Xu R, Ebraheim N A, Misson J R, Yeasting R A
Department of Orthopaedic Surgery, Medical College of Ohio, Toledo, USA.
Spine (Phila Pa 1976). 1998 Oct 15;23(20):2190-4. doi: 10.1097/00007632-199810150-00009.
This study assessed the value of using lateral radiographs in evaluating the optimal screw length in transarticular C1-C2 screw fixation.
To assess the reliability of the lateral radiograph in determining the optimal transarticular C1-C2 screw length.
Transarticular C1-C2 screw placement is usually performed using anatomic landmarks and fluoroscopy. A lateral fluoroscopic image is valuable when directing screws in the sagittal plane, but its exact role in determining screw length has not been investigated.
Eight cervical spine specimens were used in this study. Screw placements were performed in each specimen, fixed in the exact lateral position and under direct visualization. After each placement, a lateral radiograph was taken. The odontoid process was divided into three equal portions. Another portion anterior to the odontoid process was called the anterior tubercle region. The number of screw tips appearing in each portion on the radiograph was then recorded for each placement. In addition, 30 C1 specimens were measured to evaluate the anterior part of C1.
The results showed that 12.5% of the screws placed 2 mm short of reaching the ventral cortex and 0 mm overpenetrating the ventral cortex of the lateral mass of C1 projected in the radiograph on the anterior tubercle region, 37.5% on the anterior region of the odontoid process, and 50% on the middle region of the odontoid process. Twenty-five percent of the screws that were placed to overpenetrate, by 2 or 4 mm, the ventral cortex of the lateral mass of C1 were projected on the anterior tubercle region in the radiograph, and 50% and 62.5% were projected on the anterior region of the odontoid process, respectively. The mean vertical distance between the anteriormost point of the anterior tubercle of the anterior ring and the middle of the ventral cortex of the lateral in all specimens was 5.6 +/- 1 mm, and the mean transverse angle of the anterior ring relative to the frontal plane was 21.1 +/- 3.5 degrees.
This results in this study indicate that a lateral radiograph may not be reliable in determining the optimal screw length, although it is valuable in directing accurate screw angle in the sagittal plane. Preoperative computed tomographic evaluation of the C1-C2 region may be helpful in estimating the location of the screw tip on the lateral radiograph during surgery.
本研究评估了使用颈椎侧位X线片在评估经关节突C1-C2螺钉固定中最佳螺钉长度方面的价值。
评估颈椎侧位X线片在确定经关节突C1-C2螺钉最佳长度方面的可靠性。
经关节突C1-C2螺钉置入通常采用解剖标志和透视引导。透视侧位影像在矢状面引导螺钉置入时很有价值，但其在确定螺钉长度方面的确切作用尚未得到研究。
本研究使用了8个颈椎标本。在每个标本上进行螺钉置入，将标本固定在精确的侧位并直视下操作。每次置入后，拍摄颈椎侧位X线片。齿突被分为三个相等部分。齿突前方的另一部分称为前结节区。然后记录每次置入时X线片上每个部分出现的螺钉尖端数量。此外，测量30个C1标本以评估C1的前部。
结果显示，置入的螺钉距离C1侧块腹侧皮质还差2mm且未穿透腹侧皮质时，12.5%的螺钉尖端投影在X线片的前结节区，37.5%投影在齿突前部区域，50%投影在齿突中部区域。置入的螺钉穿透C1侧块腹侧皮质2mm或4mm时，25%的螺钉尖端投影在X线片的前结节区，分别有50%和62.5%投影在齿突前部区域。所有标本中，前环前结节最前点与侧块腹侧皮质中点之间的平均垂直距离为5.6±1mm，前环相对于额平面的平均横向角度为21.1±3.5度。
本研究结果表明，颈椎侧位X线片在确定最佳螺钉长度方面可能不可靠，尽管其在矢状面引导准确的螺钉角度方面很有价值。术前对C1-C2区域进行计算机断层扫描评估可能有助于在手术中估计侧位X线片上螺钉尖端的位置。
