The Orthopaedic Clinic, Mercy Specialist Centre, 100 Mountain Rd, Epsom, Auckland 1023, New Zealand.
Spine J. 2012 Feb;12(2):136-42. doi: 10.1016/j.spinee.2012.01.004. Epub 2012 Feb 15.
The anatomy of the atlantoaxial joint makes stabilization at this level challenging. Current techniques that use transarticular screw fixation (Magerl) or segmental screw fixation (Harms) give dramatically improved stability but risk damage to the vertebral artery. A novel integrated device was designed and developed to obtain intra-articular stabilization via primary interference fixation within the C1-C2 lateral mass articulation.
To assess the atlantoaxial stability achieved with a novel integrated device when compared with the intact, destabilized, and stabilized state using the Harms technique.
A biomechanical study of implants in human cadaveric cervical spines.
Six human cadaveric specimens were used. Biomechanical testing was performed with moment control in flexion-extension, lateral bending, and axial rotation. Range of motion (ROM) was measured in the intact state, after both destabilization by creation of a Type II odontoid peg fracture and sequential stabilization using the integrated device and the Harms technique.
Mean flexion-extension ROM of the intact specimens at C1-C2 was 14.1°±2.9°. Destabilization increased the ROM to 31.6°±4.6°. Instrumentation with the Harms technique reduced flexion-extension motion to 4.0°±1.4° (p<.01). The integrated device reduced flexion-extension motion to 3.6°±1.8° (p<.01). In lateral bending, the respective mean angular motions were 1.8°±1.1°, 14.1°±5.8°, 1.4°±0.7°, and 0.4°±0.3° for the intact destabilized Harms technique and integrated device. For axial rotation, the respective mean values were 67.3°±13.8°, 74.2°±16.1°, 1.4°±0.7° and 0.9°±0.7°. Both the Harms technique and integrated device significantly reduced motion compared with the destabilized spine in flexion-extension, lateral bending, and axial rotation (p<.05). Direct comparison of the Harms technique and the integrated device revealed no significant difference (p>.10).
The integrated device resulted in interference fixation at the C1-C2 lateral mass joints with comparable stability to the Harms technique. Perceived advantages with the integrated device include avoidance of fixation below the C2 lateral mass where the vertebral artery is susceptible to injury, and access to the C1 screw entry point through the blade of the integrated device avoiding extended dissection superior to the C2 nerve root and its surrounding venous plexus.
寰枢关节的解剖结构使得在这一水平进行稳定化治疗具有挑战性。目前，使用经关节螺钉固定（Magerl 技术）或节段螺钉固定（Harms 技术）的技术可显著提高稳定性，但有损伤椎动脉的风险。一种新型的一体化装置被设计并开发出来，通过在寰枢外侧关节突关节内进行原发性干扰固定，实现关节内稳定。
与完整、失稳和使用 Harms 技术稳定的状态相比，评估新型一体化装置在寰枢关节获得的稳定性。
一项对人尸体颈椎植入物的生物力学研究。
使用六具人尸体标本进行生物力学测试。采用屈伸、侧屈和轴向旋转的力矩控制进行测试。在完整状态、寰齿关节 II 型钉突骨折形成后失稳以及使用一体化装置和 Harms 技术进行连续稳定化后，测量活动度（ROM）。
寰齿关节 C1-C2 完整标本的屈伸 ROM 平均为 14.1°±2.9°。失稳后 ROM 增加到 31.6°±4.6°。使用 Harms 技术固定后，屈伸运动减少到 4.0°±1.4°（p<.01）。一体化装置使屈伸运动减少到 3.6°±1.8°（p<.01）。在侧屈方面，相应的平均角度运动分别为 1.8°±1.1°、14.1°±5.8°、1.4°±0.7°和 0.4°±0.3°，用于完整、失稳、Harms 技术和一体化装置。轴向旋转的相应平均值分别为 67.3°±13.8°、74.2°±16.1°、1.4°±0.7°和 0.9°±0.7°。与屈伸、侧屈和轴向旋转的失稳脊柱相比，Harms 技术和一体化装置均显著降低了运动（p<.05）。Harms 技术和一体化装置的直接比较显示无显著差异（p>.10）。
一体化装置在寰枢外侧关节突关节产生干扰固定，稳定性与 Harms 技术相当。一体化装置的优点包括避免在椎动脉易受伤的 C2 外侧突下方固定，以及通过一体化装置的叶片进入 C1 螺钉入口，避免在 C2 神经根及其周围静脉丛上方进行广泛的解剖。
