節段之活動度喪失所導致的補償現象，進而造成鄰近節段退化現象的產生。近年來由於3D列印技術的蓬勃發展，因此本研究針對植入物椎籠的部分，將考慮到形狀優化、複合材料與孔隙率結構的設計，並搭配不同後方固定系統來進行比較分析，然而目前少有文獻針對上述椎籠設計有完整之探討，因此本研究希望先藉由電腦輔助工程－有限元素分析的方法，找到既能維持原先脊椎的穩定度，又能提供病患術後良好活動度的植入物選擇。
本研究將使用T10-S1多節段之脊椎模型，並植入椎籠與後方固定器來進行有限元素分析的評估，假設手術節段處位於脊椎L3-L4處，針對椎籠本身不同材料比例的選擇、不同的孔隙率設計以及搭配不同的後方固定系統，在前彎、後彎、側彎、扭轉四種不同運動方向情況下，對各節椎間旋轉角度、椎間盤應力分佈、椎弓根骨螺絲應力分佈等生物力學特性進行結果比較。
分析結果發現，植入物為全鈦合金材料與無孔隙率設計的椎籠，並搭配傳統剛性後方固定系統時，整體剛性最高，雖然能夠達到良好的術後脊椎穩定效果，但在鄰近節段處之補償現象也更加明顯，而加速鄰近節段退化與椎弓根骨螺絲斷裂的風險；相反的如果植入物為複合材料比例(25%Ti-75%PEEK)與高孔隙率設計的椎籠，並搭配Dynesys動態後方固定系統時，其椎間旋轉角度與鄰近節椎間盤應力皆為最接近完整脊椎情況，最終本研究將能夠使醫生了解積層製造椎籠的生醫力學特性。

Posterior lumbar interbody fusion (PLIF) has been the most commonly used surgical method for treating damaged disc which caused by human aging、long-term bad posture or external force. But many clinical studies have showed that adjacent segment degeneration was found during the tracking observation period. In recent years, due to the flourishing development of 3D printing technology, this study will focus on the design of cage which included the shape optimum design、material selection and porous design. Each cage design will also do some simulation comparison with different posterior fixation systems. However, no research investigated on the cage design for spine motion and adjacent segment. The purpose of this study was to find the best implant design which can maintain stabilizing effect and provide good postoperative activity for patients using finite element analysis (FEM).
A 3-D nonlinear finite element model of the T10-S1 spine with cage and posterior fixation system were developed in this study. To simulate the bone fusion surgery, the cage was inserted into the L3-L4. The loading cases of flexion、extension、lateral bending and axial rotation were considered. In post-processing, intersegmental rotation、disc stress and pedicle screw stress were calculated at implant level and adjacent level.
The results showed that all Ti alloy and no porous cage with rigid fixation system can achieve good stability. However, it will also increase the risk of adjacent segment degeneration and pedicle screw breakage. Relatively, the intersegmental rotation and disc stress of the composite materials (25%Ti-75%PEEK) and high porosity cage with Dynesys dynamic fixation system are very close to intact spine situation. Finally, this study could help surgeons to understand the biomechanical performances of additive manufactured cages.

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