Postoperative nerve root displacement and scar tissue. A prospective cohort study with contrast-enhanced MR imaging one year after microdiscectomy

To investigate the association between postoperative nerve root displacement and epidural scar tissue, one hundred patients who had undergone lumbar microdiscectomy were included in a prospective cohort study with a 1-year follow-up. The patients were classified as failures or successes at the 12-month follow-up according to a clinical score. Patients with signs of recurrent disc herniation on MR were excluded from the study. All the 13 patients classified as failures were investigated with MR at the 1-year follow-up, and 40 patients classified as successes were picked at random for MR imaging; thus MR was performed in 53 patients. The MR images were independently evaluated by two neuro radiologists. The images were rated according to the presence or absence of nerve root displacement at the surgically treated disc interspace. Scar formation was rated according to two different classification systems. Nerve root displacement was observed in 13 patients. No evidence of scar formation was found in 4 patients, a small amount in 11, intermediate in 37 and extensive scar formation in 1 patient. No association between nerve root displacement and the amount of scar tissue was found. Postoperative nerve root displacement seems to be an independent clinical entity not associated to postoperative scar tissue