Fractures of the dens (odontoid process): A report of 23 cases.

Twenty three patients with natures of the dens admitted into Siriraj Hospital during the past seven year were studied and analysed. Traffic accidents (74%) and fall (22%) caused the majority of the dens fractures. These fractures were classified into three types based on the anatomic location of the fracture line. Three patients with type I (avulsion), 16 patients with type II (involving the body) and 4 patients with type III (basilar) fractures of the dens are reported. Types II fractures appeared to be the most common. They were unstable and easy to displace. Severe hyperflexion and hyperextension during the accidents caused the anterior and posterior fracture–dislocations of the dens respectively. Anterior fracture–dislocations was found to be more frequent. Patients with dens fractures may have less or no neurological deficit. Mach bands can cause confusion in the roentgen diagnosis. Differential diagnosis of the dens fracture should be made from or odontoideum.