Cervical Facet Dislocations & Fractures - Spine

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

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