Discovering the association between the pre- and post-operative 3D spinal curve patterns in adolescent idiopathic scoliosis

Background: The advantage of considering the three-dimensional curve patterns, including the patterns of the vertebral position and alignment, in classification of adolescent idiopathic scoliosis (AIS) patients and whether such classification system relates to the surgical outcomes are not fully determined.

Methods: A total of 371 AIS patients who received posterior spinal fusion surgery with 2-year follow-up were included retrospectively and consecutively. The 3D positions and orientations of the T1-L5 vertebrae were calculated from the 3D reconstructions of the spines at pre-operative and 2-year follow-up, a total of 102 variables per patient. A probabilistic clustering method was used to cluster the pre-operative and 2-year follow-up 3D spinal curve patterns separately. The distributions of the Lenke types and 3D pre-operative clusters in the post-operative clusters were determined.

Results: A total of nine pre-operative clusters including, four right thoracic types, three left thoracolumbar/lumbar types, one low apex right thoracic/thoracolumbar, and one left thoracic/right lumbar were determined. Three post-operative 3D curve patterns were Type 1 with higher residual proximal Cobb angle, Type 2 with lower T5-T12 kyphosis and highest pelvic incidence-lordosis mismatch, and Type 3 with larger lumbar curve magnitude and rotation compared to the other two groups. More than 50% of patients in each of the 3D pre-operative clusters had the same post-operative group.

Conclusion: We developed a 3D classification of the AIS patients before and two-year after spinal fusion surgery. The link between the pre- and post-operative clusters lends itself to application of this classification system in developing predictive models of the AIS surgical outcomes.