X-ray Skills 1:

Cervical Spine Rules and Use of Imaging Portal

There are several approaches to imaging the cervical spine in the patient with multiple trauma, and there is little consensus on a single consistent approach.¹ When deciding if and how to image the cervical spine, consider the following:

Consider omitting c-spine imaging in seriously injured patients with multiple trauma who will be transferred to another hospital as soon as the patient is prepared and transport is available. (The assumption is that transfer will take place within an hour or less from arrival at the initial hospital). This applies especially to cases in which c-spine imaging would delay transfer. Rational support for this approach is based on the proposition that imaging under such circumstances may not be definitive enough to ‚clear‛ the c-spine, and the patient would be transferred in full immobilization regardless. In addition, since many digital radiographic storage and retrieval systems cannot ‚talk‛ to one another, studies commonly require repetition at the receiving hospital, resulting in greatly increased cost and radiation exposure.

In less seriously injured patients whose disposition may depend on imagining results, there are several possible approaches.

The first question to address is whether the patient needs imaging at all. At least two validated systems can identify patients at very low risk of c-spine injury.

NEXUS Criteria

The first is the NEXUS (National Emergency X-Ray Utilization Study) Criteria,² which is based on a large (35 000 patient) multicenter study done in 1992. NEXUS criteria that define a low-risk patient are as follows:

No posterior midline cervical tenderness
No evidence of intoxication
Normal level of alertness
No focal neurological deficit
No painful distracting injuries.

In order to meet the standard for low risk, all 5 criteria must be met.

These have been reported as 92% to 99% sensitive in defining a population of patients who do not need imaging.^3,4

Canadian C-Spine Rule

The other system is the Canadian C-Spine Rule.⁵ This system identifies low-risk patients by applying the following decision algorithm:

Patients must be alert in order to apply the algorithm. Use imaging in non-alert patients.

Use imaging if any of the following are present:
- Age > 65 or
- Dangerous mechanism of injury (fall from >5 feet or 3 stairs; axial load to head; MVA at speed > 65 mph; vehicle rollover or ejection; motorized recreational vehicle involved; bicycle vs motor vehicle collision) -
- Paresthesias in extremities
If none of these factors are present, search for low-risk criteria.

Evaluate the following factors:

Simple rear-end collision
Sitting position in the ED
Ambulatory at any time
Delayed (not immediate) neck pain
Absence of C-spine midline tenderness

If any are present, then test for patient’s ability to actively rotate his or her neck 45 degrees left and right. If the patient is able to do so, do not perform imaging.

If the patient does not have any of the low-risk criteria, or cannot rotate his or her head as described, use imaging.

For stable, alert adult patients with minor trauma, use the Canadian C-Spine Rule to take qualified patients quickly off the backboard. This approach reduces patient discomfort and radiation exposure as well as increases ED throughput times without adverse outcomes.⁶

The evidence supporting the validity of these two different criteria for evaluation is not perfect, and it may not be possible to directly compare the sensitivities and specificities of the two systems.³ As with all clinical decision rules, these criteria must be applied from the perspective of the physician’s practice setting as well as taking into account individual patient considerations. Use of either of these criteria, plus clinical judgment, is considered acceptable, high-quality practice.

Types of Imaging

As noted previously, once it has been decided to image the c-spine, a wide variety of practices are utilized to rule out significant, unstable c-spine injury. Several approaches are outlined here:

Plain films: Typically, obtain 3 views: lateral and/or swimmer’s view, AP view, and open-mouth odontoid view. These have historically been about 90% accurate (negative predictive value) in ruling out c-spine injury, and up to 99% accurate in detecting unstable injuries.⁷ In the current practice climate, the practitioner must decide if this is adequate given the estimated likelihood of c-spine injury in any given patient. Other disadvantages of plain radiographs include the frequent difficulty in positioning and resultant tie-up of personnel.

Flexion-extension lateral plain films: Some practitioners utilize these to assess stability after a normal or minimally abnormal set of plain films. The safest practice is to ask the patient to actively flex and extend, thereby limiting this technique to patients able to cooperate. Some practitioners require a normal cervical spine CT prior to flexion-extension views, due to the known incidence of unstable injuries missed on plain film. Disadvantage of flexion-extension films include false negative results due to muscle spasm and the risk of cord injury if the spine is in fact unstable.

CT: This has become a popular modality, with higher sensitivity and specificity than plain film. CT is also convenient in conjunction with CT scans of other areas commonly scanned in the trauma patient. Ideally, the scanner should be able to do reconstructions in various planes (axial, sagittal). This is dependent on the age and type of scanner. Check with your radiologist and/or technician about any limitations of your scanner. Other considerations include increased cost and radiation exposure with CT vs plain radiographs.

MRI: This is the only modality that can directly image ligaments. Neither plain films nor CT can directly identify ligamentous injury. Theoretically, a patient may have an unstable c-spine due to ligamentous injury with normal x rays and CT. However, MRI is not commonly available on an emergency basis and may be difficult to carry out in the acute setting of a patient with multiple trauma. Once again, apply clinical judgment to determine which patient remains at risk of unstable c-spine injury after normal x-rays and/or CT. If a patient is determined to be in this risk category, he or she must remain in c-spine immobilization until an MRI has been completed and interpreted.

References

Lockey AS, Handley R, Willett K. ‘Clearance’ of cervical spine injury in the obtunded patient. Injury. 1998;29:493-497.
Hoffman JR, Mowrer WR, Wolfson AB, Todd KH, Zucker MI. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. National Emergency X-Radiography Utilization Study Group. N Engl J Med. 2000;343:94-99.
Knopp R. Comparing NEXUS and Canadian C-Spine decision rules for determining the need for cervical spine radiography. Ann Emerg Med. 2004;43:507-514.
Panacek EA, Mower WR, Holmes JF, Hoffman JR; NEXUS Group. Test performance of the individual NEXUS low-risk clinical screening criteria for cervical spine injury. Ann Emerg Med. 2001;38:22-25.
Stiell IG, Clement CM, McKnight RD, et al. The Canadian C-spine rule versus the NEXUS low-risk criteria in patients with trauma. N Engl J Med. 2003;349:2510-2518.
Koenig KL. Canadian C-Spine Rule reduces imagaing rates without missing fractures. Journal Watch Emergency Medicine. December 11, 2009.
Mower WR, Hoffman JR, Pollack CV Jr, Zucker MI, Browne BJ, Wolfson AB; NEXUS Group. Use of plain radiography to screen for cervical spine injuries. Ann Emerg Med. 2001;38:1-7.