Global and segmental thoracolumbar sagittal alignment in adolescent idiopathic scoliosis compared to normal individuals.

OBJECTIVE

To quantify differences of global and segmental sagittal thoracolumbar alignment between normal individuals and adolescent idiopathic scoliosis (AIS) according to primary curve types.

METHODS

Radiographic parameters were compared between 1115 normal adolescents and young adults versus 1779 AIS. Thoracic kyphosis (T1-T12), lumbar lordosis (L1-S1), segmental alignment (T1-T5, T5-T10), thoracolumbar junction (T10-L1), segmental lordosis (L1-L4, L4-S1), lumbar and thoracic apex, thoracolumbar inflection point, global alignment parameters (SVA C7, SVA C2, OD-HA, TPA, GT, SSA) and pelvic parameters (PI, PT, SS) were measured.

RESULTS

C2 and C7 SVA was smaller and more posteriorly located in AIS compared to normal. Primary thoracic curves (Lenke 1, 2 and 3) had the lowest TK at T5-T10 compared to normal and primary thoracolumbar curves (Lenke 5 and 6). The thoracolumbar junction T10-L1 was smallest and slightly lordotic in Lenke 1 and 2. Distal lordosis L4-S1 and PI were highest in thoracolumbar curves (Lenke 3, 5 and 6). Thoracolumbar inflexion points, thoracic and lumbar apex were located more cranial in thoracic curves (Lenke 1 and 2) compared to normal and other AIS types.

CONCLUSION

Thoracic curves (Lenke 1 and 2) were hypokyphotic in the distal thoracic segment T5-T10, had a neutral thoracolumbar junction T10-L1 and their apex and thoracolumbar junction were more cranial. Lenke 3 curves had an increased lordosis in the distal lumbar segment L4-S1. Primary lumbar curves (Lenke 5 and 6) had a higher PI and distal lordosis L4-S1, and the highest C7 SVA.