Original ArticleAnatomical Study of the Posterior Ascending Artery: Application to C2 Pedicle Screw Placement
Introduction
The dens has a rich blood supply.1 The sources of this blood supply include an anterior and posterior ascending artery (PAA) arising from the C2-C3 intervertebral level of the vertebral artery,2 a branch of the ascending pharyngeal artery that traverses the hypoglossal canal, and a pair of transverse arteries arising from the ascending pharyngeal artery.3, 4, 5 Of these, the PAA ascends through the vertebral canal posterior to the transverse and alar ligaments3 and forms an arterial arcade with the transverse arteries over the apex of the dens.3 Akobo et al,5 Althoff and Goldie,4 and Haffajee3 have depicted the PAA in their reports but have not described its detailed anatomy.
The PAA has been briefly discussed in regard to fractures of the dens.2, 4, 6, 7 As previous studies have not studied the PAA in detail and looked at its detailed anatomic relationships with nearby structures such as the alar ligaments, the present study was warranted.
Section snippets
Materials and Methods
Ten sides from 5 Caucasian cadaveric heads were used in this study. Red latex was injected into the common carotid arteries of all heads. The specimens were derived from 5 males, and the age at death ranged from 61–93 years old (with a mean of 77.6 ± 11.7 years old).
The cervical vertebrae (from C1 to C5) and small part of the occipital bone including the foramen magnum and its basilar part were removed en bloc from the head, and then the spinous processes were removed. The dura mater and spinal
Results
The PAA was identified on both sides in all specimens. The origin of the PAA was from the vertebral artery at the level between C2 and C3 on all sides (Figure 2). The PAA traveled posterior to the transverse and alar ligaments and formed the apical arcade above the apex of the dens in all specimens (Figure 3). The small branch given off from the arcade entered the hypoglossal canal on all sides (Figure 4). The number of medial and lateral branches ranged from 3–6 (mean of 3.7) and 2–3 (mean of
Discussion
Development of new surgical procedures for the cervical spine requires more detailed anatomic knowledge of cervical vertebrae and nearby neurovascular structures.8, 9 The dens receives its blood supply anteriorly, posteriorly, and superiorly. The PAA is one of these blood vessels. The importance of the PAA is its contribution to the apical arcade and thus blood supply to the dens. For this reason, from the clinical perspective, the PAA might affect healing of fractures of the dens.1, 3, 4
Conclusions
The morphometrics of the posterior ascending branch of the vertebral artery were examined. The diameter was approximately 1 mm on average, and it was located approximately 7 mm from the midline on average. The wrong trajectory of C2 pedicle screws could damage this artery if the spinal canal is partially entered. Therefore spine surgeons should be aware of this structure in the vertebral canal.
Acknowledgments
The author thanks those who donated their bodies for anatomic research.
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Conflict of interest statement: The authors have no conflict of interest to declare.