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Introduction
  • Represent spectrum of osteoligamentous pathology that includes
    • 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
    • bilateral facet dislocation
      • leads to ~50% subluxation on xray
      • often associated with significant spinal cord injury
    • facet fractures
      • more frequently involves superior facet
      • may be unilateral or bilateral
  • Epidemiology
    • location
      • ~75% of all facet dislocations occur within the subaxial spine (C3 to C7)
      • 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
  • Pathophysiology
    • mechanism
      • flexion and distraction forces +/- an element of rotation
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 clinical setting
    • based solely on static radiographs and mechanisms of injury
Allen and Ferguson Classification (of subaxial spine injuries)
1. Flexion-compression
 
2. Vertical compression
 
3. Flexion-distraction Stage 1: Facet subluxation  
Stage 2: Unilateral facet dislocation
Stage 3: Bilateral facet dislocation with 50% displacement
Stage 4: Complete dislocation (100% displacement)  
4. Extension-compression    
5. Extension-distraction    
6. Lateral flexion    
 
Presentation
  • Physical exam
    • monoradiculopathy
      • seen in patients with unilateral dislocations
        • C5/6 unilateral dislocation
          • usually presents with a C6 radiculopathy
            • weakness to wrist extension
            • numbness and tingling in the thumb
        • C6/7 unilateral dislocation
          • usually 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
Imaging
  • Radiographs
    • 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
  • CT scan  
    • essential to demonstrate
      • bony anatomy of the injury
      • malalignment or subtle subluxation of facet 
      • facet fracture
      • associated fractures of the pedicle or lamina
  • MRI 
    • indications are controversial but include
      • acute facet dislocation in patient with altered mental status 
      • failed closed reduction and before open reduction to look for disc herniation
      • any neurologic deterioration is seen during closed reduction
    • timing
      • 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
    • valuable in demonstrating
      • disc herniations
      • extent of posterior ligamentous injury
      • spinal cord compression or myelomalacia 
Treatment
  • Nonoperative
    • cervical orthosis or external immobilization (6-12 weeks)
      • indications
        • facet fractures without significant subluxation, dislocation, or kyphosis
  • Operative
    • immediate closed reduction, then MRI, then surgical stabilization 
      • indications 
        • bilateral facet dislocation with deficits in awake and cooperative patient 
        • unilateral facet dislocation with deficits in awake and cooperative patient 
      • technique
        • never perform closed reduction in patient with mental status changes
        • surgical stabilization following successful closed reduction
          • 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
          • always obtain MRI prior to surgical stabilization
            • PSF or ACDF can be performed in the absence of significant disc herniation
            • ACDF performed if significant disc herniation present
      • outcomes
        • 26% of patients will fail closed reduction and require open reduction
    • immediate MRI then 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
  • Closed reduction
    • requirements
      • adequate anesthesia
      • sedation
      • supervision of respiratory function
      • serial cross table laterals
    • technique
      • gradually increase axial traction with the addition of weights
      • a component of cervical flexion can facilitate reduction
      • perform serial neurologic exams and plain radiographs after addition of each weight
      • abort if neurologic exam worsens and obtain immediate MRI
  • Anterior open reduction & ACDF
    • 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
      • reduction technique involves distracting vertebral bodies with caspar pins and then rotating the proximal pin towards the side of the dislocation
      • not effective for reducing bilateral facet dislocations
  • Posterior reduction & instrumented stabilization
    • indications
      • when unable to reduce by closed or anterior approach
      • no anterior compression of spinal cord(no disc herniation)
    • technique
      • performed with lateral mass screws
      • usually have to fuse two levels due to inadequate lateral mass purchase at level of dislocation
  • 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
    • 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
 

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Questions (4)

(OBQ12.264) A 21-year-old patient is evaluated in the trauma bay after a motor vehicle accident. He was found to have a GCS of 3 on the scene and is presently intubated. His bulbocavernosus reflex is not intact. Radiographs and representative CT scan sequences are shown in Figures A through E. What is the next best step in management? Review Topic

