ARTHROSCOPIC MICRODISCECTOMY - COMPARISON OF PREOPERATIVE AND POSTOPERATIVE IMAGING STUDIES

Forty-three patients with symptomatic lumbar disc herniations underwen t paralumbar arthroscopic disc extraction by a uniportal or biportal a pproach and postoperative imaging studies. Thirty-one patients were su bjected to immediate postoperative computed tomography (CT) at the ope rative site. The other 12 underwent magnetic resonance imaging (MRI at varying times postoperatively. Images obtained before and after surge ry were magnified; the herniation area (H) and the spinal canal area ( C) were measured by computerized digitization. The H/C ratio was calcu lated, and the percentage of canal clearance was obtained in each case , Immediate postoperative CT imaging in 16 of 18 patients with subliga mentous and extraligamentous nonmigrated herniations showed a signific ant change in the external geometry of the annulus and canal clearance (75% to 100% canal clearance). Less compelling change in the postoper ative CT images was unexpectedly seen with extraforaminal and foramina l herniations. This result may he attributable to limitations in our s tudy methodology and not to inadequate decompression. Follow-up MRI on these patients within 8 weeks postoperatively did eventually show sig nificant change in two cases that were initially not significant. This study confirms that the arthroscopic microdiscectomy technique effect ively extracts herniated disc fragments and alters posterior annular c ontour, including removal of sequestered pieces.