Osseous and vascular anatomical variations within the C1-C2 complex: a radiographical study using computed tomography angiography.

Background: One of the limiting factors of C1-C2 fixation is the location of the vertebral artery (VA). The authors sought to assess the potential variations in atlanto-axial VA anatomy using computed tomography angiography (CTA).
Methods: Detailed measurements were made on digital images of 106 patients undergoing CTA at our institution (54 males, 52 females; mean age 56, range 20-86). Distances, diameters and angles of osseous and vascular elements of the atlanto-axial complex were measured.
Results: Optimal C1 and C2 screw trajectories demonstrated wide variations among patients. The size of the VA groove or foramen was not predictive of exact arterial location or size.
Conclusions: The size, location and path of the VA cannot be precisely predicted by the appearance of osseous structures such as the transverse foramina and/or the VA groove. CTA provides additional information regarding the atlanto-axial complex, and should be considered as a useful adjunct in the preoperative evaluation of select patients.
((c) 2008 John Wiley & Sons, Ltd.)