Validity and test–retest reliability of photogrammetry in adolescents with hyperkyphosis

ABSTRACT

Background

A variety of noninvasive instruments have been introduced in the literature to assess thoracic curvature, although the psychometric properties of many of these instruments have not been satisfactory. Photogrammetry is a safe, accessible, and reliable technique. However, its validity in adolescents with hyperkyphosis has not yet been investigated.

Objectives

To investigate the validity and test–retest reliability of photogrammetry in the measurement of thoracic kyphosis among adolescents with hyperkyphosis.

Methods

Fifty adolescents with hyperkyphosis participated in this study. The kyphosis angle was measured using radiography and photogrammetry. A two-way random model of the intraclass correlation coefficient (ICC_2,3) was used to estimate relative reliability. Absolute reliability was assessed by calculating the standard error of the measurements (SEM) and the minimal detectable change (MDC). Pearson’s correlation coefficient was calculated to evaluate the validity of the photogrammetry technique. Bland–Altman plots were plotted to determine the agreement between the angles measured by radiography and photogrammetry.

Results

There was a strong correlation between the values obtained from the photogrammetry technique and those from the radiography method (r = 0.94). The 95% limits of agreement indicated that the photogrammetric measurements of thoracic kyphosis angle might range from 2.4 degrees greater to 10.2 degrees lower than the Cobb radiographic angle. Photogrammetric measurements of thoracic kyphosis showed excellent test–retest reliability (ICC = 0.97; SEM = 1.67; MDC = 4.62).

Conclusion

High reliability of photogrammetry technique and its strong correlation with radiographic Cobb angle support the application of this technique for the measurement of thoracic kyphosis in clinical practice.

KEYWORDS:

• Psychometric properties
• round back
• limits of agreement

Acknowledgments

The authors would like to thank Iran University of Medical Sciences for the partial financial support of this study.

Disclosure statement

The authors have no conflicts of interest to declare.

Additional information

Funding

This work was supported by the Iran University of Medical Sciences [33363].