Updated: 6/19/2021

Atlas Fractures & Transverse Ligament Injuries

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  • Summary
    • Atlas Fractures & Transverse Ligament Injuries are traumatic injuries usually caused by high-energy trauma with axial loading in young patients (Jefferson Fracture) or low-energy falls in elderly. Due to the capacious nature of the spinal canal at this level these injuries usually present with neck pain without neurological deficits.
    • Diagnosis is often missed with plain radiographs so a CT scan may be required to make the diagnosis. An open-mouth odontoid radiograph is useful to evaluate for disruption of the transverse ligament which leads to lateral displacement of the lateral masses relative to each other. 
    • Stable injuries can be treated with immobilization in a cervical collar. Unstable injuries require either halo-vest immobilization or surgical stabilization with a fusion.
  • Epidemiology
    • Incidence
      • make up ~7% of cervical spine fractures 
      • atlas fractures make up to 25% of the injuries of the craniovertebral junction
      • 1-3% of all spinal injuries
      • commonly missed due to inadequate imaging of occipitocervical junction
    • Demographics
      • bimodal age distribution
        • early adulthood (20-30s)
          • high-energy axial loading mechanism
        • elderly
          • low-energy, ground-level fall
          • predisposed to injury from
            • osteoarthritic bone changes
            • limited mobility
            • gait imbalance
  • ETIOLOGY
    • Pathophysiology
      • mechanism
        • most commonly associated with high-energy injury mechanisms
          • ~85% of cases associated with MVC
        • ground level falls in elderly patients
          • osteoporosis predisposes to low energy fractures
        • injury biomechanics
          • hyperextension
            • forehead blow injury
              • posterior arch remains static
              • anterior arch continues to move
            • posterior arch injury
              • higher occurence with low-energy falls
              • higher association with odontoid fractures
            • 30% less energy requirement to cause atlas fracture when cervical spine is in extension compared to neutral
          • lateral compression
            • anterior arch fractures
          • lateral distraction
            • comminuted lateral mass fracture
          • axial compression
            • blow to the vertex
            • leads to Jefferson burst fracture
    • Associated conditions
      • spine fracture
        • 50% have an associated spine injury
        • 40% associated with axis fx
      • closed head injuries
      • neurologic injury
        • risk of neurologic injury is low
        • due to large space for the spinal cord at this level
        • injuries tend to increase the area availabe for spinal cord at C1
  • Anatomy
    • Bony anatomy
      Atlas osteology
      • atlas (C1) is a ring containing two articular lateral masses
        • it lacks a vertebral body or a spinous process
        • embryology
          • forms from 3 ossification centers
        • anatomic variation
          • incomplete formation of the posterior arch is a relatively common anatomic variant and does not represent a traumatic injury
        • C1 transverse foramen
          • houses vertebral artery
            • makes acute posteromedial bend around Occ-C1 joint and crosses sulcal groove
              • sulcal groove is a common site for posterior arch injuries/fractures
    • Ligamentous anatomy
      • occipital-cervical junction and atlantoaxial junction are coupled
      • intrinsic ligaments are located within the spinal canal, provide most of the ligamentous stability. They include
        • transverse ligament
          • primary stabilizer of atlantoaxial junction
            • prevents posterior migration of the odontoid into the spinal canal
          • connects the posterior odontoid to the anterior atlas arch, inserting laterally on bony tubercles of the lateral mass
        • paired alar ligaments
          • connect the odontoid to the occipital condyles
          • relatively strong and contributes to occipitalcervical stability
        • apical ligament
          • relatively weak midline structure
          • runs vertically between the odontoid and foramen magnum.
        • tectorial membrane
          • connects the posterior body of the axis to the anterior foramen magnum and is the cephalad continuation of the PLL
    • Articulations
      • occipitoatlantal joint (Occ-C1)
        • occipital condyles articulate with C1 superior articular processes
          • provides ~50% of cervical spine flexion and extension range of motion
        • true synovial joint
          • contains anterior and posterior joint capsules
      • atlantoaxial joints (C1-2)
        • facet joints
          • articulation between the inferior facet of C1 and superior facet of C2
          • biconcave synovial joint
        • atlantodens joint
          • synovial joint
          • aticulation between the dens (C2) and the anterior arch of the atlas
