Fig. 12

Advanced AS. (a) AP and (b) lateral radiograph in a 55-year-old man showing vertebral fusion due to syndesmophytes crossing the intervertebral spaces in addition to fusion of the apophyseal joints (bamboo spine). The interspinous ligaments are ossified, presenting as a slim ossified streak on the frontal radiograph (dagger sign; arrows). MRI, sagittal T1-weighted images of (c) the cervico-thoracic and (d) lumbar region, respectively, shows a general narrowing of the intervertebral discs with partial osseous fusion of the vertebral bodies, especially in the lumbar region (arrows). In addition a characteristic AS deformity with reduced lumbar lordosis and thoracic kyphosis