Anatomical variations of the foramen transversarium in cervical vertebrae: findings, review of the literature, and clinical significance during cervical spine surgery.

Abstract

To describe certain anatomical variations of the foramen transversarium, in spine cervical vertebrae in a contemporary specimen of an Indo-European population and approach their clinical importance during cervical spine surgery. 102 cervical vertebrae (C2-C7) from 17 different skeletons, intact without any degenerative or traumatic disorders, which belonged to the collection of the Department of Anatomy, were examined. The age of specimens at the time of their death was between 25 and 65years. All foramina were measured with a digital caliper. The average size of the normal foramina was: 6.49mm×5.74mm on the right side and 6.65mm×5.76mm on the left side. Regarding the variations, we found two cervical vertebrae (1.96%), one C3 and one C6, in which the right foramen transversarium is clearly smaller than the left. The exact dimensions of these foramina are: 2.3mm×2.5mm on the right side and 6.54mm×8mm on the left side in the first vertebra and 2.8mm×3.74mm on the right side and 6mm×7.5mm on the left side, in the second one. We also observed double foramina in 14 vertebrae (13.72%). In seven vertebrae, the duplication was bilateral (6.86%). We finally found one vertebra (0.98%) with triplication of the foramen transversarium on the left side. Summarizing, 10 out of our 17 skeletons were presented with variations (extremely narrow or multiple foramina). This finding of hypoplastic, duplicated and triplicated foramina transversaria in unexpectedly high rates raises questions about the integrity of the contained structures, the possibility of a different path for them. These variations may induce an extra-osseous position of the vertebra artery, and the ignorance of such an event may have catastrophic consequences during a surgery in the cervical spine.