Subaxial Cervical Spine Fractures

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%

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

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

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

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

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:

Neurological examination:

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)

Differential diagnosis:

The key reasoning step is separating a genuinely unstable subaxial fracture (operative threshold) from mimics that change urgency or treatment.

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 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

Pre-operative Planning

Intraoperative Troubleshooting

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

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

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

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

Global epidemiology. Subaxial injuries account for approximately half of cervical spine fractures, with C5-C6 the most frequently injured level (the mobile-to-stiff transition zone). Across resource settings the demographic is consistent: predominantly young males injured by road traffic accidents, with falls dominating in the elderly. In a meta-analysis of 11,639 patients across 16 African countries, road traffic accidents caused 49.5% of traumatic spine injuries, the cervical spine was the most common level (51.6%), patients were 81% male with a mean age of 34.5 years, and surgery was performed in only 31.9% versus a majority managed conservatively, with 12.1% mortality (Darko et al, J Neurosurg Spine 2024, DOI). This contrasts with high-income systems where most unstable injuries are operated early.

Registry & systematic-review evidence. Cervical trauma is not captured by arthroplasty joint registries; the comparative evidence base is national trauma databases and pooled reviews rather than a single implant registry. Pooled data in rigid (ankylosing) cervical spines - a high-risk subaxial subgroup - confirm the C6-C7 / C5-C6 predominance and show combined anterior-posterior constructs carry the lowest reoperation rate (1.7%) versus anterior-only fixation (11.1%) (Musa et al, Neurosurg Rev 2025, DOI).