Fig. 3.

Sagittal sections of IVD and adjacent vertebral body segments stained with picro-sirius red and examined under polarised light to visualise changes in collagenous organization (a–f) and with toluidine blue-fast green to depict anionic proteoglycan (g, h). Thickening of the anterior and posterior longitudinal ligaments is evident 26 month PO in a lesion affected disc (f). Arrows indicate the site of the initial annular lesion. In g and h controlled outer annular defects, initially involving only the outer third of the AF (large arrow), have developed into a radiating tear (g) which has propagated through the inner AF and NP to the contralateral AF 12 month PO (small arrows), and a circumferential tear involving separation of adjacent annular lamellae 26 month PO (h). Scale bars 1 cm