PERCUTANEOUS LUMBAR DISKECTOMY - PREOPERATIVE AND POSTOPERATIVE MAGNETIC-RESONANCE-IMAGING

We evaluated magnetic resonance imaging studies of thirty patients bef ore and after a contained herniation of a lumbar disc was treated with a percutaneous lumbar discectomy, The imaging studies were evaluated to determine whether the preoperative appearance of the herniated disc was predictive of the outcome of percutaneous discectomy and also to determine a possible mechanism of action of the procedure in the relie f of symptoms, The index operation was successful in seventeen (57 per cent) of the thirty patients. The preoperative imaging studies showed no differences in the appearance of the discs that went on to have a successful result and those that went on to have an unsuccessful resul t. Imaging studies made four to six weeks after the operation showed n o measurable changes in the morphology of the disc. Imaging studies ma de a mean of fourteen months after the operation showed no changes in the morphology of the disc in twenty-four (80 per cent) of the patient s, irrespective of the clinical outcome. Only three of the seventeen p atients who had a successful result had a reduction of more than two m illimeters in the size of the herniated segment, and two of the thirte en patients who had an unsuccessful result had an increase of more tha n one millimeter in the size of the herniated segment. We found that p reoperative imaging studies cannot predict the clinical outcome of per cutaneous lumbar discectomy. It is possible that the lack of morpholog ical changes in the disc in twenty-four of the patients indicates that a chemical or humoral change rather than a mechanical change accounts for the success of the percutaneous lumbar discectomy.