SUBAXIAL CERVICAL SPINE FRACTURES
C3-C7 Injuries | SLIC Score Guides Treatment | Anterior vs Posterior Approach
SLIC CLASSIFICATION
Critical Must-Knows
- SLIC score (morphology + DLC + neurology) guides surgical decision-making
- Disco-ligamentous complex (DLC) is the key determinant of instability
- MRI essential to assess DLC integrity and cord compression
- Anterior approach for disc/vertebral body pathology, posterior for facet/lamina
- Combined approach for severe instability or when anterior alone insufficient
Examiner's Pearls
- "SLIC 4 or more indicates surgical management
- "Indeterminate DLC on MRI = 1 point, disrupted = 2 points
- "Incomplete cord injury with ongoing compression = urgent surgery
- "Facet dislocations often require posterior reduction first
Critical Subaxial Cervical Spine Exam Points
SLIC Score Calculation
Three components: Morphology (0-4) + DLC status (0-2) + Neurological status (0-4). Score of 4 or more indicates surgical intervention. Know each component scoring.
DLC Assessment
Disco-ligamentous complex includes disc, ALL, PLL, ligamentum flavum, interspinous ligaments, facet capsules. MRI required for assessment. Disrupted DLC = unstable.
Approach Selection
Anterior approach: corpectomy/discectomy, kyphosis correction, ventral compression. Posterior approach: facet injuries, lamina fractures, posterior tension band disruption.
Neurological Status
Complete injury: stable neurology, timing less critical. Incomplete injury with compression: urgent decompression within 24 hours improves outcomes (STASCIS data).
Quick Decision Guide
| SLIC Score | Injury Pattern | Treatment | Key Pearl |
|---|---|---|---|
| 0-3 | Compression fracture, intact DLC | Rigid collar 6-12 weeks | Non-op if DLC intact - most common scenario |
| 4 | Indeterminate stability | Surgeon preference | MRI critical - DLC status determines treatment |
| 5-6 | Burst + DLC disruption | Surgical stabilization | Consider anterior corpectomy with cage |
| 7+ | Fracture-dislocation + incomplete SCI | Urgent surgical decompression | Within 24h for incomplete SCI with compression |
MDNSLIC Score Components
Memory Hook:MDN - Morphology, DLC, Neurology determine stability - score 4 or more means surgery!
CBDTMorphology Scoring
Memory Hook:C1-B2-D3-T4: Compression 1, Burst 2, Distraction 3, Translation 4 - easy to remember!
DAPLICDLC Components
Memory Hook:The DLC is the key - if disrupted, the spine is unstable regardless of bone injury!
AVPApproach Selection
Memory Hook:Anterior pathology = Anterior approach; Posterior pathology = Posterior approach - match the pathology to the approach!
Overview and Epidemiology
Subaxial cervical spine injuries (C3-C7) represent approximately 50% of all cervical spine fractures. These injuries carry significant morbidity due to the high rate of associated spinal cord injury.
Epidemiology:
- Bimodal age distribution (young trauma, elderly falls)
- Male predominance (3:1)
- Most common at C5-C6 level (greatest mobility)
- MVA and falls are primary mechanisms
- Associated spinal cord injury in up to 55%
Why C5-C6?
The C5-C6 level is most commonly injured because it represents the transition zone between the more mobile middle cervical spine and the relatively stiffer lower cervical spine. This biomechanical transition creates a stress concentration point.
Mechanism patterns:
- Flexion-compression: Burst fractures, teardrop fractures
- Extension-compression: Lamina fractures, hangman's variants
- Flexion-distraction: Facet dislocations, posterior ligament disruption
- Axial compression: Burst fractures
- Lateral flexion: Unilateral injuries
Anatomy and Biomechanics
Key anatomical structures:
The subaxial cervical spine (C3-C7) has consistent anatomy with:
- Vertebral body - primary load-bearing structure
- Facet joints - 45-degree orientation, guide motion
- Uncovertebral joints - resist lateral translation
- Intervertebral disc - shock absorption, motion
- Ligamentous structures - stability through ROM
The Disco-Ligamentous Complex (DLC)
The DLC is the primary determinant of stability. It includes:
- Intervertebral disc
- Anterior longitudinal ligament (ALL)
- Posterior longitudinal ligament (PLL)
- Ligamentum flavum
- Interspinous and supraspinous ligaments
- Facet capsules
If the DLC is disrupted, the injury is unstable regardless of bony injury severity.
