The postoperative lumbar spine: enhanced MR evaluation of the intervertebral disk.

PURPOSE To document the pattern of enhancement and morphologic changes on MR images that occur in the intervertebral disk and adjacent vertebral bodies after diskectomy and to correlate the presence of intervertebral disk enhancement with the preoperative and postoperative clinical findings. METHODS Preoperatively, and at 3 months and 6 months after surgery, 94 adults who had first-time surgery for a herniated lumbar intervertebral disk that was associated with radiculopathy, expressed as leg symptoms or signs (with or without lower back pain), were asked to respond to a questionnaire regarding pain, were given serial physical examinations, and were examined with contrast-enhanced MR imaging. The measures of clinical outcome that were evaluated included the straight leg raise sign, radicular pain, and lower back pain. Type of disk herniation, intervertebral disk enhancement, disk space height, and degenerative end-plate changes were also assessed. RESULTS Of the 94 patients evaluated, 19 (20%) had postoperative intervertebral disk enhancement that was not present on the preoperative study. The pattern of enhancement was remarkably consistent, with 18 of the cases showing linear enhancement within the intervertebral disk, manifested as two thin bands paralleling the end plates. End-plate enhancement was present in 7 (37%) of the 19 patients with disk enhancement. There were no significant associations between disk enhancement and specific clinical symptoms before or after surgery. CONCLUSION Our group of asymptomatic postoperative patients had anular enhancement (curette site), disk enhancement, and vertebral end-plate enhancement on MR images without evidence of disk space infection. This finding points out the need to understand asymptomatic postoperative changes that are sequelae of surgery and not necessarily indicators of infection.