            • enable ~50% of cervical spine rotation
  • Classification
    •  Landells Atlas Fractures Classification
      Type 1
      Isolated anterior or posterior arch fracture.
      Most common injury pattern
      "Plough" fracture is an isolated anterior arch fracture caused by a force driving the odontoid through the anterior arch. 
      Stable injury
      Treat with hard collar. 
      Type 2
      Jefferson burst fracture with bilateral fractures of anterior and posterior arch resulting from an axial load.
      Stability determined by the integrity of transverse ligament. 
      If intact, treat with a hard collar. 
      If disrupted, halo vest (for bony avulsion) or C1-2 fusion (for intrasubstance tear)(see Dickman classification below).
      Type 3
      Unilateral lateral mass fx. 
      Stability determined by the integrity of the transverse ligament. 
      If stable, treat with a hard collar. 
      If unstable, halo vest.
    • Dickman Transverse Ligament Injuries Classification
      Type 1
      Intrasubstance tear
      Treat with C1-2 fusion.
      Type 2
      Bony avulsion at tubercle on C1 lateral mass
      Treat with halo vest (successful in 75%)
  • Presentation
    • History
      • high-energy injury
        • MVC
        • fall from ladder
      • ground level fall
        • elderly patients
    • Symptoms
      • neck pain
      • cervical spinal muscle spasms
      • limited neck motion
      • C2 nerualgia/palsy
        • occipital neuralgia 
        • occipital numbess
        • occipital alopecia (rare)
      • vertebral artery dissection
        • loss of consciousness
        • double vision
        • vertigo
    • Physical exam
      • neuro deficits uncommon in isolated C1 fractures
        • associated C2 fractures have a higher risk of neuro deficit
      • vertebral artery injury 
        • vertigo
        • diploplia
        • blindness 
        • ataxia
        • bilateral weakness
        • dysphagia
        • nausea
      • C2 nerve palsy
        • decreased sensation in the occipital region 
        • neck flexion and extension weakness
  • Imaging
    • Radiographs 
      • recommended views
        • lateral radiographs
        • oblique radiographs
          • 60-degree oblique radiographs to indetify posterior arch fractures
        • open-mouth odontoid
          • open-mouth odontoid view important to identify atlas fractures
      • optional views
        • flexion-extension views
          • identify late instability following nonoperative treatment
      • findings
        • increased widening of C1 lateral masses compared to C2 (LMD)
        • increased distance of the atlantodental interval (ADI)
        • fracture involving the posterior or anterior arch
        • concomitant spine injuries
          • C2 injuries
          • subaxial spine injuries
          • occipitocervical distraction/dissociation 
      • measurements
        • atlantodens interval (ADI)
          • measured on lateral radiographs and flexion-extension views
            • < 3 mm = normal in adult (< 5mm normal in child)
            • 3-5 mm = injury to transverse ligament with intact alar and apical ligaments
            • > 5 mm = injury to transverse, alar ligament, and tectorial membrane
        • sum of lateral mass displacement (LMD)
          • measured on open-mouth odontoid views
            • if sum of lateral mass displacement is > 6.9 mm (rule of Spence) or 8.1mm with radiographic magnification (rule of Heller) then a transverse ligament rupture is assured and the injury pattern is considered unstable
        • retropharyngeal soft tissue
          • measured on lateral radiographs
            • increased thickening of retropharyngeal soft tissue (>9.5 mm) suggests an anterior arch injury
      • sensitivity
        • radiographs have a lower sensitivity of detecting unstable atlas fractures than CT and MRI
    • CT
      • indications
        • should be ordered for every case of suspected cervical spine injury
          • study of choice to delineate fracture pattern and identify associated injuries in the cervical spine
        • good study to assess for pseudospread of the atlas in pediatric patients 
          • thin slices parallel to the C1 arch
          • represents asymmetric growth of the atlas compared to the axis
            • greater atlantal overhang of the lateral masses
      • views
        • sagittal reconstructions
          • occult horizontal fractures of the anterior arch
        • axial reconstructions
          • identify Dickman II injuries to the TAL
        • coronal reconstructions
          • determine total lateral mass displacement
        • angiogram
          • assess the presence of a vertebral artery injury
      • findings
        • fractures involving the anterior and posterior ring
        • lateral mass fractures
        • increased radial displacement of the C1 fracture fragments (unstable)
        • bone avulsion injuries of the tubercle (TAL insertion)
        • sagittal split fractures of the lateral mass
      • sensitivity
        • highly sensitive at detecting fractures
        • lower sensitivity than MRI at detecting TAL injuries
