Facet dislocation is a traumatic spinal injury resulting from flexion-distraction forces that displace the vertebral facet joints, causing loss of articular congruence. It accounts for approximately 10% of all subaxial cervical spine fractures and may be unilateral or bilateral, with bilateral dislocations representing highly unstable injuries carrying a significant risk of spinal cord injury (SCI). [1-2] The most commonly affected levels are C5-C6 and C6-C7. [3-4]
1. History
- Mechanism of injury: High-energy trauma (MVC, fall from height, sports collision, diving); flexion-distraction, axial loading, and rotational forces are the primary mechanisms [1][5]
- Neck pain: Onset, severity, radiation (radicular vs. axial)
- Neurological symptoms: Weakness, numbness, tingling in upper/lower extremities; bowel or bladder dysfunction
- Timing: Immediate vs. delayed onset of neurological deficits
- Ambulatory status: Ability to move extremities post-injury
- Important negatives: Loss of consciousness, head injury, intoxication, distracting injuries — all affect reliability of exam and clearance [6]
2. Alarm Features
- Complete motor/sensory loss below the injury level (ASIA A) — 61% of facet dislocation patients present with SCI [7]
- Neurogenic shock: Hypotension with bradycardia, unexplained by hypovolemia [6]
- Priapism in male patients [6]
- Diaphragmatic breathing/tachypnea suggesting high cervical cord injury
- Progressive neurological deterioration — demands emergent intervention
- Bilateral facet dislocation — highly unstable, associated with greater translation and higher rates of complete SCI [2][7]
- Vertebral artery injury (VAI) — occurs in ~13% of cervical facet dislocations; suspect with maxillofacial co-injury or paravertebral hematoma [8]
3. Medications
- Acute pain management: Multimodal approach — acetaminophen, NSAIDs, and opioids for severe pain [6][9]
- Neuropathic pain: Gabapentin or pregabalin as first-line; amitriptyline as alternative [6][10]
- Muscle relaxants: May be adjunctive for associated muscle spasm [9]
- Steroids: High-dose methylprednisolone for acute SCI is no longer routinely recommended due to marginal benefit and significant side effects; practice varies
- Cautions: NSAIDs may impair bone healing with chronic use; opioids should be limited to short-term use (≤3 days) [6][9]
- DVT prophylaxis: Essential in immobilized/SCI patients
4. Diet
- NPO if surgical intervention is anticipated
- Adequate nutrition is critical for wound healing and recovery in SCI patients
- Calcium and vitamin D supplementation for bone health in prolonged immobilization
- Bowel regimen: Initiate early in SCI patients to prevent constipation/ileus
5. Review of Systems
- Neurological: Motor/sensory deficits, paresthesias, bowel/bladder dysfunction, sexual dysfunction
- Respiratory: Dyspnea, diaphragmatic breathing (high cervical injuries may compromise phrenic nerve C3-C5)
- Cardiovascular: Hypotension, bradycardia (neurogenic shock)
- GI: Ileus, abdominal distension (autonomic dysfunction)
- GU: Urinary retention, incontinence
- Musculoskeletal: Associated fractures, polytrauma
6. Collateral History and Family History
- Witnesses to mechanism: Speed, direction of force, position at impact
- Pre-existing conditions: Ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis (DISH) — dramatically increase fracture risk and VAI risk (OR 8.04) [11]
- Baseline neurological function: Pre-existing myelopathy, radiculopathy
- Anticoagulant use: Increases risk of epidural hematoma
- Substance use: Intoxication affects exam reliability [6]
7. Risk Factors
- High-energy mechanisms: MVC, falls from height, diving, contact sports [3]
- Young adults: Over-represented in MVC-related injuries; older adults more commonly injured from falls [3]
- Male sex: ~70% of cases [3][12]
- Pre-existing cervical stenosis: Smaller canal diameter at injury level is an almost perfect predictor of severe SCI (ASIA A-C) [7]
- Ankylosing spondylitis/DISH: Rigid spine increases fracture and VAI risk [11]
- Greater vertebral translation (>6.7 mm) predicts VAI [13]
8. Differential Diagnosis
- Facet fracture without dislocation: Lower-energy mechanism, may be stable, treated with immobilization [5]
- Burst fracture: Axial loading mechanism, anterior column failure
- Hangman's fracture (C2 pars interarticularis): Extension-distraction mechanism
- Ligamentous injury without fracture: MRI-detected, may present with delayed instability
- Disc herniation: May coexist (~54% incidence at injury level) [1]
- Vertebral artery dissection: Can occur independently or with facet dislocation
- Pathologic fracture: Metastatic disease, infection — consider in low-energy mechanisms
9. Past Medical History
- Prior cervical spine surgery or fusion: Alters biomechanics at adjacent levels
- Osteoporosis: Affects fixation strategy
- Ankylosing spondylitis/DISH: Rigid spine, high-risk for unstable fractures
- Previous SCI or myelopathy: Baseline neurological status critical for comparison
- Coagulopathy or anticoagulant use: Risk of epidural hematoma
10. Physical Exam
- ATLS primary survey: Airway, breathing, circulation, disability, exposure — maintain full spinal motion restriction [5-6]
- Neurological exam: Complete ASIA/AIS assessment — motor (key muscle groups C5-T1, L2-S1), sensory (light touch, pinprick), rectal tone, bulbocavernosus reflex [14]
- Cervical spine: Midline tenderness, step-off deformity, paraspinal muscle spasm
- Vital signs: Hypotension + bradycardia = neurogenic shock; tachypnea = high cervical injury
- Torticollis: Classic for unilateral facet dislocation — head rotated away from the locked facet
- Extremity exam: Lateralizing motor deficits, priapism [6]
