ABC ofEmergency Radiology

CERVICAL SPINE-I BMJ: first published as 10.1136/bmj.307.6907.785 on 25 September 1993. Downloaded from

P A Driscoll, R Ross, D A Nicholson

.. 'SP'B .~~~~~~~~~~~~~~~~~~~~~~~~~~~...... X j3 _ l _ _ 4 u > ~~m_c_,7-heF This chapter describes an effective system by which non-radiologists can analyse cervical spine

...... ~~~~~~~~~~~~radiographs and detect even the subtle signs requires the clinician to be familiar with the basic anatomy ofthe cervical spine and understand how its structure can be damaged.

FIG i-Lateral and aerial view of a .

Anatomy

Adult The cervical vertabrae are held together by a series ofligaments and paravertebral muscles, with the overall stability depending mainly on the http://www.bmj.com/ ...... V...... integrity ofthe ligaments. The anterior longitudinal ligament runs from the anterior arch of the atlas to the sacrum and is imnportant in maintaining vertebral alignment. Similarly, the posterior longitudinal ligament connects the posterior aspect ~~ohbs~~ ~ ~ ~ ~ ~ ~ofthe vertebral bodies. The posterior complex consists ofthe ligamentum

flavum and the imterspinous and supraspinous ligaments. The on 26 September 2021 by guest. Protected copyright. imtertransverse ligament connects the transverse processes and forms the lateral column. FIG 2-Lateral view of cervical column showing ligaments. The spinal cord is contained within the spinal canal, where it is covered Stability and instability with three menimgeal layers, blood vessels, and cerebrospinal fluid. The outer dural is from the canal a filled A cervicalAcervicalinjury.injury isIs considered stable ifIf layer separated bony by space loosely controlled movements of the neck will not with fat and blood vessels. The size ofthe extradural space varies with the cause a neurological deficit. With an unstable relative diameters ofthe spinal cord and the spinal canal, and this controls injury, controlled movements ofthe neck are the body's ability to adapt to injuries that reduce the size ofthe canal. At the likely to produce or aggravate neurological level ofthe axis (C2) the extradural space is large and therefore damage to damage the vertebral column in this area does not immediately impinge on the spinal cord. Disease processes or degenerative changes which reduce the size ofthe canal will also limit the vertebral column's ability to adapt to injury. Steel's rule of three The area demarcated by the bony ring of Cl is Developmental divided into thirds. One third is occupied by Congenital malformations are common and should not be confused with the odontoid, one third by an intervening traumatic lesions. They vary from minor defects to severe deformities such potential space, and one third by the spinal ruac eon.Tevayfmmordetsosvreeomti uh cord as fusion and hemivertebrae. In children normal developmental lines may I I______be mistaken for fractures and lax ligaments for subluxation (see later).

BMJ voLuME 307 25 SEPTEMBER 1993 785 Mechanism ofinjury

-l Mechanisms of injury The cervical spine is injured when it is subjected to a series offorces acting separately or

Hyperflexion Hyperextension and rotation in combination. Cervical injury is common at BMJ: first published as 10.1136/bmj.307.6907.785 on 25 September 1993. Downloaded from Hyperflexion and rotation Compression C1/C2 because ofimpaction with the skull base. Hyperextension C5-C7 is a common site for disc degeneration. Hyperflexion can cause tears in the ligamental complex which widen the interspinous gap. It can also fracture the anterior superior corner of Injuries from hyperextension the vertebral body (flexion tear drop fracture) General with posterior displacement ofthe rest ofthe Tearing ofthe anterior ligamental complex with widening ofthe anterior fractured vertebra's body. In association with interdisc space rotation, hyperflexion may produce tearing ofthe Tearing ofthe posterior ligaments allowing posterior displacement of the posterior ligamental complex, unifacet and vertebral body bifacet dislocation, and avulsion ofthe spinous of anterior inferior corner of vertebral body (extension processes of C6-T1 (clay shoveller's fracture). tear drop fracture) The injuries resulting from hyperextension Occasionally the spinous processes may be fractured depend on where the force is exerted. Atlas Hyperextension and rotation can result in fracture ofthe lamina, pedicle, transverse Fracture of the laminae of C process, and the articular surface ofvertebral Avulsion fracture of the anterior arch of C1 bodies. Axis Compression can cause vertebral bodies to Fracture through pars interarticularis of C2 (Hangman's fracture) fracture with posterior displacement ofbone fragments and soft tissue into the spinal canal. Interpreting a lateral radiograph

