Three-dimensional subclassification of Lenke type 1 scoliotic curves

Prospective study of the 3-D shape variability of spinal curve in Lenke type 1 adolescent idiopathic scoliosis (AIS).

To determine the statistical 3-D variability of Lenke type 1 curves and to evaluate clinical parameters that can be integrated to refine the Lenke et al original proposal, and to pave the road for a comprehensive 3-D subclassification of AIS.

Several classification systems based on the identification of key features from frontal and sagittal x-rays have been proposed in AIS, but these remain an oversimplification of the complex 3-D deformity because it is only based on 2-D imaging. Clinical 3-D parameter variability has been investigated in previous studies, but has never been considered in the context of the Lenke classification.

Radiographs of 68 AIS patients with Lenke type 1 curves were reconstructed in 3-dimension using a stereo-radiographic technique and were submitted to a computer algorithm to compute a set of 3-D parameters that can be used to characterize the 3-D curve. Cluster analysis was performed to determine the statistical distribution of 3-D parameters among Lenke 1 curve types.

Statistical analysis shows specific 3-D deformation patterns within Lenke type 1 curves, mostly using the best-fit plane or BFP (SD+/-22.9, +/-49.8) and geometric torsion parameters. No significant variability was found using the plane of maximum curvature or PMC.

Recent advances in computer vision facilitate the introduction of 3-D reconstruction in a standard clinical setting and can provide more information toward the spine behavior in 3-D space. A direct consequence of commonly used 3-D reconstruction would be to be able to evaluate 3-D indices and to devise a real 3-D classification system from the Lenke et al proposal.