下腰椎L4/5棘突间撑开器的生物力学研究

Biomechanical Effect of an Interspinous Process Spacer for L4/5 of Lower Lumbar:a Finite Element Analysis

应用有限元分析方法研究在L4/5植入X-STOP类型产品时该节段的稳定性,以及对相邻节段的生物力学影响.依据一名正常志愿者中立位下螺旋CT扫描资料,利用Mimics14、Geomagic Studio2012、Hypermesh12和Abaqus6.12-1等软件,构建L2～L5健康腰椎有限元模型和植入撑开器X-STOP的动态固定模型,并模拟前屈、后伸、侧弯和轴向旋转,验证健康腰椎有限元模型的有效性和动态固定对照模型的生物力学特性.根据两组模型在椎间活动度、椎间盘应力等生物力学指标,证明X-STOP可减少该节段74.83％的后伸活动度,而相邻节段活动度基本不受影响.植入物和腰椎的最大应力出现在后伸时两者的接触面上,最大应力分别为33.3和13.56 MPa.X-STOP可以显著降低椎间盘压力和后伸活动度,对相邻阶段无明显影响.植入物和腰椎的最大von Mises应力出现在接触面上.对X-STOP的改进提供理论支持,为下腰椎I4/5棘突间撑开器X-STOP临床手术提供生物力学依据.

To analyze the effect of the stability of an implanted homologous X-STOP device in the injury segment IA/5 and the biomechanical behavior of adjacent segments. A CT-scanner was used to acquire normal lumbar images. With the help of Mimicsl4, Geomagic Studio2012, Hypermesh12 and Abaqus6. 12 - 1, the finite element （FE） model （ the lower lumbar L2 - L5 segments） with or without interspinous spacer X-STOP was constructed. Upon validation, a finite element model of L2 - L5 was developed to simulate and analyze the biomechanies of the intact and X-STOP dynamic fixation states by simulating flexion, extension, lateral bending and axial rotation. The comparison of degree of freedom （DOF） and intradiscal pressure of two set models predicted that the levels adjacent to the implanted level were not significantly affected by the implanted X- STOP. There was a distinct reatriction in the range of extension and intradiscal pressure at the implanted segment, and DOF decrease to 74. 83 %. Furthermore, the largest yon Mises stress showed on the interface between the spinous process and the implant at the position of extension. Respectively, the largest stress value is 33.3 MPa and 13.56 MPa. In conclusion, the X-STOP can effectively restrict the DOF of extension and unloading disc pressure, without affect adjacent segment. Moreover, this study also provides theoretical and biomechanical analysis to support the clinical performance of the X-STOP and its further improvement of the device design.