Ebraheim N A, Tremains M R, Xu R, Yeasting R A
Department of Orthopaedic Surgery, Medical College of Ohio, Toledo, USA.
Spine (Phila Pa 1976). 1998 Feb 15;23(4):458-62. doi: 10.1097/00007632-199802150-00010.
Assessment of the value of lateral radiographs in evaluation of lateral mass screw placement in the cervical spine.
To assess the value of lateral radiographs in determining the safe or hazardous locations of the tips of screws used in lateral mass screw fixation.
Posterior plating with lateral mass screw fixation is frequently used to stabilize the cervical spine and improve fusion. Injury to the spinal nerves caused by screws that are too long must be identified quickly to minimize neurologic complication. No previous radiologic study in which lateral mass screw placement was evaluated using lateral radiographs has been reported.
Six cervical spines were removed from embalmed cadavers. Three screws using the Roy-Camille technique and another three using Magerl technique were placed into the lateral mass at C3-C5 in each specimen. Four screw placements under direct visualization, including placement of the screw tip staying the ventral cortex and 2-mm, 4-mm, and 6-mm overpenetration of the ventral cortex, were performed separately on each specimen for each of the two techniques. After each placement, a lateral radiograph was taken. Each vertebral body was divided vertically into four equal zones with Zone I the most posterior. Another equal zone, posterior to the posterior border of the vertebral body was defined as pre-Zone I. The number of screw tips seen in each zone were quantified for each placement.
In the screws placed using the Roy-Camille technique, 77.8% of screws placed without perforating the ventral cortex were found in Zone I; 72.2% placed with 2-mm overpenetration of the ventral cortex were noted in Zone II; and 61.1% of the screws with 4-mm overpenetration of ventral cortex and 77.8% with 6-mm overpenetration were located in Zone III. For the use of the Magerl technique, 44.4% of the screws placed without perforating the ventral cortex were found in pre-Zone I; 72.2% of the screws placed with 2-mm overpenetration were located in Zone I; and 66.6% with 4-mm overpenetration and 89.7% with 6-mm overpenetration were noted in Zones I and II, respectively.
Lateral radiographs may be valuable in evaluating lateral mass screw placement. Ideal screw tip positions on lateral radiograph for the Roy-Camille technique may be in Zone I, and for the Magerl technique may be in pre-Zone I.
评估颈椎侧位X线片在评价颈椎侧块螺钉置入中的价值。
评估颈椎侧位X线片在确定侧块螺钉固定时螺钉尖端安全或危险位置方面的价值。
后路钢板联合侧块螺钉固定常用于稳定颈椎并促进融合。必须迅速识别过长螺钉对脊神经造成的损伤，以尽量减少神经并发症。此前尚无使用颈椎侧位X线片评估侧块螺钉置入情况的放射学研究报道。
从防腐尸体上取下6个颈椎标本。每个标本在C3-C5侧块分别采用Roy-Camille技术置入3枚螺钉，采用Magerl技术置入另外3枚螺钉。对每个标本，针对两种技术分别在直视下进行4种螺钉置入操作，包括螺钉尖端停留在腹侧皮质以及腹侧皮质穿透2mm、4mm和6mm的情况。每次置入后均拍摄颈椎侧位X线片。每个椎体垂直分为4个相等区域，I区位于最后方。在椎体后缘后方定义另一个相等区域为I区前区。对每次置入操作，量化每个区域内可见的螺钉尖端数量。
采用Roy-Camille技术置入的螺钉中，未穿透腹侧皮质的螺钉有77.8%位于I区；腹侧皮质穿透2mm的螺钉有72.2%位于II区；腹侧皮质穿透4mm的螺钉有61.1%以及穿透6mm的螺钉有77.8%位于III区。采用Magerl技术时，未穿透腹侧皮质的螺钉有44.4%位于I区前区；腹侧皮质穿透2mm的螺钉有72.2%位于I区；腹侧皮质穿透4mm的螺钉有66.6%以及穿透6mm的螺钉有89.7%分别位于I区和II区。
颈椎侧位X线片在评估颈椎侧块螺钉置入方面可能具有重要价值。Roy-Camille技术在颈椎侧位X线片上理想的螺钉尖端位置可能在I区，而Magerl技术可能在I区前区。
