成人颈椎椎弓根螺钉在儿童腰椎应用的可行性

背景：由于1~3岁幼年儿童椎体发育未完全成熟,各种解剖径线相对较成人小得多,尚无幼儿专用的椎弓根螺钉固定器械,现有能够利用的直径最小的椎弓根螺钉是用于成人颈椎侧块或椎弓根固定的钉棒系统。目的：观察将成人颈椎椎弓根螺钉应用到成年猪颈椎与幼猪腰椎固定后的生物力学对比。方法：将6具完整新鲜成年猪颈段C3~C6脊椎标本和6具完整8周龄新鲜幼猪腰段脊柱标本自椎间盘及关节处离断,游离成单个椎体,共54个椎体108侧椎弓根。按照标准操作将成人颈椎椎弓根螺钉分别安置在成年猪颈椎标本和幼猪腰椎标本的椎弓根上,应用生物力学方法测试螺钉的最大轴向拔出力。结果与结论：颈椎标本最大轴向拔出力高于腰椎标本,但差异无显著性意义(P > 0.05);L1椎弓根螺钉的拔出力均值明显小于L3椎弓根螺钉的拔出力均值(P < 0.05);C5椎弓根螺钉的拔出力均值明显大于C3椎弓根螺钉的拔出力均值(P < 0.05);颈椎和腰椎标的骨密度差异有显著性意义(P < 0.01),椎体椎弓根力学数值与椎体骨密度之间存在线性正相关。说明取得了成人颈椎椎弓根螺钉在轴向拉力方面适应于幼儿腰椎的初步实验依据。

Feasibility of adult cervical pedicle screw in the lumbar spine of young children

BACKGROUND:Because the vertebrae of children aged 1 to 3 years are not fully mature, there is no specific pedicle screw for children. At present, the existing pedicle screw with the smallest diameter is for adult cervical lateral mass or pedicle screw fixation. OBJECTIVE:To compare the biomechanical changes of adult cervical pedicle screw used in cervical pedicle fixation of adult pigs and lumbar pedicle fixation of young pigs.METHODS:C3-6 segments for six fresh adult pigs and lumbar spinal specimens from six 8-week-old young pigs were selected to prepare 54 single vertebrae with 108 pedicles. Adult cervical pedicle screw was placed into the prepared pedicles, and the maximum axial pull-out strength was detected using biomechanical methods.RESULTS AND CONCLUSION:The maximum axial pull-out strength of the cervical specimen was lower than that of the lumbar specimen, but there was no significant difference (P > 0.05). The mean pull-out strength of L1 was significantly lower than that of L3 (P < 0.05). The mean pull-out strength of C5 was significantly higher than that of C3 (P < 0.05). There was a significant difference between the bone marrow density of the cervical and lumbar specimens (P < 0.01). From this study, we got the preliminary experimental foundation about applying adult cervical pedicle screw to the lumbar spine of young children from the viewpoint of axial pull-out strength.