Fig. 2

Mouse 1, distal thoracic spine (male mouse, 30.5 weeks old at MRI, specimen X-ray, and histology). A-G: Soft X-ray images. A, B: specimen, C-G: 5.5 weeks, 11.5 weeks, 14 weeks, 17 weeks, and 23 weeks after birth, respectively. There is a block of abnormal vertebrae with a triangular hemivertebra (HV) shown by the arrow. The border lines between vertebrae are seen as high-density lines, but the intervertebral disc space cannot be seen. H, I: Histology (H × 40, I × 100). The HV has one cortical bone surface stained in red and two GP surfaces stained in blue. The wedging vertebrae adjacent to the HV are framed by the GP. The intervertebral space surrounding the HV is very thin, containing the CEP and bone marrow (BM). The GP around the HV is thinner with random hypertrophic chondrocytes, and the layers of the cells are more irregular than those in the normal tissue. On the concave side, thick fibrous tissue (FT) of the costovertebral joint capsule is formed, bridging the adjacent malformed vertebrae. J: T1-weighted MR image. The dark low-intensity line surrounding the HV and the wedging vertebra corresponds to the GP or cortical bone, and the slightly high intensity line between the HV and the wedging vertebra corresponds to the insufficiently formed CEP and BM. The dark line of the GP borders the osseous vertebrae and FT of the costovertebral joint capsule, which has a high intensity. On T2WI, the contour of the osseous structures is unclear, but the normal NP and AF cranial to the wedging vertebra appear at higher intensity. No high-intensity structure were detected between the HV and wedging vertebra, which is consistent with the lack of NP and AF observed in the histological images. K: T2-weighted MR image. The normal NP and AF cranial to the wedging vertebra appear at higher intensity, while no bright signal is observed around the HV. Hemivertebra (HV), bone marrow (BM), cortical bone (CB), fibrous tissue (FT)