Intubating Patients with Ankylosing Spondylitis

Why AS Makes Intubation Difficult

• Fixed cervical kyphosis - loss of neck extension makes traditional head-tilt/chin-lift impossible and blocks the laryngoscope line of sight
• Temporomandibular joint (TMJ) involvement - osteophytes and erosion narrow the joint space, severely limiting mouth opening (reduced inter-incisor distance)
• Rigid thoracic cage - costovertebral joint fusion causes restrictive lung disease; poor chest wall compliance affects ventilation
• Stooped posture - these patients often cannot lie flat, requiring positioning accommodations (shoulder padding, semi-recumbent)

• Despite being rigid, the fused spine is extremely fragile - vertebral fractures occur with minimal or even no trauma
• The cervical spine (C5-C6, C6-C7) is fractured in ~80% of spinal fractures in AS
• Anterior atlantoaxial subluxation occurs in up to 14% of AS clinic patients and is often asymptomatic
• Neck extension during direct laryngoscopy has caused catastrophic neurological injury - including C6 dislocation with tetraparesis and permanent tetraplegia - in published case reports

Predictors of Difficult Intubation

1. Reduced neck extension (the single most important predictor)
2. Reduced inter-incisor distance (TMJ disease)
3. Higher Mallampati score
4. Shortened sternomental distance
5. Advanced disease severity on imaging (bamboo spine)

Technique Selection

Awake Fiberoptic Intubation (AFOI) - Gold Standard

• Allows spontaneous ventilation to be maintained throughout
• Enables neurological monitoring - the patient can report any new neurological symptoms during the procedure
• Avoids the need for neck extension entirely
• Can be performed nasally (nasotracheal route is often preferred when mouth opening is severely restricted)
• A 2025 case series from PMC confirmed that awake fiberoptic nasotracheal intubation ensures safe airway control while minimizing cervical spine mobilization in high-risk AS patients

Video Laryngoscopy (VL) - Effective Second Line

• GlideScope and similar devices have been used successfully in AS patients
• Reduces the degree of neck extension required compared to direct laryngoscopy
• However: if TMJ disease causes severe mouth-opening limitation, VL may be no safer or more effective than direct laryngoscopy
• Reports of neurological injury during VL exist in AS patients, so it is not risk-free
• Best suited when mouth opening is adequate but neck mobility is the limiting factor

Intubating Laryngeal Mask Airway (i-LMA / ILMA)

• Useful in emergent situations or as a bridge to definitive intubation
• Key advantage: laryngeal visualization is NOT required, trachea can be intubated without head or neck movement
• Ventilation can be maintained during the procedure
• A useful rescue device if primary attempts fail

Direct Laryngoscopy - Avoid if Possible

• Associated with low first-pass success rates and a high complication rate in AS
• Risk of catastrophic spinal cord injury from forced neck extension
• Should be avoided whenever a better technique is available
• If unavoidable in a crash situation, use manual inline stabilization - do NOT extend the neck

Retrograde Intubation

• A recognized option for difficult AS airways when other techniques fail
• Indicated for failure of direct laryngoscopy, cord obstruction, or when fiberoptic is unavailable

Nasotracheal Blind Intubation

• A historical technique still occasionally used (especially in resource-limited settings)
• Requires audible breath sounds to guide tube placement
• Avoids mouth opening entirely
• Less reliable than fiberoptic guidance; a 2024 Cureus case report (PMID: 39650916) described its successful use in severe cervical deformity when other options were unavailable

Practical Airway Management Algorithm

Elective case → Thorough preop assessment
  ├─ Neck ROM, inter-incisor distance, Mallampati, imaging review
  ├─ Predicted difficult → AWAKE FIBEROPTIC (first choice)
  │   └─ Topicalize airway, maintain spontaneous ventilation
  │       neurological monitoring throughout
  └─ Moderate difficulty → Video laryngoscopy (prepared for AFOI backup)

Emergency case → Cannot optimize
  ├─ Maintain inline stabilization (NO neck extension)
  ├─ Video laryngoscopy attempt
  │   ├─ Success → confirm with ETCO₂, secure tube carefully
  │   └─ Failure → i-LMA as bridge or AFOI if time allows
  └─ Cannot intubate / cannot oxygenate → surgical airway (cricothyrotomy)

Positioning and Safety Principles

• Never forcibly extend the neck - this is the single most dangerous maneuver in AS
• Pad shoulders and support the neck to maintain neutral alignment; the patient's natural kyphotic posture is their "neutral"
• A semi-recumbent or semi-sitting position may accommodate hip flexion deformities
• Have a "double setup" plan for elective cases: prepared for formal tracheostomy if oral intubation fails
• Surgical cricothyrotomy equipment must be immediately available

Other Perioperative Considerations

Key Takeaway