The variability in location of the most prominent points on the posterior torso of those without abnormal surface topography, those with Adolescent Idiopathic Scoliosis and those with Scheuermann's Kyphosis: a seven year longitudinal analysis

Abstract

The correction of adolescent scoliosis involves the recreation of torso symmetry. A symmetrical torso has equivalent areas of shape on either side of the midline. The posterior torso has two areas of prominence, known as the 'most prominent points' on either side of the midline which can be used as reference points to measure symmetry of the posterior torso. This study used the three-dimensional (3D) coordinates of the most prominent points, measured using ISIS2 surface topography and standardised by torso size, in children without abnormal surface topography, with adolescent idiopathic scoliosis (AIS) (right thoracic curves) and with Scheuermann's kyphosis (SK).The purpose was to demonstrate the variability of the position of the points in these three groups. The variability of the 3D coordinates was calculated for each group (mean, standard deviation and range in millimetres) and the standardised data were illustrated using 3D 95% confidence interval ellipsoids. In those without deformity, the position of the left and right point was mirrored with little difference. The AIS group showed a difference between the left and right points, with the right becoming further from the midline and more prominent than the left but with the left becoming more superior than the right. For the SK cohort, both left and right points moved inwards towards the midline and became more prominent. Linear mixed effect modelling was used to examine the contribution of age, kyphosis and scoliosis to the position of the most prominent points. In the cohort without abnormal surface topography, the x parameter increases with the covariates of age and kyphosis, with the covariate of age likely reflecting torso growth. The left side becomes more prominent and inferior compared to the right. In the AIS cohort, age follows the cohort without abnormal surface topography. This is added to by the scoliosis which is observed to make the right side more lateral, less inferior and more prominent, whereas the left becomes more medial, less inferior and less prominent. Kyphosis in the AIS cohort leads to the right point becoming more lateral, less inferior and less prominent whereas in the left becomes more lateral, more inferior and more prominent. In the SK cohort, the effects of the covariates of age and kyphosis are not clear reflecting the small number of cases with more than one surface topography image over time. | 1245GARDNER Et Al. | INTRODUC TI ONAdolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) deformity of the spine and torso (Stokes, 1994). One of the presenting features of AIS is the asymmetric prominence of the back, known as the rib hump and this is best seen on clinical examination in the Adams' forward bend position (Adams, 1865). These prominences will capture the attention of the observer if large or asym-

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“…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)…”