LUMBAR SPINE FOLLOWING SUCCESSFUL SURGICAL DISKECTOMY - MAGNETIC-RESONANCE-IMAGING FEATURES AND IMPLICATIONS

In an attempt to determine the expected long-term appearance of the lu mbar spine in patients who have undergone successful lumbar discectomy , follow-up magnetic resonance (MR) examinations were performed on 23 patients (26 levels). All patients in the study had undergone at surge ry at least one year prior to the study. All patients met rigorous cri teria for a successful outcome. In nine cases, the postoperative study indicated a virtually total resolution of the previously identified d isc herniations. In 13 cases, the study noted moderate, persistent pos terior contour defects in the disc that contributed to persistent mass effect on the thecal sac or corresponding nerve root. In the remainin g four cases, the postoperative study indicated virtually no change in the apparent contour of the posterior disc margin. Gadolinium contras t examinations demonstrated enhancement of the persistent contour abno rmalities in 18 of 19 disc levels, suggesting the common presence of f ibrosis, which was at times ''mass-like,'' in these successful patient s. These findings suggest that localized discal contour abnormalities morphologically simulating recurrent disc herniations and variably con tributing to mass effect, may be commonly encountered in long-term fol low-up imaging studies of successful discectomy patients.