rABCs approacha to Lateral anteroposterior, and open mouth views are the routine radiographs ofthe cervical spine. Occasionally special projections, such as Alignment flexion-extension, swimmer's, and oblique views are required. It is important to follow a strict protocol when studying any radiograph Cartilage and joints so that subtle and multiple abnormalities are not missed. Therefore, once the adequacy ofthe film has been determined we advocate an ABCs Soft tissue approach. http://www.bmj.com/ ...... 2.b ...... A lateral cervical radiograph should show all the cervical ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~... vertebrae as well as the C7/T1 .!..,.. r Ol ...... i :...illi tjunction. Such a radiograph will ...... detec 80...... -90% of cervical injuries. Although ligaments cannot be - - ;-!seen,;- - the; effect oftheir disruption on 26 September 2021 by guest. Protected copyright...... isvisible.

FIG 3-Left: lateral radiograph showing no abnormality in the upper six cervical vertebrae; C7 and Ti are not seen. Right: the radiograph was repeated with the being pulled down, when a compression fracture of C7 became evident (line drawing).

786 BMJ VOLUME 307 25 SEPTEMBER 1993 1 Check the adequacy and quality ofthe film Count the number ofvertebrae and make sure T1 is visible. Most diagnostic difficulties occur at the junctions (atlantoaxial and cervicothoracic). Most missed lesions occur at the cervicothoracic junction, usually because ofan indequate view. BMJ: first published as 10.1136/bmj.307.6907.785 on 25 September 1993. Downloaded from Anterior displacement greater than 3.5 mm in adults implies that the longitudinal ligaments are torn and, 2 Alignment consequently, the cervical spine is The anterior and posterior longitudinal lines, as well as the posterior facet unstable margins, should trace out a smooth lordotic curve from T1 to the base ofthe skull. The spinolaminar line should also be a smooth curve, except at C2, where there can be a posterior displacement ofup to 2 mm. Normally the spinous processes are nearly equidistant but tend to converge to a point behind the neck. Widening ofthe interspinous spaces is called divergence or "fanning." It is an abnormal sign and indicates that the posterior ligamental complex may be torn. A break in the contour ofthese lines may be due to facetal dislocation or a fractured vertebra. The commonest sites are Ci/C2 and C6/C7.

Anterior arch Occipital of atlas Dens of axis'

-Po Psteior arch ofaxis

*______Transverseie /Li\.J0JN ( Spinousof ~~~~~~~axisprocessprocess nuperior facet x ~~~~~articular surface

Facet joint

FIG 4-Lateral radiograph and line drawing with the four curves Ti marked out. The anterior and posterior borders ofthe spinal http://www.bmj.com/ 112 3 4 I canal are demarcated by the second Longitudinallines and third longitudinal line.

A unifacetal dislocation produces an anterior displacement ofless than halfofthe width ofa vertebral body. Inspection ofthe facet joint may show the inferior facet in the anterior position instead ofthe normal parallel articular surfaces with a joint space less than 2 mm. There is usually soft on 26 September 2021 by guest. Protected copyright. tissue swelling and the vertebrae above the dislocation are rotated so both facet surfaces are seen on the lateral view-the bow tie sign. Below the lesion the vertebrae are normally aligned. Ifunifacetal dislocation is suspected oblique views should be taken.

Ifthe displacement is over 50% ofthe width ofthe vertebral body bifacet dislocation is present. This is associated with fanning, narrowing of disc-disc space, and soft tissue swelling but no rotation (fig 6).

A simple loss ofthe cervical lordosis may be due to muscular spasm, age, previous injury, radiographic positioning, or a hard collar.

FIG S-Lateral radiograph showing unifacet dislocation at C3/C4 with anterior displacement of C3 on C4. Below this level both facets are visible because of rotation. The increase in the soft tissue shadow is masked by the oesophagus starting at this level.

BMJ VOLUME 307 25 SEPTEMBER 1993 787 3 Bones BMJ: first published as 10.1136/bmj.307.6907.785 on 25 September 1993. Downloaded from The cortical surface should be inspected first for steps, breaks, or abnormal angulations (figs 7-10). Start at the anterior inferior corner ofthe vertebra and then proceed in a clockwise fashion around the whole of the surface. Difficulty in following the cortical margins suggests overlapping of bone. This can result from a fracture or dislocation.

The rest of the vertebra is then inspected for alterations in the internal trabecular pattern, lucencies, and increases in density indicating a possible overlap ofbone fragments (figs 9 and 10).

FIG 6-Lateral radiograph showing anterior slippage greaterthan 3.5 mm due to bifacet dislocation. Fanning and narrowing of the disc space are visible. Soft tissue swelling is obscured by an endotracheal tube.

