Rheumatoid arthritis

• The upper cervical spine is involved in 44–88% of Rheumatoid Arthritis (RA) cases.
• Anterior atlantoaxial subluxation, the most common manifestation of RA in the cervical spine, is found in up to 25% of patients with RA.
• Basilar impression, an upward translocation of the odontoid process, is found in approximately 8% of patients with RA.
• C1–2 pannus refers to chronic inflammatory granulation tissue that forms around the odontoid, a characteristic of RA.