Cervical Spine X-Ray

Cervical spine radiography shows the seven cervical vertebrae, the intervertebral discs, the facet joints and the prevertebral soft tissues. The trauma series has three views: a lateral view, an anteroposterior view and an open mouth (peg) view of the dens and atlanto axial joints.

The lateral film must include the base of the skull and all seven vertebrae down to the top of T1 (the cervicothoracic junction is missed in up to a quarter of films; a swimmer's view or CT is used when it is not shown). Flexion and extension views assess ligament stability in selected stable patients and are not done in the acute setting with pain or reduced consciousness.

Oblique views show the intervertebral foramina in degenerative disease. The effective dose is about 0.2 mSv for three views.

In trauma, the decision to image is based on validated clinical decision rules (high risk features such as age 65 years or over, dangerous mechanism, paraesthesia, or inability to rotate the neck 45 degrees to each side; low risk features allow assessment of range of movement).

In adults with a high risk mechanism, reduced consciousness, or neurological signs, CT is the first line test, because plain films miss 20 to 50% of significant fractures, particularly at the occipitocervical and cervicothoracic junctions. In children, radiographs are used for low risk assessments, and the radiation burden favours MRI for neurological deficit.

In non-traumatic disease, plain films evaluate degenerative change, kyphosis, rheumatoid and spondyloarthropathy involvement and congenital anomalies, but MRI is needed for nerve root and cord assessment.

Indications. Blunt neck trauma that meets high risk clinical criteria in settings without CT, or low risk trauma with persisting pain. Neck pain with red flags (fever, cancer history, trauma, neurological deficit, immunosuppression). Suspected atlanto axial instability in rheumatoid arthritis, Down syndrome or before anaesthesia. Known ankylosing spondylitis.

Cervical radiculopathy or myelopathy as a first look (oblique views). Congenital anomalies (Klippel-Feil, cervical rib, odontoid hypoplasia). Position of fixation hardware. Not for routine non-specific neck pain without red flags.

Contraindications and precautions. The neck must be immobilised in a rigid collar until the spine is cleared, and the patient is not moved or asked to flex the neck. Do not request flexion and extension views in the acute stage. Pregnancy: low dose to the foetus with shielding. In an unconscious or intubated patient, plain films are not used to exclude injury, and CT is used instead.

Preparation and technique. Lateral cross-table film with the shoulders pulled down (gentle traction on the arms) to show C7 and T1. Open mouth view with the mouth wide open and the central beam on the mouth. If the first lateral film does not show C7-T1, repeat with traction, use a swimmer's view, or do CT.

Normal appearances. Smooth cervical lordosis. Four continuous curves on the lateral film: the anterior vertebral line, the posterior vertebral line, the spinolaminar line (posterior margin of the spinal canal) and the line joining the tips of the spinous processes.

Vertebral bodies of uniform height, intervertebral disc spaces of similar height, and facet joints that overlap like roof tiles. Prevertebral soft tissue thickness: under 7 mm at C2 and under 22 mm at C6 in adults (under 14 mm at C6 in children, where the soft tissue appears thicker on expiration or crying). Atlanto dental interval 3 mm or less in adults (up to 5 mm in children).

On the open mouth view, the lateral masses of C1 align with C2 and the dens lies centrally with equal spaces on each side. Interspinous distances equal between levels.

Interpretation. Systematic review is by "ABCs": adequacy and alignment, bones, cartilage (discs and joints), and soft tissues.

