Quantitative evaluation of the location of the vertebral artery in relation to the transverse foramen in the lower cervical spine

Study Design. This study assessed the relationship of the vertebral artery and the transverse foramens in the lower cervical spine by computer tomographic angiography (CTA) measurements. Objective. To study the location and the size of the vertebral artery in relation to the transverse foramens in the lower cervical spine. Summary of Background Data. Although many transverse foramen violations had been reported during pedicle screw insertion, the vertebral artery injury seems not as much as expected. The location and size of the vertebral artery in relation to the transverse foramen in the lower cervical spine is not very clear until now. Methods. Fifty patients were selected in our study group. Several parameters were measured on the CTA axial imagines of C3-C7, including the maximal width (W) and the maximal height (H) of transverse foramen, the diameter of vertebral artery (AL), the shortest distance between the vertebral artery and the border of transverse foramen medial (M), lateral (L), anterior (A) and posterior (P), the shortest distance between the vertebral artery and pedicle (h), the area of vertebral artery (AVA) and transverse foramen (AF), and the ratio between AVA and AF (AVA/AF). Results. W, H, and AF increase from C3-C6. M is shorter than L at all measurements. A is shorter than P at C3, C4, and C5, a little bit longer than P at C6 on the contrary. The shortest distance between vertebral artery and pedicle (h) vary from C3-C7, the shortest 0.5 +/- 0.2 mm at C3, the longest 7.3 +/- 2.7 mm at C7. AVA/AF decrease from C3-C6, 35.7 +/- 15.7% at C3 and 27.4 +/- 12.8% at C6. Conclusion. Vertebral artery is in the medial part of transverse foramen. There is a relative "abundance space" for vertebral artery in transverse foramen.