Dens Fractures: A Review

Radiology Corner

Dens Fractures: A Review

Alicia M. Yochum RN, DC, DACBR, RMSK

Published: March 2017

Journal of the Academy of Chiropractic Orthopedists

March 2017, Volume 14, Issue 1

This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The article copyright belongs to the author and the Academy of Chiropractic Orthopedists and is available at: © 2017 Yochum and the Academy of Chiropractic Orthopedists.

Figure 1: Horizontal fracture through the base of the dens (arrow). Note the lateral tilt of the dens >5° indicating the underlying fracture.

A dens fracture has also been termed an odontoid process fracture or a peg fracture. This fracture can occur in both flexion or extension with or without axial loading. It is a common fracture, which makes up approximately 40- 50% of axis fractures. Up to 30% of dens fractures will be associated with other fractures in the cervical spine therefore careful evaluation of the entire cervical spine is indicated when a dens fracture is present.

Radiographic signs that would indicate dens fracture include a fracture line, displacement, enlargement of the C2 body, lateral tilting of the odontoid process > 5°, alteration in the posterior cervical line, and enlargement of the retropharyngeal soft tissues (retropharyngeal swelling). If there is suspicion for a dens fracture without clear evidence on plain film radiography, a computed tomography (CT) examination can be performed to better evaluate the fracture line. Magnetic resonance imaging (MRI) may also be beneficial to evaluate the integrity of the spinal cord. An MRI should be performed if there are symptoms of spinal cord compression or a upper motor neuron lesion on clinical examination.

The classification system that is most commonly used for dens fractures is called the Anderson and D’Alonso classification. This classification system is based on the location of the fracture and is divided into three types.

The type I dens fractures include the uppermost part of the dens. It has been considered a form of avulsion fracture due to the attachment of the alar ligament in this location. It is usually considered a stable fracture and is the least common form of dens fracture. The appropriate treatment for this type of injury, if isolated, is immobilization.

A type II dens fracture is the most common type of odontoid process fracture. It occurs at the base of the dens at its junction with the axis (Figure 1). This type of fracture has a very high risk of non-union due to the reduced blood flow to the fracture fragment. The type II dens fracture is considered unstable and patients should undergo surgical stabilization when there is displacement (> 5 mm) which reduces the possibility of non-union. If there is no displacement, halo immobilization can be used for treatment.

The type III dens fracture occurs through the dens but also includes a portion of the lateral masses of the axis. This type of the fracture has the best prognosis for healing because of the larger surface area of the fracture in the lateral masses. This fracture is usually stable if there is minimal displacement and treatment would include immobilization. There is no need for surgical intervention in most cases.