Odontoid (C2) fracture, also known as a dens fracture, accounts for 10% to 15% of all cervical fractures. The most common mechanism of injury is blunt force trauma to the head causing cervical hyperextension or hyperflexion. Odontoid fractures are often missed in the elderly, as fractures can occur after a simple fall. The Anderson and D’Alonzo classification system uses the anatomical location of the fracture line to classify odontoid fractures into three types. Type I is an avulsion fracture off the tip of the odontoid process representing an alar ligament avulsion, type II is a fracture through the waist of the odontoid, and type III is a fracture extending into the vertebral body and C1-C2 articulation.1,2

Most type I and III fractures can be managed with external immobilization, while treatment for type II fractures remains controversial. The waist of the odontoid has a limited blood supply and less trabecular bone, which causes type II fractures to have more trouble healing. Patients prone to nonunion (elderly, smokers, etc) are generally treated with surgery. Patients with no neurologic deficits and less than 5 mm of displacement may be treated conservatively with collar immobilization (Philadelphia collar) or a halo vest. A collar has fewer complications and equal union rates compared with a halo vest and therefore is generally the preferable nonoperative treatment. Relative indications for surgical treatment include advanced age (older than age 50 years), posterior fracture displacement greater than 5 mm, fracture comminution, or history of tobacco use.1,2

Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor-in-chief of the Journal of Orthopedics for Physician Assistants (JOPA).


  1. Hsu WK, Anderson PA. Odontoid fractures: update on management. J Am Acad Orthop Surg. 2010;18:383-394.
  2. Moore D. Odontoid fracture. Ortho Bullets. https://www.orthobullets.com/spine/2016/odontoid-fracture-adult-and-pediatric. Accessed October 24, 2017. 
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