Volume 10 Supplement 1

IRSSD 2014 Meeting Abstracts

Open Access

The effect of endplate preselection when measuring supine versus standing cobb angle change in idiopathic scoliosis

  • Bethany E Keenan1,
  • Maree T Izatt1,
  • Geoffrey N Askin1,
  • Robert D Labrom1,
  • Mark J Pearcy1 and
  • Clayton J Adam1
Scoliosis201510(Suppl 1):O43

https://doi.org/10.1186/1748-7161-10-S1-O43

Published: 19 January 2015

Objectives

The primary aim of this study was to determine whether endplate pre-selection makes a difference to the Cobb Angle change between supine and standing which is known to occur in idiopathic scoliosis. A secondary aim of this study was to identify which (if any) patient characteristics were correlated with supine versus standing Cobb change.

Methods

Female Adolescent Idiopathic Scoliosis (AIS) patients with right-sided thoracic major curves were included in the retrospective study. Clinically measured Cobb Angles from existing standing coronal radiographs and fulcrum bending radiographs were compared to existing low-dose supine CT scans taken within 3 months of the reference radiograph. Reformatted coronal CT images were used to measure supine Cobb Angle variability with and without endplate pre-selection (end-plates selected on the radiographs used on the CT images). Inter and intra-observer measurement variability was assessed. Multi-linear regression to investigate whether there was a relationship between supine to standing Cobb angle change and eight variables: patient age, mass, standing Cobb angle, Risser sign, ligament laxity, Lenke type, fulcrum flexibility and time delay between radiograph and CT scan.

Results

Fifty-two patients were included, with mean age of 14.6 (SD 1.8) years; all curves were Lenke Type 1 with mean Cobb Angle on supine CT without pre-selection of endplates of 41.8° (SD 6.4°) and 51.9° (SD 6.7°) on standing radiographs. The mean Cobb angle on supine CT images with endplate pre-selection was 40.5° (SD 6.6). The mean fulcrum bending Cobb Angle for the group was 22.6° (SD 7.5°). The 10° increase from supine to standing is consistent with existing literature. Pre-selecting vertebral endplates was found to increase the mean signed Cobb change by 0.6° (SD 2.3, range -9 to 6)°. When free to do so, observers chose different levels for the end vertebrae in 39% of cases. Multi-linear regression revealed a statistically significant relationship between supine to standing Cobb Angle change with: fulcrum flexibility (p=0.001), age (p=0.027) and standing Cobb Angle (p<0.001). In patients with high fulcrum flexibility scores, the supine to standing Cobb Angle change was as great as 20° (Figure 1). The 95% confidence intervals for intra-observer and inter-observer measurement variability were 3.1° and 3.6°, respectively.
Figure 1

An example of a reformatted supine CT image Cobb 46° (left) and the corresponding standing radiograph Cobb 58° (right)

Conclusions

Pre-selecting vertebral endplates causes minor changes to the mean supine to standing Cobb change. There is a statistically significant relationship between supine to standing Cobb change and fulcrum flexibility such that this difference can be considered a potential alternative measure of spinal flexibility.

Authors’ Affiliations

(1)
QUT/Mater Paediatric Spine Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology and Mater Health Services

Copyright

© Keenan et al; licensee BioMed Central Ltd. 2015

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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