Percutaneous laser discectomy: MR findings within the first 24 hours after treatment and their relationship to clinical outcome.

Abstract Objective: The purpose of this study was to evaluate the early MR appearances of the intervertebral disc obtained within 24h after percutaneous laser discectomy and to determine if a correlation exists between the MR images and the clinical outcome. Subjects and Methods: Twenty-nine discs in 26 patients with contained lumbar disc herniation treated by laser were included. Laser intervention was performed using Ho:YAG laser system. The results were quantitatively analysed by measuring areal changes of the herniated mass on axial T1-weighted images and signal changes within the disc on sagittal T2-weighted images. Clinical outcomes were evaluated according to Japanese Orthopaedic Association score (JOA score), and recovery rates based on JOA score immediately and 1 year after treatment were calculated. Results: The recovery rate immediately after treatment was 53.1%, and increasing to 64.6% 1 year later. The size of the disc herniation ranged from 7% to 55% of the axial cross-section of the spinal canal pre-operatively and no significant changes were noted postoperatively. Also no correlation was found between the pre-operative herniation size and the recovery rate. The signal changes within the disc increased significantly after treatment, but no correlation was present between the signal changes and the recovery rate. In five patients, soft-tissue changes along the laser tract were well demonstrated on MR imaging. Conclusion: Although immediate postoperative MR imaging shows early tissue changes induced by laser, our study has not proven that immediate postoperative MR imaging could predict the clinical outcome after percutaneous laser discectomy.