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Updated: 5/25/2021

Occipital Condyle Fractures

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  • Summary
    • Occipital condyle fractures are traumatic injuries that involve articulation between the base of the skull and the cervical spine.
    • Diagnosis of the fracture is best made with a CT scan. An MRI and/or flexion-extension radiographs are used to evaluate for associated occipitocervical instability.
    • Most fractures are treated with immobilization with a cervical orthosis. Occipitocervical fusion is indicated in the rare cases where occipitocervical instability is present.
  • Epidemiology
    • Incidence
      • relatively uncommon.
      • approximately 1-3% of population with blunt craniocervical trauma.
      • often missed due to low diagnosis sensitivity of plain radiographs.
        • reported incidence is increasing due to increased utilization of CT scans.
  • ETIOLOGY
    • Pathophysiology
      • terminology
        • occipital condyle fractures represent a subset of basilar skull fractures.
      • mechanism
        • high energy trauma to the head/neck
          • motor vehicle accident
          • fall from height.
        • low energy trauma to head and neck
          • occasionally seen in ground level falls in elderly due to direct blow to the skull.
      • pathoanatomy
        • fracture patterns are dependent on the directional forces applied to the craniocervical junction at the time of the injury including
          • axial compression
          • horizontal sheer due to a direct blow on the skull
          • rotation
          • lateral bending
    • Associated injuries
      • orthopaedic manifestations
        • cervical spinal cord injuries (31%)
          • neurological deficits may be acute (63% of cases) or delayed (37% of cases)
        • cervical fractures
        • vertebral artery injury
        • polytrauma
      • medical manifestations
        • intracranial bleeding 
        • brainstem and vascular lesions
        • elevated ICP
  • Anatomy
    • Osteology
      • occipital condyle morphology
        • occipital condyles are paired oval prominences of the occipital bone.
        • form the lateral aspects of the foramen magnum.
      • occipitoatlantal joint (occiput/C1)
        • articulation
          • each occiput articulates with a shallow dish-like joint on the superior aspect of the lateral mass of C1.
          • joint morphology allows for large range of flexion and extension of craniocervical junction.
        • ligamentous stability
          • provide by a combination of
            • occipitoatlantal joint joint capsule
            • alar ligaments (dens to each occipital condyle)
    • Ligaments
      • intrinsic ligaments are located within the spinal canal, provide most of the ligamentous stability. They include
        • transverse ligament
          • connects the posterior odontoid to the anterior atlas arch, inserting laterally on bony tubercles.
          • primary stabilizer of atlantoaxial junction.
        • paired alar ligaments
          • connect the odontoid to the occipital condyles.
          • relatively strong and contributes to occipitocervical stability.
        • apical ligament
          • runs vertically between the odontoid and foramen magnum.
          • relatively weak midline structure.
        • tectorial membrane
          • connects the posterior body of the axis to the anterior foramen magnum and is the cephalad continuation of the PLL.
    • Vascular system
      • vertebral artery
        • occipital condyles are in proximity to vertebral arteries.
    • Nervous system
      • occipital condyles in close proximity to
        • medulla oblongata
        • spinal cord
        • lower cranial nerves (CN IX - CN XII)
        • C2 nerve root
    • Biomechanics
      • occipitoatlantoaxial complex (craniocervical junction)
        • function
          • an anatomic complex that provides stability and function of craniocervical junction (occiput to C2).
        • includes 6 articulations
          • 2 occipitoatlantal joints
          • 2 paired lateral C1-C2 facets/joints
          • 1 dens-anterior arch of C1 articulation
          • 1 posterior midline atlantoaxial joints
        • three ligamentous structure connect C2 directly to base of skull (thereby skipping C1)
          • apical ligament
          • alar ligament
          • tectorial membrane
  • Classification
      • Anderson and Montesano Classification of Occipital Condyle Fractures
      • Type I
      • 3% of OC fracture
      • IImpaction-type fracture with comminution of the occipital condyle
      • Due to compression between the occipitoatlantal joint
      • Stable injury due to minimal fragment displacement into the foramen magnum
      • Type II
      • 22% of OC fractures
      •  Basilar skull fracture that extends into one- or both occipital condyles
      • Due to a direct blow to skull and a sheer force to theoccipitoatlantaljoint
      • Stable injury as the alar ligament and tectorial membrane are usually preserved
      • Type III
      • 75%
      •  Avulsion fracture of condyle in region of the alar ligament attachment (suspect underlying occipitocervical dissociation)
      • Due to forced rotation with combined lateral bending.
