目的    建立T11～12前路病灶清除植骨+单钉单棒固定系统三维有限元模型，分析单钉单棒所受应力对其进行改进。  方法    对一名成年男性进行螺旋CT扫描，将所得数据导入计算机，通过Mimics13.0软件和Ansys11.0有限元软件建立T11～12前路病灶清除植骨+单钉单棒固定系统三维有限元模型，并在在椎体上表面施加500N压力和10Nm的力矩模拟腰椎前屈、后伸、侧屈和旋转四种生理载荷，观察不同载荷下固定器械的应力分布，并对其进行比较。  结果   下位椎体钉尾部与连接棒下段为应力较集中部位，两部位在侧弯时最小，旋转时最大，旋转运动容易导致这两部位疲劳性断裂。  结论    侧前方单钉棒固定系统应增粗螺钉尾部与连接棒的下端或术后严格限制腰椎的各方向活动尤其是旋转，以减小两部位的应力，降低螺钉疲劳断裂的可能性。

Objective    To develop a 3-D finite element (FE) model of anterior screw fixation on lower thoracic vertebra, evaluate and modify the stress of screw and the stick.  Methods    The geometrical model was created by Mimics13.0 based on CT data of T11～12 motion segment from one adult male, and then, the above models were imported into the Ansys11.0 for establishing the 3-D FE of anterior screw fixation on lower thoracic vertebra. The 3D FE models were further imported into Ansys11.0 and analyzed under 500N pressure loading on the upper surface of T11, and 10Nm torque loading for simulating thoracic axial compression, anteflexion, extension, lateral bending and rotation. The Von mises stress of screws and stick were recorded and analyzed statistically the difference of different stress distribution of the screws and stick. Results    It was obviously that, the Von mises of the screw concentrated on the tail of screws, with the bigger stress at the inferior part than that at the superior part. Rotation movement resulted in breakage of the tails of screw and lower part of stick.  Conclusions    Anterior screw fixation system on lower thoracic vertebra will thicken the tails of screws and lower segment of stick. It is necessary to limit patients' activities by a waist-brace protection after operation.