Relationship between odontoid fracture angle and cervical sagittal balance

Fractures can occur in various locations within the odontoid process with differing orientations. However, little is known about what factors contribute to the anterior versus posterior angles/orientation of these fractures.

We evaluated 74 patients with odontoid fractures (2013-2018) from a single-institution. Patients' fracture angles/orientations were measured on computed tomography studies, and were grouped into oblique posterior (OP) or oblique anterior (OA) groups. We also took into account cervical sagittal balance utilizing upright x-rays. Other variables studied included patients' ages, sagittal balance measurements, and the mechanisms of injury.

Fracture angles were significantly steeper in the OP group. OP fractures had larger C2-C7 sagittal vertical axis, occiput-C2 angles, and occiput-C7 angles versus anteriorly oriented fractures. In our linear regression model, advanced age and large occiput-C2 angles were predictive of the odontoid fracture angle. Patients who sustained ground-level falls also had significantly steeper fracture angles versus those involved in motor vehicle accidents.

The odontoid tends to fracture at a steep, posterior angle in elderly patients who demonstrate a large positive sagittal balance when the head is extended following a ground-level falls.