Background: Traumatic upper cervical spine leads to instability and neurological deficit. At
present, C2 (axis) pedicle or lamina screws for fixation are popular because further
external immobilization is not needed. However, these techniques demand experience
inserting the screws and carry the risk of vertebral artery or spinal cord injury.
In some patients, the C2 screws cannot be inserted because of limited C2 size. Objective: To determine the width, length, height, and angle in the C2 pedicle and lamina in
the Thai population. Materials and Methods: Patient data were collected from the Picture Archiving and Communication System at
the Faculty of Medicine, Prince of Songkla University from January 2016 to December
2017. The C2 parameters, i.e., width, length, height, and angle of the pedicle and
lamina were recorded. Results: The CT C-spine scans of 270 patients were enrolled. The mean Thai C2 pedicle dimensions
were width 5.51 mm, length 23.78 mm, angle 39.04°, and height 8.64 mm. The mean C2
lamina dimensions were width 5.88 mm, length 32.17 mm, angle 49.46°, and height 12.27
mm. Twenty-four patients from the 270 patients (8.8%) had a pedicle width <3.5 mm
but all patients had a lamina width ≥3.5 mm. Conclusion: In the Thai samples, 8.8% had a C2 pedicle width <3.5 mm which would not allow insertion
of screws; however, they could be replaced with lamina screws since the lamina width
was ≥3.5 mm. In this study, all of the patients who could not be inserted pedicle
can be replaced with lamina screws inserted.
Key-words:
Axis - lamina - morphometry - pedicle
