This study aims to analyze the biomechanical stability of Magic screw in the treatment of acetabular posterior column fractures by finite element analysis. A three-dimensional finite element model of the pelvis was established based on the computed tomography (CT) and magnetic resonance imaging (MRI) data of a volunteer and its effectiveness was verified. Then, the posterior column fracture model of the acetabulum was generated. The biomechanical stability of the four internal fixation models was compared. The 500 N force was applied to the upper surface of the sacrum to simulate human gravity. The maximum implant stresses of retrograde screw fixation, single-plate fixation, double-plate fixation and Magic screw fixation model in standing and sitting position were as follows: 114.10, 113.40 MPa; 58.93, 55.72 MPa; 58.76, 47.47 MPa; and 24.36, 27.50 MPa, respectively. The maximum stresses at the fracture end were as follows: 72.71, 70.51 MPa; 48.18, 22.80 MPa; 52.38, 27.14 MPa; and 34.05, 30.78 MPa, respectively. The fracture end displacement of the retrograde tension screw fixation model was the largest in both states, and the Magic screw had the smallest displacement variation in the standing state, but it was significantly higher than the two plate fixations in the sitting state. Magic screw can satisfy the biomechanical stability of posterior column fracture. Compared with traditional fixations, Magic screw has the advantages of more uniform stress distribution and less stress, and should be recommended.
通过有限元法分析Magic螺钉治疗髋臼后柱骨折的生物力学稳定性。基于志愿者计算机断层扫描（CT）和磁共振成像（MRI）数据建立骨盆三维有限元模型并验证其有效性，然后生成髋臼后柱骨折模型，模拟采用经坐骨结节逆行拉力螺钉、后柱单钢板、后柱双钢板和Magic螺钉进行固定，比较四种固定模型的生物力学稳定性差异。在骶骨上部施加500 N压力模拟人体重力，站位以及坐位状态下逆行拉力螺钉、后柱单钢板、双钢板以及Magic螺钉固定模型的植入物最大应力分别为：114.10、113.40 MPa；58.93、55.72 MPa；58.76、47.47 MPa；24.36、27.50 MPa；骨折端最大应力分别为：72.71、70.51 MPa；48.18、22.80 MPa；52.38、27.14 MPa；34.05、30.78 MPa。两种状态下逆行拉力螺钉固定模型骨折端位移均为最大，Magic螺钉在站立状态下位移变化量最小，但是坐位状态明显高于两种钢板固定。Magic螺钉可以满足髋臼后柱骨折的稳定性需要，与传统拉力螺钉、钢板固定方式相比具有应力分布更均匀、受力更小等优点，是一种值得推荐的内固定方法。.
Keywords: Acetabular fracture; Biomechanics; Finite element analysis; Internal fixation of fracture.