Computed tomography after lumbar disc surgery.

Computed tomography (CT) findings following lumbar disc surgery were analyzed in a series of 53 patients one week after surgery and in another series of 43 patients 6 months to 20 years (average 4.3 years) after surgery. In addition to changes caused by the surgical exposition (laminotomy or laminectomy, gas bubbles) a mass lesion was found on the posterior aspect of the disc in all cases. Hypodensity of the disc interspace as well as vacuolization were found in several cases. These changes were less in the patients examined late after surgery but the CT findings were never completely normal. Findings characteristic of recurrent prolapse included disc-like attenuation values within the mass and non-enhancement with contrast medium. Hypodensity of the disc interspace is associated with discitis but as a non-specific finding it is insufficient in itself for diagnosis of discitis.