Radiological Studies And Feasibility Analysis On Cervicothoracic Anterior Transpedicular Screw Fixation

Objective To explore the entry point and trajectory of anterior transpedicular screws in the cervicothoracic junction(CTJ)and investigate its feasibility of screw placement by anterior approach by radiological studies.Methods From December 2013 to July 2014,50 patients were scanned by cervical and upper thoracic spine by spiral CT,including 29 males and 21 females with the age ranging from 23 to 61years(average 37.3 years).The data of outer pedicle width(OPW),Pedicle Axis length(PAL),transverse Pedicle Angle(t PA),Distance transverse Intersection Point(Dt IP)were measured on Sequential raw cervicothoracic transaxial CT image.The region where the entry point located in the anterior border of each vertebral body was recorded.Sequential raw cervicothoracic transaxial CT image data of each segment were processed by multiplanar reformation(MPR)in Advantage Workstation 4.2.The data of outer pedicle height(OPH),anterior vertebral body height(a VBH),sagittal Pedicle Angle(s PA),Distance sagittal Intersection Point(Ds IP)of each pedicle were measured on reconstructed sagittal pedicle view.The region where the entry point located in the anterior border of each vertebral body was recorded.The prozone of cervicothoracic junction was devided into three different regions by two lines,and the distribution of the trajectory of sagittal pedicle axis in three regions was recorded.All the data above were processed with the software of SPSS 13.0.Results There was no statistical difference in gender about the OPW,OPH and aVBH.The gender differences about the Dt IP,Ds IP and PAL was statistical significance(P<0.05).From C6 to T2,The Dt IP increased from-0.34 to 4.75 mm.The Ds IP of C6(5.18±1.02mm)was minimum,and the maximal Ds IP was at level T2(9.82±2.28mm).The PAL changed irregularly,from 31.01 to34.21 mm.The difference about the Dt IP and Ds IP of the same sex between each segment has statistical significance(P<0.05).There was no statistical difference in gender about the t PA and s PA of the cervicothoracic junction and the data for male and female patients were merged for analysis.From C6 to T2,The t PA decreased from 46.77°to 20.02°.The sagittal pedicle axis all were to tilt to caudal side.From C6 to T1,the s PA decreased from 18.10°to 14.54°.however,Sagittal pedicle angle of T2(20.62°±5.04°)was largest.The difference between each segment has statistical significance(P<0.05).The sagittal pedicle axis of C6 and C7 all was located in region above the manubrium.The sagittal pedicle axis of T1 was mainly in manubrium region followed by the region above the manubrium.The sagittal pedicle axis of T2 was mainly located in manubrium region followed by the region below the manubrium.There was no statistical significance of the regional distribution between sexes.Conclusion The relevant parameters of anterior transpedicular screw placement on CTJ have some differences among diffirent vertebral levels.Judged from the view of radiography,the ATPS techniques at level C6,C7,and few T1 is feasible through the anterior low cervical approach,while anterior approach fixation involved in level T2 and almost all T1,the anterior low cervical approach is limited by bony obstructions such as manubrium and clavicle.