Adontoid peg fractures:
Account for more than half of C2 fractures
Hyperextension injury
Type 1: rare, tip of dens (attachment of alar ligament)
Type 2: most common, transverse fracture through base of dens, high incidence of non-union (50%)
Type 3: horizontal fracture through superior body of C2, good prognosis.
Open mouth views depict these fractures. Prevertebral soft tissue swelling is seen in 2 & 3 fractures. Ddisruption of C2 ring on lateral view is suggestive of type 3 fracture
CT is indicated in all fractures for assessment of displacements
Hangman's fracture (traumatic spondylolisthesis):
2nd most common C2 fracture (25%)
Unstable hyperextension injury with prdominant loading on the posterior aspect
Vertical fractures through both pars interarticularis
Severe injury indicators are wide C2-3 space and bilateral interfacetal dislocation
CT indicated
Hyperextension teardrop fracture of C2:
Triangular avulsion fracture from anteroinferior aspect of C2
Due to avulsion of anterior longitudinal ligament from anterior aspect of inferior endplate
Common in porosis
Little or no soft tissue swelling
Stable fracture
References:
Rao SK et al. Spectrum of Imaging Findings in Hyperextension Injuries of the Neck. RadioGraphics 2005;25:1239-1254
