Texas Back Institute, 6020 West Parker Road, Plano, TX, 75093, USA.
Orthofix Medical, Inc, Lewisville, TX, USA.
Eur Spine J. 2021 Feb;30(2):554-559. doi: 10.1007/s00586-020-06638-7. Epub 2020 Oct 26.
The traditional teaching has been that proper function of a cervical disc replacement is dependent upon appropriate placement, which includes centering the device in the coronal plane. The purpose of this study was to identify the most reliable anatomical landmark for determining midline placement of an implant within the cervical disc space under fluoroscopy.
Digital fluoroscopy images were taken for each cervical level at 0 °, 2.5 °, 5 °, 7.5 °, 10 °, and 15 ° from the mid-axis by rotating the C-arm beam of six cadavers. Thin-slice CT scanning of the same levels was subsequently performed. Three independent reviewers measured the distance between anatomic structures: (a) tip of the right uncinate; (b) medial border of the right pedicle; and (c) center of the spinous processes for different x-ray angles across cervical levels C3-7.
Both the uncinate and pedicle demonstrated superior overall accuracy to that of the spinous process (p ≤ 0.02) at all angles except at 0 ° for the pedicle where the difference was not statistically significant. Overall (pooled C3-7), the accuracy of the uncinate did not differ significantly from that of the pedicle at any fluoroscopic angle. The center of the spinous process measurement was particularly sensitive to deviations from the perfect anteroposterior fluoroscopy image.
The results of this investigation suggest that the tip of the uncinate and the medial border of the pedicle are more accurate measures of midline in the cervical spine than the center of the spinous process and are less susceptible to inadvertent off-axis imaging.
传统教学认为，颈椎间盘置换的正常功能取决于适当的位置，包括在冠状面使器械居中。本研究的目的是确定在透视下确定颈椎间盘间隙内植入物中线位置的最可靠解剖标志。
对 6 具尸体的每个颈椎水平，在从中轴线旋转 C 臂束 0°、2.5°、5°、7.5°、10°和 15°的情况下，分别获得数字透视图像。随后对相同水平进行薄层 CT 扫描。3 位独立评审员测量了不同 X 射线角度的解剖结构之间的距离：（a）右钩突尖端；（b）右椎弓根内侧缘；（c）棘突中心。
在所有角度下，钩突和椎弓根均比棘突具有更高的总体准确性（p≤0.02），除了椎弓根在 0°时差异无统计学意义。总体（C3-7 合并），在任何透视角度下，钩突的准确性均与椎弓根无显著差异。棘突中心的测量结果特别容易受到与完美前后透视图像偏差的影响。
本研究结果表明，在颈椎中，钩突尖端和椎弓根内侧缘比棘突中心更能准确测量中线，并且不易受到无意的轴外成像影响。
