Degenerative Changes in the Disc, Facet Joint, and Paraspinal Muscle After Adolescent Idiopathic Scoliosis Surgery: A Five-Year MRI-Based Follow-Up.

Background and objectives This study aimed to comprehensively assess degenerative changes in the intervertebral disc, facet joint, and paraspinal muscle after adolescent idiopathic scoliosis surgery and to evaluate clinical outcomes at a five-year follow-up using magnetic resonance imaging (MRI). We hypothesized that the pattern of degeneration would differ based on the distal level of fusion. Materials and methods We retrospectively reviewed patients with adolescent idiopathic scoliosis who underwent surgery between 2006 and 2015. The patients were divided into two groups based on the lowest instrumented vertebra (LIV): a proximal LIV group (L2 or above) and a distal LIV group (L3 or below). Degeneration was evaluated using MRI with the Pfirrmann and Fujiwara scoring systems. Fatty infiltration of paraspinal muscles was specifically assessed at the L5/S1 disc level, distal to the surgical field, using the Goutallier scoring system. Clinical outcomes were measured using the Scoliosis Research Society-22 (SRS-22) Patient Outcome Questionnaire. Statistical comparisons were performed using the Mann-Whitney U test and Wilcoxon signed-rank test. Results The proximal LIV group comprised 21 patients, while the distal LIV group had 19 patients. Postoperatively, six of 40 patients (15%) exhibited progression of disc degeneration in mobile segments, with no significant difference between groups. The proximal LIV group showed significant progression of facet joint degeneration up to three levels below the fusion, whereas the distal LIV group showed similar changes up to two levels. However, the distal LIV group demonstrated greater overall facet degeneration. Paraspinal muscle degeneration at the L5/S1 level was observed in 19 of 40 patients (47.5%), with a higher prevalence in the distal LIV group (73.7% vs. 23.8%). Clinical outcomes were satisfactory and did not differ significantly between the groups. Conclusions At the five-year mark, this study suggests an association between a more proximal LIV (L2 or above) and less facet joint and paraspinal muscle degeneration in patients undergoing fusion for adolescent idiopathic scoliosis. However, these preliminary radiological findings did not correlate with clinical symptoms, which remained satisfactory in both groups. These results should be interpreted with caution, and extended follow-up is necessary to determine the long-term clinical significance of these degenerative changes.