    • MRI
      • indications
        • should be ordered in any case there is a confirmed fracture of the atlas
          • rule out associated unstable ligamentous injuries 
      • views
        • sagittal and coronal views
          • increased T2 signal in the TAL suggests intrasubstance injury 
      • findings
        • TAL injuries
          • increased T2 signal intensity in the TAL on the sagittal and coronal views 
        • spinal cord injury
          • edema
            • increased T2 signal intensity in the spinal cord
          • hematoma
            • depends on age of injury 
        • prevertebral soft tissue swelling
          • increased prevertebral soft tissue T2 signal intensity at C1-2
      • more sensitive at detecting injury to transverse ligament
        • increaed T2 signal intensity in the TAL is suggestive of injury
  • Treatment
    • Nonoperative
      • hard collar vs. halo immobilization for 6-12 weeks
        • indications
          • stable Type I fx (intact transverse ligament)
          • stable Jefferson fx (Type II) (intact transverse ligament)
          • stable Type III (intact transverse ligament)
          • Dickman type II TAL injuries
        • technique
          • controversy exists around optimal form of immobilization
            • cervical collar
            • halo vest
          • reduce with halo traction before immobilization
          • immobilization for 3 months
          • require post treatment flexion-extension radiographs to assess for late instability
    • Operative
      • posterior C1-C2 fusion vs. occipitocervical fusion
        • indications
          • unstable Type II (controversial)
          • unstable Type III (controversial)
          • Dickman type I TAL injuries
          • combined C1 and C2 fractures
            • most often type II odontoid and hangman's fractures
            • higher association with neurologic injury
          • some authors prefer Occ-C2 fusion as opposed to C1-2 fusion
            • no significant downside and lower risk of revision surgery
        • technique
          • may consider preoperative traction to reduce displaced lateral masses
      • C1 internal fixation
        • indications
          • C1 lateral mass split fractures (controversial)
          • described in a few small case serioes
        • preserves C1-2 motion
        • technique
          • anterior and posterior techniques described
            • transoral approach
        • further randomized trials needed to ascertain role of this treatment
  • Techniques
    • Posterior C1-C2 fusion
      • preserves motion compared to occipitocervical fusion
      • fixation
        • C1 lateral mass - C2 pedicle screw construct (Harm's technique)
          • may be sufficient if adequate purchase with C1 lateral mass screws
        • C1-2 transarticular screw placement
        • sublaminar wiring
          • not commonly performed in isolation
          • need intact posterior arch
    • Occipitocervical fusion (C0-C2)
      • used when unable to obtain adequate purchase of C1 (comminuted C1 fracture)
      • leads to significant loss of motion 
      • fixation
        • occipital plate
        • C1 lateral mass screws
        • C2 pedicle screws
    • C1 internal fixation
      • anterior and posterior approaches described
        • standard posterior approach
      • fixation
        • plate and screw construct
        • screw and rod construct
        • screws alone
  • Complications
    • Vertebral artery injury
      • rare complication with displaced posterior ring fractures
        • fractures involving the sulcal groove
    • Neurologic injury
      • rare in isolated atlas fractures
        • radial displacement of fracture increased the surface area of the spinal canal'
    • Cock robin deformity
      • displaced unilateral sagittal split lateral mass fracture
        • occipital condyle settles onto the C2 superior articular facet
      • treat with occipitocervical fusion +/- osteotomy to correct the deformity
    • Nonunion
      • ~20% of cases treated nonoperatively
    • Neck pain
      • present in 20-80% of patients after immobilization
    • Delayed C-spine clearance
      • higher rate of complications in patients with delayed C-spine clearance so it is important to clear expeditiously
    • Pseudoarthrosis
    • Stiffness
      • loss of ~50% of cervical rotation with C1-2 arthrodesis
      • loss of ~50% cervical flexion with Occ-C2 arthrodesis
    • Infection
      • a complication of surgical treatment
      • higher infection rates in patients treated with posterior approaches
  • Prognosis
    • Natural history (conservative treatment)
      • 8-20% complaints of neck stiffness
      • 14-80% complaints of neck pain
      • ~34% complaints of activity limitations
      • contact athletes may not return to play
    • Prognostic variables
      • stability dependent on degree of injury and healing potential of transverse ligament
      • worse long-term patient reported outcomes in fractures with >7 mm of displacement
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Questions (7)

