A 60-year-old man with longstanding rheumatoid arthritis has cervical spine involvement. Pre-operative assessment for elective hip replacement reveals atlantoaxial instability on flexion-extension X-rays with anterior atlantodental interval (AADI) of 6 mm. What is the CORRECT anaesthetic implication?

• A Spinal anaesthesia is absolutely contraindicated; GA with intubation is preferred
• B Normal intubation with Macintosh laryngoscope is safe as AADI is below the surgical threshold of 10 mm
• C The hip replacement must be deferred until posterior cervical fusion is performed first
• D Fibreoptic intubation with cervical spine precautions is required; avoid forced flexion during laryngoscopy ✓

Explanation

An anterior atlantodental interval (AADI) >3 mm in adults with rheumatoid arthritis indicates atlantoaxial instability. An AADI of 6 mm is significant — values >5 mm carry a risk of odontoid migration into the foramen magnum. For any anaesthesia requiring intubation, awake fibreoptic intubation with in-line cervical spine stabilisation (hard collar) and avoidance of forced neck flexion or extension is mandatory to prevent spinal cord injury. Spinal anaesthesia itself does not require intubation and may be safer, but if GA is needed, fibreoptic intubation is essential. The surgical threshold for prophylactic fusion is AADI >8–10 mm or posterior cord space <14 mm.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.