[Computerized tomography in surgically treated lumbar disk hernia. Multicenter study]

Results are reported of a multicenter analytic-statistical CT study on 128 postoperative lumbar herniated disk (HD) cases (50 at L4-L5, 64 at L5-S1, 2 at L3-L4, 12 multiple). CT was performed from 10 days to 204 months (47.7 months of mean) after surgery, in 51 patients without and in 77 with intravenous contrast medium (42 in bolus, 35 in perfusion). In 59 cases (38%) a recurrent hernia was found, and in 8% a new hernia. In 81% of patients epidural fibrous scars were demonstrated, in a rough 50% of cases associated with recurrent/new hernia: posterior fibrosis was found in 81% of cases, while unilaterally, bilaterally, or anteriorly extended fibroses were present in 20%, in 4.7%, and in 29% of cases respectively. In 72% of the patients injected with contrast medium, various kinds of fibrosis contrast enhancement were detected. In 8% neither fibrosis nor recurrent herniation was found. In 22% of cases lateral and/or central bony canal stenosis was present, in 26% vacuum disk, in 9% intracanalar calcifications, in 39% and in 19.5% dural sac stretching and compression respectively. In 5 cases a pseudomeningocele was found, and in 3 only a postoperative diskitis. Fibrosis is an almost inevitable postoperative consequence (4 out of 5 cases); it can be demonstrated by CT with high sensitivity and good specificity. A series of diagnostic criteria, such as the post-contrast media reaction, allow fibrosis to be discriminated from recurrent hernia. However, the possible association must be kept in mind of both diseases and/or of included roots in the scar. Myelography is hardly ever able to supply further resolutive diagnostic elements, while Myelo-CT is sometimes more useful. The importance of bone changes is questionable, with the exception of evident cases of canal stenosis, also because in most cases the radiologist cannot count on a preoperative CT study. Furthermore, the correlation between CT and clinical findings (possible asymptomatic fibrosis) is often difficult, which gives way to contrasting therapeutic attitudes.