Tong Zhizhong, Xiao Bin, Yan Kai, Xing Yonggang, Zhang Yanbin
Department of Radiology, Beijing Jishuitan Hospital, Beijing, China.
Department of Spine Surgery, Beijing Jishuitan Hospital, Beijing, China.
Front Surg. 2021 Sep 8;8:706597. doi: 10.3389/fsurg.2021.706597. eCollection 2021.
Ankylosing spondylitis (AS) is a chronic disorder characterized by an imbalance between bone formation and resorption. Spinal fractures often occur after minor trauma in patients with AS. For thoracolumbar fractures, transpedicular screw (TPS) fixation through the posterior approach has been suggested. The cortical bone trajectory (CBT) technique has also been used to prevent screw pull-out in patients with poor bone quality. The aim of current study was to assess the biomechanical characteristics of the TPS and CBT technique in thoracolumbar AS fracture fixation by finite element analysis. The three-dimensional finite element models of the AS spine were created. The CBT and TPS methods of screw insertion were used in AS spinal fracture models. An intact AS spine model was considered the control. An axial force and torsion in rotation, flexion/extension and lateral flexion were applied in all models in CBT, TPS, and control groups. The AS spine showed similar construct stiffness after posterior fixation by CBT and TPS techniques under axial, rotational, and flexion/extension loading conditions. The TPS technique showed better intact stability under all loading conditions. Similarly, the TPS technique provided superior fracture regional stability against axial and rotational loads than did the CBT technique. The maximum von Mises stresses were 1714.4 ± 129.8 MPa and 1208.7 ± 107.3 MPa ( < 0.001), which occurred in the CBT and TPS groups under compressive loading. The TPS technique provides better biomechanical strength under axial, rotational, flexion/extension, and lateral flexion loading than does the CBT technique. Compared with CBT, TPS is more effective in maintaining the stability of AS thoracolumbar fractures from a finite element analysis perspective.
强直性脊柱炎（AS）是一种以骨形成与骨吸收失衡为特征的慢性疾病。AS患者常因轻微外伤而发生脊柱骨折。对于胸腰椎骨折，有人建议采用后路经椎弓根螺钉（TPS）固定。皮质骨轨迹（CBT）技术也被用于骨质较差患者以防止螺钉拔出。本研究的目的是通过有限元分析评估TPS和CBT技术在胸腰椎AS骨折固定中的生物力学特性。建立了AS脊柱的三维有限元模型。在AS脊柱骨折模型中采用CBT和TPS螺钉置入方法。将完整的AS脊柱模型作为对照。在CBT组、TPS组和对照组的所有模型中施加轴向力以及旋转、屈伸和侧屈时的扭矩。在轴向、旋转和屈伸加载条件下，CBT和TPS技术后路固定后，AS脊柱显示出相似的结构刚度。在所有加载条件下，TPS技术显示出更好的完整稳定性。同样，与CBT技术相比，TPS技术在抵抗轴向和旋转载荷方面为骨折区域提供了更好的稳定性。在压缩载荷下，CBT组和TPS组的最大冯·米塞斯应力分别为1714.4±129.8 MPa和1208.7±107.3 MPa（<0.001）。在轴向、旋转、屈伸和侧屈加载条件下，TPS技术比CBT技术提供更好的生物力学强度。从有限元分析的角度来看，与CBT相比，TPS在维持AS胸腰椎骨折稳定性方面更有效。
