Original articleTraumatic Injuries of the C1/C2 Complex: Computed Tomographic Imaging Appearances
Section snippets
Embryology and Anatomy of the Atlantoaxial Complex
In utero, the vertebral column develops as a series of hyaline cartilaginous rings from the mesodermal tissue lying adjacent to the notochord. Centers of ossification develop in each lateral mass of the atlas in the seventh fetal week. From each lateral mass, ossification extends into the posterior arch and the ossification centers unite in the midline at 4 years of age. A third ossification center develops in the anterior arch of the atlas in the first year of life which fuses with each
Atlas Fractures
Fractures of the atlas account for 2 to 13% of cervical spine fractures and are generally not associated with neurological deficit.1 C1 fractures are frequently associated with fractures elsewhere in the cervical spine particularly at the C2 and C7 levels.3 A variety of fracture patterns of the atlas have been described by Levine and coworkers and Gehweiler and coworkers (Table 1).1, 4, 5 Gehweiler and coworkers classified C1 fractures into five types including fractures of the anterior arch,
Axis Fractures
There are a variety of fracture patterns encountered at C2. The most common injury is fracture of the odontoid process, which accounts for approximately 55% of axis fractures.16
Summary
The wide range of C1/C2 complex injuries is described. The common posterior arch fracture of the atlas, the well-described Jefferson and Hangman’s fractures, odontoid peg fractures, and rarer injuries including atlantoaxial rotatory fixation and Plough fracture are discussed. The appearance of anomalies and fractures, in particular, posterior arch clefts of the atlas, is compared.
The key points are as follows:
- 1
The C1/C2 complex produces a variety of injury patterns, most of which are not seen
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