Mechanisms and radiological features of Cervical spine trauma

1. CERVICAL SPINE TRAUMA
Dr. Soe Moe Htoo

2. EPIDEMIOLOGY
• Cervical spine trauma is a common problem with a wide range of
severity from minor ligamentous injury to osteo-ligmentous instability
with spinal cord injury.
• C-spine is injured in 2.4% of blunt trauma victims.
• Most common mechanism of injury are accidental falls and motor
vehicle transport injuries.
• Most common site of injury is atlanto-axial region, C6 and C7.
• Among the spine injuries, Cervical spine is the most common level for
spinal cord injury, representing 55% of all spinal cord injuries.

3. Standard Radiographs
• At least three views are recommended for alert and stable trauma
patients:
1. Anteroposterior view
2. Lateral view (Horizontal beam)
3. Open-mouth view

4. Oakley introduced a simple system (Radiological ABC) for analyzing plain films:
• A1: Appropriateness: correct indication and right patient
• A2: Adequacy: extent (occiput to T1, penetration, rotation/projection)
• A3: Alignment:
(1) anterior aspect of vertebral bodies,
(2) posterior aspect of vertebral bodies,
(3) spinolaminar line (bases of spinous process),
(4) tips of spinous process,and relationships
• B: Bones
• C: Connective tissues:
(1) pre-vertebral soft tissue,
(2) pre-dental space,
(3) intervertebral disc spaces,
(4) interspinous gaps

5. NORMAL RADIOLOGICAL ANATOMY (LATERAL XR)
• The cervical spine is normally lordotic.
• This may be absent due to:
(1) patient positioning
(2) presence of a hard collar or
(3) muscular spasm.
• All seven cervical vertebrae (including the C7–T1 junction) must be
visualized.
• May require a swimmer’s view if they are not demonstrated on the
lateral view

6. We must demonstrate all seven cervical vertebrae.
(A) Initial lateral C-spine XR reveals only six cervical vertebrae.
(B) A repeat examination was obtained while pulling down on the shoulder, which demonstrates a
fracture dislocation at C6–7 not apparent on the initial XR.

7. • Four imaginary continuous curves:
(1) Anterior vertebral body line
(2) Posterior vertebral body line
(3) Spinolaminar line and
(4) Posterior spinous process line

8. • The cervical spine is divided into 3 columns:
i. Anterior column: anterior half of the vertebral body, the anterior
part of the intervertebral disc and the anterior longitudinal
ligament
ii. Middle column: the posterior half of the vertebral body and the
posterior part of intervertebral disc and the posterior longitudinal
ligament
iii. Posterior column: the posterior Osseo-ligamentous complex
consisting of the pedicles, facet joints, posterior bony arch,
interspinous and supraspinous ligaments

10. Perfectly Positioned Lateral View
• Right and left facet joints are superimposed (otherwise the facet
joints partially overlap)
• Facet joint overlap should be uniform at all levels
• An abrupt change in the amount of overlap within adjacent levels
indicates abnormal rotation along the longitudinal axis of the spine
• The articular surfaces of each facet must be superimposed
• This may otherwise indicate a subluxed or dislocated facet

12. • The odontoid process is usually tilted posteriorly on the body of C2 –
however this may otherwise indicate an odontoid fracture
• Atlantoaxial distance (Predental space)
- measured at the base of the dens
- between the anterior cortex of the dens and posterior cortex of
the anterior arch of C1:
Adults: < 3mm
Children: < 5mm

13. • Assessment of the prevertebral tissues (to exclude a retropharyngeal
haematoma):
Adults: < 5mm (at the level of C3 and C4)
< 22mm (at the level of C6)
Children: no more than ⅔ of the width of the C2 body
(at the level of C3 and C4)
< 14mm (at the level of C6)

