# 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).

![Sagittal CT reformats demonstrating Type II odontoid fracture and Type II Hangman's fracture of C2 with displacement](c2-fracture-types-sagittal-ct.png)

## 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.

![Sagittal CT demonstrating bilateral facet dislocation at C5-C6 with anterior listhesis greater than 50% and associated spinal canal compromise](bilateral-facet-dislocation-ct.png)

![Axial CT showing unilateral facet dislocation with the naked facet sign and reversal of the normal facet joint relationship](unilateral-facet-dislocation-axial.png)

## 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

1. 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.
2. Anderson PA, Montesano PX. Morphology and Treatment of Occipital Condyle Fractures. *Spine*. 1988;13(7):731-736.
3. Levine AM, Edwards CC. The Management of Traumatic Spondylolisthesis of the Axis. *J Bone Joint Surg Am*. 1985;67(2):217-226.
4. 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.