Spinal cord considerations:
- Cervical cord enlargement (C4-T1) - higher injury consequence
- Space available for cord = canal diameter minus cord diameter
- Normal canal diameter approximately 17mm
- Cord diameter approximately 10mm
- Stenosis increases injury severity for same energy
Biomechanical Motion Segments
| Level | Primary Motion | Clinical Significance |
|---|---|---|
| C3-C4 | Flexion/extension | Early degenerative changes |
| C4-C5 | Flexion/extension | Common stenosis level |
| C5-C6 | Maximum motion | Most common injury level |
| C6-C7 | Transition zone | Stress concentration |
| C7-T1 | Cervicothoracic junction | Mechanically critical |
Neurological anatomy:
- Cervical nerve roots exit above their numbered vertebra (C6 root exits C5-C6 foramen)
- Exception: C8 root exits below C7 (no C8 vertebra)
- Root injury more common than cord injury in unilateral facet injuries
- Cord injury more common with bilateral facet dislocations
Classification Systems
Subaxial Cervical Spine Injury Classification (SLIC)
The SLIC system is the most widely used classification for guiding treatment decisions.
Component 1: Morphology (0-4 points)
| Pattern | Points | Description |
|---|---|---|
| No abnormality | 0 | Normal alignment and structure |
| Compression | 1 | Loss of anterior height, intact posterior |
| Burst | 2 | Anterior and posterior cortex involved |
| Distraction | 3 | Abnormal separation of vertebrae |
| Translation/rotation | 4 | Horizontal displacement or rotation |
Component 2: Disco-Ligamentous Complex (0-2 points)
| DLC Status | Points | MRI Findings |
|---|---|---|
| Intact | 0 | Normal signal, no disruption |
| Indeterminate | 1 | Isolated interspinous widening, subtle changes |
| Disrupted | 2 | High signal in disc, widened facets, ligament rupture |
Component 3: Neurological Status (0-4 points)
| Status | Points | Modifier |
|---|---|---|
| Intact | 0 | No neurological deficit |
| Root injury | 1 | Single nerve root deficit |
| Complete cord injury | 2 | ASIA A |
| Incomplete cord injury | 3 | ASIA B, C, or D |
| Ongoing compression with incomplete SCI | +1 | Add to incomplete score |
SLIC Treatment Threshold
- SLIC 0-3: Non-operative (rigid collar 6-12 weeks)
- SLIC 4: Indeterminate (surgeon preference)
- SLIC 5+: Operative treatment recommended
Clinical Assessment
History:
- Mechanism of injury (high vs low energy)
- Time since injury
- Any neurological symptoms (weakness, numbness, bladder/bowel)
- Previous cervical spine problems
- Medical comorbidities affecting surgical decision
Physical examination:
General Assessment
- Airway: Consider early intubation if unstable
- Breathing: Diaphragmatic if high cord injury
- Circulation: Neurogenic shock (bradycardia + hypotension)
- Associated injuries: Head, chest, polytrauma
Spine Examination
- Inspection: Bruising, deformity, step-off
- Palpation: Tenderness, interspinous widening
- Range of motion: Do NOT test if unstable suspected
- Log-roll: Clear entire spine
Neurological examination:
ASIA Impairment Scale
| Grade | Description | Motor/Sensory |
|---|---|---|
| A | Complete | No motor or sensory below level |
| B | Sensory incomplete | Sensory but no motor below level |
| C | Motor incomplete | Motor below level, less than half key muscles grade 3+ |
| D | Motor incomplete | Motor below level, at least half key muscles grade 3+ |
| E | Normal | Normal motor and sensory |
Document Neurological Status
Complete neurological examination documented at presentation is essential for:
- Baseline for monitoring deterioration
- Surgical decision-making
- Prognostication
- Medicolegal protection
Key dermatomal landmarks:
- C4: Shoulder
- C5: Lateral arm, deltoid
- C6: Thumb, wrist extensors
- C7: Middle finger, triceps
- C8: Little finger, finger flexors
- T1: Medial arm, intrinsics
Myotomal testing:
- C5: Deltoid, biceps
- C6: Wrist extensors, brachioradialis
- C7: Triceps, wrist flexors
- C8: Finger flexors
- T1: Finger abduction (intrinsics)
Investigations
Imaging Protocol
First-line imaging for trauma. Thin-cut CT from occiput to T1. Sagittal and coronal reconstructions essential. Sensitivity more than 99% for fractures.
Essential for DLC assessment. Shows disc herniation, ligament rupture, cord contusion, epidural hematoma. STIR sequences best for ligament injury.
Extend imaging to assess cervicothoracic junction. Often obscured on plain films.
Thin-cut CT at 3-6 months to assess fusion. Earlier if concerns about hardware.
