下颈椎经关节螺钉植入深度的侧位X线片评价

Lateral radiological evaluation of transarticular screw placement in the lower cervical spine

目的 运用侧位X线片评价下颈椎经关节螺钉植入深度的安全性。方法 采用6具新鲜颈椎标本（C1-T1），每具标本均在直视下植入下颈椎经关节螺钉（每侧4枚螺钉：C3、4、C4、5、C5、6、C6、7各1枚），分别在植入螺钉尖端穿出最后一层皮质0、2、4、6mm时摄标准侧位X线片，将侧位X线片上椎体垂直等分为四部分，定义为1-4区，并定义椎体后缘之后相当宽度的区域为前1区。每次植入时记录螺钉尖端在X线侧位片的位置，以综合评价螺钉植入的安全性。结果 在C3、4和C4、5，螺钉尖端穿出最后一层皮质0mm时，87．5％在1区，穿出2mm时，54．2％在1区。当螺钉尖端穿出4mm时，75．0％在2区，穿出6mm时58.3％在3区。在C5、6和C6、7，穿出0mm时75．0％位于前1区，穿出2mm时，54．2％位于前1区；穿出4mm时83.3％位于1区，穿出6mm时，50．0％位于2区。结论 侧位X线片可用于评价下颈椎经关节螺钉植入深度的安全性。在侧位X线片上，理想的螺钉尖端位置为C3、4和C4、5应位于1区，而在C5、6和C6、7应位于前1区。

Objective To assess the value of lateral radiographs in determining the safe or hazardous locations of the tips of screws used in transarticular screw fixation in the lower cervical spine. Methods Six cervical spines were removed from embalmed cadavers. Four transarticular screws were placed into the lower cervical spine at C3.4 to C6,7 on both sides for each specimen. Four screw placements under direct visualization, including placement of the screw tip staying the ventral cortex, 2 mm, 4 mm and 6 mm overpenetration of the ventral cortex, were performed on each specimen. Following each placement, a lateral radiograph was taken. Each vertebral body was divided vertically into four equal zones with Zone I being most posterior, and another equal zone posterior to the posterior border of the vertebral body was defined as PreZone I. The numbers of screw tips seen in each zone were quantified for each placement. Results At C3.4 and C4.5, 87.5% of the screws without perforating the ventral cortex and 54.2% screws over-penetratlng 2mm were found in Zone Ⅰ; 75.0% of the screws over-penetrating the ventral cortex for 4 mm were located in Zone Ⅱ; 58.3% screws over-penetrating for 6 mm were noted in Zone Ⅲ. At C5,6 and Cs,7, 75.0% of the screws without perforating the ventral cortex and 54.2% screws over-penetrating 2mm were found in pre- Zone Ⅰ; 83.3% of the screws over-penetrating the ventral cortex for 4 mm were located in Zone Ⅰ; 50.0% screws over-penetrating for 6 mm were noted in Zone Ⅱ. Conclusion Lateral radiographs may be valuable in evaluation of transarticular screw placement in the lower cervical spine. Ideal screw tip positions on lateral radiograph for transarticular screw may be in Zone Ⅰ at C3,4 and C4,56, in pre-Zone Ⅰ at C5,6 and C6,7.