Association of convex-side spinal canal elongation with distraction spinal cord injury during severe adolescent scoliosis correction: a retrospective cohort study.

Abstract

Objective: To evaluate the association between spinal canal elongation during deformity correction and distraction spinal cord injury (DSCI) in severe adolescent idiopathic scoliosis.

Methods: We retrospectively analyzed 79 patients with severe AIS (Major Cobb angle > 80°) who underwent posterior correction and had both preoperative and postoperative computed tomography scans available for three-dimensional reconstruction. Spinal canal length (SCL) was measured preoperatively and postoperatively at the concave, central, and convex aspects of the canal. The cross-sectional area of the spinal canal (CSA) was also recorded. Logistic regression was used to assess associations between spinal canal parameters and postoperative neurological injury. Receiver operating characteristic (ROC) analysis was performed to evaluate discriminative performance and to derive cohort-specific candidate cut points using the maximum Youden index.

Results: Among 79 included patients, 13 (16.5%) developed DSCI. The DSCI group showed a smaller CSA (151.3 ± 19.8 vs. 181.1 ± 40.7 mm², p = 0.010) and greater SCL elongation at the concave side (10.1 ± 5.6 vs. 7.5 ± 3.6 mm, p = 0.008), central line (8.8 ± 3.9 vs. 5.0 ± 3.0 mm, p < 0.001), and convex side (7.6 ± 3.3 vs. 3.4 ± 2.7 mm, p < 0.001). Multivariate analysis identified convex SCL elongation (OR = 2.230, 95% CI 1.329-3.739, p = 0.002) and CSA (OR = 0.950, 95% CI 0.916-0.985, p = 0.006) as independent factors associated with DSCI. Convex SCL showed the highest discriminative ability on ROC analysis (AUC = 0.86).

Conclusion: Excessive convex-side SCL elongation combined with reduced CSA represents a high-risk morphological pattern for DSCI in severe AIS correction. Postoperative neurological risk is multifactorial-driven by complex three-dimensional corrective forces, osteotomies, and baseline anatomical reserve, rather than simple longitudinal distraction. Preoperative evaluation of canal reserve and anticipated elongation may provide a morphological framework for risk stratification in complex deformity surgery.