Postoperative Time Course of Avulsion-Type Herniation Focused on the Development of New Modic Changes and Their Effect on Short-Term Residual Low Back Pain.

Abstract

Retrospective study. To investigate the characteristics of newly developing Modic changes following discectomy and their impact on residual low back pain (LBP) in the early postoperative stage of lumbar disc herniation. We included 96 patients who underwent microscopic discectomy. Through MRI, we assessed new developments of Modic changes and the progression of disc degeneration at the surgical level. The presence of cartilaginous endplates was evaluated using resected specimens, and the main outcome was assessed using the visual analog scale (VAS). Further, the prevalence and time course of Modic changes, and their effects on clinical outcomes in the early postoperative period were examined. A new development of Modic changes was detected in 28% of cartilaginous herniations at 6 months. Modic changes were observed more frequently in patients with cartilaginous herniation than in those without cartilaginous herniation postoperatively (P < .001). The VAS scores for LBP up to 6 months were greater in patients with Modic changes (P < .001) than those without; however, no significant differences were identified in the presence or absence of Modic changes over the year follow-up. The development of Modic changes was closely associated with residual LBP at 6 months (β:0.511, P < .001). Modic changes develop predominantly in patients with avulsion-type herniation than in those with annular rupture at an earlier phase after discectomy. Furthermore, disc herniation with cartilaginous endplates may be associated with a slower decrease in LBP for up to 6 months, supporting the notion that newly developing endplate changes may cause residual LBP.