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

(ALL = Anterior Longitudinal Ligament)

References

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