椎弓根钉道参数的变异性及其相关因素的研究

目的研究椎弓根钉道相关参数的变异性及引起变异的具有临床意义的相关因素。方法用PickerPQ6000螺旋CT扫描仪对C3～L5椎体进行扫描。共扫描198例(男118例,女80例)的736个椎体。测量每个椎体的椎弓根横径、钉道长度、及e角(椎弓根轴线与矢状面夹角),观察椎体形态及椎体、棘突、人体三者各自矢状轴间的关系,如有异常则测量并记录。同时记录受检者的性别、身高、体重。以上数据用SPSS软件进行统计学处理。结果统计结果显示:每一节椎体的椎弓根宽度、钉道长度及e角均有较大的极差及四分位数间距。虽然t检验显示不同性别间的钉道长度、椎弓根宽度均有明显的统计学差异,但在进一步以协方差分析法分析各因素的交互效应时发现,在消除体重、身高两因素后,椎弓根宽度及钉道长度均与性别无关。泊松相关分析显示身高、体重均与椎弓根宽度及钉道长度呈显著正相关,而e角与后两者无显著相关性。对椎体畸变的观察显示:14(1.9%)个胸腰椎椎体矢状轴与人体矢状轴不一致;11(1.0%)个椎体棘突轴与椎体矢状轴不一致;T9以下,14(4.9%)个椎体的椎弓根横径小于4mm;4个椎体椎弓根外凸变形,影响置钉位置。结论人体椎弓根钉道参数具有较大的变异性,不同个体、不同节段水平均有显著不同;体重和身高是两个影响变异性重要的相关因素。偶发

A study of the variability of the parameters of the pedicle screw path and its related factors

Objective To study the variability of the parameters of the pedicle screw path and influencing factors of clinical significance. Methods A Picker PQ6000 Spiral CT was used to scan 736 vertebrae from C 3 to L 5 of 118 men and 80 women aged between 17 and 58. The largest transverse diameter, screw path length and e angle (the angle between the axis of the pedicle and sagittal plane) of each pedicle were measured. The contour of the vertebrae and the relationship of the sagittal axis of the spinal process, vertebral body and human body were inspected. Any discrepancy of these axes was measured and recorded. The gender, age, height and weight were recorded at the same time. Results Measurement of the biggest transverse diameter, screw path length and e angle at each vertebral level showed a wide range of value and quantity. Although the screw path length and the transverse diameter of the pedicle showed significant difference between man and woman, further covariance analysis for between subject effects revealed that no inter gender difference existed after the effects of height and weight were removed. Both height and weight showed significant positive correlation with the screw path length and transverse diameter of the pedicle, but no correlation with the e angle. Observation on the deformity of the vertebrae showed that the sagittal axes of the vertebral body and human body was discrepant in 14 thoracic and lumbar vertebrae; the sagittal axes of the spinal process and vertebrae was discrepant in 11 vertebrae; the transverse diameter of the pedicle was smaller than 4 mm in 14 vertebrae below T 9; 4 vertebrae showed lateral convex pedicle. Conclusion The parameters of the pedicle screw path varied in different subjects and different vertebral level with a large variability. The weight and height are two important factors to influence the parameters. Deformity is another factor which may lead to mistake of placement of the pedicle screw. To improve the accuracy of the pedicle screw, individual identification of the entering point and orientation should be considered and in some circumstances even special screws, should be used.