BACKGROUND:The surgical management to reconstruct the stability in lumbosacral region is very chal enging. There are many techniques to reconstruct the stability of the lumbosacral region, but the internal fixation loosening, fracture and pseudoarthosis are not uncommon. OBJECTIVE:Finite element analysis was used to analyze the stability of two types of reconstruction procedures and the stress of the internal fixation system. METHODS:A 64-slice spiral CT scan was used in a subject from L1 to pelvis. The scan data were imported into the Mimics 15.0 software to generate a three-dimensional surface model. The three-dimensional solid model was established using in the SolidWorks software. The solid geometry model of the L3, 4 pedicle screws combined with single iliac screw fixation and L3,4 pedicle screws combined with dual iliac screws and anterior titanium mesh cage support fixation were constructed by the Solidworks software. Two kinds of reconstruction procedures were simulated. The models were given material properties and analyzed by using the ABAQUS software. RESULTS AND CONCLUSION:(1) The maximum stress was 195.3 MPa in the complete model, 189.5 MPa in single iliac screw model, and 149.2 MPa in dual iliac screw+titanium cage model when constrained the roof of double acetabulum and applied a vertical load of 1 000 N. (2) The axial compression rigidity was 551.572 N/mm in the complete model, 613.87 N/mm in the single iliac screw model and 1 683.50 N/mm in the dual iliac screw+titanium cage model. (3) The bending rigidity of the dual iliac screw+titanium cage model was bigger than other models at 6 directions when applied 7 N•m bending loads. The maximum stress of single iliac screw model was bigger than other models. (4) The results suggest that the dual iliac screw+titanium mesh cage reconstruction can effectively restore the stability of the lumbosacral area. The stress of internal fixation system is smal er and more dispersed. There is obvious stress concentration in the connecting rod and the tail of the single iliac screw. The single iliac screw internal fixation system is easy to fatigue fracture and loosening.%背景：严重腰骶部缺损及不稳如何进行稳定性重建是很有挑战性的问题。目前有多种技术来重建腰骶部稳定性，但内固定松动、断裂、假关节形成等不少见。目的：有限元法分析2种腰骶部重建方式的稳定性以及内固定系统的应力分布。方法：采用64排螺旋CT自L1-骨盆水平薄层扫描的数据导入到Mimics 15.0医学图像处理软件中，构建三维表面模型，再导入SolidWorks 逆向工程软件建立实体模型。用Solidworks软件构建L3，4椎弓根螺钉联合髂骨单钉固定(单钉)和L3，4椎弓根螺钉联合髂骨双钉并前路支撑(双钉+钛笼)并装配。模拟腰骶部缺损的情况，以上述2种手术方式进行腰骶部稳定性重建。对模型进行赋值，用ABAQUS软件分析。结果与结论：①在约束臼顶，在L2上缘施加1000 N的轴向载荷模拟站立负重情况下，完整模型最大应力值为195.3 MPa，单钉模型为189.5 MPa，双钉+钛笼模型为149.2 MPa；②计算轴向压缩刚度完整模型为551.572 N/mm，单钉模型为613.87 N/mm，双钉+钛笼模型为1683.50 N/mm；③在施加6个方向的7N•m弯曲载荷下，在6个方向的弯曲刚度上，双钉+钛笼支撑模型最大。模型在6个方向的最大应力值比较，单钉模型最大；④结果提示，髂骨双钉+钛笼支撑重建可有效恢复腰骶部的稳定性，内固定系统承受的应力较小也较分散。髂骨单钉重建连接棒处及螺钉尾部有明显的应力集中，内固定容易疲劳断裂及松动。
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