(SBQ18SP.74) A 17-year-old male jumped headfirst into a shallow lake and sustained a comminuted C1 fracture. On exam, he is alert and oriented with normal motor and sensation in the upper and lower extremities. Which of the following radiographic parameters measurements suggests transverse ligament rupture?

QID: 211916
1

Space available for cord 15 mm

3%

(43/1646)

2

Atlanto-dens interval 2 mm

9%

(155/1646)

3

Basion-dens interval 11 mm

12%

(193/1646)

4

Combined lateral mass displacement 9 mm

74%

(1220/1646)

5

5 mm of prevertebral soft tissue swelling at C2

1%

(23/1646)

L 3 A

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(OBQ13.55) A 28-year-old male patient dives head first into a shallow pool. He presents to the emergency room and radiographs and a CT are performed and shown in Figures A-D. Which of the following statements are true regarding these radiographic findings.

QID: 4690
FIGURES:
1

The transverse ligament is disrupted, the fracture is unstable and should be treated with either a rigid orthosis, halo immobilization, or surgical stabilization

68%

(3479/5082)

2

The transverse ligament is intact, the fracture is stable and can be treated in a soft cervical collar

16%

(830/5082)

3

It is classified as Anderson and D'Alonzo Type II because the fracture extends into the C1/C2 facet

3%

(176/5082)

4

It is classified as Anderson and D'Alonzo Type III because the fracture extends into the C1/C2 facet

4%

(227/5082)

5

The imaging findings are relatively common and represent a congenital incomplete formation of the posterior arch and not a traumatic injury

6%

(325/5082)

L 4 B

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(OBQ12.255) A 35-year-old patient sustains a bilateral anterior and posterior arch (C1) injury with an intact transverse ligament. Which of the following treatment options is most appropriate?

QID: 4615
1

Observation alone

1%

(45/4218)

2

Soft collar orthosis for 4-6 weeks

4%

(164/4218)

3

Occipitocervical fusion

7%

(308/4218)

4

Rigid collar orthosis for 6-12 weeks

80%

(3387/4218)

5

Posterior C1-C2 fusion

7%

(300/4218)

L 2 B

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(OBQ10.71) Figure A shows the coronal and axial CT images of a 27-year-old male that suffered a fall from a significant height. Which of the following radiographic measurements would best indicate disruption of the transverse ligament?

QID: 3159
FIGURES:
1

Atlantodental interval (ADI) of 2mm

6%

(250/4240)

2

Posterior atlanto-dens interval (PADI) of 16mm

10%

(414/4240)

3

C2 pars horizontal displacement of 3 mm

3%

(140/4240)

4

Combined lateral mass displacement of 8.2mm

77%

(3279/4240)

5

A Power's ratio of 1.2

3%

(133/4240)

L 2 B

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(OBQ05.67) A Gallie C1-2 fusion with sublaminar wiring of C1 to the spinous process of C2 is a valid treatment option for which of the following injury patterns?

QID: 953
1

occipital-cervical dissociation

5%

(83/1728)

2

comminuted C1 burst fracture

8%

(138/1728)

3

type I odontoid fracture

4%

(70/1728)

4

type III odontoid fracture

13%

(230/1728)

5

transverse ligament disruption

69%

(1197/1728)

L 2 C

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(OBQ04.176) Biomechanical studies have shown that an atlanto-dens interval of >7mm is likely associated with?

QID: 1281
1

an intact transverse ligament, with ruptured alar and apical ligaments

6%

(223/3735)

2

a ruptured transverse ligament, with intact alar and apical ligaments

21%

(769/3735)

3

a ruptured transverse and apical ligament, with an intact alar ligaments

9%

(326/3735)

4

a ruptured transverse and alar ligament, with an intact apical ligaments

19%

(704/3735)

5

a ruptured transverse and alar ligament, and a ruptured tectorial membrane

45%

(1691/3735)

L 4 C

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