14. • Disc spaces should be the equal and symmetric

15. HARRIS’ RING:
- The ring should be complete
- Aid in diagnosing Low (Type 3)
Odontoid Fractures.

16. The spinolaminar line should intersect
the opisthion

17. Basion-Dental Interval:
- Distance between the tips of the clivus
(basion) and dens should be <12mm
(XR) and <8.5mm (CT)

18. Posterior axial line:
-a line drawn along the posterior VBs
should be <12mm from the basion

19. NORMAL RADIOLOGICAL ANATOMY (AP VIEW)
• The spinous processes should form a continuous (although often
slightly irregular) line
• The C2–7 vertebrae should be of a similar height
AP view of the C-spine showing:
Normal alignment of the vertebral bodies.
No loss in vertebral body height.
Posterior elements are intact.

21. NORMAL RADIOLOGICAL ANATOMY
(OPEN-MOUTH VIEW)
• To detect an odontoid process fracture and confirm integrity of the C1
ring
• Neutral position: the lateral margins of the lateral masses of C1
should align with C2
• With rotation, the atlas normally moves as a unit with lateral facet
displacement on one side and medial offset on the opposite side
• Adults: bilateral displacement indicates a C1 ring fracture
• Children: bilateral displacement is a normal variant (due to discrepant
growth of C1 and C2)

23. Open-mouth view of the cervical spine shows the normal
alignment of the lateral masses of C1 with C2 (arrows).

24. Computed Tomography
• CT is the first choice for unconscious or polytraumatized patients.
– the ease of performance,
– speed of study,
– the greater ability of CT to detect fractures other than
radiography.
– the mid-sagittal fracture through the posterior vertebral wall
and lamina.
– rotatory instability at the atlantoaxial joints.
– shows if the dens separates from the anterior arch of C1 with
increased rotation.
• The craniocervical scans should be of a maximum 2 mm thickness, because
dens fractures can even be invisible on 1-mm slices with reconstructions

25. MRI
• Magnetic resonance imaging is the imaging study of choice to exclude
disco-ligamentous injuries, if lateral cervical radiographs and CT are
negative.
• MRI is the modality of choice for evaluation of patients with
neurological signs or symptoms.
• Particularly, STIR sequences are very helpful in visualizing posterior
soft tissue injuries.

26. • Instability is suggested if there is:
(1) Abnormal spinous process fanning
(2) Widened disc space
(3) Horizontal displacement of one body on another (> 3.5mm)
(4) Angulation > 11º
(5) Disrupted facets or multiple fractures
• Instability is more likely if more than one column is disrupted
i. Stable: fractures limited to the vertebral body or posterior
elements
ii. Unstable: fractures involving both the vertebral body and posterior
elements
RADIOGRAPHIC SIGNS OF INSTABILITY

27. Stable Injuries
• Vertebral components are not displaced by normal movement
• Undamaged spinal cord
• No deformity or pain
Unstable Injuries
• Further displacement of injury may occur.
• Loss of 50% of vertebral height.
• Angulation of thoracolumbar junction >20 degrees.
• Failure of at least 2 of Denis’s 3 columns.
• Compression fracture of three sequential vertebrae can lead to post
traumatic kyphosis.
STABLE VS UNSTABLE INJURIES

28. Degree of Stability In C-Spine Injuries
STABLE
1. Anterior subluxation
2. Unilateral facet dislocation
3. Simple wedge fracture
4. Burst fracture of lower cervical
vertebrae
5. Posterior neural arch fracture of
atlas
6. Pillar fracture
7. Clay-Shoveler’s fracture
UNSTABLE
1. Bilateral facet dislocation
2. Flexion teardrop fracture
3. Extension teardrop fracture
4. Hangman’s fracture
5. Jefferson fracture of atlas
6. Hyperextension fracture-dislocation

29. • All fractures involving the middle column and at least one other
column should be regarded as UNSTABLE
• Only 10 per cent of spinal fractures are unstable
• Fractures and dislocations are most common in the lower cervical
spine (C4–C7)
• Usually the upper vertebral body is displaced anteriorly relative to
the lower vertebral body
• There is often an anterior wedge compression fracture of the lower
vertebral body and fractures involving the laminae, facets, or spinous
processes

