Characterization of progressive changes in pedicle morphometry and neurovascular anatomy during growth in adolescent idiopathic scoliosis versus adolescents without scoliosis

Study design: Prospective cohort study. Objectives: Investigate the progressive changes in pedicle morphometry and the spatial relationship between the pedicles and neurovascular structures in patients with AIS during growth. Summary of background data: Adolescent idiopathic scoliosis (AIS) is a complex three-dimensional spine deformity. AIS pedicles are known to be asymmetrical when compared to adolescents without scoliosis. Defining the anatomical changes occurring progressively in scoliosis as it increases with time and growth is essential for understanding the pathophysiology of scoliosis and for treatment planning. MRI is the ideal method to study the growing spine without ionising radiation. Methods: 24 females with AIS (mean 12.6\ua0years, right sided main thoracic curves) and 20 non-scoliotic females (mean 11.5\ua0years) were selected from an ongoing database. Participants underwent two 3D MRI scans (3\ua0T scanner, T1, 0.5\ua0mm isotropic voxels) approximately 1\ua0year apart (AIS: mean 1.3 ± 0.05\ua0years, control: mean 1.0 ± 0.1\ua0years). The pedicle width, chord length, pedicle height, transverse pedicle angle, sagittal pedicle angle, distance from vertebrae to aorta and distance from pedicle to dural sac were measured from T5 to T12. Inter- and intra-observer variability was assessed. Results: From scans 1–2 in the AIS group, the dural sac became closer to the left pedicle (p < 0.05, T6, T8–T10 and T12) while the distance from the vertebrae to the aorta increased (p < 0.05, T6–T10). No significant changes in these measurements were observed in the non-scoliotic group. Between scans, the AIS chord length and transverse pedicle angle increased on the left side around the apex (p < 0.05) creating asymmetries not seen in the non-scoliotic cohort. The mean pedicle height increased symmetrically in the non-scoliosis cohort (p < 0.05) and asymmetrically in the AIS group with the right side growing faster than the left at T6–T7 (p < 0.05). Conclusion: Asymmetrical growth patterns occur in the vertebral posterior elements of AIS patients compared to the symmetrical growth patterns found in the non-scoliotic participants. Level of evidence: Level II prospective comparative study