Investigation

Patients, whose cervical spine cannot be clinically cleared, will require imaging to permit identification or exclusion of significant injury.
Plain radiographs

Plain radiographs do not detect all cervical spine fractures. In 29 published studies 16% of fractures (range 0 to 67%) were missed [11]. Plain lateral x-rays alone have a sensitivity of 63-85%, while the three view ‘trauma series’ (anterior-posterior (AP), lateral and peg views) improved diagnostic sensitivity to over 93%. Plain radiographs are not adequate to exclude significant cervical spine injury in unconscious patients and these patients will require CT (or MRI) imaging (see sections below).

Normal imaging of the cervical spine consists of three views (AP, lateral and peg). In children under 5, the peg view is considered unnecessary [12].

Lateral view

• Adequacy – visible base of skull to top of body of T1
• Alignment:
  • Along anterior margins of vertebral bodies
  • Posterior margins of vertebral bodies
  • Bases of spinous processes
• Bone – inspection of vertebral bodies
• Intervertebral discs – uniform height
• Soft tissues:
  • C1-4 max of 7mm (30% of vertebral body width)
  • C7-5 max of 22mm (100% of vertebral body width)
• Peg – anterior arch of C1 no more than 3 mm in adults (5 mm in children) space between anterior arch of C1 and peg

AP view

• Spinous processes should be in a straight line except if bifid spinous process
• Distance between spinous processes approximately equal

Odontoid peg view

• Lateral margins of C1 should lie within lateral margins of C2
• Spaces on each side of peg should be equal slight variation if neck is slightly rotated

Swimmers view

In the case of an inadequate lateral view (Fig 1):

• An ‘arm pull’ view in which the patient’s arms are pulled down to try to lower the shoulders so the lower cervical spine can be visualised or
• A ‘swimmers’ view is obtained in which the arm nearest the x-ray machine is elevated and the arm nearest the plate is kept extended (Figs 2 and 3). This view can be difficult to interpret due to overlying bones.

Fig 1: Inadequate plain lateral x-ray	Fig 2: Position for ‘swimmers’ view	Fig 3: ‘Swimmers’ view now demonstrating C7/T1

Flexion/extension views

For many years flexion/extension views used to be recommended for the clearing of the cervical spine. A number of studies have demonstrated flexion/extension views find fractures which may not be visible on initial plain films, although these fractures are invariably visible on CT. In a review of the NEXUS study data [13], 86 of the 818 patients with cervical spine injuries had flexion/extension views. Four dislocations and 15 out of 16 subluxations were seen. However, all the dislocations and all but four of the subluxations were visible on plain films. These four patients had significant injuries of the c-spine, such that subsequent imaging would have shown these injuries. Other studies have demonstrated that flexion/extension views may find injuries which are not visible on plain films, however, these patients are either intoxicated or have significant neck pain and the injuries were apparent on CT. Flexion/extension views should not be performed on unconscious/uncooperative patients as there have been cases of paraplegia following this procedure.

Clinical bottom line: There is no role for flexion/extension views in the acutely injured neck.

Computerised tomography (CT)

It has been recommended that thin cut axial CT scans with sagittal reconstruction should be used to view areas that were suspicious or poorly visualised on plain radiographs. However, the indication for CT scanning needs to be carefully considered because patients undergoing CT of their whole cervical spine have a 14-fold increase in the dose of radiation to their thyroid gland compared with standard three view plain radiography.

The recent introduction of spiral CT has reduced radiation dose and is faster, with a reported sensitivity as high as 99% and a specificity of over 93% [15]. The missed injuries are normally ligamentous, and may only be detected with magnetic resonance imaging (MRI) or flexion/extension views. There are well documented cases of conscious and cooperative patients with normal plain films and normal CT scans who were subsequently found to have unstable ligamentous injury on MRI scanning.

Magnetic resonance imaging (MRI)

MRI scanning is very sensitive for soft tissue injuries including ligament injuries, disc herniation and haemorrhage, which are less well visualised on CT. Many of these injuries will not be clinically significant, but a minority will represent unstable injuries. MRI is, however, less sensitive than CT at imaging the posterior elements of the spine and the craniocervical junction.

MRI is indicated if there is any neurology referable from the cervical spine, or if there is severe pain, despite a normal CT scan as some unstable ligamentous injuries may only be seen on MRI.

Summary – Guidelines for imaging

Adults

1.5.6 Perform CT in adults (16 or over) if: imaging for cervical spine injury is indicated by the Canadian C-spine rule (see recommendation 1.4.7) or there is a strong suspicion of thoracic or lumbosacral spine injury associated with abnormal neurological signs or symptoms.

1.5.7 If, after CT, there is a neurological abnormality which could be attributable to spinal cord injury, perform MRI.

1.5.8 For imaging in adults (16 or over) with head injury and suspected cervical spine injury, follow the recommendations in section 1.5 of the NICE guideline on head injury.

Children

1.5.2 Perform MRI for children (under 16s) if there is a strong suspicion of:

cervical spinal cord injury as indicated by the Canadian C-spine rule and by clinical assessment or cervical spinal column injury as indicated by clinical assessment or abnormal neurological signs or symptoms, or both.

1.5.3 Consider plain X-rays in children (under 16s) who do not fulfil the criteria for MRI in recommendation 1.5.2 but clinical suspicion remains after repeated clinical assessment.

1.5.4 Discuss the findings of the plain X-rays with a consultant radiologist and perform further imaging if needed. Spinal injury: assessment and initial management (NG41)

NICE 2016. All rights reserved. Page 12 of 23

1.5.5 For imaging in children (under 16s) with head injury and suspected cervical spine injury, follow the recommendations in section 1.5 of the NICE guideline on head injury.

Above guidelines are from NICE February 2016 Spinal Injury: Assessment and Initial Management

CT vs. MRI scanning

In unconscious patients there is some concern about the possibility of ligamentous instability which may be missed by CT, and so some authors consider that patients should have MRI to ‘clear the spine’ in these patients. Isolated ligamentous injury in the cervical spine is rare (0.04% incidence of ligamentous injury without fracture) [18]. The incidence in patients with altered mental state is higher, but is still only 0.7%. MRI in an unconscious polytrauma patient is not straightforward, and in many patients may not be practical for many days.

The current NICE Guidelines do not recommend that MRI is routinely used to clear the cervical spine. The EAST guidelines from the USA are non-committal, leaving the decision to use MRI up to the individual hospital.