ABC of Emergency Radiology

CERVICAL SPINE-IIP A Driscoll, R Ross, D A Nicholson

The lateral view is the routine radiograph forexamining the cervical spine

In addition to the lateral cervical radiograph discussed last week, furtherviews are commonly requested in trauma patients. However, the patientusually has to be moved to the radiology department for these radiographsto be taken. This should not be done until resuscitation is completed andthe patient is stable from a respiratory and haemodynamic point of view.The radiographs must be examined using the same principles described

for the lateral view. Therefore once the adequacy of the film has beenassessed the ABCs are inspected. .- A +-- -

Anteroposterior cervical radiographFIG 1-Anleroposteriorradiograph and linediagram showing T2-C2.The spinous processesare aligned normally.

~,- T2

AdequacyEnsure that Ti to C3 are visible. The mandible

and occiput overlies C 1-3 in this projection andmay obscure them from view.

AlignmentCheck alignment ofspinous processes.

Malalignment may indicate a unifacet dislocationor a fracture ofthe lateral articular surface. Theseinjuries cause the spinous processes to rotate tothe side ofthe injury.

FIG 2-Anteroposteriorradiograph showingunifacet dislocation of C6.The spinous process of C6is rotated to the right andthe C6/7 intervertebralspace is widened.

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FIG 3-Anteroposterior radiograph showing crush fracture of C6.The height of C6 is reduced.

BonesThe cortical surface of each vertebra must be

inspected for steps, breaks, or abnormalangulations. Start at the right inferior corner ofthe vertebra and then proceed clockwise aroundthe whole of the surface. Vertebral bodies shouldbe rectangular. A careful inspection will revealany compression, vertical fissures, and steps inthe end plates.The rest ofthe vertebra is then inspected for

alterations in the internal trabecular pattern,lucencies, and increases in density indicating apossible overlap ofbone fragments.

Cartilage andjointsCheck each intervertebral joint space. The

height should be similar to that found at adjacentvertebral levels and the articulating surfacesshould be parallel to one another (compare figs 1and 3).

Soft tissuesThe paravertebral tissue must be assessed.

Disruption of the normal air shadow may indicatean underlying fracture or dislocation.

Open mouth view

FIG 4-Left: Open mouth view. The dens and the spinous process of C2 are aligned normally, there is no lateral overriding of Cl on C2, andthe dens is symmetrically placed between the two lateral masses of Cl. Notice the artefact created by the occiput overlying-the dens.This can be mistaken for a fracture. Right: Line diagram of the radiograph.

AdequacyCheck that the open mouth view shows the C 1/C2 articulation.

AlignmentCheck the alignment of the odontoid peg and C1/C2. Normally the dens

and spinous process ofC2 are in the same vertical line as are the lateralborders ofC 1 and C2. In adults there should be less than 2mm lateraloverriding between C 1 and C2. The distances between the lateral masses ofthe atlas and the odontoid peg (dens) are normally symmetrical.

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Jefferson fractures are often seen clearly in this view. Rotatorysubluxation of the odontoid in children is also best shown by the openmouth view. Up to the age of 8, incomplete ossification of the dens andligamental laxity allows up to two thirds of the anterior arch of Cl to lieabove the odontoid peg.

BonesCheck the odontoid peg and examine the dens carefully. Fractures can

occur in the peg itself (type 1) or at its base (type 2) or can extend into thebody of C2 (type 3). Type 2 fractures are the commonest and lead toinstability of the cervical spine. The dark shadow of either the overlyingteeth or the epiphyseal plate is often mistaken for fracture (fig 4). Theepiphysis is V-shaped and should have fused by 12 years of age. Non-unionof this secondary ossification centre leads to formation of an osodontoideum, which appears as a characteristic smooth convex border atthe tip of the dens.

FIG 5-Open mouth view showing a Jefferson fracture.Both lateral masses of Ci are overlapping the lateralborders of C2. Notice the artefact created by theincisors overlapping the dens.

)en mouth view showing a type 2 tracture Ot tne aens.

Special views

Cartilage and jointsCheck the joint space between C 1 and C2. The

articulating surfaces should be parallel to oneanother.

Soft tissuesThe paravertebral tissue must be assessed.

Normally soft tissue shadows are not evident onthis view.

FIG 7-Swimmer's view and linediagram showing C5-T1. Theanterior longitudinal line is brokenbecause of the forward slip of 07 onTi. This resulted from a unifacetdislocation. A normal air shadowcaused by the trachea is clearlyseen.

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Swimmer's viewThe swimmer's view should be requested if C7IT1 cannot be seen on the

normal lateral cervical radiograph. The film looks strange because it isshowing a focused oblique view of the C7/T1 junction. However, thefeature to concentrate on is the anterior alignment of the vertebralbodies.

FIG 8-Oblique view and line diagram of the cervical column. The superior facet of C6 is fractured and displaced intothe intervertebral foramina. This view clearly shows the facet joints and intervertebral foramina.

