Discography causes end plate deflection.

Thoracolumbar cadaver spine segments were studied by biplane radiography techniques during intradiscal injection of radiographic contrast agent. In these radiographically nondegenerated discs, significant deformation of the end plate accompanied these in vitro discograms. End plate deflections averaged 0.3 mm. The intervertebral disc bulges averaged 0.5 mm. These results suggest that the end plate itself, or events within the bone, are possible pain sources during clinical discography.