Extension teardrop, odontoid and Chance fractures

Rib fractures:

Multiple bilateral rib fractures may indicate severe thoracic trauma.

Fractures of the 1^st-3^rd ribs indicate high energy trauma because a significant amount of force is required to fracture them. Hence, they may be associated with brachial plexus or great vessel injuries¹.

Fractures of the lower three ribs may be associated with liver, spleen and kidney injures.

Flail chest:

This occurs when there are three of more contiguous ribs with fractures in two or more places¹. This creates a flail segment which can move paradoxically relative to the reminder of the chest during respiration.

Hyperextension injuries of the neck:²

Hyperextension of the neck can result in injury to both the osseous and soft tissue structures. Rotational and lateral tilting may occur in addition to hyperextension and result to additional patterns of injury². Hyperextension can result from either a direct contact mechanism (eg impact to the forehead) or a noncontact mechanism (eg unrestrained neck motion in a car accident)².

Hyperextension injuries include a spectrum of injuries ranging from relatively stable to unstable injuries². 

Fracture of the Atlas:

A fracture through the anterior arch is best visualised on sagittal reformats. It results from an avulsion mechanism and is typically a transverse fracture through the inferior pole or mid portion².

The posterior arch can be compressed between the occiput and spinous process of C2 and is typically a vertically orientated fracture². Congenital non fusion can mimic a posterior arch fracture.

Prevertebral soft tissue swelling should always be inspected for.

Fracture of the Axis

- Fracture of the dens

Odontoid fractures are the most common injury of the axis and can result from a variety of mechanisms². They are classified into 3 types. Type II fracture are the most common².

Type I: fracture of the tip of the odontoid

Type II: fracture of the base of the dens. This is an unstable fracture and often requires fixation.

Type III: Involves the dens and body of C2. This fracture is more likely to heal without fixation due to the larger surface area.

Fractures of the odontoid process can be subtle on axial images and fractures are often better visualised on sagittal reformats. An os odontoidum can mimic a fracture.

-Traumatic spondylolisthesis of C2 (Hangman fracture)

This is the second most common fracture of C2 and typically occurs following direct upward impact to the face or chin causing hyperextension, loading the posterior aspect of the axis². This results in bilateral vertically orientated fractures through the pars interarticularis.

Hyperextension teardrop fracture

This is represented by an anteroinferior vertebral body fragment. The triangular shaped fracture fragment represents an avulsion fracture as the anterior longitudinal ligament pulls away from the inferior aspect of the vertebral body² (compared with a flexion teardrop fracture in which the fragment is produced by compression rather than avulsion). 

In elderly patients, C2 is typically involved due to fusion deformities in the lower cervical spine². In younger patients, the lower cervical is more commonly involved². In older patients, less force is required to cause the fracture and hence there is often little soft tissue swelling and no neurologic impairment². In younger patients, a much great degree of force is required and hence central cord syndrome is common (seen in up to 80% of patients)².

Central cord syndrome can occur due to buckling of the ligamentum flava into the spinal canal during hyperextension. The injury is stable in flexion but unstable in extension.

Hyperextension dislocation

In severe hyperextension injury, hyperextension dislocation can occur in which there is momentary posterior dislocation of the involved cervical verterbrae². The anterior longitudinal ligament, annulus, intervertebral disc and ligamentum flavum are disrupted². The posterior longitudinal ligament is also stripped and the paraspinal muscles torn. An osseous component is seen in two-thirds of cases. Neurologic impairment is almost always present².

CT can often underestimate the extent of the injury as the vertebrae can be normally aligned due to immediate realignment following the injury. The presence of diffuse prevertebral soft tissue swelling with normally aligned vertebrae is the most reliable indicator of the injury. There may also be widening of the disk space anteriorly. MRI is indicated to assess for ligamentous and cord injury².

Laminar fracture

Isolated fractures of one or both laminar are common and if isolated are stable fractures². Extension into the adjacent spinous process is common². These fractures can also occur as part of a burst or flexion teardrop. There may be neurological symptoms if fracture fragments are located within the spinal canal.

Hyperextension-Rotation injuries

Simultaneous hyperextension and lateral tilting typically results in an oblique or vertical fracture through the articular pillar². This may extend into the adjacent structures including the facets and transverse foramen². Separation of the articular pillar is an unstable injury.

Nasal bone fractures:

Nasal bone fractures can occur in isolation or be associated with other facial fractures. They can easily be overlooked if not actively assessed for and hence are frequently missed.  The nasal septum must be checked as the presence of a septal haematoma may require treatment to avoid complications.

Naso-orbitalethmoid factures are more complex, involving the nasal bones as well as the central upper midface.

The teardrop fragment comes from the anteroinferior aspect of the vertebral body in both types. However in the flexion type, there is posterior displacement of the larger part of the vertebral body which can result in spinal cord injury. In extension tear drop fractures, the neck is stable when flexed but unstable in extension. However, in young patients, a high degree of trauma is required to produce this injury and hence spinal cord injury is common.