腰椎替代物設計與應力分析

當脊椎得到骨腫瘤、外傷等其他疾病損壞到椎體時，需切除而進行骨融合手術，一節椎體經手術切除後需植入腰椎替代物以維持脊椎的穩定及幫助脊椎的復原，本研究使用有限元素法將設計出腰椎替代物放入腰椎中進行模擬，了解腰椎替代物在不同負載條件、不同材料、不同結合方式之生物力學情形。並藉由壓力實驗，測試腰椎替代物是否產生破壞。模擬結果顯示，腰椎替代物結合後方固定器後，能有效的降低腰椎替代物上的應力值及椎體上應力集中的地方，在扭轉時後方固定器發揮的功能較小。選擇材料上，使用鈦合金材質之腰椎替代物，其安全係數及使用壽命都較PEEK材質來的好，且固定器上的螺絲所受應力也比PEEK材質來的小。假如腰椎替代物要選用PEEK材質時需加強結構的強度。在選擇結合方式上，前方固定器只有在側彎時能有效的降低腰椎替代物整體應力值，在其他負載下減少值就很不明顯，且固定器上的螺絲承受了很大的應力，螺絲會有破壞的危險，所以使用後方固定器對於不同的負載都能降低整體應力值、增加脊椎、替代物的壽命及穩定性、減少應力遮蔽的現象產生。實驗結果顯示設計出腰椎替代物能輕易的通過壓力測試而無破害的產生。在上端版及下椎龍的凸齒能輕易刺入塑膠塊中而無破壞。

關鍵字

腰椎替代物；後方固定器,應力

並列摘要

When a tumor growing in a vertebra, or other spine diseases, or an accidental trauma, the spine needs to proceed corpectomy vertebral body. A vertebral body replacement (VBR) is needed to implant in the spine to keep it stable and restore function. The purpose of this study is that used the finite element method to simulate a VBR that was implant in lumbar spine, to understand biomechanics conditions of the VBR made of various materials in different loading conditions. The simulation results show that when a VBR with the help of using posterior fixation could reduce stress in the VBR, and also decreased stress concentration in the vertebral body. However posterior fixation had small influence under rotation. The vertebral body replacements made of Ti-alloy were better than those made of PEEK when taking account of safety factor and using life. Stress values in pedicle screws were also smaller when using Ti-alloy VBR than that of using PEEK VBR. The results also show that anterior fixation could only reduce stress in VBR subjected to lateral bending. However, the screws of fixation can reduce stresses in VBR, increase its life and, decrease stress shielding. The experimental results show that the present designs of VBR can easily pass through compression tests without fracture. Raised teeth in upper endplate and lower cage can easily prick into polymer blocks without fracture.

並列關鍵字

vertebral body replacement ； posterior fixation ； stress

參考文獻

【1】Claes L., Schultheiss M., Steffen W., Wilke H. J., Arand M. and Kinzl L., “A new radiolucent system for vertebral body replacement : its stability in comparison to other systems”, John Wikcy & Sons, Inc., Vol. 48, pp. 82-89, 1999.

【2】Mizrahi J., Silva M. J., Keaveny T. M., Edwards W. T., Hayes W. C., “Finite-element stress analysis of the normal and osteoporotic lumbar vertebral body”, Spine, Vol. 18, No. 14, pp. 2088-2096, 1993.

【3】Roy-Camille R., Saillant G. and Mazel C.,“Internal fixation of the lumbar spine with pedicle screw planting”, Clin Orthop , Vol. 203, pp. 7-17, 1986.

【4】Eisenstein S.,“Lumbar vertebral canal morphometry for computerized tomography in spinal stenosis”, Spine, Vol. 8, pp. 187-191, 1983.

【5】Berry J. L., Moran J. M., Berg W. S. and Steffee A. D., “A morphometric study of human lumbar and selected thoracic vertebrae”, Spine, Vol. 12, No. 4, pp. 362-367, 1987.

國際替代計量

腰椎替代物設計與應力分析

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