Changes in the disc space after fractures of the thoracolumbar spine

We have studied the intervertebral discs adjacent to fractured vertebral bo dies using MRI in 63 patients at a minimum of 18 months after injury. There were 75 thoracolumbar fractures of which 26 were treated conservatively an d 37 by posterior reduction and fusion with an AO internal fixator. We iden tified six different types of disc using criteria based on the morphology a nd the intensity of the MRI signal. The inter- and intraobserver variabilit y of this system was good. Most of the discs showed predominantly morpholog ical changes with no variation in signal intensity. Some disc types were as sociated with progressive kyphosis in patients treated conservatively. In t hose managed by operation, recurrent kyphosis appeared to result from creep ing of the disc in the central depression of the bony endplate rather than from disc degeneration. Changes in the disc space after posterior fixation should not be seen as a form of chronic instability but as a redistribution of the disc tissue in the changed morphology of the space after fractures of the endplate.