From the Department of Orthopaedic Surgery, Shengjing Hospital of China Medical University, Shenyang City, Liaoning Province, P.R. China.
Spine (Phila Pa 1976). 2013 Oct 15;38(22):E1397-404. doi: 10.1097/BRS.0b013e3182a40869.
Anatomical measurements and in vitro biomechanical testing were performed to evaluate a new method for posterior C1 fixation.
This study sought to assess C1 posterior arch crossing screw fixation for posterior C1-C2 fixation, using anatomical measurements and biomechanical testing with traditional C1 pedicle screws (PS) in a cadaveric model.
Atlantoaxial instability often requires surgery, and the current methods for atlas fixation incur some risk to the vascular and neurological tissues. Thus, new, effective, and safe methods are needed for salvage operations.
Morphometric analysis of the C1 posterior arch was performed using 3-dimensional computed tomography. Six fresh ligamentous human cervical spines (C0-C4) were evaluated for their biomechanics. The specimens were tested in their intact condition and after stabilization (C1-C2 PS, C1 posterior arch screws [PAS] with C2 PS) and injury due to 1.5 N·m of pure moment in flexion, extension, lateral bending, and axial rotation. During testing, 3-dimensional angular motion was measured with a motion capture platform (Vicon Nexus). Data for all scenarios were recorded, and statistical analysis was performed.
Anatomical assessment indicated that 91.51% of C1 posterior tubercles exceeded 7 mm in thickness, 93.40% had a width of the posterior arch of greater than 3.5 mm, and 65.57% had a unilateral screw length of greater than 15 mm, indicating that the posterior arch fixation could be achieved by two 3.5 × 15-mm screws placed in a crossed manner. Twenty-two cases (11%) were not suitable for crossing screw placement because the posterior arch was flat and the entry point was present on the same side. Biomechanical testing showed that the PS and PAS rod-screw systems significantly reduced flexibility in flexion, extension, and rotation compared with the intact position. For lateral bending, there was a trend for the C1 PS and PAS systems toward decreased flexibility in comparison with the intact position. At the same time, C1 PAS decreased C1-C2 movement by 33.0% in left bending (P = 0.171) and 24.4% in right bending (P = 0.095); however, no significant difference was observed for left bending with C1 PAS compared with C1 PS, and the C1 PS and PAS systems significantly reduced the flexibility more than destabilization.
Crossing screw fixation of the C1 posterior arch is straightforward and imposes little risk of injury to the neural and vascular structures as long as the implants remain intraosseous. According to the results of our anatomical and biomechanical study, C1 posterior arch crossing screw fixation may constitute an alternative method for posterior atlantoaxial fixation.
进行解剖测量和体外生物力学测试，以评估一种新的 C1 后路固定方法。
本研究旨在通过解剖测量和生物力学测试，评估传统 C1 椎弓根螺钉（PS）在尸体模型中用于后路 C1-C2 固定的 C1 后弓交叉螺钉固定方法。
寰枢椎不稳常需手术治疗，目前的寰椎固定方法存在一定的血管和神经组织风险。因此，需要新的、有效的、安全的方法进行挽救性手术。
使用三维计算机断层扫描对 C1 后弓进行形态计量分析。评估 6 个新鲜的韧带性人颈椎（C0-C4）的生物力学特性。在完整状态下以及在 C1-C2 PS 固定和损伤后（C1 后弓螺钉[PAS]与 C2 PS）进行测试，损伤由 1.5 N·m 的纯矩在屈伸、侧屈和轴向旋转中引起。在测试过程中，使用运动捕捉平台（Vicon Nexus）测量三维角运动。记录所有场景的数据，并进行统计分析。
解剖评估表明，91.51%的 C1 后结节厚度超过 7mm，93.40%的 C1 后弓宽度大于 3.5mm，65.57%的单侧螺钉长度大于 15mm，这表明可以通过两个交叉的 3.5×15mm 螺钉实现后弓固定。22 例（11%）不适合交叉螺钉放置，因为后弓平坦，进钉点位于同一侧。生物力学测试表明，与完整位置相比，PS 和 PAS 杆-螺钉系统显著降低了屈伸和旋转的灵活性。对于侧屈，与完整位置相比，C1 PS 和 PAS 系统有降低灵活性的趋势。同时，C1 PAS 在左侧弯曲时使 C1-C2 运动减少了 33.0%（P=0.171），在右侧弯曲时减少了 24.4%（P=0.095）；然而，与 C1 PS 相比，C1 PAS 对左侧弯曲的影响没有显著差异，C1 PS 和 PAS 系统比失稳更显著地降低了灵活性。
只要植入物保持在骨内，C1 后弓交叉螺钉固定方法简单，对神经和血管结构造成损伤的风险很小。根据我们的解剖学和生物力学研究结果，C1 后弓交叉螺钉固定可能是后路寰枢固定的另一种方法。
3 级
