Limthongkul Worawat, Wannaratsiri Nutthee, Sukjamsri Chamaiporn, Benyajati Chi-Na, Limthongkul Pimpa, Tanasansomboon Teerachat, Yingsakmongkol Wicharn, Singhatanadgige Weerasak
Department of Orthopedics, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, Bangkok, Thailand.
Center of Excellence in Biomechanics and Innovative Spine Surgery, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Int J Spine Surg. 2023 Jun;17(3):442-448. doi: 10.14444/8441. Epub 2023 Jan 23.
Posterior long-segment (LS) fixation, short-segment (SS) fixation, and short segment fixation with intermediate screws (SI) have shown good outcomes for the treatment of thoracolumbar burst fractures. However, limited data compared the biomechanical properties between LS fixation and SI. The purpose of this study was to compare the von Mises stresses on the pedicular screw system and bone between posterior LS fixation, SS fixation, and SI for the treatment of thoracolumbar burst fracture.
The finite element model of thoracolumbar spines from T11 to L3 was created based on the computed tomography image of a patient with a burst fracture of the L1 vertebral body. The models of pedicular screws, rods, and locking nuts were constructed based on information from the manufacturer. Three models with different fixation configurations-that is, LS, SS, and SI-were established. The axial load was applied to the superior surface of the model. The inferior surface was fixed. The stress on each screw, rod, and vertebral body was analyzed.
The motion of the spine in SS (0.5 mm) and SI (0.9 mm) was higher than in LS (0.2 mm). In all models, the lowest pedicle screws are the most stressed. The stress along the connecting rods was comparable between SI and LS (50 MPa). At the fracture level, stress was found at the pedicles and vertebral bodies in SI. There was relatively little stress around the fractured vertebral body in LS and SS.
Posterior SI preserves more spinal motion than the LS. In addition, it provides favorable biomechanical properties than the SS. The stress that occurred around the pedicle screws in SI was the least among the 3 constructs, which might reduce complications such as implant failure. SI produces more stress in the fractured vertebral body than LS and SS, which could potentially aid in bone healing according to the Wolff law.
SI has proved to be a biomechanically favorable construct and helps preserve the spinal motion segment. It could be an alternative surgical option for treating patients who present with thoracolumbar burst fractures.
后路长节段（LS）固定、短节段（SS）固定以及使用中间螺钉的短节段固定（SI）在胸腰椎爆裂骨折的治疗中均显示出良好效果。然而，比较LS固定和SI之间生物力学特性的数据有限。本研究的目的是比较后路LS固定、SS固定和SI治疗胸腰椎爆裂骨折时椎弓根螺钉系统和骨上的von Mises应力。
基于一名L1椎体爆裂骨折患者的计算机断层扫描图像创建了从T11至L3的胸腰椎有限元模型。根据制造商提供的信息构建椎弓根螺钉、棒和锁定螺母的模型。建立了三种不同固定构型的模型，即LS、SS和SI。将轴向载荷施加于模型的上表面，下表面固定。分析每个螺钉、棒和椎体上的应力。
SS（0.5mm）和SI（0.9mm）中脊柱的运动高于LS（0.2mm）。在所有模型中，最下方的椎弓根螺钉应力最大。SI和LS沿连接杆的应力相当（50MPa）。在骨折节段，SI的椎弓根和椎体出现应力。LS和SS中骨折椎体周围的应力相对较小。
后路SI比LS保留更多的脊柱运动。此外，它比SS具有更好的生物力学特性。SI中椎弓根螺钉周围产生的应力在三种结构中最小，这可能减少诸如植入物失败等并发症。SI在骨折椎体中产生的应力比LS和SS更多，根据沃尔夫定律，这可能有助于骨愈合。
SI已被证明是一种生物力学上有利的结构，有助于保留脊柱运动节段。它可能是治疗胸腰椎爆裂骨折患者的一种替代手术选择。
