CT-diskography in the evaluation of the postoperative lumbar spine. Preliminary results

Thirty-three patients with recurrent sciatica after lumbar-disk surgery were studied for recurrent herniated nucleus pulposus (HNP) by CT alone and CT-diskography (CTD). Twenty-six patients underwent surgical reexploration allowing correlation with CTD. CTD made a correct diagnosis of recurrent HNP in twenty-one patients showing an extravasation of the contrast medium from the disk space into the medullary canal. In two cases CTD was positive for recurrent HNP but surgery showed only fibrosis. The amount of contrast leak was very small in these two cases along the posterior common longitudinal ligament, and the junction with the disk was very narrow. Because of their clinical presentation three patients with negative studies were operated upon. One showed only fibrosis and the two others showed an associated disk fragment. Among the twenty-one true-positive cases, seven showed a combination of recurrent HNP and scarring. Contamination of CSF by the contrast medium through the dura was observed in two patients. Although a prospective comparative study between CTD and IV-contrast-enhanced CT is necessary, CTD appears to be a useful diagnostic procedure for recurrent HNP after surgery of the lumbar spine.