Fractures and Dislocations: Dens

Fractures of the dens are commonly classified into 3 types with type II being the most common:

• TYPE 1 - Avulsion fracture of the tip. It is considered stable, but may represent detachment of the alar ligament (atlanto-occipital disassociation). Rare.
• TYPE II -   Fracture at base of ondontoid (poor blood supply kind of like scaphoid, non-union in 65%). Most Common. Poor blood supply. Unstable.
• TYPE III -  Fracture through  base of ondontoid into body of axis: (best prognosis for healing, but unstable.

Anterior tilt of ondontoid on lateral view is highly suspicious for fracture. 

Prevertebral soft tissue swelling may be the only sign.              

Bureau of Medicine and Surgery
Department of the Navy
2300 E Street NW
Washington, D.C
20372-5300

Operational Medicine
 Health Care in Military Settings
CAPT Michael John Hughey, MC, USNR
NAVMED P-5139
  January 1, 2001