Hyperkyphosis and the Cobb angle: is the Cobb angle affected by posture in older adults?

Hyperkyphosis, an excessive curvature of the thoracic spine in the sagittal
plane, is present in 20 to 40% in community-dwelling older adults and up to 55%
in geriatric outpatients. Since multiple studies show an association between
hyperkyphosis and negative health effects, like a decreased physical
performance and a doubled fall risk, measuring hyperkyphosis is clinically
relevant and should be done adequately.
The current gold standard, the Cobb angle, is the angle between the fourth and
twelfth thoracic vertebra on a lateral radiograph. Some studies report a Cobb
angle measured in supine position and some in standing position. As the
kyphosis angle is influenced by many factors, such as the anatomy of the
vertebra and back extensor muscle strength, we hypothesize that the posture of
the patient influences the Cobb angle. Furthermore, to be able to compare
previous studies using different kyphosis measurement methods, we aim to
investigate the correlation between the Cobb angle and two clinimetric kyphosis
measurement methods: the blocks method and the occiput-to-wall distance.

To investigate:
(1) the difference in degrees between a Cobb angle measured in supine position
and standing position with standard instructions of the radiographer (main
objective)
(2) the correlation between the Cobb angle in both supine position and standing
position, the blocks method and the occiput-to-wall distance (OWD)
(3) the interrater and intrarater variability of the Cobb angle

Cross-sectional, single-center, observational cohort

The risks and burden of this study is considered to be low for participants. A
lateral radiograph is standard care. Immediately after this radiograph, the
additional radiograph will be made, and the two clinimetric kyphosis
measurements will be performed. Altogether, this will take less than 10
minutes. No additional visits or questionnaires are needed.The radiation
exposure of the additional radiograph of the chest is low: 0.02 mSV [1]. In
comparison the radiation exposure in the Netherlands is 2.6 mSv per person
yearly in the Netherlands.The lifetime attributable risk of cancer incidence
for radiation exposure up to 10 mSV per year varies from 0.0002 to 0.0310,
depending of age and gender of the patient.