Oblique viewThis gives a good view of the intervertebral formina and the facet joints.

It is requested by specialists when a unifacet dislocation is suspected fromthe routine films.

Flexion and extension viewsThese radiographs are taken when a specialist

has reviewed the standard radiographs andconsiders there is cervical malalignent with nocorresponding significant soft tissue swelling,subluxation, or widening of facet joints. All neckmovements must be carried out by a doctor andthe patient must be conscious. This allows theprocedure to be stopped immediately any pain orneurological symptoms develop.These views are modified lateral radiographs

and should be examined using the ABC systemlisted previously.

FIG 9-Lateral radiograph showing a flexion view of thecervical spine. The standard view appeared normal, buton flexion Cl subluxates forward and an abnormallywide gap develops between the dens and the anteriorarch of Cl.

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Catches to avoid

The emergency clinician must be aware-thatthe absence of radiological abnormalityreduces the chances of spinal injury but doesnot exclude it. About 8% of patients haveinjuries to the cervical spine in more than oneplace and 15% of patients with cervical injuryalso have a thoracolumbar injury

Make sure all seven cervical vertebrae and the C7/T1 junction are visible.The spinous processes may not be clear. Ifyou suspect an injury obtain afurther view.

Physiological subluxation of the bodies ofC2 on C3 (seen in a quarter ofcases) and C3 on C4 (seen in 15% of cases) occurs up to 8 years of age.However, the posterior spinal line is maintained.

Artefactual shadows can sometimes cause confusion. In the open mouthview the vertical cleft between the upper two incisor teeth may be mistakenfor a vertical fracture ofthe peg. Do not forget to examine the soft tissueshadows; these may be the only clues to an underlying fracture.

SummaryAdequacy and qualityEnsure that the vertebrae C1-C7 and the C7/T1 junction are visible

AlignmentAssess the contours of the cervical spine and appendagesBonesCheck each vertebra for shape, height, and fracturesCheck the shape of the odontoid pegCheck spinal canal size

Cartilage andjointsCheck the intervertebral disc spacesCheck the facet jointsCheck the interspinous distanceCheck the C1/C2 distance

Soft tissuesCheck the precervical and paracervical spaces

P A Driscoll is senior lecturer in emergency medicine,R Ross a consultant orthopaedic surgeon, and D A Nicholsona consultant radiologist at Hope Hospital, Salford.

The ABC ofEmergency Radiology has been edited byDavid Nicholson and Peter Driscoll.

The line drawings were prepared by Mary Harrison,medical illustrator.

Economic Evaluation and Health Care

Cost-utility analysis

Ray Robinson

This is thefourth in a series ofarticles that describes the waysin which methods ofeconomicevaluation may be used toassess the economic costs andconsequences associated withdifferentforms ofhealth careintervention

Institute for Health PolicyStudies, University ofSouthampton,Southampton S09 5NHRay Robinson, professor ofhealth policy

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Decisions have to be made about allocating healthresources. Currently the best economic evaluationmethod for doing this is cost-utility analysis. Thiscompares the costs ofdifferent procedures with theiroutcomes measured in "utility based" units-that is,units that relate to a person's level ofwellbeing. Themost commonly used unit is the quality adjusted lifeyear (QALY). QALYs are calculated by estimatingthe total life years gained from a procedure andweighting each year to reflect the quality of lifein that year. To compare outcomes of differentprogrammes the Rosser index is one measure that iswidely used to assign quality of life scores topatients. Combined with a measure of life yearsgained from a procedure, this enables QALYs to becalculated and procedures ranked according to costper QALY gained. In this article Ray Robinsonexplains the measures used and discusses howQALY league tables can be used to guide decisionson resource allocation.

Cost-utility analysis is a form ofeconomic evaluation inwhich the outcomes of alternative procedures or pro-grammes are expressed in terms of a single, "utilitybased" unit of measurement. Utility is a term used by

health economists to refer to the subjective level ofwellbeing that people experience in different states ofhealth. The most widely used utility based measure incost-utility analysis is the quality adjusted life year(QALY). To calculate the number of QALYs resultingfrom a particular intervention, the number of addi-tional years of life obtained are combined with ameasure of the quality of life in each of these years toobtain a composite index of outcome. Comparisonbetween altemative procedures or programmes canthen be based on the marginal cost per QALY gained.

Measuring qualityMeasuring a person's quality of life is, of course,

difficult. None the less, it is important to have somemeans for doing so because many modern health careprogrammes are concerned primarily with improvingthe quality of a patient's life rather than extending itslength. For this reason various quality of life scaleshave been developed in recent years. These seek tomeasure quality on a number ofdifferent dimensions.The Nottingham health profile is one quality of life

scale that has been used quite widely in Britain.' Thiscomprises two parts. The first measures health statusby asking for yes or no responses from patients to

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