Residency · Residency · Diagnostic Radiology
Cervical Spine Trauma: Fracture Classification and Stability
Introduction
Cervical spine injuries occur in approximately 2-3% of blunt trauma patients and carry the risk of devastating neurological consequences if unstable fractures are missed. CT of the cervical spine has replaced plain radiography as the primary screening tool in moderate- and high-risk trauma patients. The radiologist must recognize fracture patterns, classify them according to established systems, and determine stability to guide clinical management.
Imaging Approach
Clinical Decision Rules
The NEXUS criteria and Canadian C-Spine Rule guide the need for imaging. CT is indicated for altered mental status, focal neurological deficit, high-risk mechanism, midline tenderness, or distracting injury. MRI is reserved for suspected ligamentous injury, spinal cord injury, or neurological deficit not explained by CT findings.
CT Technique
Thin-section (0.625-1.25 mm) axial acquisition from the occiput to T1 (or T4 for adequate coverage) is standard. Sagittal and coronal reformats are essential and often more diagnostic than axial images. The evaluation includes vertebral body alignment, disc spaces, facet joints, spinous processes, and prevertebral soft tissues.
Anatomy and Stability Concepts
Three-Column Model (Denis, applied to cervical spine)
The anterior column includes the anterior longitudinal ligament (ALL) and anterior vertebral body. The middle column includes the posterior vertebral body and posterior longitudinal ligament (PLL). The posterior column includes the pedicles, facet joints, laminae, spinous processes, and posterior ligamentous complex (ligamentum flavum, interspinous and supraspinous ligaments). Injury to two or more columns is generally considered unstable.
Prevertebral Soft Tissue Thickening
Prevertebral soft tissue thickening is an indirect sign of occult fracture or ligamentous injury. Normal values are less than 7 mm at C2 (retropharyngeal) and less than 22 mm at C6 (retrotracheal). It may be absent acutely, so sensitivity is limited.
Upper Cervical Spine Injuries (Occiput-C2)
Occipital Condyle Fractures
The Anderson and Montesano classification describes Type I (comminuted, stable), Type II (basilar skull fracture extension), and Type III (avulsion by alar ligament -- potentially unstable). CT findings include a fracture line through the occipital condyle, with or without displacement.
Atlanto-Occipital Dissociation (AOD)
AOD is a life-threatening craniocervical disruption identified when the basion-dental interval (BDI) exceeds 12 mm or the basion-axial interval (BAI) exceeds 12 mm on sagittal CT. It is often fatal; survivors require occipitocervical fusion.
Atlas (C1) Fractures
The Jefferson fracture is a burst fracture of the C1 ring from axial loading, producing bilateral fractures of the anterior and posterior arches. Lateral mass offset of 7 mm or greater (combined bilateral overhang on open-mouth odontoid view or coronal CT) suggests transverse ligament rupture (unstable). An isolated posterior arch fracture from hyperextension is typically stable.
Axis (C2) Fractures
| Type | Location | Stability | Clinical Significance |
|---|---|---|---|
| I | Tip of dens | Usually stable | Rare |
| II | Base of dens | Unstable | Most common; high nonunion rate |
| III | Extends into C2 body | Usually stable | Better healing potential |
Odontoid (dens) fractures follow the Anderson and D'Alonzo classification. Type I involves the tip of the dens (rare, usually stable). Type II involves the base of the dens and is the most common and most clinically significant, with a high nonunion rate and unstable classification. Type III extends into the C2 body and has better healing potential.
The Hangman's fracture (traumatic spondylolisthesis of C2) involves bilateral pars interarticularis fractures of C2. The Levine-Edwards classification categorizes these as Type I (less than 3 mm displacement, stable), Type II (greater than 3 mm displacement, angulated, unstable), Type IIA (severe angulation without translation), and Type III (C2-C3 facet dislocation, highly unstable).
Subaxial Cervical Spine Injuries (C3-C7)
Subaxial Cervical Spine Injury Classification (SLIC)
| Category | Finding | Points |
|---|---|---|
| Morphology | No abnormality | 0 |
| Compression | 1 | |
| Burst | 2 | |
| Distraction | 3 | |
| Rotation/translation | 4 | |
| Disco-ligamentous complex | Intact | 0 |
| Indeterminate | 1 | |
| Disrupted | 2 | |
| Neurological status | Intact | 0 |
| Root injury | 1 | |
| Complete cord injury | 2 | |
| Incomplete cord injury | 3 | |
| Total Score | <4: nonoperative | |
| 4: surgeon discretion | ||
| >=5: surgical stabilization |
The SLIC system guides surgical decision-making based on three categories: morphology, disco-ligamentous complex integrity, and neurological status. For morphology, no abnormality scores 0, compression scores 1, burst scores 2, distraction scores 3, and rotation/translation scores 4. For the disco-ligamentous complex, intact scores 0, indeterminate scores 1, and disrupted scores 2. For neurological status, intact scores 0, root injury scores 1, complete cord injury scores 2, and incomplete cord injury scores 3. A SLIC less than 4 indicates nonoperative management, SLIC of 4 is at surgeon discretion, and SLIC of 5 or greater warrants surgical stabilization.
Common Subaxial Injury Patterns
A compression fracture shows anterior vertebral body height loss with intact posterior cortex and is stable if isolated. A burst fracture features comminution with retropulsed fragment into the spinal canal, involving the anterior and middle columns. Flexion-distraction injury produces widening of the posterior interspinous distance, facet subluxation or dislocation, and anterior vertebral body compression.
Facet injuries include unilateral facet dislocation (anterior subluxation less than 50% of vertebral body width with a rotational component, producing a "perched" or "locked" facet) and bilateral facet dislocation (anterior subluxation of 50% or greater, highly unstable, with high risk of spinal cord injury).
An extension teardrop fracture involves avulsion of the anteroinferior corner of the vertebral body, is common in the elderly with osteoporosis, and is usually stable. A flexion teardrop fracture produces a triangular fragment from the anteroinferior vertebral body with posterior displacement of the remaining body into the canal; it is highly unstable and often associated with severe cord injury.
Key Clinical Pearls
Type II odontoid fractures are the most common cervical spine fracture in the elderly and carry a high nonunion rate; always evaluate for posterior displacement. In suspected bilateral facet dislocation, the vertebral body is displaced anteriorly 50% or more of the vertebral body AP width on the sagittal image -- this is an unstable injury requiring urgent stabilization. The "naked facet" sign on axial CT (empty superior articular facet without an opposing inferior articular facet) indicates facet dislocation. The Clay-shoveler's fracture (avulsion fracture of the C6-T1 spinous process) is a stable injury but may be a marker of more significant ligamentous damage. When CT findings are equivocal for ligamentous injury, MRI with STIR or fat-saturated T2 sequences is the definitive study.
References
- Vaccaro AR, Hulbert RJ, Patel AA, et al. The Subaxial Cervical Spine Injury Classification System: A Novel Approach to Recognize the Importance of Morphology, Neurology, and Integrity of the Disco-Ligamentous Complex. Spine. 2007;32(21):2365-2374.
- Anderson PA, Montesano PX. Morphology and Treatment of Occipital Condyle Fractures. Spine. 1988;13(7):731-736.
- Levine AM, Edwards CC. The Management of Traumatic Spondylolisthesis of the Axis. J Bone Joint Surg Am. 1985;67(2):217-226.
- Patel AA, Hurlbert RJ, Bono CM, et al. Classification and Surgical Decision Making in Acute Subaxial Cervical Spine Trauma. Spine. 2010;35(21 Suppl):S228-S234.