      • Has the potential to be unstable due to craniocervical disruption
  • Presentation
    • History
      • clinical presentation is highly variable
      • often a history of high energy trauma with associated head injury (head injury, vertebral artery injury, spinal cord injury)
    • Symptoms
      • high cervical pain
      • neck stiffness
      • double vision
      • upper and lower extremity weakness
    • Physical examination
      • inspection
        • look for trauma to skull (e.g, skull laceration)
      • ROM
        • remove collar and evaluate limited motion
          • limited cervical ROM may elicit pain
      • neurologic
        • extremity exam
        • rectal exam
        • lower cranial nerve exam
          • deficits most commonly affect CN IX, X, and XI
  • Imaging
    • Radiographs
      • recommended views
        • AP, lateral, open-mouth AP view
      • alternative views
        • flexion and extension views
      • findings
        • diagnosis rarely made on plain radiographs due to superimposition of structures (maxilla, occiput) blocking view of occipital condyles
        • open-mouth AP view may depict occipital condyle injuries
      • measurements
        • Powers ratio
          • used to diagnosis occipitocervical dislocation
          • technique
          • Powers ratio = C-D/A-B
            • C-D: distance from basion to posterior arch
            • A-B: distance from anterior arch to opisthion
          • significance
            • ratio of ~ 1 is normal
            • if > 1.0 concern for anterior dislocation
            • if ratio < 1.0 raises concern for posterior dislocation, odontoid fractures, or ring of atlas fractures
        • O-C2 angle
          • technique
            • angle between McGregor line and C2
          • significance
            • needs to be established prior to OC fusion to prevent postoperative dysphagia by causing a significant change relative to the preoperative O-C2 angle
        • C2 to T1 lordotic alignment
    • CT
      • indications
        • diagnostic method of choice
        • usually obtained as routine CT imaging in high-energy trauma patients
        • clinical criteria
          • altered consciousness
          • occipital pain and tenderness
          • impaired CCJ motion
          • lower cranial nerve paresis
          • motor paresis
      • views
        • must include cranial-cervical junction with thin-section technique
      • findings
        • occiput fracture
          • may see migration of fragment into spinal canal
        • joint diastasis (2mm or less is considered normal)
    • CT angiogram
      • indications
        • concern for vertebral artery injury
        • surgical planning to identify location of vertebral artery
    • MRI
      • indications
        • evaluation of soft-tissue craniocervical trauma
        • spinal cord or brain stem ischemia
      • findings
        • edema or fluid collection in the occipitoatlantal joint representing rupture of the occipitoatlantal joint capsule
        • edema or fluid collection consistent with avulsion injury of alar ligament from dens or occiput
    • MRA (Magnetic Resonance Angiogram)
      • indications
        • considered with suspected vascular injury
  • Differential
    • Key differential
      • occipitocervical instability
      • atlas fractures
      • odontoid fracture
  • Treatment
    • Nonoperative
      • immobilization with cervical orthosis
        • indications
          • indicated in vast majority of low energy fractures
          • Type 1 and 2
          • Type 3 without overt instability
        • modalities
          • semi-rigid or rigid cervical collar
          • usually worn for 6 weeks
    • Operative
      • occipitocervical fusion
        • indications
          • very rarely indicated
          • Type 3 with overt instability
          • neural compression from displaced fracture fragment
          • associated occipital-atlantal or atlanto-axial injuries
  • Techniques
    • Occipitocervical fusion
      • approach
        • posterior midline incision with patient in prone position
        • Mayfield retractor used to obtain proper craniocervical alignment
          • establish preoperative O-C2 angle with lateral fluoroscopy prior to draping
      • deep dissection
        • if performing C1 lateral mass screw fixation work within safe zone and do not dissect above the posterior arch of C1 more than 1 cm lateral to midline to avoid injury to vertebral artery
      • instrumentation
        • length
          • posterior segmental instrumented fusion is usually performed from the occiput to C3
        • occipital
          • occipital plates usually allow for 3 or 4 total screws with adjustable rod holders
          • occipital screws
            • usually unicortical to avoid injury to venous sinus
              • major dural venous sinuses are located just below the external occipital protuberance and are at risk of penetrative injury
              • some institutions prefer bicortical screws but they come at increase risk
            • occipital screw safe zone
              • the safe zone for occipital screws is located within an area measuring 2 cm lateral and 1 cm inferior to the external occipital protuberance along the superior nuchal line
        • C1 lateral mass screws
          • often skipped due to angle at base of skull making it more difficult to place a rod
          • may choose a unilateral screw to provide some rotational stability to C1 ring
        • C2 fixation
          • pars, pedicle screws, transarticular, or translaminar screws all options
        • C3 fixation
          • standard lateral mass screws aimed cephalad and lateral to avoid vertebral artery
      • arthrodesis
        • perform decortication of occiput, posterior arch of C1, and lamina of C2
        • may require autogeneous bone grafting or bone allograft
      • postoperative immobilization
        • patients frequently immobilized in halo or hard cervical orthosis for 6-12 weeks to obtain fusion
  • Complications
    • Nonoperative
      • neck pain & stiffness
    • Operative
      • intracranial venous sinus injury (occipital screws)
      • vertebral artery injury (C1 lateral mass screws)
      • adjacent segment disease
      • neck pain & stiffness
  • Prognosis
    • high mortality rate (11%) due to associated injuries.
      • rate has decreased due to improvement in first responder cervical spine precautions.
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