CT interpretation:
Key features to document:
- Vertebral body morphology (compression, burst, translation)
- Facet alignment (subluxation, perched, locked)
- Canal compromise (percentage)
- Fragment retropulsion
- Spinous process widening (suggests posterior ligament injury)
MRI for SLIC
MRI is mandatory for SLIC scoring because DLC status cannot be determined from CT alone. Indeterminate or disrupted DLC significantly changes the score and treatment recommendation.
MRI interpretation:
- T2/STIR high signal in disc: Disruption
- Widened interspinous space with edema: Posterior ligament injury
- Facet fluid/widening: Capsule disruption
- Cord signal change: Contusion/hemorrhage (poor prognostic sign)
- Epidural hematoma: May require urgent decompression
Imaging Modality Selection
| Scenario | Primary Imaging | Additional Imaging |
|---|---|---|
| Trauma, neurologically intact | CT cervical spine | MRI if surgery planned |
| Trauma with neurological deficit | CT then urgent MRI | CT angiography if high suspicion dissection |
| Indeterminate stability on CT | MRI for DLC | Flexion-extension rarely indicated acutely |
| Post-operative assessment | X-ray series | CT at 3-6 months for fusion |
Management Algorithm
Initial Management
All patients with suspected cervical spine injury require:
- Immobilization with rigid collar
- Log-roll precautions
- Neurological documentation
- MAP optimization (target 85-90mmHg for incomplete SCI)
Indications for Non-Operative Treatment
SLIC score 0-3 with:
- Intact disco-ligamentous complex
- No neurological deficit
- Minimal displacement
- Stable fracture pattern
Protocol:
- Hard collar (Miami J, Philadelphia) for 6-12 weeks
- Serial lateral X-rays at 2, 6, and 12 weeks
- Assess for progressive kyphosis or translation
- ROM exercises after collar removed
- Physiotherapy for strengthening
Monitoring:
- Kyphosis progression more than 10 degrees = surgical consideration
- Development of neurological symptoms = urgent MRI
- Failure to heal at 12 weeks = consider surgery
When Non-Op Fails
Conversion to surgery indicated for:
- Progressive kyphosis more than 10-15 degrees
- Late neurological deterioration
- Persistent instability on flexion-extension films
- Non-union at 3-6 months
Surgical Technique
Pre-operative Planning
Consent Points
- Neurological injury: Risk of worsening (1-2%)
- Infection: Superficial 2-3%, deep less than 1%
- Dysphagia (anterior): 50% early, 5% persistent
- Hardware failure: 5-10%
- Adjacent segment disease: Long-term risk
- Recurrent laryngeal nerve (anterior): 2-5%
Equipment Checklist
- Imaging: Fluoroscopy or navigation
- Implants: Plates/screws (anterior), lateral mass screws (posterior)
- Cage/graft: Structural allograft or cage for corpectomy
- Neuromonitoring: SSEPs and MEPs
- Cell saver: For multilevel procedures
Anterior Cervical Approach (Smith-Robinson)
Step-by-Step Technique
Supine on radiolucent table. Head in neutral with gentle traction (Gardner-Wells if needed). Shoulder roll to extend neck. Arms tucked at sides.
Transverse incision at appropriate level (C5-6 at thyroid cartilage). Develop plane between carotid sheath laterally and trachea/esophagus medially. Retract longus colli muscles.
Identify level with fluoroscopy. Mark with needle if uncertain. Expose vertebral bodies and discs. Preserve anterior longitudinal ligament if possible.
Discectomy or corpectomy as indicated. Remove PLL to decompress canal. Visualize dura. Remove retropulsed fragments.
Cage or graft to restore height. Size appropriately (1-2mm larger). Position centrally. Confirm alignment on fluoroscopy.
Anterior plate spanning construct. Bicortical screws (4-5mm engaging posterior cortex). Confirm position with lateral fluoroscopy.
Avoid Esophageal Injury
Esophageal perforation is rare but devastating. Risk factors include:
- Previous anterior surgery
- Prominent osteophytes
- Excessive retraction
- Long operative time
Protect with gentle retractor placement and intermittent release.
