Introduction: A precise anatomical description of the alar ligaments is important to better understand their biomechanical and pathological implications. Although there are several studies regarding their anatomy, the literature is inconsistent. To our knowledge there are no reports comparing cadaveric morphologic findings with CT images of the alar ligaments.

Methods: Eight sides from four fresh frozen cadaveric specimens were used in this study. Following routine dissection of the craniocervical junction the alar ligaments were exposed. We carried out measurements of the alar ligaments, their position within the CVJ and their relation to the dens and adjacent structures. Fine cut CT of the specimens were performed and the measurements were later compared to the original cadaveric dissections.

Results: Alar ligaments were attached to the upper half of the lateral surface of the dens and ran laterally to its insertion just medial to the occipital condyle. The ligaments were found to have an ovoid cross-sectional area with a nearly horizontal caudo-cranial trajectory and comparable diameters in both anteroposterior and superoinferior directions between the CT and cadaveric measurements.

Conclusions: There were small but not statistically significant differences in the measurements between the cadaver specimens and the CT images. There was however, a strong correlation between the proximal and distal insertions, as well as the orientation of the fibers that suggests CT images can be an appropriate approach to the study of the anatomical and three-dimensional features of the alar ligaments.

Patient Care: A detailed anatomic description of the alar ligaments that includes their insertions and relationships to adjacent structures will allow for a better understanding of their biomechanical and pathological implications regarding traumatic lesions and craniovertebral junction pathology. We observed an adequate correlation between morphologic measurements and CT images of the alar ligaments, which proves this study modality to be an accurate diagnostic tool for pathologies involving the alar ligaments.

Learning Objectives: By the conclusion of this session, participants should be able to comprehend in detail the anatomy and relationships of the alar ligaments and their morphologic correlation with CT images. Also they should be able to acknowledge the usefulness of CT images as an appropriate approach to the study of the anatomical and three-dimensional features of the alar ligaments. Finally, it should open a window for further studies regarding the biomechanical implications of the alar ligaments in cranio-cervical junction pathologies.

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