Department of Neurosurgery, Yonsei University College of Medicine, Seoul, Korea.
Spine (Phila Pa 1976). 2018 Aug 1;43(15):E891-E897. doi: 10.1097/BRS.0000000000002584.
Finite element analysis.
To compare the biomechanical stability imparted to the C1 and C2 vertebrae by the transarticular (TA), C1 lateral mass (LM)-C2 pedicle (PS), C1LM-C2 pars, and C1LM-C2 translaminar (TL) screw fixation techniques.
Cadaveric biomechanical studies of several atlantoaxial posterior fixation techniques have been performed, showing significant heterogeneity in biomechanical properties among the studies.
From computed tomography images, a nonlinear intact three-dimensional C1-2 finite element model was developed and validated. Four finite element models were reconstructed from different C1-2 fixation techniques. The range of motion (ROM) and maximum von Misses stresses for the four screw techniques were compared under flexion, extension, lateral bending, and axial rotation.
C1LM-C2PS showed the greatest decrease in ROM with flexion/extension and lateral bending. C1-2TA and C1LM-C2 pars showed less ROM reduction than the other techniques, in flexion/extension. C1LM-C2TL showed the least decrease in ROM during axial rotation. For C1-2TA, the maximum stress was in the C1-2 joint region. In the C1LM-C2PS, the C1 rod head, C2 pars screw, and C2TL screw were stressed at the C2 rod head. The maximal von Mises stress on the C1-2TA at the C1-2 joint site was the highest at flexion/extension, whereas the C1LM-C2PS had the lowest stress on the screw at flexion/extension and lateral bending. The C1LM-C2TL showed the highest stress in axial rotation and lateral bending.
In this study, C1LM-C2PS fixation was the most stable technique. If surgeons have to use other fixation methods besides the C2 pedicle screw, they need to be aware that additional fixation or postoperative immobilization may be required to achieve ROM restriction. Careful observation at the maximum stress site on the screw including screw loosening, screw-bone interface disruption or screw fracture will be necessary during follow-up imaging examinations (x-ray and computed tomography scan) after atlantoaxial fixation.
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有限元分析。
比较经关节突（TA）、C1 侧块（LM）-C2 椎弓根（PS）、C1LM-C2 椎板和 C1LM-C2 经椎板螺钉固定技术对 C1 和 C2 椎体的生物力学稳定性。
已经对几种寰枢后路固定技术进行了尸体生物力学研究，研究结果表明，生物力学特性在研究之间存在显著的异质性。
从 CT 图像中，建立并验证了非线性完整的三维 C1-2 有限元模型。从不同的 C1-2 固定技术中重建了四个有限元模型。在屈伸、侧屈和轴向旋转下，比较了四种螺钉技术的活动范围（ROM）和最大 von Misses 应力。
C1LM-C2PS 在屈伸和侧屈时 ROM 减小最大。C1-2TA 和 C1LM-C2 椎板的 ROM 减少比其他技术少，在屈伸时。C1LM-C2TL 在轴向旋转时 ROM 减小最小。对于 C1-2TA，最大应力在 C1-2 关节区域。在 C1LM-C2PS 中，C1 杆头、C2 椎板螺钉和 C2TL 螺钉在 C2 杆头处受力。C1-2TA 在 C1-2 关节部位的最大 von Mises 应力在屈伸时最高，而 C1LM-C2PS 在屈伸和侧屈时螺钉的应力最低。C1LM-C2TL 在轴向旋转和侧屈时应力最高。
在这项研究中，C1LM-C2PS 固定是最稳定的技术。如果外科医生必须使用除 C2 椎弓根螺钉以外的其他固定方法，他们需要注意，可能需要额外的固定或术后固定以限制 ROM。在寰枢固定后的随访影像学检查（X 线和 CT 扫描）中，需要仔细观察螺钉上的最大应力部位，包括螺钉松动、螺钉-骨界面破裂或螺钉断裂。
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