Intravenous contrast-enhanced CT of the postoperative lumbar spine: improved identification of recurrent disk herniation, scar, arachnoiditis, and diskitis.

Unsuccessful relief of symptoms after back surgery is usually attributable to hypertrophic extradural scar or recurrent herniated disk. Their clinical and myelographic differentiation is difficult, yet important because reoperation is not always beneficial for scar removal. This article examines the usefulness of intravenous contrast-enhanced computed tomography for this problem. Forty-five postsurgical patients were studied; eight had subsequent surgery. In the four with hypertrophic scars, intravenous contrast enhancement of the scar allowed its recognition in each case; in the four with recurrent disk herniation, nonenhancement of the extruded disk allowed its recognition in three. In the other 37 patients who were not reoperated, 33 were believed to have scar on the basis of contrast enhancement. Continuous contrast infusion during scanning, absolute avoidance of patient movement, and careful consideration of other structures in the spinal canal are important in interpretation. The method seems promising for more accurate evaluation of failed back surgery, including the recognition of diskitis.