Traumatic intervertebral disc lesion--magnetic resonance imaging as a criterion for or against intervertebral fusion.

Lesions of the intervertebral disc accompanying vertebral fractures are the subject of controversy and discussion regarding the extent and manner of surgical intervention. The question of when to perform disc resection and intervertebral fusion, in particular, has not been answered satisfactorily. In order to evaluate short- and medium-term lesions of the discoligamentous complex associated with thoracolumbar burst fractures, magnetic resonance images made after stabilisation and again after implant removal were compared. Between 1997 and 1998, 20 patients who had suffered thoracolumbar burst fractures (AO classification A3 and B1 [26]) underwent posterior reduction and stabilisation using a Universal Spine System (USS, Synthes, Switzerland) titanium internal fixator. The implant was removed after an average of 10 months. Magnetic resonance imaging (MRI) scans were performed 1 week after both operations, allowing the changes in a total of 40 intervertebral discs adjacent to the fractured vertebral body to be investigated. The analysis was based on signal intensity of the intervertebral disc in T2-weighted scans and on morphological criteria. A total of 81% of the discs with initially normal T2-weighted signal showed the same signal after implant removal; 5 discs with initially increased signal intensity in T2-weighted scans normalised, 5 showed a decrease in intensity and 3 suffered a partial loss of signal. Among the 9 discs with initially decreased T2-weighted signal, only one had normalised by the time the implant was removed. A total of 86% of the 14 morphologically intact discs retained their structural integrity. Of the 25 discs with minor defects, only one could be considered as intact after implant removal, 15 remained the same and 9 deteriorated in structure. No disruption of the fibrous ring or of the posterior longitudinal ligament was observed, nor was there any prolapse of intervertebral discs. When the intervertebral disk is intact and has normal morphology and a normal T2-weighted MRI signal, resection or fusion of the fracture adjacent discs appears unjustified. In our opinion, the results do not support the possibility of predicting degradation in those discs that showed an altered T2-weighted signal after the first operation.