Morphometric Study of the Cervical Spinal Canal Content and the Vertebral Artery

Background: The morphological features of the cervical spinal nerves (C1-C8), their dimensions, and their anatomical relations with the vertebral artery are important for safe spinal surgery. The aim of the present study is to give detailed morphological data of the region to avoid complications. Methods: Five formalin-fixed adult cadavers were studied. The cervical spinal nerves and the vertebral artery were exposed via the posterior approach, and detailed anatomy and morphometric measurements were evaluated. The following measurements were documented: angles between the spinal nerve and the spinal cord of C1 to C8, width of the C1 to C8 spinal nerves at their origin, distance of the spinal cord to the vertebral artery, number of dorsal rootlets, length of the dorsal root entry zone of C1 to C8, and distance between respective spinal nerves. Further, the average length and width of the transverse foramen were measured. Results: The average angle between the spinal cord and the spinal nerve within the vertebral canal ranged between 54 and 87 degrees and were most acute at C5 (54 degrees) compared to the rest of the cervical spinal nerves. The average width of the spinal nerves (mean +/- SD), was thickest at C5 (5.7 +/- 1.2 mm) and C6 (5.8 +/- 0.7 mm). The average largest distance between the vertebral artery and the spinal cord was at C2 (14.3 +/- 1.7 mm) and the smallest at C5 (7.3 +/- 0.9 mm) and C6 (7.3 +/- 2.2 mm) spinal levels. The number of dorsal rootlets was most numerous at C6 (8.25 +/- 0.6) and C7 (7.25 +/- 0.9). The dorsal root entry zone length was the largest at C5 (13.0 +/- 1.6 mm) and C6 (13.75 +/- 0.5 mm). The distance between respective spinal nerves was largest between C2 and C3 (11.8 +/- 2.2) and C7 and C8 (11.5 +/- 0.6). Conclusion: The knowledge of detailed anatomy of the cervical spine (C1-C8) and its relations with the vertebral artery will reduce the unwanted damage to the vital structures of the region.