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Rheumatoid arthritis of the craniovertebral junction
Rheumatoid arthritis destroys the transverse ligament and the C1-C2 joints and produces three lesions: anterior atlantoaxial subluxation (the commonest), cranial settling (in which the dens rises into the foramen magnum) and "staircase" subaxial subluxations; a posterior interval (PADI) under 14 mm predicts paralysis.
Why it matters in the exam
The inflammatory pannus around the dens erodes the transverse ligament and the dens itself. An anterior interval (ADI) over 3 mm is abnormal, but the measure that predicts neurological risk is the posterior interval — the space available for the cord: a PADI under 14 mm indicates a high risk of paralysis and is an indication for fixation, and patients operated on with a PADI of 14 mm or more recover better. Cranial settling is judged by lines: the tip of the dens more than 3 mm above Chamberlain's line, or more than 4.5 mm above McGregor's line, indicates basilar invagination. Presentation: occipital pain, myelopathy (clumsy hands, unsteady gait, hyperreflexia) — hard to recognise in a patient with joint deformities — and sometimes sudden death from brainstem compression.
Before general anaesthesia in a patient with long-standing rheumatoid arthritis, flexion and extension neck radiographs are taken, because flexion and extension of an unstable neck during intubation can injure the cord; awake fibreoptic intubation is sometimes preferred. Surgical treatment: for reducible atlantoaxial subluxation — C1-C2 fixation (Magerl transarticular screws or Harms C1 lateral mass and C2 pedicle screws); for cranial settling — occipitocervical fixation, sometimes with anterior odontoid resection when the compression is not corrected. After stable fixation the pannus tends to shrink on its own. Good disease control (biological drugs) has reduced the frequency of cervical involvement.
Key points
- Three lesions: anterior atlantoaxial, cranial settling, "staircase".
- PADI under 14 mm — paralysis risk — fixation.
- Chamberlain over 3 mm, McGregor over 4.5 mm — basilar invagination.
- Flexion and extension radiographs before anaesthesia.
- After fixation the pannus shrinks.
Summary table
| Lesion | Measure | Threshold | Treatment |
|---|---|---|---|
| Anterior atlantoaxial subluxation | ADI / PADI | ADI over 3 mm; PADI under 14 mm — paralysis risk | C1-C2 fixation |
| Cranial settling | Chamberlain / McGregor line | Over 3 mm / over 4.5 mm | Occipitocervical fixation, sometimes odontoid resection |
| Subaxial subluxations | "Staircase" | Translation at several levels | Long fixation |
| Before anaesthesia | Flexion and extension radiographs | Instability | Careful intubation, sometimes awake fibreoptic |
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Sources
- Boden et al., rheumatoid arthritis of the cervical spine: posterior atlanto-odontoid interval as predictor of paralysis, 1993 — Indications for surgery
- Youmans and Winn Neurological Surgery, 8th edition (2022) — Rheumatoid arthritis and the craniovertebral junction
- EULAR recommendations for the management of rheumatoid arthritis, 2022 update — Disease control and perioperative considerations
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.