Three-Dimensional Radiographic Analysis of Two Distinct Lenke 1A Curve Patterns

Abstract

Study design: Retrospective review of three-dimensional (3D) imaging from a multicenter database of surgically treated adolescent idiopathic scoliosis (AIS) patients.

Objective: To use 3D analysis software to compare Lenke 1AR and 1AL curves in the coronal, sagittal, and axial planes.

Background data: The Lenke 1AR and AL curve patterns have been shown to be two distinct curve types, with 1AL curves being more likely to add on after fusion. Analysis in 3D may help define some of the intricacies of these two curves.

Methods: Ninety-four AIS patients with Lenke 1A curves and upright biplanar scanned radiographs were reviewed. Analysis was performed using 3D reconstruction software to evaluate the 3D coronal, sagittal and axial plane deformities. Coronal L4 tilt was used to distinguish between the two curve patterns.

Results: The main thoracic Cobb was not significantly different between the AR (n = 43) and AL (n = 51) curves (52° ± 8° vs. 50° ± 5°; p = .25). The thoracolumbar/lumbar Cobb was significantly smaller in the AR curves (28° ± 8° vs. 32° ± 7°; p = .02). In the sagittal plane, T5-T12 kyphosis and T12-S1 lordosis were not significantly different (p >.2); however, the T10-L2 alignment was significantly more lordotic in the AR curves (11° ± 8° vs. 4° ± 10° lordosis; p <.001). In the axial plane, thoracic apical rotation was significantly greater in AR curves (21° ± 6° vs. 14° ± 6°; p <.001) and lumbar apical rotation was significantly smaller in AR curves (1° ± 5° vs. 6° ± 5°; p <.001).

Conclusion: 3D spinal analysis demonstrates that 1AR and AL curves are distinctly different in all three planes. Although the treatment-based Lenke classification system combines these two curve patterns into one curve type, the 3D assessment suggests there are clear features that differentiate these curve patterns. The differing features of the nonstructural lumbar curves may help define the variance in fusion level selection and risk of adding-on for these two curve patterns.

Level of evidence: Level II, prognostic.

Keywords: 1AL; 1AR; 3D; Adolescent idiopathic scoliosis; Lenke classification.