How to interpret a cervical spine X-ray (X-ray)?

How to Interpret a Cervical Spine X-ray

For trauma evaluation, obtain a three-view cervical spine series (cross-table lateral, open-mouth odontoid, and anteroposterior views), but recognize that this approach has significant limitations with only 89.4% sensitivity for detecting injuries, and CT is now the gold standard for suspected cervical spine trauma. 1, 2, 3

Essential Views and Their Limitations

The Three-View Cervical Trauma Series

The standard radiographic evaluation consists of: 1

• Cross-table lateral view - Must visualize from the craniocervical junction (occipito-atlantal articulation) to the cervicothoracic junction, including all seven cervical vertebrae and the C7-T1 interspace 1, 4
• Open-mouth odontoid view - Evaluates the upper cervical spine, though frequently compromised by anterior artifacts from endotracheal tubes, gastric tubes, and cervical collars 1
• Anteroposterior (AP) view - Adds minimal diagnostic value, as no injuries are detected on AP view that aren't visible on lateral or odontoid views 5

Critical Performance Limitations

The lateral view alone detects only 73.4-89.7% of cervical injuries, missing approximately 15% even when interpreted by experts. 1 In the landmark NEXUS study of 34,069 trauma patients, an adequate three-view series had only 89.4% sensitivity (95% CI: 86.9-91.4%), meaning 2.81% of all injuries may be missed. 1

The most common reason for missed cervical spine injuries is technically inadequate radiographs - up to 49% of cases fail to visualize the cervicothoracic junction where 60% of cervical injuries occur. 1, 4

Systematic Approach to Reading Cervical Spine X-rays

The "ABCs" Method 6

Evaluate sequentially:

• Alignment - Check anterior vertebral line, posterior vertebral line, spinolaminar line, and posterior spinous process alignment 6
• Bony integrity - Examine each vertebral body, pedicles, facets, and spinous processes for fractures 6
• Cartilaginous structures - Assess disc spaces and facet joints 6
• Soft tissues - Measure prevertebral soft tissue spaces 1

Soft Tissue Measurements

Prevertebral soft tissue thickening has high specificity but low sensitivity for cervical injury: 1

• >6 mm at C3 - Only 59% sensitivity for actual cervical injury
• >22 mm at C6 - Only 5% sensitivity for actual cervical injury

Critical pitfall: These measurements become unreliable after endotracheal intubation, gastric tube placement, or while wearing a cervical collar. 1

When X-rays Are Insufficient

Indications for CT Instead of X-rays

CT cervical spine without contrast is now the gold standard for trauma evaluation, with 88.6-100% sensitivity compared to X-ray's 36.4% sensitivity. 2, 3, 7 CT detects three times more fractures than plain radiographs. 3

Obtain CT instead of X-rays when: 2, 3

• Altered level of consciousness or obtunded patients (X-ray sensitivity drops to only 51.7% for unstable injuries) 1
• Age ≥65 years (NEXUS criteria have reduced sensitivity of 66-89% in older adults) 2
• Focal neurologic deficits present 2
• High-energy mechanism of injury 2
• Intoxication 2
• Painful distracting injury 2
• Inability to actively rotate neck 45° bilaterally 2

Pediatric Considerations

In children, two or more radiographic views detect cervical spine injuries with 90% sensitivity (95% CI: 85-94%), but lateral view alone has only 73% sensitivity. 1 However, CT remains superior with 81-100% sensitivity in pediatric patients. 1

Important pediatric pitfalls: Normal variants in children <8 years (pseudosubluxation of C2-C3, absence of lordosis, C3 vertebral wedging, widened atlantodental interval) can mimic injury and adversely affect interpretation accuracy. 1

Role of MRI

MRI is superior for soft-tissue injuries (ligaments, cord contusion, epidural hematoma, disc herniation) with 88.5% sensitivity and 96.9% specificity. 3

Obtain MRI when: 1, 2, 3

• Neurological deficits present despite negative CT
• Suspected ligamentous injury
• Persistent neck pain despite negative CT
• Obtunded patients with negative CT (to evaluate for ligamentous injury)

Common Pitfalls to Avoid

• Never rely on X-rays alone in obtunded patients - sensitivity drops to 51.7% for unstable injuries 1
• Never accept inadequate visualization of C7-T1 - arm traction only reveals the cervicothoracic junction in 7.7% of cases when initially not visible 1
• Never ignore persistent symptoms with normal X-rays - 10-20% of missed injuries result from misinterpretation of suboptimal radiographs 1
• Never skip MRI in neurologically symptomatic patients - CT misses critical soft-tissue injuries requiring surgical intervention 3

Non-Trauma Cervical Spine Imaging

For acute neck pain without trauma or "red flag" symptoms, radiographs are often unnecessary and do not influence management or improve clinical outcomes. 1 MRI is not useful as first-line imaging in the absence of red flag symptoms due to high rates of abnormalities in asymptomatic patients. 1