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European Spine Journal
Published in: European Spine Journal 6/2012

01-06-2012 | Original Article

Use of the iPhone for Cobb angle measurement in scoliosis

Authors: Matthew Shaw, Clayton J. Adam, Maree T. Izatt, Paul Licina, Geoffrey N. Askin

Published in: European Spine Journal | Issue 6/2012

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Abstract

Purpose

The Cobb technique is the universally accepted method for measuring the severity of spinal deformities. Traditionally, Cobb angles have been measured using protractor and pencil on hardcopy radiographic films. The new generation of mobile ‘smartphones’ make accurate angle measurement possible using an integrated accelerometer, providing a potentially useful clinical tool for assessing Cobb angles. The purpose of this study was to compare Cobb angle measurements performed using a smartphone and traditional protractor in a series of 20 adolescent idiopathic scoliosis patients.

Methods

Seven observers measured major Cobb angles on 20 pre-operative postero-anterior radiographs of Adolescent Idiopathic Scoliosis patients with both a standard protractor and using an Apple iPhone. Five of the observers repeated the measurements at least a week after the original measurements.

Results

The mean absolute difference between pairs of smartphone/protractor measurements was 2.1°, with a small (1°) bias toward lower Cobb angles with the iPhone. 95% confidence intervals for intra-observer variability were ±3.3° for the protractor and ±3.9° for the iPhone. 95% confidence intervals for inter-observer variability were ±8.3° for the iPhone and ±7.1° for the protractor. Both of these confidence intervals were within the range of previously published Cobb measurement studies.

Conclusions

We conclude that the iPhone is an equivalent Cobb measurement tool to the manual protractor, and measurement times are about 15% less. The widespread availability of inclinometer-equipped mobile phones and the ability to store measurements in later versions of the angle measurement software may make these new technologies attractive for clinical measurement applications.
Footnotes
1
Measurement of Cobb angles using the iPhone involved measuring the angle of the inferior and superior vertebral endplates selected and then adding these numbers together to obtain the Cobb angle. Since performing this study, a newer version of the software application enables the addition of the two angles automatically thus avoiding a potential error in simple addition by the observer.
 
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Metadata
Title
Use of the iPhone for Cobb angle measurement in scoliosis
Authors
Matthew Shaw
Clayton J. Adam
Maree T. Izatt
Paul Licina
Geoffrey N. Askin
Publication date
01-06-2012
Publisher
Springer-Verlag
Published in
European Spine Journal / Issue 6/2012
Print ISSN: 0940-6719
Electronic ISSN: 1432-0932
DOI
https://doi.org/10.1007/s00586-011-2059-0

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