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The Validity and Reliability of Noninvasive Methods for Measuring Kyphosis

Azadinia, Fatemeh MSc*; Kamyab, Mojtaba PhD, MSc, CPO(ir)*; Behtash, Hamid MD; Ganjavian, Mohammad Saleh MD; Javaheri, Masoud R. M. MD§

doi: 10.1097/BSD.0b013e31829a3574
Original Articles

Study Design: This is a cross-sectional study.

Objective: To examine the interrater and intrarater reliability and validity of tools for measuring thoracic kyphosis, namely the digital inclinometer and the flexicurve.

Summary of Background Data: Various methods are used to measure kyphosis, and each has its own advantages and disadvantages. Radiography is common, highly reliable, and valid but unsuitable for regular use because of radiation exposure and cost. Other clinical methods allow safe and rapid assessment of spinal curvature. The validity and reliability of some nclinometers have been confirmed; however, there are no data that compare inclinometers and flexicurves using radiography for measuring thoracic kyphosis.

Methods: We enrolled 105 patients with hyperkyphosis, aged between 10 and 80 years. The Cobb angle was measured radiographically by a spine specialist. Two other examiners, blinded to the Cobb angles, measured thoracic kyphosis using the flexicurve and digital inclinometer.

Results: Comparing the kyphosis angle with the radiographic Cobb angle, as a gold standard, revealed that the digital inclinometer was reasonably valid for patients aged below 30 and above 50 years, whereas the validity of the flexicurve in both age ranges was poor. On the intrarater evaluation, the digital inclinometer provided a high reliability in patients aged below 30 and above 50 years; however, the flexicurve was also acceptable in this regard. In contrast, on the interrater evaluation, the digital inclinometer provided a high reliability in subjects aged below 30 and above 50 years. The flexicurve provided a poor interrater reliability in subjects aged below 30 years and an acceptable level of reliability in those aged above 50 years.

Conclusions: The digital inclinometer is a valid and reliable instrument for measuring thoracic kyphosis and can be used for regular screening. In contrast, the flexicurve has poor interrater and intrarater reliability.

*Department of Orthotic & Prosthetic, School of Rehabilitation

Department of Orthopaedic Surgery, Hazrat Rasoul Hospital

Department of Orthopaedic Surgery, Shafa Yahyaiian Hospital, Tehran University of Medical Sciences, Tehran

§Department of Clinical Sciences, Faculty of Medicine, Kashan University of Medical sciences, Kashan, Iran

Supported by Tehran University of Medical Sciences (Grant No. 944).

The authors declare no conflict of interest.

Reprints: Mojtaba Kamyab, PhD, MSc, CPO(ir), Department of Orthotics & Prosthetics, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran (e-mail:

Received July 1, 2012

Accepted April 21, 2013

© 2014 by Lippincott Williams & Wilkins, Inc.