Hyperextension tear drop fracture:
Stable hyperextension fracture
Vertical diameter greater than transverse diameter indicates tear drop injury rather than hyperextension-dislocation
Hyperextension-dislocation:
Hyperextension unstable injury
Due to disruption of ALL, annulus, disk, ligamentum flavum, PLL, paraspinal muscles
Anteroinferior endplate fracture is seen in 2/3 cases
Plain film usually underestimates the severity of injury. Diffuse prevertebral soft tissue swelling with normal alignment is most important clue for this injury. Transverse diameter is greater than vertical diameter suggests hyperextension dislocation rather than extension tear drop fracture
Wide anterior disk space with vacuum may be seen
MR is indicated
Hyperextension-rotation injury (articular pillar fracture):
Oblique/vertical practure through articular pillar with or without comminution with facets, transverse foramina, pedicles or laminae
Isolated pillar fracture is neuologically stable, but mechanical unstable due to injury to ALL and PLL, interspinous ligament, facet capsule
Poorly seen on plain films; on lateral view, double outline sign may be seen due to posterior displacement of fracture fragment
CT indicated
MR evaluates ligamentous disruption seen as increased signal in facet capsule and ligamentous structures on T2 is consistent
Pediculolaminar fracture-seperation:
Unstable injury with high prevelance of neurological deficits
Type of hyperextension-rotation injury, also seen in hyperflexion-rotation injuries
Results in pedicolaminar fragment
CT indicated
Laminar fracture:
Uncommon hyperextension injury
Associated with spinous process fractures, burst fracture, pedicolaminar fracture-separation, flexion teardrop fracture
Isolated ones are mechanically stable, but neurologically may be unstable
CT indicated
References:
Rao SK et al. Spectrum of Imaging Findings in Hyperextension Injuries of the Neck. RadioGraphics 2005;25:1239-1254
