Computed Tomography-Based Morphometric Analysis of the Odontoid Groove: An Indirect Marker for Transverse Atlantal Ligament Location

The transverse atlantes ligament (TAL) is a principal stabilizer of the atlantoaxial complex. The odontoid groove, a cortical imprint on the posterior surface of the dens formed by the TAL, may serve as an anatomical marker of its location on computed tomography (CT) imaging. This study evaluated the incidence of the odontoid groove and its concordance with commonly used C1 reference landmarks. In this retrospective morphometric study, thin-slice cervical spine CT scans of adult trauma patients (18–60 years) without C1 to C2 injury or craniovertebral anomalies were analyzed. The groove center (point C) was assessed relative to the inferior margin of the anterior C1 arch (L1) and the combined inferior margins of the anterior and posterior arches (L2). Proportions were expressed with 95% confidence intervals (CI), and nonparametric tests were applied where appropriate. Fifty patients (median age: 30.5 years; interquartile range: 18; 74% male) were included. The odontoid groove was identified in 39 of 50 patients (78%; 95% CI: 63.7–88.9%). Groove presence was associated with higher age (p = 0.018) but not with gender (p = 0.14). L1 did not coincide with the groove in any case (0%; 95% CI: 0–9.0%), lying above in 64.1% and below in 35.9%. L2 coincided in 17.9% (95% CI: 7.5–33.5%), with substantial positional variability. Although the odontoid groove is identifiable in most adults. The anatomical relationship of odontoid groove center and the anterior C1 landmarks was found to be nonconcordant. Atlas-based reference lines may not reliably represent the TAL footprint on CT, warranting cautious interpretation during odontoid fracture evaluation.