利用Unigraphics软件三维模拟寻找枢椎侧弓安全钉道的研究

目的:对枢椎标本进行薄层CT扫描,利用Unigraphics NX软件进行计算机虚拟三维实体重建和模拟,寻找安全的侧方椎弓螺钉钉道.方法:对4例干燥标本和8例新鲜枢椎标本进行薄层CT扫描(层厚、层距均为0.6 mm),利用Unigraphics的自由建模功能进行三维重建.根据需要建造出不同直径和形状的螺钉模拟体模拟侧方椎弓螺钉进钉,寻找出安全的进针点和进针方向.结果:薄层CT扫描可见枢椎侧方椎弓横突孔区域的外侧骨皮质很薄,部分标本存在滋养动脉孔,使得横突孔区域侧方椎弓外侧骨皮质先天不完整.以横突后结节为界,侧方椎弓的前部与后部的走行方向不一致,左右侧不相同.横突孔区域上部的走行方向与中下部的走向亦不一致.侧方椎弓的安全钉道方向同侧方椎弓的前部与后部的走行方向均不相同,但主要由横突孔区域的中下部分的外界所限定.对4例干燥标本按照计算机模拟的安全钉道方向进针取得了成功.结论:横突孔区域滋养动脉孔的存在使得传统的判定螺钉钉道是否正确的方法受到挑战.利用UG软件对枢椎标本进行计算机三维重建可模拟出安全的进针点和钉道,并测出螺钉直径和长度,为术中提供参考.

Determining a Safe Lateral Ach Screw Trajectory of Vertebra Dentata by Employing Unigraphics Software to Simulate three Dimensional Body

Objective:To search for a safe lateral screw trajectory on the reconstructed 3D computer imaginary body based on thin-slice CT scanning of vertebra dentata.Methods:Four isolated dry dentata and eight fresh specimens were enrolled in this experiment.Consecutive CT images of each sample were scanned with 0.6 mm in thickness and interval distance.With help of UG software(NX edition),3D reconstruction body of vertebra dentata axis was built up.The screws in various diameters and shapes meeting special demands were simulated,then positioned according to imaginary trajectory and readjusted until satisfactory entrance point and inclination of needling.Results:CT images showed that the lateral cortex at transverse foramen region(anterior region of lateral arch) was obvious thinner.Some specimen possessed a hole for nutrient artery,which induced congenital deficient in the lateral cortex of vertebral arch.Distinguished by transverse process,the route orientation of lateral vertebral arch in anterior region did not parallel to that in posterior region;and the orientation in upper part of cervical foramen region was different from that in median and lower parts.By simulating different entrance point and end point in imaginary axis with computer,a satisfactory screw trajectory can finally be obtained,which parallel neither to the orientation of upper part of anterior portion nor to that of posterior portion,but was largely restricted by the orientation of median and lower part of anterior portion of lateral arch.Conclusions:Existence of nourishing vessel hole at the lateral cortex of anterior region of lateral arch of axis makes the cortex of lateral arch congenital deficient.The conventional methods to judge the screw safe trajectory is questionable.A safe screw trajectory of lateral arch of axis can be got by UG-software simulating methods,and appropriate length and diameter of screw could be determined preoperatively.