Outcomes of selective thoracic fusion for Lenke 1 adolescent idiopathic scoliosis: predictors of success from the sagittal plane.

PURPOSE

To determine the link between the rate of spontaneous lumbar curve correction (SLCC) and the sagittal profile characteristics both before and after selective thoracic fusion in Lenke 1 adolescent idiopathic scoliosis (AIS).

METHODS

Sixty-three Lenke 1 B and C were enrolled and followed up to 2 years. Twenty non-scoliotic controls were included. 3D reconstruction of the spine was generated from bi-planar X-rays at pre-operative, first erect post-operative, and the most recent follow-up. The 3D spinal models were used to determine the frontal and sagittal Cobb angles and 3D coordinate of each vertebral centroid. A K-mean cluster analysis allocated patients into two groups based on the rate of SLCC between the pre-operative and the most recent follow-up visits (SLCC and SLCC groups). The ratio of the thoracic to lumbar curve apical translations in sagittal plane was determined. ANOVA test compared the sagittal apical translation ratio between the three visits of the AIS clusters and between the AIS groups and controls.

RESULTS

The rate of the SLCC was significantly different between the two clusters: 31% (SLCC) versus 76% (SLCC). No significant difference was found between the two clusters pre-operative Cobb angles, kyphosis, and lordosis. The pre-operative ratio of the thoracic to lumbar apical translation in the sagittal plane was significantly lower in SLCC compared to SLCC group, a magnitude of 1.2 and 2.2, respectively, p < 0.05.

CONCLUSION

In Lenke 1, patients with a higher pre-operative sagittal thoracic to lumbar apical translation ratio are associated with lower rate of SLCC at the most recent follow-up. These slides can be retrieved under Electronic Supplementary Material.