A Jefferson fracture occurs when both the anterior and posterior aspects Assessment of bones of the bony ring of C I are compressed and fractured between the occipital condyles and C2. Open mouth and specialist views are used to distinguish Check each vertebra for deformity this injury from isolated fractures of the lamina in Cl (fig 8). However, Check the spinal canal anterior soft tissue swelling usually indicates there is an anterior fracture as well. A third ofthese injuries are associated with fractures ofC2. http://www.bmj.com/ on 26 September 2021 by guest. Protected copyright.

FIG 7-Lateral radiograph showing compression FIG 8-Lateral radiograph showing fracture ofthe fracture of C5. The cortical surface is disrupted, the lamina of Cl with anterior soft tissue swelling. height ofthe vertebral body reduced, and trabecular The posterior border of the mandible should not pattern lost. Part of the posterior inferior corner of be mistaken for the true soft tissue line. the vertebral body is projected backwards into the spinal canal.

788 BMJ VOLUME 307 25 SEPTEMBER 1993 The heights ofthe anterior and posterior aspects ofeach vertebral body BMJ: first published as 10.1136/bmj.307.6907.785 on 25 September 1993. Downloaded from from C3 to Ti should be the same. A disparity ofgreater than 2 mm suggests a compression fracture (fig 9). A disparity greater than 25% can occur only ifthe posterior longitudinal ligament and posterior ligamental complexes are torn. It is therefore a sign ofmechanical instability. Never rush the examination ofthe lower vertebrae and, in particular, their spinous processes. These are prone to develop crush fractures after hyperextension and oblique avulsion fractures after hyperflexion with rotation.

FIG 9-Lateral radiograph showing a hangman's fracture, anterior displacement of C2 on C3, opening of the posterior intervertebral disc space and an extension tear drop fracture. Soft tissue swelling is present along with signs of ankylosing spondylitis.

FIG lo-Lateral radiograph showing a fracture of the dens with posterior displacement into the spinal canal. This displacement causes the anterior longitudinal line to run along the front of the anterior part of Cl, rather than along the front of the dens. http://www.bmj.com/ The spinal canal should be over 13 mm wide from the posterior surface of the vertebral body to the spinolaminar line (fig 4). Narrowing ofthe canal Radiological features of possible can result from dislocations and compression fractures which displace cervical instability segments ofbone and soft tissue posteriorly (figs 9 and 10). Pre-existing disease and degeneration can also lead to narrowing ofthe canal. Facet joint overriding

Facet joint widening 4 Cartilage andjoints on 26 September 2021 by guest. Protected copyright. Interspinous fanning Check the disc spaces, facet joints, and interspinous gaps. The joint Greater than 25% compression of vertebral spaces should be similar to that at an adjacent vertebral level and the body articulating surfaces should be parallel to one another. Calcification ofthese Over 100 angulations between vertebral joints, associated ligaments, and intervertebral discs indicates ankylosing bodies spondylitis (fig 7). Over 3.5 mm anterior vertebral body It is essential to assess the gap between the anterior surface ofthe dens overriding with fracture and the posterior surface ofthe body of C 1. This should be less than 3 mm Tear drop fracture (flexion and extension) in an adult and less than 5 mm in a child. Remember that the transverse Hyperextension fracture atlantal ligament can rupture without there being any bony injury (for Hyperextension fracture-dislocation example, in rheumatoid arthritis). Jefferson fracture 5 Soft tissue shadows Hangman's fracture Fractures to the cervical vertebrae produce haematomas that impinge on the black shadow ofthe oropharynx (figs 5, 8, 9). In children this gap can be wider because ofcrying, neck flexion, and pre-sphenoidal adenoidal P A Driscoll is senior lecturer in emergency medicine, enlargement. Pre-sphenoidal adenoidal enlargement increases the R Ross a consultant orthopaedic surgeon, and pre-vertebral soft tissue gap at C 1/C2. Soft tissue dimensions in adults D A Nicholson a consultant radiologist at Hope Hospital, should be 7 mm (third ofvertebral body) at C1-C4/5, and 21 mm (one Salford. vertebral body) at C4/5-T1. In childrenthe dimension at C4/5-T1 is 14 mm. The line drawings were prepared by Mary Harrison, medical illustrator. Several radiological features indicate possible cervical instability. The ABC ofAssessing Emergency Radiographs has However, until specialist advice is available it is safer to assume the lesion been edited by David Nicholson and Peter Driscoll. seen on the radiograph is unstable and to immobilise the neck accordingly.

BMJ VOLUME 307 25 SEPTEMBER 1993 789