30. • There may be disruption of the joint capsule of the facet joints and
interspinous ligament without associated fractures
• There may be no significant fracture associated with a dislocation,
since the injury is limited to the intervertebral disc, facet joint
capsules and intervening ligaments
• Paraspinal haematomas (e.g. a retropharyngeal mass) may point to an
obscure fracture or dislocation

31. MECHANISM OF SPINAL INJURY
1. Traction injury
2. Direct injury: Penetrating injuries to the spine, particularly from firearms
and knives
3. Indirect injury: Most common cause. A variety of forces may be applied to
the spine (often simultaneously):
› axial compression flexion
› lateral compression
› flexion-rotation
› Shear
› flexion-distraction
› Extension
4. Insufficiency fractures may occur with minimal force in bone which is
weakened by osteoporosis or a pathological lesion

32. Pathomechanics of spinal injury
Each force produces a characteristic injury as visualized on the lateral XR.

33. Flexion
Flexion
(ant. wedged fracture)
• Anterior wedged deformity of the vertebral body.

34. Extension(Pars fracture)
Extension
(pars fracture)
Small triangular fragment separated from the
anterior inferior margin of the vertebral body.

35. Distraction
Distraction
(tension)
(chance fracture)
i. Horizontal fractures in the posterior element
ii. Little or no wedging of the vertebral body.

36. Flexion-distraction
Flexion-distraction
(teetter-totter fracture)
i. Horizontal fracture of the posterior elements
ii. Anterior wedging of the vertebral body.

37. Axial compression
Axial compression
(burst fracture)
Characterized by
i. Anterior wedging of the vertebral body
ii. Retropulsion of the posterior superior margin of the
vertebral body as in burst fractures.

38. Shearing
Shearing
(ant. fracture dislocation)
• Results in fracture–dislocations
• Manifested by
- anterior displacement of the vertebra above
the level of dislocation
- triangular avulsed fragment from the anterior
superior margin of the vertebral body below.
• Fractures of the laminae and superior facets are
commonly encountered.

39. Rotation-shearing
• Rotational forces are combined with shearing
• Produce an anterior lateral dislocation of the
spine.
Rotation-shearing
(lat. fracture dislocation)

40. Biomechanics of Cervical Spine Trauma
• Vertical loading of the lower cervical spine in the forward flexed
position  pure ligamentous injuries, bilateral facets dislocation
without fracture.
(unilateral dislocation was produced if lateral tilt or axial rotation
occurred as well)
• Axial loading less than 1 cm anterior to the neural position  anterior
compression fractures of the vertebral body.
• Burst fractures can be produced by direct axial compression of a
slightly flexed cervical spine.
• Tear-drop fracture results from a flexion/compression injury with
disruption of the posterior ligaments.

41. JEFFERSON FRACTURE (C1)
• Fracture of the bony ring of C1, uncommon injury
• Characterized by lateral masses splitting and transverse ligament tear
anterior and posterior arches of the atlas disruption (there can be a
single disruption of each arch)
• Mechanism  An axial compression injury to the top of the skull
(Diving into shallow water, RTA)
• STABLE injury (unless there is associated disruption of the tranverse
atlantal ligaments)

42. AP XR
• Bilateral offset of the lateral masses of C1 relative to the lateral
margin of the C2 vertebral body
• Widened space between the dens and medial border of the C1 lateral
masses

43. (A) Lateral XR demonstrates fracture of the posterior
arch of atlas (arrow) – indistinguishable from an isolated
fracture of the C1 posterior arch.
(B) Open-mouth view demonstrates bilateral
displacement of the C1 lateral masses (arrows).

