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Updated: Jun 7 2021

Cervical Facet Dislocations & Fractures

4.4

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Images
https://upload.orthobullets.com/topic/2064/images/lat xray bilateral facet dislocation C4-5_moved.jpg
https://upload.orthobullets.com/topic/2064/images/Lat Xray - Unilateral facet dislocation_moved.jpg
https://upload.orthobullets.com/topic/2064/images/CT bilateral facet dislocation combined_moved.jpg
https://upload.orthobullets.com/topic/2064/images/MRI bilateral facet dislocation C5-6_moved.jpg
  • Summary
    • Cervical Facet Dislocations and Fractures represent a spectrum of traumatic injury with a varying degree of cervical instability and risk of spinal cord injury.
    • Diagnosis can be confirmed with radiographs or CT scan. An MRI should be performed before surgery to identify an associated disk herniation.
    • Treatment usually involves closed or open reduction followed by surgical stabilization.
  • Epidemiology
    • Demographics
      • high energy trauma in young
        • motor vehicle accidents and motor cycle accidents
          • high speed deceleration injury
        • contact sports injuries
      • low energy trauma in elderly
    • Anatomic location
      • 17% of all injuries are fractures of C7 or dislocation at the C7-T1 junction
        • this reinforces the need to obtain radiographic visualization of the cervicothoracic junction
  • Etiology
    • Pathoanatomy
      • represent spectrum of osteoligamentous pathology that includes
        • facet fractures
          • more frequently involves superior facet
          • may be unilateral or bilateral
          • decreases the threshold for facet dislocation
            • loss of tethering effect of interlocked facets
        • unilateral facet dislocation
          • most frequently missed cervical spine injury on plain xrays
          • leads to ~25% subluxation on xray
          • associated with monoradiculopathy that improves with traction
            • inferior facet of the cephalad vertebrae encrouches the neuroforamina
        • bilateral facet dislocation
          • leads to ~50% subluxation on xray
          • often associated with significant spinal cord injury (~80% of cases)
      • mechanism
        • flexion and distraction forces +/- an element of rotation
          • rotational moment associated with unilateral facet dislocation
    • Associated injuries
      • head injuries
      • noncontiguous spinal injuries
        • often occurs in the thoracolumbar, cervicothoracic, and occipitocervical junction
      • appendicular injuries
  • Classification
    • Descriptive classification (subaxial cervical spine injuries)
      • includes
        • compression fracture
        • burst fraction
        • flexion-distraction injury
        • facet dislocation (unilateral or bilateral)
        • facet fracture
      • more commonly used in clinical setting
      • Allen and Ferguson Classification (of subaxial cervical spine injuries)
      • Typically used for research and not in a clinical setting
      • Based solely on static radiographs and mechanisms of injury
      • 1. Flexion-compression
      • 2. Vertical compression
      • 3. Flexion-distraction
      • Stage 1: Facet sprain with slight subluxation, focal kyphosis <10°
      • Stage 2: Unilateral facet dislocation
      • Stage 3: Bilateral facet dislocation with 50% displacement (perched facets)
      • Stage 4: Complete dislocation (100% displacement)
      • 4. Extension-compression
      • 5. Extension-distraction
      • 6. Lateral flexion
  • Presentation
    • History
      • history of trauma involving flexion-distration mechanism
      • obtain relevant past history
        • ankylosing spondylitis / DISH
        • previous cervical spine fusion
    • Symptoms
      • pain
        • neck pain in setting of flexion-distraction mechanism
      • unilateral dislocation
        • numbness and tingling radiating down a single arm
          • C5/6 presents with numbness in thumb
          • C6/7 presents with numbness in index and middle finger
      • bilateral dislocation
        • subjective weakness in b/l upper and lower extremeties
        • paresthesias and sensory changes in b/l lower extremities
    • Physical exam
      • inspection
        • gross spinal alignment
          • angular deformity may suggest a unilateral facet dislocation
        • scalp and head lacerations or contusions
          • suggest a overlying head injury
      • monoradiculopathy
        • seen in patients with unilateral dislocations
          • C5/6 unilateral dislocation
            • presents with a C6 radiculopathy
              • weakness to wrist extension
              • numbness and tingling in the thumb
          • C6/7 unilateral dislocation
            • presents with a C7 radiculopathy
              • weakness to triceps and wrist flexion
              • numbness in index and middle finger
      • spinal cord injury symptoms
        • seen with bilateral dislocations
        • symptoms worsen with increasing subluxation
        • perform thorough neruologic examination
          • assess motor and sensory status
          • neurologic reflexes
          • document findings via ASIA scoring
  • Imaging
    • Radiographs
      • views
        • ap, lateral, oblique, open-mouth odontoid
      • findings
        • lateral shows subluxation of vertebral bodies
        • unilateral dislocations lead to ~ 25% subluxation
        • bilateral facet dislocation leads to ~ 50% subluxation on xray
        • loss of disc height might indicated retropulsed disc in canal
        • widening of the interspinous distance
        • hypolordosis, especially at the injury level
        • soft tissue swelling
      • additional views
        • flexion-extension lateral radiographs
          • indications
            • required whenever facet fracture seen due to possibility of spontaneous reduction and occult instability