Intraoperative Troubleshooting
Common Problems and Solutions
| Problem | Cause | Solution |
|---|---|---|
| Cannot reduce facet | Locked facet, interposed fragment | Increase distraction, open facet capsule, remove fragment |
| Vertebral artery bleeding | Lateral screw trajectory, dissection too lateral | Pack with hemostatic agent, complete surgery, do NOT attempt repair |
| CSF leak | Dural tear during decompression | Primary repair if possible, dural sealant, lumbar drain |
| Neuromonitoring changes | Cord compression, hypotension, positioning | Stop, check BP, optimize positioning, consider wake-up test |
Complications
Complications of Subaxial Cervical Fractures and Surgery
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Neurological deterioration | 1-3% | Careful reduction, neuromonitoring, appropriate timing |
| Dysphagia (anterior) | Up to 50% early | Gentle retraction, minimize operative time |
| Recurrent laryngeal nerve injury | 2-5% | Right-sided approach (unless revision), careful retraction |
| Hardware failure | 5-10% | Appropriate construct length, bone quality assessment |
| Non-union/pseudarthrosis | 5-10% | Adequate graft, smoking cessation, consider BMP |
| Adjacent segment disease | Up to 25% at 10 years | Limit fusion length, preserve motion where possible |
| Infection | 1-3% | Prophylactic antibiotics, meticulous technique |
| Vertebral artery injury | Less than 1% | Preoperative CT angiography, careful screw placement |
Neurological deterioration:
- Most feared complication
- Risk higher with incomplete SCI
- Prevention: neuromonitoring, careful reduction, avoid over-distraction
Dysphagia after anterior surgery:
- Very common early (50%)
- Usually resolves within weeks
- Persistent in 5-10%
- Consider thin liquids initially, speech pathology review
Right vs Left Approach
Left-sided approach is traditionally preferred because the recurrent laryngeal nerve has a more consistent course in the tracheoesophageal groove. On the right, it loops around the subclavian artery and has a variable course. However, right-sided revision is preferred if previous left approach.
Postoperative Care and Rehabilitation
Rehabilitation Timeline
- ICU monitoring if SCI or high-risk
- Neurological checks every 4 hours
- DVT prophylaxis
- Early mobilization assessment
- Speech pathology if anterior (nil by mouth initially)
- Transition to ward if stable
- Begin mobilization with collar
- Physiotherapy assessment
- Diet advancement (anterior)
- Wound check
- Wound review at 2 weeks
- Continue hard collar
- X-ray at 6 weeks
- Progressive mobilization
- SCI rehabilitation if indicated
- X-ray assessment of fusion
- Consider collar weaning if stable
- Increase activity
- Physio for strengthening
- CT to confirm fusion
- Collar removal if fused
- Return to work assessment
- Long-term follow-up for adjacent segment disease
Collar protocol:
- Most surgeons use hard collar for 6-12 weeks post-operatively
- Earlier removal if rigid internal fixation and good bone quality
- Longer if osteoporosis, multilevel, or concern about stability
Outcomes and Prognosis
Neurological outcomes:
- Complete SCI (ASIA A): Minimal recovery expected, focus on rehabilitation
- Incomplete SCI: Significant potential for recovery, especially with early decompression
- Root injury: Usually good recovery over 6-12 months
Factors affecting outcome:
- Severity of initial injury
- Timing of decompression (for incomplete SCI)
- Quality of reduction and stabilization
- Patient factors (age, comorbidities, smoking)
- Compliance with rehabilitation
STASCIS Outcomes
Early surgery (less than 24 hours) for incomplete SCI results in:
- 19.8% improve at least 2 ASIA grades (vs 8.8% late)
- Lower complication rates
- Shorter ICU stay
- Faster rehabilitation
Long-term considerations:
- Adjacent segment disease in up to 25% at 10 years
- Hardware removal rarely needed unless symptomatic
- Ongoing surveillance for late instability
- Return to contact sports controversial
Evidence Base
STASCIS: Surgical Timing in Acute Spinal Cord Injury Study
- Multicenter prospective cohort study of 313 patients
- Early surgery (less than 24h) vs late (more than 24h) for acute SCI
- Early surgery: 19.8% improved at least 2 ASIA grades vs 8.8%
- No increase in complications with early surgery
SLIC Validation Study
- Development and validation of SLIC classification
- High inter-rater reliability (kappa 0.71)
- SLIC score correlated with treatment recommendations
- Score 4 or more reliably identifies surgical candidates
AO Spine Subaxial Classification
- Comprehensive morphological classification
- Incorporates neurological status and modifiers
- High reliability across centers
- Complements SLIC for detailed description
Anterior vs Posterior Approach Comparison
- Systematic review of approach selection
- Anterior better for ventral pathology and kyphosis
- Posterior better for multilevel and facet injuries
- Combined approach for severe instability
Australian Cervical Spine Guidelines
- Early involvement of spinal surgery team
- MRI within 24 hours for neurological deficit
- MAP target 85-90mmHg for SCI
- Standardized collar protocols
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: SLIC Score Application
"A 35-year-old motorcyclist presents after an MVA. CT shows a C5 burst fracture with 50% canal compromise. He has weakness in his right deltoid (4/5) but otherwise intact neurology. MRI shows high signal in the C5-6 disc and widened interspinous space at C5-6. What is your assessment and management?"
