Fig. 19

Cervical PsA. (a) Lateral radiographs in the neutral position and (b) during flexion in a 61-year-old woman show atlanto-axial instability with a 4-mm distance between the anterior arc and the dens (white line). Additionally, ankylosis of the apophyseal joints (black arrows) and new bone formation anterior to the C4-7 vertebral bodies (white arrows). CT, (c) axial slice and coronal reconstruction of the dens area, demonstrates new bone formation in the atlanto-axial region (arrows); (d) coronal reconstruction of the lower cervical region shows voluminous new bone formation on the right side of the vertebral bodies (arrows). MRI, (e) sagittal STIR and (f) T1-weighted images, shows homogeneous osseous inflammation corresponding to the dens (arrows) with surrounding irregular oedema compatible with a mixture of osteitis and enthesitis. Note that the anterior new bone formation visualised by radiography is difficult to detect on MRI