QID:4624
FIGURES:
1

Closed reduction under anesthesia

15%

(431/2794)

2

Open reduction under anesthesia

10%

(276/2794)

3

Overnight monitoring

2%

(55/2794)

4

Closed reduction with internal stabilization

6%

(161/2794)

5

MRI

67%

(1861/2794)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

Based on clinical findings and the imaging shown, this patient has bilateral facet dislocations at C5-6. Considering that he is intubated with concern for spinal cord injury, obtaining an MRI is the next best step.

Facet dislocations predominantly occur in the subaxial spine via flexion distraction mechanisms. Bilateral facet dislocations are often associated with severe spinal cord injury. In a patient who has an altered mental status, obtaining an MRI is critical. This will help identify injuries to the posterior ligamentous complex and the presence of myelomalacia. Of particular importance is the ability to identify disc herniations. Closed reductions completed in the setting of disc herniations can cause further injury to the spinal cord.

Kwon et al. review subaxial cervical spine trauma. They indicate that closed reduction prior to obtaining an MRI should only be completed in a patient who is awake, cooperative and neurologically intact. Open reduction should be completed when closed reduction fails (ie. Fractured facet or lateral mass dissociation) or neurologic deterioration occurs.

Patel et al. review a new classification scheme for subaxial cervical spine trauma. The SLIC (Subaxial Injury Classification and Severity Score) system defines morphology of the injury, status of the discoligamentous complex and neurologic status. The recommend clinical use of this system as it overcomes limitations faced by prior classifications.

Figure A shows a lateral radiograph of the cervical spine with translation of the C5 inferior facet anterior to the superior facet of C6. Figures B, C and D show CT scan sequences of the upper cervical spine. They demonstrate bilateral facet dislocations at the level of C5-6. Figure E is an axial image at the C5-6 level showing the inferior facet of C5 lying anterior to the superior facet of C6 (the inverted hamburger sign) bilaterally.

A video is provided below that reviews cervical spine trauma and management.

Incorrect Answers
Answers 1, 4: In a neurologically intact, awake and cooperative patient, closed reduction is warranted without anesthesia. Internal fixation may be applied after closed reduction is completed.
Answer 2: Open reduction is indicated when fractures of the facets or lateral mass dissociation have prevented closed reduction. Progressive neurologic decline is an indication to proceed with an open reduction
Answer 3: Observation alone is not indicated.

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(OBQ11.89) A 35-year-old female is involved in a high speed motorcycle crash. Work-up reveals the presence of an open right femur fracture, and neck pain. A CT scan of the cervical spine is obtained and shows a right sided C6/7 facet dislocation. Which of the following images is most representative of this injury? Review Topic

QID:3512
FIGURES:
1

Figure A

2%

(41/1863)

2

Figure B

19%

(357/1863)

3

Figure C

74%

(1382/1863)

4

Figure D

4%

(75/1863)

5

Figure E

0%

(2/1863)

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PREFERRED RESPONSE 3

Figure C shows a right sided C6/C7 facet dislocation represented by the abnormal articular facet relationship. This is demonstrated by the labeled image in Illustration B, compared to the normal anatomic facet relationships shown in Illustration A. When viewing the cervical spine on the axial cuts of a CT, the superior facet lies anterior to the inferior facet.

Daffner et al describe two new signs, the "hamburger bun" sign of normal facet joints and the "reverse hamburger bun" sign that should be useful in establishing a diagnosis of facet dislocation. They state that normal facet joints are oriented on a CT examination so that they resemble the sides of a hamburger bun, whereas facet dislocations upset this relationship and reverse the orientation of the "bun" halves to each other.

Pal et al performed a cadaveric study to evaluate the orientation of the superior articular facets in relation to their inclination with the sagittal and transverse planes between C3 and T3 vertebrae in each column. They then associated their findings with various cervical movements and associated clinical conditions.

