Uneven and Asymmetric Changes in Spinal Canal Length After Correction of Severe Kyphoscoliosis: A 3D CT-Based Study

Background: Changes in spinal canal length in severe kyphoscoliosis are critical for surgical strategy and preventing neurological complications. However, the specifics of these changes are not fully understood. Objective: This study investigates spinal canal length changes in severe kyphoscoliosis correction. Methods: Severe kyphoscoliosis patients (Cobb angle > 90°) were retrospectively analyzed. 3D models from CT images were constructed using Mimics software to measure spinal canal on cross-sections at the pedicle level. Lengths of the spinal canal were measured across various segments and compared between concave and convex sides. Correlation with Cobb angle correction rates was analyzed. Results: The study finally enrolled 11 patients. After surgery, the main curve Cobb angle improved by 42.5%±7.3%. The concave side of T1-S1 elongated by (5.0±7.0) mm, while the convex side shortened by (4.0±6.0) mm (P>0.05 for center). Within the main curve, the convex side shortened by (16.0±6.5) mm, and the center by (9.0±6.1) mm (P>0.05 for concave side). In compensatory curves, all sides elongated more on the concave side. In the osteotomy segment, each side showed significant shortening except the concave side. No significant correlation between segmental spinal canal length changes and Cobb angle correction rates. Conclusion: Central spinal canal length remained stable post-operation, but uneven changes were found on the main curve and compensatory curves. Asymmetric differences were observed of spinal canal changes between the concave and convex sides. differences were noted between concave and convex sides. There was no correlation between length changes and Cobb angle correction rates, The study provides insights for surgical strategies and neurological complication prevention.