    • CT scan
      • indications
        • most cases require a CT scan
      • findings
        • bony anatomy of the injury
        • malalignment or subtle subluxation of facet
        • facet fracture
        • associated fractures of the pedicle or lamina
    • MRI
      • indications
        • acute facet dislocation in patient with altered mental status
          • must be performed emergently followed by open reduction and stabilization
        • failed closed reduction and before open reduction to look for disc herniation
        • any neurologic deterioration is seen during closed reduction
        • any patient going to OR for surgical stabilization needs an MRI in advance
      • timing (controversial)
        • timing of MRI depends on severity and progression of neurologic injury
        • an MRI should always be performed prior to open reduction or surgical stabilization
          • if a disc herniation is present with compression on the spinal cord, then you must go anterior to perform a anterior cervical diskectomy
      • findings
        • disc herniations
          • need to know if large anterior disc is present prior to surgery
        • extent of posterior ligamentous injury
          • disruption of the supraspinous and interspinous ligaments
          • posterior longitudinal ligament and posterior annulus disruption
            • 40% of cases in unilateral dislocation
            • 80% of cases in bilateral dislocation
          • sprain or disruption of the posterior facet capsules
        • spinal cord compression or myelomalacia
        • spinal cord hematoma
          • poor prognostic sign for motor recovery
  • Differential
    • Cervical Lateral Mass Fracture Separation
      • important to identify as cervical lateral mass fracture separations require fusing two levels while a facet dislocation only requires fusing a single level
  • Treatment
    • Nonoperative
      • external immobilization x 6-12 weeks
        • indications
          • stable facet fracture
            • unilateral reduced facet fractures without radiographic instability and involving <40% of the lateral mass or an absolute height <1 cm
              • must first rule out instability with flexion-extension radiographs
        • technique
          • halo vs. hard orthosis depending on degree of instability and age of patient
        • outcomes
          • >30% rate of subluxation or redislocation
            • increased pain associated with late redislocations
          • high incidence of persistent pain and instability
    • Operative
      • single level instrumented stabililzation
        • indications
          • unstable facet fracture
            • bilateral facet fracture
            • unilateral fracture involving >40% of the lateral mass or an absolute height >1 cm
        • technique
          • if no anterior disc herniation can be performed from anterior or posterior approach
      • emergent closed reduction, emergent MRI, then urgent surgical stabilization
        • indications
          • bilateral facet dislocation with deficits in awake and cooperative patient
          • unilateral facet dislocation with deficits in awake and cooperative patient
            • for a unilateral dislocation there is no spinal cord injury so urgency is much less than with a bilateral dislocation
        • timing
          • emergent to obtain reduction especially when you have bilateral dislocation
          • once reduction is obtain, and patient in a collar, then obtain MRI emergently. If MRI shows reduction and no significant compression on spinal cord, then can perform stabilization on urgent (within 24 hours basis)
        • technique
          • closed reduction
            • usually precedes surgical intervention
              • rarely closed reduction followed by immobilization performed
                • medically frail patients
              • facet dislocations associated with high degree of instability and ligamentous injuries
            • technique
              • never perform closed reduction in patient with mental status changes
              • unilateral dislocations are more difficult to reduce but more stable after reduction
              • bilateral dislocation are easier to reduce (PLL torn) but less stable following reduction
            • outcomes
              • 26% of patients will fail closed reduction and require open reduction
              • unilateral facet dislocations effectively closed reduced in 25% of cases
          • anterior cervical discectomy and fusion (single level)
            • indications
              • large disc herniation present following reduction with compression on the spinal cord or nerve roots
              • if closed reduction is failed, may attempt open reduction from anterior approach by distracting across casper pins with simulatenous rotation
              • 1-level interbody arthrodesis with anterior plating
          • posterior reduction & instrumented stabilization
            • indications
              • when no anteior disc present
              • bilateral or unilateral facet dislocations that are not reducible from the front or through closed reduction
          • combined anterior decompression and posterior reduction / stabilization
            • indications
              • when disc herniation present that requires decompression in patient that can not be reduced through closed or open anterior technique
      • emergent MRI then emergent open reduction surgical stabilization
        • indications
          • facet dislocations (unilateral or bilateral) in patient with mental status changes
          • patients who fail closed reduction
        • technique
          • always obtain MRI prior to open reduction and stabilization
          • if disc herniation with presence of spinal cord compression then you must use an anterior approach and do a discectomy
  • Techniques
    • Halo external immobilization
      • technique
