Fig. 5

a–c Representative case of the isolated posterior-annular fibrosus type. a CT image: The high-density area was interpreted as a collection of small lesions instead of a single high-density area. b Three dimensional reconstruction image: The high-density area was present at isolated intervertebral levels and had no continuity to the vertebra. c Pathological image: These cases typically showed the prolapse of degenerated nucleus pulposus with previous rupturing of annular fibrosus of the intervertebral disc, accompanied by fibrosis, calcification and/or ossification