• Alignment disruption: a step of more than 3.5 mm or more than 20% of vertebral body width suggests ligament injury or facet dislocation. Bilateral facet dislocation (translation over 50% of the vertebral body width, "perched" or "locked" facets) is unstable with high spinal cord injury risk, and unilateral dislocation shows about 25% displacement with a rotated appearance.
• Angulation over 11 degrees between adjacent vertebrae, increased interspinous distance (fanning), or widened facet joints indicates posterior ligament injury.
• Atlas (C1): Jefferson burst fracture, with lateral mass overhang on the open mouth view (combined overhang over 7 mm suggests transverse ligament rupture).
• Odontoid fractures: type I (tip), II (base, commonest, with poor healing), III (into the C2 body). Widening of the atlanto dental interval over 3 mm suggests transverse ligament rupture, and over 5 mm indicates complete rupture.
• Hangman fracture (traumatic spondylolisthesis of C2): bilateral pars interarticularis fractures with anterior displacement of C2 on C3.
• Wedge compression fractures (loss of anterior height), burst fractures (posterior cortex involvement with retropulsion, and widened interpedicular distance), and teardrop fractures (flexion injury with a triangular anteroinferior fragment and posterior displacement, highly unstable).
• Spinous process fractures: C6 and C7 (clay shoveler fracture) are stable.
• Prevertebral swelling indicates haematoma, abscess or tumour; air in the prevertebral space suggests oesophageal or tracheal injury.
• Degenerative changes: disc space narrowing, osteophytes, uncovertebral and facet joint hypertrophy, foraminal narrowing on oblique views, and loss of lordosis. These are present in most people over 40 and correlate poorly with symptoms.
• Rheumatoid arthritis: atlanto axial subluxation (flexion view atlanto dental interval over 3 mm), erosion of the dens, and cranial settling.
• Ankylosing spondylitis: bamboo spine with syndesmophytes and fusion, fragile and prone to fracture after minor trauma.
• Infection and tumour: disc space loss with endplate erosion (discitis), vertebral collapse or lytic and sclerotic lesions.
• Congenital: Klippel-Feil (fused vertebrae), cervical ribs, odontoid hypoplasia (Down syndrome, Morquio syndrome), and pseudosubluxation of C2 on C3 in children (up to 4 mm of anterior step, with an intact spinolaminar line).

Critical values and findings needing immediate action.

• Any fracture or malalignment suggesting an unstable injury (bilateral facet dislocation, teardrop fracture, odontoid fracture, Jefferson burst fracture with transverse ligament rupture, hangman fracture): keep the collar and immobilise, call the spinal team urgently and arrange CT and MRI.
• Neurological deficit (weakness, sensory level, priapism, hypotension with bradycardia): spinal cord injury, immediate spinal protection, MRI, and neurosurgical review.
• Inadequate film that does not show C7-T1: repeat or CT, and keep the collar.
• Prevertebral soft tissue widening with air or neurological signs: CT, and consider an airway or oesophageal injury.
• Atlanto axial instability before anaesthesia (rheumatoid arthritis, Down syndrome): neck immobilisation and anaesthetic plan.
• Cervical spine infection or tumour with cord compression: urgent MRI and surgical review.

Limitations and artefacts.

• A normal three view series does not exclude a significant injury: sensitivity for fracture is about 50 to 80% and for ligament injury lower. Missed injuries are commonest at C1-C2 and C7-T1.
• Poor technique (rotation, inadequate coverage, shoulders overlapping the lower vertebrae) causes false negatives and false positives; the film must be adequate before being called normal.
• Mimics of fractures include the dark "Mach" band over the dens from overlapping teeth, vertebral epiphyses and synchondroses in children, normal accessory ossification centres, the unfused ring apophysis, and pseudosubluxation in children.
• Ligament injury without bone fracture (spinal cord injury without radiographic abnormality, especially in children) is not visible on plain films, and MRI is required.
• Degenerative changes are very common and mostly incidental.
• Patients with altered consciousness, intoxication, or distracting injuries cannot be cleared clinically, and CT with a set clinical routine is used.
• Flexion and extension films cause pain and spasm in the acute stage and are unreliable.
• Radiation dose to the thyroid is low but cumulative in children, and CT doses are higher; use the lowest dose necessary.

Special groups.

• Children: higher injury risk at C1-C3, use age adjusted soft tissue measurements, avoid CT unless needed, and use MRI for neurological signs or when injuries cannot be excluded.
• Older adults: low energy falls cause odontoid and central cord injuries with osteoporosis and spondylosis; CT is the first line test and MRI follows if neurology is present.
• Patients with ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis: fractures from minor trauma are unstable, may be missed on plain films, and CT is required.
• Down syndrome and rheumatoid arthritis: screen for atlanto axial instability before anaesthesia and contact sport.
• Regions: in many hospitals without CT, plain films with strict clinical cervical spine rules direct transfer decisions, and diving, falls from trees and road traffic injuries are common causes; spinal tuberculosis affects the cervical spine in a minority of cases.

Follow up tests. CT cervical spine with sagittal and coronal reconstructions for suspected fracture, CT angiography for vertebral artery injury in fractures through the foramen transversarium, MRI for ligament injury, cord injury, disc herniation, infection and tumour, flexion and extension films after the acute stage for suspected instability when pain has settled, bone density scan, inflammatory markers, and neurosurgical or orthopaedic spine review.