The gold-standard orthopaedic technique for assessment of thoracic kyphosis is standing lateral spine radiographs. In elderly persons, spinal radiographs may be taken in the supine position for comfort. The Cobb’s angle of kyphosis is calculated from perpendicular lines drawn on a standard thoracic spine radiograph: a line extends through the superior endplate of the vertebral body, marking the beginning of the thoracic curve (usually at T4), and the inferior endplate of the vertebral body, marking the end of the thoracic curve (usually at T12) ().29
While this method is the gold-standard, it is limited by the need for radiography.
FIGURE 1 Cobb’s angle of kyphosis, calculated from a lateral radiograph. (A) Draw the first line (line a) through the superior end plate of T3, and a second line (line b) that is perpendicular to line a. (B) Draw a third line (line c) through the inferior (more ...)
Acceptable alternatives are the Debrunner kyphometer and the flexicurve ruler.41
Both methods are performed standing. The kyphometer measures the angle of kyphosis, the arms of the protractor-like device are placed at the top and bottom of the thoracic curve, usually over the spinous processes of T2 and T3 superiorly, and T11 and T12 inferiorly ().41
The flexicurve ruler is a plastic, moldable device that is aligned over the C7 spinous process to the L5–S1 interspace; the ruler is molded to the curvature of the spine and the thoracic and lumbar curves are traced (). The kyphosis index is calculated as the width divided by the length of the thoracic curve, multiplied by 100 ().47
A kyphosis index value greater than 13 is defined as hyperkyphotic.40
FIGURE 2 Debrunner kyphometer measurement of kyphosis. (A) Place the upper foot of the kyphometer over the interspace of T2 and T3 spinous processes, and the lower foot of the kyphometer over the interspace of T11 and T12 spinous processes. (B) Ask the patient (more ...)
FIGURE 3 Flexicurve ruler measurement of kyphosis. (A) Mark the C7 spinous process and the L5–S1 interspace on the patient’s skin with a grease pencil. (B) Place the superior end of the ruler at C7 and the inferior end over the lumbar spine, molding (more ...)
Lundon et al41
compared the reliability of standing radiographic, kyphometer, and flexicurve methods of measuring kyphosis in a group of 24 postmenopausal women with osteoporosis. There was excellent intrarater and interrater reliability (intraclass correlation coefficients [ICCs] = 0.87–0.92) for each method, indicating the strength of each instrument for measuring kyphosis.41
Kado et al29
compared the agreement between standing kyphometer and supine radiologic measure of Cobb’s angle of kyphosis in older women. While the overall agreement was acceptable (ICC = 0.68), the agreement between the kyphosis measurements greater or equal to 50° was poor (ICC = 0.44). Thus, while all measures can be used to reliably quantify kyphosis, the standing kyphometer method for measuring a kyphotic spine may overestimate the degree of kyphosis compared with supine radiographs. However, the external methods do not involve radiographic exposure and are inexpensive and easy to use in the clinical setting.
Other clinical measures are sometimes used to quantify hyperkyphotic posture. Standing measurements of tragus to the wall or occiput to the wall, and supine measurement of the number of 1.5-cm blocks needed to support the head have been described2,33
; however, reliability of these methods has not been investigated and there are no studies comparing these measures to the gold-standard radiograph.