Occurrence of comminution (type IIA) in type II odontoid process fractures: a multi-slice CT study.

The classification of odontoid process fractures introduced by Anderson and D'Alonzo in 1974 has gained wide acceptance among researchers and clinicians. In type II fractures the injury is located in the base of the odontoid process. In 1988 Hadley et al. introduced a comminuted subtype of this fracture, type IIA. Since then several authors have recommended a more aggressive surgical approach in treatment of this subtype. However, only a few cases of comminuted type II fractures have been reported. The objective of this study is to assess the occurrence of comminution in type II fractures. Twenty-six type II fractures imaged by multislice CT were reviewed. Subtle comminution of the fracture was observed in 12 of the cases. We conclude that, when imaged by multislice CT, subtle comminution in type II odontoid fractures is seen more commonly than previously reported in the literature.