四种内固定方式治疗耻骨联合分离生物力学特性的有限元分析

Biomechanical characteristics of four fixation methods in treatment of pubic symphysis disruption： afinite element analysis

目的通过有限元分析单重建钢板、双重建钢板、单空心拉力螺钉、双空心拉力螺钉治疗耻骨联合分离的生物力学特性。方法对5名健康志愿者行完整骨盆薄层螺旋cT扫描，获取Dicom格式的原始二维cT数据，输入Mimics15．0软件对双侧髋骨及骶骨分别进行三维重建，通过Abqus6．13软件进行网格划分及赋值获得骨性骨盆有限元模型。通过切断单侧骶髂前韧带、骶棘韧带、骶结节韧带、耻骨上韧带、耻骨弓状韧带模拟耻骨联合分离模型。按照标准手术方式将单重建钢板、双重建钢板、单空心拉力螺钉、双空心拉力螺钉4种内固定安装至模型，加载垂直和旋转负荷进行有限元分析，记录并分析整体结构刚度、耻骨联合局部位移量、内固定物应力。结果垂直载荷下，耻骨联合分离间距〉25mm，骨盆的垂直和旋转整体结构刚度由正常组的（442．738±29．946）N／mm和（10．118±1．432）N·m／Deg大幅下降至（14．754±0．876）N／mm和（0．328±0．119）N·m／Deg。双重建钢板和双空心拉力螺钉表现出最佳抗垂直载荷能力，结构刚度达到（117．647±9．193）、（131．443±4．348）N／mm。在抗旋转载荷方面，双空心拉力螺钉表现最佳，可以重建完整结构刚度的68．6％。对于耻骨联合局部稳定性而言，双重建钢板具有较强的局部抗旋转能力，而双空心拉力螺钉具有很好的局部抗牵拉能力，其中双空心拉力螺钉组垂直载荷下位移仅为（-0．240±0．119）mm，双重建钢板组旋转载荷下角位移仅为0．218°±0．182°。单重建钢板承受较大应力且应力集中现象明显。结论双空心拉力螺钉在耻骨联合分离治疗中具有生物力学优势。

Objective To evaluate the biomechanical characteristics of 4 fixation methods （single reconstruction plate, dual reconstruction plates, single cannulated screw and dual eannulated screws） in the treatment of pubic symphysis disruption. Methods Miniature spiral CT scans were performed on the complete pelvis in 5 healthy volunteers. The primary two-dimensional CT scan data at Dicom format were im- ported into software Mimics 15.0 for three-dimensional reconstruction of bilateral hips and sacrums. The finite element model of skeletal pelvis was obtained by grid partitioning and assignment using software Abqus 6. 13. Models of pubic symphysis disruption were simulated by cutting off the unilateral sacroiliac ligament, sacral spine ligament, sacral tuberosity ligament, pubic ligament and pubic arch. Four implants（single reconstruction plate, dual reconstruction plates, single cannulated screw and dual cannulated screws） were simulated and emplaced onto the models according to standard surgical procedures. Compressive and rotational loads were implemented in all models for finite element analysis. The biomechanical properties were recorded and analyzed, including construct stiffness, micromotion of the pubic symphysis and von Misses stress. Results Under vertical load, the space of pubic symphysis disruption 〉 25 mm. The vertical stiffness and rotational construct stiffnessof the pelvis decreased significantly from 442. 738 ±29. 946 N/ram and 10. 118 ± 1. 432 N · m/Deg in the normal group to 14. 754 ±0. 876 N/mm and 0. 328 ±0, 119 N ＂ m/Deg, respectively. Dual reconstruction plates and dual eannulated screws displayed the best vertical tensile strength; their construct stiffness achieved 117. 647 ± 9. 193 N/mm and 131. 443 ± 4. 348 N/mm, respectively. Under anti-rotation load, dual cannu- lated screws displayed the best performance because they rebuilt 68.6% of the whole structural stiffness. For the local stability of the pubic symphysis, dual reconstruction plates showed a strong local anti-rotatlon capa- bility and dual cannulated screws a good local anti-tensile capability. The displacement in the dual cannulated screws group was only -0. 240±0. 119 mm under vertical load while the angular displacement in the dual reconstruction plates group only 0. 218°±0. 182°. Single reconstruction plate endured the maximum yon Misses stress which was obviously concentrated. Conclusion Dual cannulated screws may have biome- ehanical advantages for treatment of pubic symphysis disruption.