Variability in Cobb angle measurements using reformatted computed tomography scans

Adam, Clayton J., Izatt, Maree T., Harvey, Jason R., & Askin, Geoffrey N. (2005) Variability in Cobb angle measurements using reformatted computed tomography scans. Spine: an international journal for the study of the spine, 30(14), pp. 1664-1669.


Study Design: Survey of intra and inter-observer measurement variability. Objectives: To assess the use of reformatted computed tomography (CT) images for manual measurement of coronal Cobb angles in idiopathic scoliosis. Summary of Background Data: Cobb angle measurements in idiopathic scoliosis are traditionally made from standing radiographs, whereas CT scans are often used for assessment of vertebral rotation. Correlating Cobb angles from standing radiographs with vertebral rotations from supine CT is problematic since the geometry of the spine changes significantly from standing to supine positions, and two different imaging modalities are involved. Methods: We assessed the use of reformatted thoracolumbar CT images for Cobb angle measurement. Pre-operative computed tomography scans of twelve idiopathic scoliosis patients were used to generate reformatted coronal images. Five observers measured coronal Cobb angles on three occasions from each of the images. Intra and inter-observer variability associated with Cobb measurement from reformatted CT scans was assessed and compared with previous studies of measurement variability using plain radiographs. Results: For major curves, 95% confidence intervals for intra and inter-observer variability were ±4.3 degrees and ±7.5 degrees respectively. For minor curves, the intervals were ±5.1 degrees and ±7.4 degrees. Intra and inter-observer TEMs were 2.4 degrees and 2.7 degrees, with reliability coefficients of 88% and 84%. There was no correlation between measurement variability and curve severity. Conclusions: Reformatted CT images may be used for manual measurement of coronal Cobb angles in idiopathic scoliosis with similar variability to manual measurement of plain radiographs.

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31 citations in Web of Science®
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ID Code: 3714
Item Type: Journal Article
Refereed: Yes
Additional Information: Author contact details:
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Keywords: Idiopathic scoliosis, Cobb angle, computed tomography, measurement variability
ISSN: 1528-1159
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > BIOMEDICAL ENGINEERING (090300) > Biomechanical Engineering (090302)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Copyright Owner: Copyright 2005 Lippincott, Williams & Wilkins
Copyright Statement: This is the author-version of the work. The final, definitive version of this article has been published in the Journal, < Spine : An international journal for the study of the spine 30(14):pp. 1664-1669, 2005 © < Lippincott, Williams & Wilkins.
Deposited On: 16 Mar 2006 00:00
Last Modified: 29 Feb 2012 13:16

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