Axial Cervical Spine Trauma

Atlanto-Occipital Dissociation

  • High-energy injury – RTA
  • High mortality rate & incidence of neurologic injury

Stability of the AO joint

  • Reliant virtually only on ligamentous structures
    1. Anterior Atlanto-occipital membrane - continuation of ALL
    2. Posterior Atlanto-occipital membrane – continuation of flavum
    3. Tectorial membrane - continuation of PLL
    4. Alar and Apical ligaments from Dens to foramen magnum
    5. Bony congruity of Occipital condyles & C1 Lateral masses (poor)

Classification

  • Type 1
    • Anterior displacement of the occipital condyles (most common)
  • Type 2
    • Superior migration of the Occipital condyles
  • Type 3
    • Posterior displacement of occipital condyles (least common)

Radiographic Assessment

  • Can be very subtle
  • Powers Ratio
    • Basion to Anterior arch : Opisthion to anterior arch
    • BC:OA
    • Normal = <1 (higher indicates dissociation)
  • Harris intervals
    • Most sensitive measurement
    • Basion Dens & Basion Axis Intervals (BDI & BAI)
    • Both should be <12mm

Management

  • Definitive treatment is C2-Occipital posterior instrumented fusion
  • HALO can be temporising but not definitive
  • Because instability is due to loss of ligamentous support

Fractures of the Atlas (C1)

  • Axial loading injury with an element of bending depending on pattern
  • Neurologic injury is rare
  • Problem is late instability with burst fractures involving transverse ligament
  • Fracture fragments move away from cord
    • Steels rule of 1/3’s – at C1 level space available is occupied by:
      • Odontoid
      • Cord
      • CSF (free space) – provides buffer zone for cord displacement in trauma

Levine Classification

  • A-E (order different in each book!)
    • A Transverse process fracture
    • B Posterior Arch Fracture
    • C Anterior Arch Fracture
    • D Lateral mass fracture
    • E Burst Fracture (Jefferson)
      • Transverse Ligament intact
      • Transverse ligament disrupted (very unstable)

Radiology

  • What is the fracture pattern?
  • Is the transverse ligament disrupted (primary C1/2 stabiliser)
    • Open mouth combined lateral mass widening of 7mm = TL rupture

Management

  • Almost all treated in HALO for 8-12 weeks
  • If an associated odontoid fracture – manage - unstablement based on PEG fracture
  • If TL ruptured (widening of 7mm) surgery should be considered:
    • Lateral mass screws (motion sparing)
    • C1/2 or C2-Occiput fusion – more reliable

Isolated Transverse Ligament Disruption

  • Rare usually fatal injury
  • Occurs in >50 year old patients
  • Mechanism is high energy forced flexion

Radiology

  • Look for bony avulsions around dens
  • Lateral mass widening >7mm combined
  • AD1 >4mm

Management

  • Bony avulsions can be treated in HALO till union occurs
  • Fusion for pure ligamentous avulsions

Fractures of the Axis – C2

  • Traumatic C2-3 Spondylolisthesis (Hangman’s fracture)
    • Most are stable
    • Low rate of neurologic compromise in type 1 & 2, higher in type 3
    • Risk of vertebral artery injury

Mechanism

  • Hyperextension & rebound flexion causing some variants
  • Causes a traumatic pars defect

Hangmans Fracture (Traumatic C2 Spondylolisthesis)

Classification (Levine & Edwards)

  • Type 1
    • <3mm displacement, minimal angulation, disc intact
  • Type 2

    • 3mm displacement, minimal angulation, disc intact

    • Most common type
  • Type 2a
    • Angulation rather than displacement – may look like type 1
    • Flexion distraction mechanism
    • Disc may be extruded
  • Type 3
    • Spondylolisthesis with associated facet dislocation
    • Rare
    • Hyperextension with rebound flexion
    • Bilateral facet dislocation occurs first, then hyperextension causes SL
    • Highest rate of Neurologic compromise

Management

  • HALO immobilisation enough for types 1 & 2
  • Do not apply traction to type 2a – will risk cord injury & increase displacement
  • Disc may be extruded; Flexion-Distraction injury
  • Reduction & fusion advised for type 3

Odontoid Fractures

  • Most common injury of the axial spine
  • High correlation with other C-spine injuries
  • Odontoid is an important C1/2 stabiliser
  • Therefore PEG displacement can compromise C1/2 stability

Mechanism

  • Flexion after a blow to the occiput – fall or RTA

Classification (Anderson)

  • Type 1
    • Avulsion fractures of the tip – oblique or superior
    • Apical/alar ligament avulsions
    • Benign usually but rule out features of AO dissociation
  • Type 2
    • Fracture of the waist – junction between PEG & C2 body
    • Most common type
  • Type 2a
    • Waist fracture but comminuted
  • Type 3
    • Fracture of PEG extending into bone of C2 +/- into facets

Management

  • Goal of management in all odontoid fractures is to reduce and maintain anatomic alignment
  • This minimises risk of C1/2 instability and neurologic compromise
  • Type 1 & 3
    • Non-operative in HALO or collar
    • Fix if irreducible, neurologic compromise or unstable - rare
  • Type 2 & 2a
    • High rate of non-union & late displacement
    • Blood supply enters from tip & C2 body with watershed area at waist
    • Risk factors for non-union
      1. Displaced or angulated fracture (especially posterior angulation)
      2. Late presentation of fracture
      3. Elderly patient
      4. Comminution of fracture
    • If fracture is reduced or reducible and stable treat in a HALO
    • Consider treating all elderly patients operatively – HALO problems
    • Any displaced, irreducible fracture in a young patient treat surgically
    • Options
      • Anterior screw placement
        • Favoured if possible (fx pattern, patient habitus)
      • Transarticular C3-C2 screws
      • Posterior fusion
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