Background: The arcuate foramen is an important osseous anomaly of
the first cervical vertebra (the atlas) that must be taken into consideration
during placement of lateral mass screws into the atlas.
Methods: The prevalence of this anomaly in our patient population
was determined through a retrospective review of 464 lateral radiographs of
the neck. The anatomy of the arcuate foramen was identified in a study of
cadavers.
Results: Seventy-two arcuate foramina, complete or incomplete, were
identified on the 464 lateral radiographs of the neck; thus, the prevalence
was 15.5% in our patient population.
Conclusions: Although the arcuate foramen is a common anomaly, it is
often not recognized. Proper identification of this anomaly on preoperative
lateral radiographs should alert the surgeon to avoid using the ponticulus
posticus as a starting point for a lateral mass screw in order to not injure
the vertebral artery.
Level of Evidence: Diagnostic Level IV. See Instructions
to Authors for a complete description of levels of evidence.