Pedicle screw fixation of the cervical spine: guidance by computed tomography

This is an anatomic, preclinical study using computed tomography and computerized simulation to describe the morphologic features and ideal screw insertion trajectories for cervical pedicles in the southern Chinese population. The morphologic features of the pedicle of vertebrae (C3-C7) from 20 human cadaver spines were evaluated with computed tomography and with manual measurements. There was no difference between the two data sets. The topography of the cervical pedicles was recreated graphically, calculating the safe range of the insertion angle with and without consideration of the pedicle screw diameter. Neglecting the diameter of the screw, the average safe ranges of the insertion angle at each cervical level (C3-C7) in the transverse plane were 18.7 degrees , 20.4 degrees , 22.4 degrees , 22.5 degrees , and 27.6 degrees , respectively, and in the sagittal plane 27.6 degrees , 30.3 degrees , 27.7 degrees , 29.0 degrees , and 34.9 degrees , respectively. Including the diameter of the 3.0-mm screw, the safe ranges narrowed to 7.3 degrees , 8.6 degrees , 11.0 degrees , 13.1 degrees , and 15.5 degrees in the transverse plane, and 16.4 degrees , 18.7 degrees , 16.4 degrees , 18.3 degrees , and 23.1 degrees in the sagittal plane. We think computed tomography measurements can provide individual quantitative data for transpedicle screw fixation in the cervical spine.