Impact of the flexibility of the spinal deformity on low back pain and disc degeneration in adult patients nonoperatively treated for adolescent idiopathic scoliosis with thoracolumbar or lumbar curves

Purpose To evaluate the impact of the flexibility of thoracolumbar or lumbar (TL/L) curves on low back pain (LBP) and disc degeneration in adult patients nonoperatively treated for adolescent idiopathic scoliosis (AIS). Methods Forty-seven adult patients (46 women; mean age, 40.5 years) nonoperatively treated for AIS with TL/L curves were included. The patients completed radiological examinations, magnetic resonance imaging, and a questionnaire survey for LBP evaluation. The flexibility of the spinal deformity was evaluated using supine side-bending radiographs. Radiographic measurements were correlated with scores for LBP and disc degeneration. Results The average magnitude and flexibility of the TL/L curve were 49.0 degrees and 56%, respectively. The magnitudes of the TL/L curve and disc wedging were significantly correlated with LBP (|r|= 0.3-0.4). The flexibility of the TL/L curve and disc wedging, and the lumbar lateral range of motion (ROM) were significantly correlated with LBP and disc degeneration (|r|= 0.3-0.5). After controlling for the magnitudes of the TL/L curve and disc wedging, the flexibility of L4/5 disc wedging and the lumbar lateral ROM remained significantly correlated with the Scoliosis Research Society-22 pain score (partial correlation coefficient [r '] = 0.5 and 0.3), Oswestry Disability Index (- 0.3 and - 0.3), and disc degeneration (- 0.4 and 0.3). Conclusion In AIS patients with TL/L curves, the flexibility of L4/5 disc wedging and the lumbar lateral ROM were significantly correlated with LBP and disc degeneration, independent of the magnitudes of the coronal deformities. Our findings indicate that maintaining or improving lumbar flexibility may be beneficial for preventing or treating LBP.