46. POSTERIOR ARCH FRACTURE (C1)
• Commonly non-displaced and bilateral and neurologically benign
• Take care with differentiating it from neural arch gaps that are normal
variations
• Results from compression of the arch between the occiput and
spinous process of C2 during hyperextension
• STABLE injury

47. Fracture of the posterior arch of C1 (white arrow) combined with
fracture at the base of the dens.
Note the posterior dislocation (black arrow).

48. Classification system for posterior C1 ring anomalies

49. HANGMAN’S FRACTURE (C2)
• Mechanism  Hyperextension injury (Hanging or hitting a dashboard)
• Bilateral fractures of the neural arch anterior to the inferior facets
(traumatic spondylolysis of the axis)
• It is often associated with dislocation of C2 on C3
• There may be an associated avulsion fracture of C2 at the antero-
inferior margin.
• Fracture lines tend to be oblique and symmetrical
• Any neurological deficit is often less severe than anticipated (as the
normal cervical cord occupies only up to 50% of the spinal canal AP
diameter and bilateral isthmus fractures can produce canal
decompression)
• UNSTABLE injury

50. • Fracture through the pedicle at pars interarticularis of C2 secondary
to hyperextension
• Best seen on lateral view
• Signs:
› Prevertebral soft tissue swelling
› Avulsion of anterior inferior corner of C2 associated with
rupture of the anterior longitudinal ligament
› Anterior dislocation of the C2 vertebral body
› Bilateral C2 pars interarticularis fractures

51. Lateral view Axial view
Hangman’s fracture with subluxation
of C2 upon C3 and a widely
displaced fracture in the neural arch.

52. ODONTOID (DENS) FRACTURE (C2)
• Mechanism  Hyperflexion or hyperextension injury
• This can be mistaken for an os odontoideum (either congenital or
post traumatic)
• Type 1 (high): an avulsion fracture of the superolateral portion of the
tip of the dens by the intact alar ligament – STABLE injury
• Type 2 (high): a transverse fracture at the base of the dens (the
commonest type) – UNSTABLE injury
• Type 3 (low): a fracture of the superior portion of the axis body with
extension through one or both of its superior articular facets (it is not
technically a dens fracture) – UNSTABLE injury

53. ODONTOID (DENS) FRACTURE

54. AP XR
• The Mach effect (due to the inferior cortical margin of the posterior
arch of the atlas crossing the base of the dens) may mimic a dens
fracture
Lateral XR
• Anterior tilt of the odontoid
• Prevertebral soft tissue swelling

55. High (Type 2) dens fracture
The fracture lines (arrowheads) are confined entirely to the base of
the dens.*

56. Low (Type 3) dens fracture.
(A) No fracture line is apparent. This is frequently the case in this type of
fracture.
(B) A lateral tomogram clearly demonstrates the fracture line and the
tilting of the dens.*

57. EXTENSION TEARDROP FRACTURE (C2)
• Mechanism  An extension injury
• A fracture of the anteroinferior corner of body of C2 (which is avulsed
by an intact anterior longitudinal ligament)
• It is not associated with a neurological deficit
• It may occur in isolation or be associated with a hangman’s fracture
• it may occasionally involve the lower cervical vertebral bodies
• UNSTABLE injury

58. C2 extension teardrop fracture.
Note the triangular fragment arising from the anteroinferior vertebral
body margin and the marked swelling in the retropharyngeal tissue
(haematoma).
There is slight posterior subluxation of C2 upon C3 (hyperextension
mechanism and disruption of the intervertebral disc).*

59. FLEXION TEARDROP FRACTURE (C3–C7)
• Mechanism  Hyperflexion and axial compression (e.g. diving into
shallow water)
• Best seen on lateral view
• A fracture–dislocation that is usually associated with a spinal cord
injury
• UNSTABLE injury

60. XR
• It is characterized by a triangular fragment at the anteroinferior
aspect of the involved vertebral body (the ‘teardrop’)
• Reduced anterior vertebral body height with associated prevertebral
soft tissue swelling
• Posterior displacement of the fractured vertebra and diastasis of the
interfacetal joints (indicates longitudinal ligament, intervertebral disc
and posterior ligament complex disruption)

