多平面CT重建下个体化改良寰椎椎弓根进钉路径的测量

目的:通过对寰椎椎弓根轴位、矢状位多平面CT重建,测量个体化改良椎弓根进钉路径数据,以期提高寰椎椎弓根置钉准确率。方法:20具成人颈椎标本,男11具,女9具,年龄不详。进行螺旋CT薄层扫描多平面重建,在寰椎椎弓根轴位像上建立改良的椎弓根进钉路径,即经椎管外缘和齿突孔外缘划切线L1线,经椎动脉孔内缘画L2线平行于L1线,经L1、L2线之间中点画A线平行于L1、L2线,A线即为改良的寰椎椎弓根进钉路径。根据A线确定并测量椎弓根进钉点、进钉方向等个体化置钉参数,根据测量的置钉参数在标本的寰椎椎弓根置入直径3.5mm皮质骨螺钉。置钉后行螺旋CT扫描,按Ludwing椎弓根置钉安全标准统计椎弓根螺钉误置率。结果:多平面CT重建后影像学测量表明,改良寰椎椎弓根进钉路径的进钉点距寰椎后结节:右侧25.8±1.9mm,左侧25.7±1.8mm,比传统的进钉点(距寰椎后结节18~20mm)更偏外;进钉内倾角度:右侧21.1°±4.6°,左侧20.0°±4.9°,比传统的内倾角(0~10°)更大。20具颈椎标本共置钉40枚,按照Ludwing椎弓根置钉安全标准:0级36枚(90%),1级4枚(10%)。结论:寰椎椎弓根多平面CT重建下建立的改良椎弓根进钉路径,能够获取进钉点、进钉角度的个体化置钉参数。该路径比传统的方法进钉点更偏外,内倾角更大,能够提高寰椎椎弓根置钉准确率。

Multi-planar computerized tomography reconstruction for individualized and modified atlas pedicle screw placement

Objectives: To investigate the accuracy of individualized and modified atlas pedicle screw placement assisted by multi-planar computerized tomography(MSCT) reconstruction.Methods: 20 vertebral specimens(11 males,9 females) were examined by MSCT reconstruction.Modified pedicle insertion in atlas was determined as followings: parallel line(line A) between tangent line sited lateral side of vertebral channel(line L1) and line L2 sited medially to the transverse foramen.Related parameters such as entry point and orientation of atlas pedicle screw were determined.Based on these parameters,3.5mm screws were inserted into atlas of 20 specimens.After insertion of screws,MSCT scanning and reconstruction were performed again to evaluate the accuracy of instrument.Results: According to individualized and modified C1 pedicle placement on MSCT,the distance between entry point of C1 pedicle screw and midline of C1 posterior arch averaged 25.8±1.9mm for the right side and 25.7±1.8mm for the left side,which sited more laterally than traditional anchoring point(18-20mm).The introversion angle was 21.1°±4.6°for the right side and 20.0°±4.9°for the left side,which was larger than traditional introversion angle(0 or 10 degrees).40 pedicle screws were placed in C1 accurately.According to the Ludwing classification,there were 36(90%,36/40) grade zero,4(10%) grade one and no grade two.Conclusions: Multi-planar computerized tomography reconstruction can establish modified pedicle screw instrumentation including entry point and orientation,which has more lateral entry point and more introversion angle so as to improve accuracy of instrumentation.