How likely is a stable C6 vertebral fracture to become displaced while immobilized in a rigid cervical collar?

Risk of Displacement of Stable C6 Fracture in Rigid Cervical Collar

A stable C6 fracture is unlikely to displace while in a rigid cervical collar, but the collar itself provides inadequate mechanical immobilization and does not reliably prevent displacement if the fracture is truly unstable. 1, 2

Critical Evidence on Collar Effectiveness

The fundamental issue is that rigid cervical collars do not effectively restrict displacement of unstable cervical injuries, with paradoxical movement of adjacent vertebrae occurring particularly at the cervicothoracic junction where C6 is located. 1 Biomechanical cadaver studies demonstrate that neither one-piece nor two-piece collars significantly reduce segmental motion in unstable cervical spine conditions. 2

Key Points on Mechanical Stability:

• Collars provide incomplete immobilization at the cervicothoracic junction, ironically one of the two most common injury sites 1
• In cadaveric models with mid-cervical instability, collars failed to significantly reduce motion across all planes (flexion-extension, lateral bending, rotation) 2
• The collar serves more as a reminder to limit neck motion rather than providing true mechanical stability 3

Clinical Context for "Stable" Fractures

The critical distinction is whether your C6 fracture is truly stable:

• 86.7% of missed cervical spine injuries in one study were subsequently classified as stable 1
• Only 8.6% of injuries missed on plain radiographs were ultimately unstable 1
• Stable fractures (like isolated Jefferson fractures) can be successfully managed with rigid collar alone for 10-12 weeks with good outcomes 4

Stability Confirmation Requirements:

• High-resolution CT at 1.5-2mm collimation should confirm stability before considering any collar removal during bed rest 3
• If imaging confirms stability, the fracture is unlikely to displace with appropriate precautions 3

Balancing Risks: Displacement vs. Prolonged Immobilization

The risks of prolonged collar immobilization beyond 48-72 hours often exceed the risks of the injury itself for truly stable fractures. 3 These complications include:

• Pressure sores requiring skin grafting (each costing ~$30,000) 1, 3
• Increased intracranial pressure (collars raise ICP by 4.69 mm Hg) 3
• Ventilator-associated pneumonia with mortality approaching that of unstable spine injury 3
• Airway complications and failed enteral nutrition 1, 3

Practical Management Algorithm

For confirmed stable C6 fractures:

1. Remove collar during bed rest to minimize complications 3
2. Apply collar during mobilization, transfers, and upright activities 3
3. Monitor for skin breakdown at every shift 3
4. Continue for 4-6 weeks for stable injuries managed conservatively 3

For questionable stability or unstable features:

• Consider surgical stabilization rather than relying on collar alone 4, 5
• If surgery contraindicated, halo immobilization is superior to collar for unstable injuries 5

Common Pitfalls

• Overestimating collar effectiveness: Collars do not mechanically prevent displacement in truly unstable injuries 1, 2
• Underestimating immobilization complications: Secondary injury from prolonged collar use may exceed primary injury risk 3
• Failing to confirm stability with adequate imaging: CT is essential before liberalizing collar use 3