Incorrect Answers:
Answer 1-Figure A shows normal facet anatomy.
Answer 2-Figure B shows a left sided facet dislocation
Answer 4 and 5-Figures D and E show bilateral facet dislocations

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Question COMMENTS (9)

(OBQ10.228) Cervical facet dislocations are characteristically caused by which of the following mechanisms of injury? Review Topic

QID:3327
1

Flexion-compression

4%

(96/2556)

2

Vertical compression

0%

(8/2556)

3

Flexion-distraction

87%

(2211/2556)

4

Extension-compression

1%

(35/2556)

5

Extension-distraction

8%

(201/2556)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

The Allen and Ferguson classification of cervical spine injuries breaks injuries of the subaxial spine into six phylogenic groups based on mechanism of injury. These include: 1) flexion-compression 2) vertical-compression 3) flexion-distraction 4) extension-compression 5) extension-distraction 6) lateral flexion. Facet dislocation is caused by flexion-distraction forces. Therefore, in a facet dislocation the posterior structures (interspinous ligament, facet capsule, liagmentum flavum, posterior annulus) are likely disrupted, whereas the anterior structures (anterior longitudinal ligament) are usually preserved. Sutterlin et al showed in a biomechanical bovine model, and Coe et al in a cadaveric model, that anterior plating was inferior to posterior techniques (Rogers' wiring method, Bohlman's triple-wire technique, sublaminar wiring, and posterior hook plate stabilization) for stabilization of flexion-distraction injuries of the cervical spine.


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(OBQ08.40) An awake and cooperative patient presents to the emergency room with the injury seen in the CT scan in Figure A. Prior to the CT scan he had an ASIA Impairment Scale of E. Upon returning from the CT scanner he has an ASIA Impairment Scale of D. What is the most appropriate first step in management? Review Topic

QID:426
FIGURES:
1

MRI

13%

(298/2368)

2

Immediate closed reduction with cervical traction

74%

(1744/2368)

3

Immediate anterior open reduction and surgical fixation

7%

(156/2368)

4

Spinal dose steroids

4%

(86/2368)

5

Cervical immobilization, observation, and serial neurologic exams

3%

(75/2368)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

The patient presents with a deteriorating neurologic exam in the presence of a bilateral C5-6 facet dislocation. Because the patient is alert, cooperative, and sober, the next step in management is closed reduction with cranial traction while the patient is awake.

An ASIA Impairment Scale of E is a normal exam. An ASIA Impairment Scale of D shows preserved motor function below the neurological level, but with more than half of key muscles below the neurological level showing weakness but with a muscle grade greater than 3. Therefore his exam is worsening. You know it is a bilateral facet dislocation as there is 50% subluxation of the vertebral bodies. Because the patient is alert, cooperative, and sober, the next step in management is closed reduction with cranial traction while the patient is awake. Because of his rapid decline in neurologic function you would not want to delay reduction by obtaining an MRI. All facet dislocations need to be stabilized surgically following reduction. Following closed reduction an MRI should be obtained to look for a cervical disc herniation, as the presence of one will determine the approach for stabilization.

The cited reference by Star et al is a case series (LOE4) of 53 patients who underwent closed reduction. They found that contrary to prior beliefs, adding weights of > 50 lbs and up to 100 lbs was safe and effective. In their series, 39 patients required greater than 50 lbs to obtain reductions and there was no associated complications with this additional weight.

Vaccaro et al performed prereduction and postreduction magnetic resonance imaging in eleven consecutive patients with cervical spine dislocations. They found the process of closed traction reduction appears to increase the incidence of intervertebral disc herniations. The relation of these findings, however, to the neurologic safety of awake closed traction reduction remain unclear.

Illustration A shows a simple algorithm to determine the ASIA Impairment Score (AIS).

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