This case demonstrates a type 2 odontoid process fracture, a transverse fracture through the base of the dens and represents the most common type of dens fracture. It can be caused by either hyper-flexion or hyperextension mechanisms of injury. Important prognostic factors for fracture healing (union versus non-union) are the degree of fracture fragment displacement and angulation. These fractures are at higher risk of displacement and angulation (in comparison to the type 1 and 3 subtypes) due to distractive forces from the ligamentous attachment of apical and alar ligaments to the proximal fragment. Management of this fracture type can be non-operative (with a halo-thoracic vest) or operative (posterior atlantoaxial arthrodesis or anterior screw fixation).
A type I odontoid fracture involves the tip of the dens. This is the point of insertion for the alar ligaments. This fracture is therefore described as an oblique avulsion fracture of the tip of odontoid resulting from avulsion of the alar ligament. This is the least common type of odontoid fracture and is generally stable. Management comprises of conservative measures with external immobilization using a hard cervical collar. There is a very low incidence of non-union, and surgery is seldom indicated for these fractures
A Type III odontoid fracture is characterized by a horizontal fracture through the odontoid with extension into the lateral masses of C2. This fracture is considered mechanically unstable, as it allows the atlas and the occiput to now move together as once unit and independent of the rest of the cervical column. This fracture type has the best prognosis for healing because of the larger surface area of the fracture. Successful treatment options include external immobilization with either a hard cervical collar or halo-thoracic vest, or operative management through anterior/posterior fusion techniques.
Conventional radiography is frequently firstly used as it is generally readily available, with measurements of fracture displacement and angulation that can be made on lateral cervical views. CT is considered a superior modality for fracture visualization and characterization. Furthermore, as odontoid fractures are in the axial plane, CT allows coronal and sagittal reformatting for better depiction. MRI is used for evaluation of ligamentous, disk, spinal cord and soft tissue injuries.
Case courtesy of Associated Professor Pramit Phal