A cluster analysis describing spine and torso shape in Lenke type 1 adolescent idiopathic scoliosis

Abstract

Purpose The purpose of this work is to identify the variability and subtypes of the combined shape of the spine and torso in Lenke type 1 adolescent idiopathic scoliosis (AIS). Methods Using ISIS2 surface topography, measures of coronal deformity, kyphosis and skin angulation (as a measure of torso asymmetry) in a series of children with Lenke 1 convex to the right AIS were analyzed using k-means clustering techniques to describe the combined variability of shape in the spine and torso. Following this, a k-nearest neighbor algorithm was used to measure the ability to automatically identify the correct cluster for any particular datum. Results There were 1399 ISIS2 images from 691 individuals available for analysis. There were 5 clusters identified in the data representing the variability of the 3 measured parameters which included mild, moderate and marked coronal deformity, mild, moderate and marked asymmetry alongside normal and hypokyphosis. The k-nearest neighbor identification of the correct cluster had an accuracy of 93%. Conclusion These clusters represent a new description of Lenke 1 AIS that comprises both coronal and sagittal measures of the spine combined with a measure of torso asymmetry. Automated identification of the clusters is accurate. The ability to identify subtypes of deformity, based on parameters that affect both the spine and the torso in AIS, leads to as better understanding of the totality of the deformity seen.

The use of statistical modelling to identify important parameters for the shape of the torso following surgery for adolescent idiopathic scoliosis

“…Normative data along with multiple linear regression equations for the most prominent points in those WVSD are also described to give context to the information from the AIS group. It is of note that even in the WVSD group, there is an amount of asymmetry between the left and right sides of the posterior torso and the spinal parameters do contribute differing amounts to the final position, and this is in agreement with previous work (Gardner, Berryman, & Pynsent, 2021; Gardner, Berryman, Sur, et al, 2021).…”

“…The positions of the most prominent points have been shown to alter with increasing asymmetry secondary to scoliosis (Gardner, Berryman, & Pynsent, 2021; Gardner, Berryman, Sur, et al, 2021). Through comparison of the 3D position of these points on the left and right sides of the posterior torso, an appreciation of the amount of bilateral asymmetry can be gained.…”

“…The 3D posterior torso shape has been described using ISIS2, as the ‘most prominent points’ (Gardner, Berryman, & Pynsent, 2021; Gardner, Berryman, Sur, et al, 2021). The ‘most prominent points’ represent the two points of maximum distance from the coronal plane defined by the vertebra prominens (VP) and the sacrum, with the x and y planes orthogonal to this plane (Figure 1).…”

“…Of note the most prominent points are surface points and are not fixed to underlying bony anatomy. However, these points are seen over the medial border of the scapula unless very kyphotic when they become the posterior elements of the vertebral column (Gardner, Berryman, & Pynsent, 2021; Gardner, Berryman, Sur, et al, 2021).…”

“…An image of the posterior torso demonstrating the most prominent points along with the definitions of the x , y and z coordinates from the origin at the vertebra prominens (Gardner, Berryman, & Pynsent, 2021; Gardner, Berryman, Sur, et al, 2021)…”