The Alar Ligaments: A Cadaveric and Radiologic Comparison Study.

OBJECTIVE:A precise anatomical description of the alar ligaments is important to better understand their biomechanical and pathologic implications. Although there are several studies regarding their anatomy, the literature is inconsistent. To our knowledge, there are no reports that compare cadaveric morphologic findings with computed tomography (CT) images of the alar ligaments. METHODS:Eight sides from 4 fresh-frozen cadaveric specimens were used in this study. After routine dissection of the craniocervical junction, the alar ligaments were exposed. We carried out measurements of the alar ligaments, their position within the craniovertebral junction, and their relation to the dens and adjacent structures. Fine-cut CT of the specimens was performed, and the measurements were later compared with 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 caudocranial 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 3-dimensional features of the alar ligaments.