        • halo is suboptimal in lower cervical spine and therefore hard orthosis may be satifactory without complications associated with a halo
        • requires close radiographic follow-up
          • risk of redislocation or subluxation
        • morbidly obese patients may not fit or be adequately stabilized in a halo brace
    • Closed reduction
      • requirements
        • adequate anesthesia
        • sedation
        • supervision of respiratory function
        • serial cross table laterals
        • ability to perform serial neurologic examinations
      • technique
        • application of Gardner-Wells tongs
          • 1 cm above the pinna and in line with the external auditory meatus
          • below the equator of the skull
            • avoids pin migration and slippage
        • gradually increase axial traction with the addition of weights
          • usually in 5 to 10 lbs increments
          • can add up to 140 lbs of weight or 70% body weight
          • average weigh required for reduction ~9.4 to 9.8 lbs per segment above the injury level
        • a component of cervical flexion can facilitate reduction
          • flexion moment can be created with pulley system or posterior placement of the Gardner-Wells tongs pins
        • once reduced, decrease traction weight be 10-15 lbs and apply an extension moment to the cervical spine
          • adjusting pulley system
          • placing pad underneath thorax
        • perform serial neurologic exams and plain radiographs after addition of each weight addition
          • abort if there is over distraction of the spinal segment
            • >1.5 times that if the adjacent uninjured disc space
        • can switch to carbonfiber Gardner-Wells tongs if need to obtain MRI in traction
          • traction limit ~80 lbs
        • abort if neurologic exam worsens and obtain immediate MRI
    • Anterior cervical diskectomy and fusion +/- open reduction
      • indications
        • facet dislocations reduced through closed methods with a MRI showing cervical disc herniation with significant compression on the spinal cord
        • unilateral facet dislocations that fail closed reduction with a disc herniation with significant compression on the spinal cord
      • anterior open reduction techniques
        • can be used to reduce a unilateral facet dislocation
        • standard Smith-Robinson approach
          • generous removal of the anterior-inferior aspect of the cephalad vertebra
            • allows disc space visualization
        • unilateral dislocations can be reduced by distracting vertebral bodies with caspar pins and then rotating the proximal pin towards the side of the dislocation
        • bilateral dislocations are reduced by placing converging Caspar pins (10-20° angle) and then compressing the ends together to unlock the facets
          • posterior directed force applied to rostral vertebral body with currette
        • alternatively, lamina spreaders applied to the endplates
        • not effective for reducing bilateral facet dislocations
      • pros and cons
        • overdistraction of the disc space
          • often the PLL and posterior ligaments are disrupted
          • excessively large graft may be used to obtain a press-fit interbody graft
          • will demonstrate the facet joints being gapped posteriorly
          • places hardware at risk for failure
          • over distraction also has risk of added spinal cord injury
    • Posterior instrumented stabilization +/- open reduction
      • indications
        • when unable to reduce by closed or anterior approach
        • no anterior compression of spinal cord(no disc herniation)
      • technique
        • instrumentation performed with lateral mass screws
        • reduction
          • Penfield 4 inserted between facets and used to lever back into position
            • can remove the superior aspect of the superior facet of the caudad vertebrae to facilitate difficult reductions
          • distraction of the affected level between the affected spinous processes or lamina with use of lamina spreaders
        • usually have to fuse two levels due to inadequate lateral mass purchase at level of dislocation
    • Combined anterior decompression and posterior reduction / stabilization
      • technique
        • go anterior first, perform discectomy, position plate but only fix plate to superior vertebral body
        • this way the plate will prevent graft kick-out but still allows rotation during the posterior reduction
        • this technique eliminates the need for a second anterior procedure
  • Complications
    • Surgical site infections
      • increased risk with posterior surgery
      • tissue trauma from injury increases risk of infection
    • Recurrent dislocation
      • unilateral dislocations treated with immobilization
      • treated with anterior diskectomy, reduction, and interbody fusion
    • Respiratory complications
      • ARDS
        • higher risk in the multitraumatized patient
      • pneumonia
        • due to prolonged recumbency and need to tracheostomy
    • Vertebral artery injury
      • occurs in up to 11% of patients with cervical spine injuries
        • increased risk when injury involves lateral mass and transverse process
      • often go unrecognized and untreated
    • Esophageal injury
      • related to anterior reduction and fixation
      • primary repair with throacic surgeon upon identification
    • Pin tract infections
      • associated with Halo vest immobilization
      • can result in decreased pin purchase
      • rarely result in meningitis if ther inner table of the skull is violated
      • treat with local care and antibiotics
  • Prognosis
    • Neurologic recovery
      • lower probability of motor improvement with increasingly severe neurologic injury
      • increased age associated with decreased neurologic recovery
      • poor motor recovery potential with spinal cord hematoma
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