Abstract
Purpose
When C1 arch displaced laterally in C1 bursting fracture, anatomical change between displaced bone and surrounding neurovascular structures can make placing C1 screw more challenging. This study was to describe the effect of the C1 bursting fracture on the location of the internal carotid artery (ICA) around the atlas.
Methods
The authors analyzed the morphology of the atlas and the ICA in 15 patients with C1 bursting fracture and compared the anatomical parameters with control group (77 patients) without any bone fractures or pathologies. All patients were evaluated with CT angiography for the assessment of anatomical parameter. The laterality of the ICA was classified into the following four groups: group 1 (lateral to the C1 lateral mass), group 2 (lateral half of the lateral mass), group 3 (medial half of the lateral mass), and group 4 (medial to the lateral mass). The distances of the ICA from the midline, anterior tubercle, and ventral surface of the C1 lateral mass were compared between two groups. The distance between the lateral margin of the longus capitis muscle and the inner edge of the transverse foramen was also measured.
Results
Medially located ICA (laterality groups 2 and 3) was more common in the C1 bursting fracture group than control group (76.7 vs. 42.8%). There were no significant differences between two groups for the distance from the midline, the distance from the anterior tubercle, and the distance from the ventral surface of the C1 lateral mass, respectively. The distance of the longus capitis muscle to transverse foramen was 2.52 ± 2.09 and 4.15 ± 3.09 mm in each group, and there was statistically significant difference (p < 0.01).
Conclusion
Lateral displacement of the bony structure of C1 bursting fracture changes the relative location of the ICA medially, which increase the injury risk during the bicortical C1 screw insertion. These data suggest that CT angiography or enhanced CT scans may be essential study for C1 bursting fracture. These preoperative imaging studies can give information to choose the ideal fixation technique and the proper trajectory of the screws.