Investigation of in vivo three‐dimensional changes of the spinal canal after corrective surgeries of the idiopathic scoliosis

Abstract Objective To determine the three‐dimensional (3D) changes of the spinal canal length (SCL) after corrective surgeries and their association with the radiographic and clinical outcomes of idiopathic scoliosis patients. The length of the spinal cord has been demonstrated to be strongly correlated with the SCL. Understanding the changes in SCL could help determine the morphologic changes in the spinal cord to prevent spinal cord injury. Methods Twenty‐seven scoliotic patients' 3D spinal canal were investigated using computed tomography images. The SCL between the upper and lower end vertebrae (U/L‐EV) was measured at five locations. The radiographic parameters of each patient and the patient‐reported outcomes (PROs) scores were also collected. The correlations of the changes of the SCLs with the other factors were analyzed. Results The SCL between the U/L‐EV changed non‐uniformly at different locations. The post‐operative SCLs were significantly elongated by 7.5 ± 3.5 mm (6.0 ± 2.5%, P < .001) at the concave side and compressed by −2.6 ± 2.6 mm (−1.9 ± 1.9%, P < .001) at the convex side. The elongations of the SCL at the concave and posterior locations were correlated with the radiographic parameters including the pre‐operative main Cobb angles ( r = .511, P = .006; r = .613, P = .001) and apical vertebral translation (AVT) ( r = .481, P = .011; r = .684, P = .000). No PRO scores were found to correlate with the SCL changes. Conclusion The corrective surgeries elongated the spinal canal mainly at the concave side and compressed at the convex side. The main thoracic Cobb angle, the changes of AVT, and Cobb angles were moderately associated with the changes of the SCLs, but no PRO score was found to associate with the changes of the SCLs. The data could be instrumental for the improvement of corrective surgeries that are aimed to maximize the correction of scoliosis and minimize the negative effect on the spinal cord to prevent neurological complications.