Fig. 1

Standard radiography of the cervical spine in rheumatoid arthritis (RA). (a) Lateral radiographs in neutral position and (b) during flexion in addition to (c) lateral and (d) anterior-posterior (AP) open-mouth view of the atlanto-axial region (45-year-old woman). The flexion view (b) shows abnormal distance (>3 mm) between the posterior aspect of the anterior arc of the atlas and the anterior aspect of the dens (black line). Note that the spino-laminar line of the atlas (arrow) does not align with that of the other vertebrae, confirming the presence of anterior subluxation, but there is no stenosis of the atlanto-axial canal; the posterior atlanto-dental interval (white line) is >14 mm. The open-mouth view (d) shows erosion at the base of the dens (arrow). (a) and (b) show concomitant disc degenerative changes at the C4–C6 level