Disruption of the neural arch of the axis predominately affects the narrow zone of the pars interarticularis and may be associated with more complex soft tissue injuries.
Injuries to this structure are popularly known as hangman’s fracture.
The term hangman’s fracture originally referred to neck injuries incurred during the hanging of criminals. The most common cause of hangman’s fracture now is a motor vehicle accident with hyperextension of the head on the neck. The occiput is forced down against the posterior arch of the atlas, which is forced against the pedicles of C2.
Hangman’s fractures are the second most common type of axis injuries after odontoid fractures.
A classification of these injuries has been given by Effendi et al. was later modified.
Type I Fractures
Type I fractures are minimally displaced and are believed to be caused by hyperextension and axial loading with failure of the neural arch in tension. Because ligamentous injury is minimal, these fractures are stable.
Atypical fractures that are obliquely displaced are unstable fractures.
Type II Fractures
Type II fractures have more than 3 mm of anterior translation and significant angulation. These injuries result from hyperextension and axial loading that cause the neural arch to fail with a predominantly vertical fracture line, followed by significant flexion resulting in stretching of the posterior anulus of the disc and significant anterior translation and angulation.
The C2-3 disc may be disrupted by the sudden flexion component involved in this injury.
A subtype Type IIa is unstable due to their associated C2–3 disc and interspinous ligament disruption.
Type III Fractures
Type III injuries are relatively rare and constitute a complete unilateral or bilateral C2–3 facet dislocation. A C2–3 dislocation is highly unstable and cannot be expected to be reducible by nonsurgical means
The instability of a traumatic spondylolisthesis of the axis largely hinges on the integrity of the C2–3 discoligamentous elements. These fractures frequently are associated with neurological deficits
The assessment of instability is determined by the amount of sagittal C2–3 translation, and angulation between the end plates and is then assigned to one of five categories
- Grade I – Translation < 3.5 mm, angulation < 11 degrees.
- Grade II- Translation< 3.5-mm , > 11 degrees of kyphosis.
- Grade III – Translation >3.5-mm, <than 11 degrees of kyphosis.
- Grade IV – >3.5-mm translation, >11 degrees of angulation.
- Grade V- Complete disc disruptions.
Treatment
Type I fractures usually heal with 12 weeks of immobilization in a rigid cervical orthosis.
For type II treatment consists of application of skull traction through tongs or a halo ring with slight extension of the neck over a rolled-up towel for 3 to 6 weeks to maintain anatomical reduction. The patient can be mobilized in a halo vest for up to 3-month period.
These fractures usually unite with an initial gap in the neural arch and develop a spontaneous anterior fusion at C2-3
Type IIA fractures are a variant of type II fractures that show severe angulation between C2 and C3 with minimal translation.
They usually have a more horizontal than vertical fracture line through the C2 arch. The recommended treatment is application of a halo vest with slight compression applied under image intensification to achieve and maintain anatomical reduction.
When reduction has been obtained, halo vest immobilization is continued for 12 weeks until union occurs.
Type III injuries usually have severe angulation and translation of the neural arch fracture and an associated unilateral or bilateral facet dislocation at C2-3. Type III injuries are the only type of hangman’s fracture that commonly require surgical stabilization.
Open reduction and internal fixation usually are required because of inability to obtain or maintain reduction of the C2-3 facet dislocation.
After posterior cervical fusion at the C2-3 level, halo vest immobilization for 3 months is necessary for the bipedicular fracture and for consolidation of the fusion mass.
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