A Study On The Angles Of The Free Hand Pedicle Screw Placement And The Adjacent Anatomic Landmarkers In The Sagittal Plane Of The Pedicle Of The Cervicothoracic Segments

[Objective]:To find a new placement technique for cervicothoracic spine(C6-T6)operation pedicle screw on sagittal screw angle(Sagittal Srew Angle,SSA)by measuring the angle between the different anatomic landmarks and between the plane of the upper vertebral end-plate.[Methods]:Sixty cases(thirty males and thirty females)of normal adult human cervicothoracic segments(C6-T6)computer tomography were obtained for study,and the angle between the plane of the upper vertebral end-plate and the line between vertex of spinous process and the upper one(method one);and the lower one(method two);the superior margin line of spinous process(method three);the left vertebral laminae plane of the same spine(method four);the right vertebral laminae plane of the same spine(method five)were measured respectively.We choose one or several methods as a new placement technique for cervicothoracic spine operation(C6-T6)pedicle screw on sagittal screw angle by measuring the reference values of each method in C6-T6 and comparing the pros and cons of different methods.[Results]:The angle between the plane of the upper vertebral end-plate and the line between vertex of spinous process and adjacent ones was 100° to 110°with a great deal of deviation in C6 to C7,and from T1 to T6,the angle was approaching 90° with less deviation;the angle between the plane of the upper vertebral end-plate and the left vertebral laminae plane was decreasing gradually from C6 to T6;as well as the angle between the plane of the upper vertebral end-plate and the vertebral laminae plane was 90° that was vertical position.[Conclusion]:If the angle of pedicle screw agianst vertebral laminae plane is about 90° at C6 to T6,the sagittal srew angle is 0°,vertebral laminae plane can be the identification marker for cervicothoracic spine(C6-T6)operation pedicle screw on sagittal screw angle.