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Updated: Jun 19 2021

Atlas Fractures & Transverse Ligament Injuries

Images
https://upload.orthobullets.com/topic/2015/images/type 3 atlas.jpg
https://upload.orthobullets.com/topic/2015/images/plough.jpg
https://upload.orthobullets.com/topic/2015/images/incomplete c1.jpg
https://upload.orthobullets.com/topic/2015/images/xray_jefferson_fx.jpg
  • 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
            • hard cervical collar
              • typically used in stable fracture patterns with intact transverse ligament
            • halo vest
              • typically used in the transverse ligament is compromised
          • 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
            • 10° medial screw trajectory protects the internal carotid artery
        • 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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