Scenario 2: Approach Selection
"Walk me through your approach selection for a C6-7 fracture-dislocation with bilateral facet dislocation and an associated C6-7 disc herniation causing cord compression. The patient has ASIA C incomplete SCI."
Scenario 3: Complication Management
"You have performed an anterior cervical discectomy and fusion at C5-6 for a trauma patient. Post-operatively, he develops increasing stridor and respiratory distress 6 hours after surgery. How do you manage this?"
MCQ Practice Points
SLIC Scoring Question
Q: A patient has a C6 burst fracture (CT), high signal in disc on MRI, and no neurological deficit. What is the SLIC score? A: Morphology (burst) = 2 + DLC (disrupted) = 2 + Neurology (intact) = 0 = SLIC 4 (indeterminate - surgeon discretion)
DLC Assessment Question
Q: Which MRI finding indicates disrupted disco-ligamentous complex? A: High signal in disc, widened interspinous space with edema, facet widening with fluid. All three suggest DLC disruption = 2 points on SLIC.
Approach Selection Question
Q: What is the preferred approach for a C5 burst fracture with retropulsed fragment causing cord compression? A: Anterior corpectomy - allows direct decompression of ventral canal compression and restoration of anterior column height.
Timing Question
Q: What does STASCIS show about timing of surgery for incomplete SCI? A: Surgery within 24 hours results in 19.8% improving at least 2 ASIA grades vs 8.8% for late surgery.
Lateral Mass Screw Question
Q: What is the trajectory for lateral mass screws in the subaxial cervical spine? A: Entry 1mm medial and caudal to center of lateral mass. Trajectory 30 degrees lateral and 15-20 degrees cephalad (Magerl technique).
Nerve Root Anatomy Question
Q: A C5-6 disc herniation will compress which nerve root? A: C6 nerve root - cervical nerve roots exit above their numbered vertebra (C6 root exits C5-6 foramen).
Australian Context and Medicolegal Considerations
Trauma System
- Major trauma centers have 24/7 spine surgery capability
- State-based trauma networks coordinate care
- Early transfer for SCI to specialized units
- STASCIS principles adopted nationally
Australian Guidelines
- ANZCA/ASA perioperative guidelines for cervical spine
- State trauma guidelines (Victoria, NSW)
- Spinal cord injury units (Austin, Royal North Shore)
- Emphasis on early definitive care
Medicolegal Considerations
Key documentation requirements:
- Baseline neurological examination before ANY intervention
- Imaging review and interpretation documented
- SLIC score or equivalent classification recorded
- Informed consent including neurological risks, approach-specific complications
- Timing decisions documented with rationale
Common litigation issues:
- Delayed diagnosis of cervical injury
- Inadequate imaging (missed on plain films)
- Neurological deterioration during transfer or reduction
- Failure to document baseline neurology
Transfer considerations:
- All incomplete SCI should be transferred to major trauma center
- Early notification of receiving spinal team
- Optimize MAP during transfer (85-90mmHg)
- Avoid secondary insults (hypoxia, hypotension)
SUBAXIAL CERVICAL SPINE FRACTURES
High-Yield Exam Summary
SLIC Classification
- •Morphology: Compression=1, Burst=2, Distraction=3, Translation=4
- •DLC: Intact=0, Indeterminate=1, Disrupted=2
- •Neurology: Intact=0, Root=1, Complete SCI=2, Incomplete=3, +1 if ongoing compression
- •SLIC 0-3=non-op, 4=indeterminate, 5+=surgical
Key Anatomy
- •C5-C6 most common injury level
- •DLC = disc + ALL/PLL + posterior ligaments + facet capsules
- •Cervical roots exit ABOVE numbered vertebra (C6 at C5-6)
- •Vertebral artery at risk with lateral screw trajectory
Approach Selection
- •Anterior: burst, disc, ventral compression, kyphosis
- •Posterior: facet injury, posterior ligaments, multilevel
- •Combined: severe instability, 3-column injury
- •Posterior first if facet dislocation + disc herniation
Surgical Pearls
- •Lateral mass screws: 1mm medial/caudal, 30deg lateral, 15-20deg cephalad
- •Neuromonitoring essential for reduction
- •Right approach traditionally preferred (RLN anatomy)
- •Consider combined if DLC disrupted with corpectomy
Complications
- •Dysphagia 50% early, 5% persistent
- •RLN injury 2-5%
- •Hardware failure 5-10%
- •Adjacent segment disease 25% at 10 years