- Perineal sensation: Even slight preservation (ASIA B) portends better neurological outcome than complete loss (ASIA A) [14]
11. Lab Studies
- CBC: Baseline hemoglobin (low hemoglobin associated with VAI) [13]
- BMP/CMP: Renal function, electrolytes
- Coagulation studies: PT/INR, PTT — especially if on anticoagulants or surgical intervention planned
- Type and screen/crossmatch: If surgical intervention anticipated
- Lactate: Assess for occult hemorrhage/shock
- Blood alcohol/toxicology screen: Assess exam reliability
12. Imaging
- CT cervical spine without contrast: First-line and reference standard — sensitivity ~98% for clinically significant injuries; identifies fracture morphology, translation, facet alignment [15]
- Key findings: "Reverse hamburger bun" sign on axial images (dislocated facet), "headphones sign" (uncovertebral mal-alignment), "empty facet" sign [16-17]
- Unilateral dislocation: typically <25% vertebral body translation
- Bilateral dislocation: typically ≥50% translation
- MRI cervical spine: Essential complementary study — evaluates disc herniation (~54% incidence), ligamentous injury, spinal cord edema/hemorrhage, DLC integrity [14][18]
- CT angiography (CTA) of the neck: Screen for vertebral artery injury — recommended for all facet dislocations (OR 3.8-4.4 for BCVI) [6][12][20]
- Plain radiographs: Low sensitivity (36%); largely supplanted by CT [15]
13. Special Tests
The SLIC (Subaxial Injury Classification) score is the key decision-support tool:
Facet dislocations score 4 points for morphology (rotation/translation) alone. With DLC disruption (+2) and any neurological deficit (+1 to +3), SLIC scores are typically ≥5, indicating operative management. [6][21]
Additional scoring/classification tools:
- ASIA Impairment Scale (AIS): Grades A-E for SCI severity [14]
- AO Spine Subaxial Classification: Type C injuries (translational) encompass facet dislocations [22]
- NEXUS/CCR criteria: For initial decision to image [15]
- Biffl grading: For vertebral artery injury severity [13]
14. ECG
- Indicated in all trauma patients and specifically when neurogenic shock is suspected
- Bradycardia: Classic finding in neurogenic shock from cervical SCI (loss of sympathetic tone)
- Cardiac arrhythmias: May occur with high cervical cord injuries due to autonomic dysregulation
- Rule out cardiac contusion: In high-energy blunt trauma
15. Assessment
- Facet dislocations exist on a spectrum from subluxation to locked dislocation [1]
- Unilateral: Rotationally unstable; ~40% present with radiculopathy, ~42% with SCI [23]
- Bilateral: Highly unstable; majority present with SCI, 76% with complete neurological loss in thoracolumbar injuries; cervical bilateral dislocations carry 61% SCI rate [7][24]
- Severity stratification: Greater translation and smaller canal diameter at injury level correlate with worse neurological outcomes [7]
- Complications: Disc herniation (54%), vertebral artery injury (13%), neurogenic shock, DVT/PE, pressure injuries, respiratory failure (high cervical)
16. Treatment Plan
Initial stabilization
- ATLS protocols; maintain strict cervical spine immobilization [5]
- Hemodynamic support: IV fluids, vasopressors (phenylephrine or norepinephrine) for neurogenic shock; target MAP ≥85 mmHg in acute SCI
Reduction
- Closed reduction with skull traction (Gardner-Wells tongs): Appropriate in alert, cooperative patients — success rate ~55-71%. Some experts advocate pre-reduction MRI; others consider it unnecessary in awake patients [1][4][19][25]
- Open surgical reduction: Required when closed reduction fails or patient is obtunded [26]
Surgical fixation
- Anterior approach (ACDF with plating): Effective for reduction and stabilization; 96% satisfactory realignment in one large series. Allows direct disc decompression [4]
- Posterior approach (lateral mass or pedicle screw fixation): No surgical failures reported; allows direct facet manipulation [26-27]
- Combined anterior-posterior: For irreducible, delayed, or complex injuries [2]
- Neither approach has demonstrated clear superiority for neurological improvement [27]
Conservative management
- rigid cervical orthosis[6]
17. Disposition
- Admission criteria: All facet dislocations require admission — ICU for bilateral dislocations, SCI, neurogenic shock, or polytrauma
- Observation: Unilateral facet fractures without neurological deficit managed conservatively may be observed with serial exams
- Specialist consultation triggers:
- Spine surgery (neurosurgery or orthopedic spine): All facet dislocations [5]
- Vascular surgery/interventional radiology: If VAI identified on CTA
- Trauma surgery: Polytrauma management
- PM&R/SCI rehabilitation: Early consultation for SCI patients
- Discharge criteria: Not applicable acutely for true dislocations; stable minimally displaced facet fractures without neurological deficit may be discharged with rigid collar and close follow-up after spine consultation [6]
18. Follow Up / Return Precautions
- Post-operative: Follow-up at 2 weeks (wound check), 6 weeks (dynamic radiographs to assess alignment and fusion), then 3, 6, and 12 months [6]
- Conservative management: Dynamic cervical radiographs at 6 weeks to assess stability [6]
- Return precautions (patient counseling):
- New or worsening weakness, numbness, or tingling in arms/legs
- Loss of bowel or bladder control
- Increasing neck pain or new deformity
- Difficulty breathing or swallowing (post-anterior surgery: watch for hematoma, dysphagia)
- Expected recovery: Patients with incomplete SCI (ASIA B-D) frequently show neurological improvement; complete SCI (ASIA A) has poor recovery prognosis. Late kyphotic deformity and persistent radiculopathy are recognized complications requiring reoperation in ~18% [14][23][25]
References
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