Aim: To determine the histological changes in discs retrieved at the time of fusion following failed Intra-Discal Electrothermal Therapy (IDET).

Method: Three patients who had failed IDET treatment underwent lumbar interbody fusion. At the time of the operation the disc material and the endplate were sent for histopathology. The histological changes were compared to a degenerate disc and endplate. The staining techniques used were Haematoxylin Eosin stain, Elastic Van Geison and Alcian stains.

Results: In the post IDET specimens there was stromal disorganisation, paucity of chondrocytes and chondrocyte degeneration. These changes were seen in the nucleus pulposus, annulus fibrosis and the endplate as well. Comparatively cadaveric studies using intra-discal radiofrequency thermocoagulation showed histological change only in the nucleus pulposus.

Conclusion: The endplate changes at the cellular level can be widespread following IDET therapy, which can potentially cause alteration of its mechanical properties.