Finite Element Analysis of Cage Subsidence in Cervical Interbody Fusion

頸椎融合器於融合手術後之沈陷分析－有限元素分析

蔣明富(Ming-Fu Chiang) ； 鄧瑞民(Jui-Min Teng) ； 黃昌弘(Chang-Hung Huang) ； 鄭誠功(Cheng-Kung Cheng) ； 陳振昇(Chen-Sheng Chen) ； 張定國(Ting-Kuo Chang) ； 趙士輝(Shi-Hui Chao)

《Journal of Medical and Biological Engineering》 24卷4期 (2004/12) Pp. 201-208

摘要

進行頸椎間融合手術時以融合器輔助可獲得良好的椎骨融合，然而使用融合器也可能造成融合器與鄰近椎體間的沈陷，此研究利用有限元素分析法分析融合器與鄰近椎骨間的生物力學表現。三維頸椎模型(C3-C5)的建立為根據本實驗室先前所建立的方式建構，先確定合理的植入位置後再置入椎體模型進行後續之生物力學分析。研究參數包括模擬不同的頸椎彎曲、融台器的幾何外型、材料性質以及改變鄰近椎骨骨密度等不同因素來瞭解各項參數對於生物力學表現的差異。研究結果顯示，頸椎伸直對於沈陷的影響最大，高於平均值31.8%，之後為彎曲(13.8%)和側向彎曲(10.8%)。圓柱狀融合器相較於環型狀融合器，具有較大的沈陷傾向約高6.6%，應力值約高10.1%。減少骨密度質增加21.2%的沈陷危險。此研究建議病患進行頸椎間融合對手術應避免大角度的伸直運動。融合器的幾何外型宜圓滑，且使用的材料性質近於椎骨骨質將可減少沈陷危險，此外具有骨質疏鬆的病患應顧慮融合手術後的沈陷危險。

關鍵字

融合器 ； 頸椎融合術 ； 有限元素分析 ； 運動範圍 ； 沈陷

並列摘要

Cages were used frequently in cervical spine interbody fusion to get better fusion rate. However, the fusion cage would subside in adjacent vertebral body. Three dimensional cervical spine model of C4-C6 was constructed referring to our previous model procedure (FEM). The suitable location of fusion cage had discussed with experienced surgeons and then cervical interbody fusions were simulated by finite element analysis. Factors caused subsidence, including (1) different moment loadings; (2) cage geometry; (3) cage material and (4) bone mineral density were also simulated. The results showed that extension of cervical spine caused remarkable subsidence than average value about 31.8%, next were flexion (13.8%), lateral bending (10.8%), and torsion. Cylindrical shape cage (BAK) appeared a higher risk of subsidence (6.6%) and von-Mises stresses (10.1%) than ring-liked shape cage (SOLIS). Comparing the cage material, the BAK cage made the settlement higher to 11% and the stress increased to 33.8%. The subsidence increased to 21.2% related to intact model in both cages while osteopenia of bony density were simulated. h conclusion, in the ROMs, extension motion caused remarkable subsidence after cages fusion. The geometry of the cage should keep from the cylinder or sharp angle, and the composed material of the cage is suggested to be closed to bone density for avoiding stress shielding. Patients with osteopenia will increase subsidence in cage interbody fusion

並列關鍵字

Cage ； Cervical interbody fusion ； Finite element analysis ； Range of motion ROM ； Subsidence