C1 and C2 Spine Fractures

Author: Michelle Lin, MD
Updated: 9/24/2010

Fractures, C1 and C2 Spine

Atlanto-occipital dislocation

Mechanism Stable
Flexion No
  • Often instantly fatal
  • More common in children because small horizontally-oriented occipital condyles
  • Dislocation can be anterior (most common), superiorly distracted, or posterior

Anterior atlantoaxial dislocation

Mechanism Stable
Flexion No
  • Associated with transverse ligament rupture
  • Most commonly occurs in patients with rheumatoid arthritis and ankylosing spondylitis from ligament laxity
  • Widening of predental space seen on lateral plain film

Jefferson fracture = C1 burst fracture

Mechanism Stable
Axial Compression No
  • 33% with associated C2 fracture
  • Low incidence of neurologic injury because of wide C1 spinal canal
  • Usually involves fractures of both the anterior and posterior C1 arches, often with 3 or 4 fracture fragments
  • Complication: transverse ligament rupture, especially if C1 lateral masses are ≥7 mm wider than expected (MRI recommended)
  • Complication: vertebral artery injury (CT angiography recommended)

C1 posterior arch fracture

Mechanism Stable
Extension Yes
  • An associated C2 fracture (occurs 50% of time) makes the posterior arch fracture unstable
  • On plain films, no displacement of lateral masses on the odontoid view and no prevertebral soft tissue swelling, unlike Jefferson burst fracture

C2 dens fracture

Mechanism Stable
Flexion +/-
  • Type I (stable): Avulsion of dens with intact transverse ligament
  • Type II (unstable): Fracture at base of dens; 10% have an associated rupture of the transverse ligament-- MRI provides definitive diagnosis of ligament rupture
  • Type III (stable): Fracture of dens extending into vertebral body

Hangman's fracture = C2 spondylolisthesis

Mechanism Stable
Extension No
  • Bilateral C2 pedicle fractures
  • At risk for disruption of the posterior longitudinal ligament (PLL), C2 anterior subuxation, and C2-C3 disk rupture
  • Low risk for spinal cord injury because of C2 anterior subluxation, which widens spinal canal

Extension teardrop fracture

Mechanism Stable
Extension No
  • Small triangular avulsion of anteroinferior vertebral body, at insertion point of anterior longitudinal ligament
  • Occurs most frequently at C2 level, but can occur in lower cervical spine
  • Complication: Central cord syndrome due to ligamentum flavum buckling during hyperextension
  • Requires CT differentiation from very unstable flexion teardrop fracture

C1-C2 fracture diagram

(ALL = Anterior Longitudinal Ligament)


  • Lin M and Mahadevan S. "Spine and Spinal Cord Injuries" in Adams J et al (eds), Emergency Medicine. New York: Elsevier, 2007. [Source]