经前路枕颈融合术斜坡置钉的影像学研究

Anterior screw placement in occipital clivus for craniovertebral fusion: an imaging study

中文关键词:  枕颈融合  CT扫描  螺钉固定  前路手术

英文关键词:Craniovertebral fusion  CT scans  Screw placement  Anterior approach surgery

中文摘要:

  【摘要】 目的：探讨经前路枕颈融合术斜坡置钉的影像学参数。方法：2006年5月~2011年4月在我院行颅颈区多层螺旋CT扫描的患者中，排除：（1）<20岁；（2）术后CT扫描；（3）枕颈部解剖异常，如先天性颅寰枕融合、颅底凹陷等；（4）肿瘤、外伤或感染患者。共有30例患者入选，男19例，女11例，年龄20~64岁，平均38.8岁。将30例患者的颅颈区CT扫描原始数据输入MXV工作站，进行多平面二维重建（MPR），重建好的图像保存于PACS系统并进行分析测量：在矢状位上确定颅底斜坡最佳进钉点A2再作水平线即为A线，斜坡最高点水平线即为C线，两线中点等距水平线即为B线，三线上分别有3个相距为3.5mm（即Zephir钢板螺钉孔直径）的进钉点，A线3个点作为最佳进钉点，B线3个点为候选进钉点，C线3个点为极限进钉点；在其矢状位图像上测量每个进钉点分别以水平角度（HA）、垂直角度（VA）以及极限向上倾斜角度（LA）进钉的安全角度和螺钉长度范围，并测量颅颈区内固定钢板或钛笼所需的折弯角度。结果：斜坡置钉相对安全的进钉范围呈一个不规则的梯形区域，在分别以A、B和C线的点为进钉点、以最佳进钉角度（VA）进钉时，平均钉道长度为（7.57±1.38）mm、（10.13±2.46）mm和（15.60±3.12）mm，三者间差异有显著性（P<0.05）。通过重建矢状位图像测量斜坡螺钉结果显示， 29例患者在B线达到了VA，13例在C1和C2达到VA，12例在C3达到VA，其中1例在C1达到VA而在C2和C3处未达到，1例在C1和C2处达到但C3处未达到VA。矢状位图像测量中最佳进钉点、候补进钉点及极限进钉点的最大安全进钉角度分别为130.19°±8.00°、125.23°±13.24°和85.72°±24.33°，三者间差异有显著性（P<0.05）。内固定钢板或者钛笼所需的折弯角度为121.36°~140.18°（130.19°±8.00°）。结论：经前路枕颈融合术在颅颈区斜坡置钉内固定是一种可行的选择，并且存在一个安全进钉角度和螺钉长度范围。

英文摘要:

  【Abstract】 Objectives: To study the imaging parameters related to anterior screw placement in occipital clivus for craniovertebral fusion. Methods: CT scans on craniovertebral region between May 2006 and April 2011 in our institution were collected for analysis. Exclusion criteria included: (1)patients aged <20 years; (2)after operation; (3)craniovertebral deformities, such as congenital atlantooccipital assimilation, and (4)patients with tumor, trauma, or infection. Finally, 30 healthy East Asian patients(19 males, 11 females) with an average age of 38.8 years(range, 20-64 years) were included. The original data were imput into the MXV work station, and 2-dimensional(2-D) image reconstruction was performed using multiplanar reconstruction(MPR) methods. And then, angles and lines were drawn and measured using Star PACS. A2 was the optimal entry point on the extracranial clivus, C2 was just at the top portion of the middle line of extracranial clivus, and B2 was determined as the midpoint between B2 and C2. The line A, B, C was the horizontal line that went through the point A2, B2 and C2 respectively. The distance between adjacent points on a line was 3.5mm(the pitch diameter of Zephir plate). The points on line A were regarded as the optimal entry points, the points on line B as the candidate points, and the points on line C as the limit entry points. In the reconstructed midsagittal images, the safe scope for the screw length and angle for every entry point at the horizontal angle(HA), vertical angle(VA) and limit angle(LA) were measured. At the same time, the bending angle that the plate or net cage required was measured. Results: At the optimal entry angle(VA), the total mean screw length was （7.57±1.38）mm, （10.13±2.46）mm and （15.60±3.12）mm for the optimal entry points, candidate points and limit entry points respectively, and there was significant difference among the three points(P<0.05). The measurement of clivus screw placement in 2-D CT reconstruction images showed that 29 cases had line B settled to VA, and 1 case did not reach it at the points of B1, B2 and B3. And yet, only 13 cases met the vertical angle at C1 and C2. 12 cases met it at C3, of them, 1 case reached the vertical angle at C1 other than C2 and C3, and 1 case settled to it at C1 and C2 rather than C3. The maximum uptroversion angle for the optimal entry points, the candidate points, the limit entry points was approximately 130.19°±8.00°, 125.23°±13.24° and 85.72°±24.33° respectively, which showed significant difference among the three points(P<0.05). The bending angle that the plate or net cage required was 130.19°±8.00°(121.36°-140.18°). Conclusions: Anterior screw placement in occipital clivus for craniovertebral fusion is feasible. There exists a safe zone and screw length requirements for screw placement.