61. Flexion teardrop fracture.
Lateral C-spine XR with the cervical spine in the flexed attitude.
A single large fragment (antero-inferior corner of the C5 body) is present.
The 5th vertebral body is posteriorly displaced.
Widened interfacetal and interspinous spaces between C5 and C6 indicate complete
disruption of the posterior ligament complex and bilateral interfacetal dislocation.*

62. UNILATERAL LOCKED FACETS/UNLATERAL INTERFACETAL
DISLOCATION (C3–C7)
• Mechanism  A simultaneous flexion and rotation injury
• Dislocation of the interfacetal joint on the side opposite to the
direction of rotation (the dislocated facet comes to rest anterior to
the subjacent facet and is thus ‘locked’)
• STABLE injury

63. AP XR
• The spinous processes cephalad to the level of the dislocation are
rotated off the midline (in the direction opposite to that of the
rotation) and point to the side of the dislocation
Lateral XR
• The dislocated vertebra is anteriorly displaced by <50% of the sagittal
vertebral body diameter
• the spine above the level of dislocation is obliquely oriented (the
spine below is in direct lateral orientation)
• ’Bow tie’ or ‘butterfly’ appearance: the appearance of the articular
masses on an oblique projection

64. Unilateral locked facets.
(A) Frontal XR – the spinous processes from C6 and above (arrowheads) are rotated off the
midline.
(B) Unilateral locked facets (C5–6). The ‘bow tie’ or ‘butterfly’ configuration of the facet is
characteristic of this lesion (dashed lines). Note that at the level of dislocation, the
vertebrae above are in the oblique projection and those below are in the lateral
projection. One can see that the inferior facet of one side (arrow) lies anterior to the
vertebra below.*

65. (A) Lateral diagram. (B) AP diagram. The spinous
processes above the injury are rotated off the midline.

66. BILATERAL LOCKED FACETS/BILATERAL INTERFACETAL
DISLOCATION (C3–C7)
• Mechanism  Extreme neck flexion
• Both facet joints at the level of injury are dislocated and all the interosseous
ligaments (including the intervertebral disc) are disrupted
• It is usually associated with a neurological deficit
• UNSTABLE injury
• Lateral XR Anterior displacement of the involved vertebra for at least 50% of the
sagittal vertebral body diameter
• the articular masses of the superior vertebrae lie anterior to the articular masses
of inferior vertebrae (thus ‘locking’ the facets)
• there are often associated bilateral laminar fractures of the superior vertebrae

67. Bilateral locked facets at C4–5 (interfacetal dislocation)
Note that the lateral mass of the inferior facet of C4 is locked
anteriorly to the superior facet of C5.*

68. CLAY SHOVELLER’S FRACTURE (C6–T1)
• A spinous process avulsion (C6–T1)
• Mechanism  It is usually caused by rotation of the upper trunk with
a fixed cervical spine (occasionally as the result of a direct blow)
• STABLE injury (isolated fractures of the other indent posterior
elements are rare)

69. Clay shoveller’s fracture (arrow) of the spinous process of C6–7.*

70. HYPERFLEXION SPRAIN (C3–C7)
• Mechanism  Acute flexion without axial compression
• A pure soft tissue and posterior ligamentous injury
• STABLE injury

71. Lateral XR
• Localized kyphotic angulation
• Widening of the interspinous and interlaminar space (‘fanning’)
• Interfacetal joint subluxation
• Posterior widening and anterior narrowing of the intervertebral disc
( 1–3mm of vertebral anterior displacement)
• It is accentuated by flexion views (but must be supervised by a
radiologist)
• Injury is associated with delayed instability

72. Hyperflexion sprain
Note widening of the interspinous distance at C5–6 with
additional widening of the facet joints, and superior
subluxation of the facets of C4 on C5 and posterior
intervertebral joint. This picture indicates severe
ligamentous disruption.