CT重建椎弓根轴线投影点定位研究

目的:建立椎弓根螺钉最佳入钉点,提高椎弓根螺钉内固定术的准确性和安全性。方法:高速螺旋CT共扫描检查40例国人的200个L1~L5脊椎。重建后测量400个椎弓根的入点坐标(x,y),即椎弓根轴线在椎骨后表面的投影点与后正中线的距离(x)及与横突中线的垂直距离(y)。结果:x坐标从L1~L5逐渐增大,男性大于女性(P<0.05);y坐标从L1到L4逐渐下移,在L4与横突中线接近重叠,但L5突然上升,与L2节段水平相当,L1~L5y坐标基本上都在横突中线以上,但每组数据变异较大。就y坐标而言,椎弓根轴线投影点与传统入点比较均有差异。结论:横突中线是椎弓根螺钉置入的重要参照标志,但椎弓根轴线投影点并不在横突中线上,不同个体、节段之间y坐标存在的较大差异是高误置率发生的重要原因。对个体而言,术前常规通过CT测量椎弓根轴线在椎骨后表面的投影点数据对椎弓根螺钉的置入有重要指导意义。

The position study of the projection point of the lumbar pedicle axis on the posterior aspect by reconstructed CT

Objective:To establish the best starting point for fixing a pedicle screw to the axial center of the pedicle,which promotes safety and accuracy of transpedicular procedures.Method:A total of200vertebrae from L1~L5of40Chinese people were scanned on a GE LightSpeed QX/i computerized tomographic scanner in the axial plane.After images were reconstructed,the coordinates including the distance from the projection point of the lumbar pedicle axis to the midline of back(x)and to the midline of transverse process(y)were measured.Result:X coordinates increased from L1to L5,which showed male was longer than female(P<0.05).The average of y coordinates stepped down from L1to L4where it was very close to mid-transverse process.But y was up to L5.Most of y coordinates were above mid-TP(transverse process),where as the variance was considerable.As far as y was concerned,there was significant difference between projection point and traditional position ways.Conclusion:Mid-TP was thought as an important landmark during the transpedicular procedures.But the projection point of lumbar pedicle is not in mid-TP.There are diversity in different person and segments,which become the main issue of high misplace rates.The coordinates of projection point of lumbar pedicle axis obtained individually from reconstructed CT images preoperatively could ensure utmost safety and accuracy of transpedicular procedures.