Fig. 3.1
Cobb measurement (original drawing)
A modified method of Cobb measurement is also used (Fig. 3.2) [5]. Thoracic kyphosis is defined as the angle of intersection between the inferior border (not the superior border) of T4 and that of the transition vertebra, and lumbar lordosis is defined as the angle of intersection between the inferior border (not the superior border) of the transition vertebra and the superior border of the sacrum. The reason to use only the inferior border is to let one vertebral body have one inclination angle, which is expressed by the inclination of the inferior vertebral border. According to Cobb’s method, one vertebral body has two inclination angles: the superior border and the inferior border. These two inclination angles are almost the same when there is no vertebral deformity, whereas they are far separated when the vertebral body has a wedge deformity. In order to define the tilt of the transition vertebra, one inclination angle seems to be preferable.
Fig. 3.2
Modified Cobb measurement [5]. One of the co-authors of this manuscript (EI) is the author of this paper in Spine. There is no specific method to obtain a permission to use this figure. I (EI) originally drew this figure
Additional benefit of using X-ray measurement is that it visualizes not only the spinal curvature but also the shape of each vertebral body. It is especially useful to assess the patients with osteoporosis, who have a high risk of vertebral fractures. Vertebral fractures may cause a change in the spinal curvature, which may affect the back muscle and cause back muscle fatigue and pain. Also, the vertebral fractures may cause neurological disorders when compressing the spinal cord or spinal nerves.
SpinalMouse®
SpinalMouse® (Idiag, Volketswil, Switzerland) is a device, composed of a handheld device and a computer (Fig. 3.3). The handheld device has two rollers, with which the examiner moves the device on the skin along the spinous processes. The data are transmitted to the computer and analyzed immediately. With this device, not only the contour of the spinal column or the posture but also the movement of the spinal column can be measured. The greatest advantage of this device is that it transmits real-time recording data into a computer, whereas the X-ray method requires some time to make the X-ray images available for measurements. Of course, there is no risk of X-ray radiation. There are several validation studies showing high reliability of this device with intraclass correlation coefficients (ICCs) ranging from 0.67 to 0.99, but validity is reported not to be as high as reliability with correlation coefficient ranging from 0.39 to 0.47 [8].
Fig. 3.3
SpinalMouse®. Not only the curvature of the spine (a) but also the mobility of the spine (b, c) can be measured with this device. Our original photos
Because of high reliability, this device has been widely used in the clinical setting. Miyakoshi et al. demonstrated that there was a positive correlation between spinal mobility and the back muscle strength [9]. Prescription of the back strengthening exercise has been shown to improve the QOL, but no significant effect on spinal mobility [10].
Flexicurve
The flexicurve is a flexible ruler, which maintains its shape once it is bent or curved (Fig. 3.4). An examiner gently presses the flexicurve ruler onto the back of a subject, which in turn adopts the thoracic and lumbar curvatures of the subject. The examiner traces the ruler’s retained shape onto a sheet of paper, measures the kyphosis height (E) and the length of curve (L), and calculates the kyphosis index by dividing “E” by “L” (Fig. 3.5) [13]. The kyphosis angle “θ” can be calculated by measuring the intersection between the perpendicular lines to the line “AB” and the line “AC” [14].
Fig. 3.4
Flexicurve ruler (from de Oliveira et al. 2012) [11]. The flexicurve ruler (a) is gently pressed onto the back of a subject (b). The ruler adopts the spinal curvature and maintains its shape (c), which is then traced onto a sheet of paper for various measurements (d). This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Fig. 3.5
Measurements of flexicurve (from Greendale et al. 2011) [12]. The arc BC is the thoracic flexicurve ruler, where B is the upper end vertebra (T4) and C is the lower end vertebra (T12). Then, the point A, where the distance from the line BC becomes the greatest, defines the apex “A.” The height of apex “A” from the line BC is defined as kyphosis height “E,” and the length of the line BC is defined as the kyphosis length “L.” The kyphosis index is defined as E/L. The angle between the two perpendicular lines to the lines AB and AC is defined as kyphosis angle “θ”. Your order details and publisher terms and conditions are available by clicking the link below: http://s100.copyright.com/CustomerAdmin/PLF.jsp?ref=d7e4d0ba-c5ca-4420-adc7-4776e9c1132f Order Details Licensee: Yu Mori License Date: Feb 15, 2015 License Number: 3570560006756 Publication: Osteoporosis International Title: The reliability and validity of three non-radiological measures of thoracic kyphosis and their relations to the standing radiological Cobb angle Type Of Use: Springer-owned imprint Total: 0.00 USD
Kyphosis index showed high reliability, even in the novice testers [15]. Especially, thoracic kyphosis showed higher reliability than lumbar lordosis. Kyphosis index and kyphosis height showed high correlation coefficients (0.93, 0.89) between the testers, but kyphosis length showed lower correlation (0.56) [16]. This lower correlation comes from a difficulty of determining the upper and lower ends of the thoracic curve.
Kyphosis angle, another parameter of flexicurve method, showed high inter-rater correlation (0.831–0.942) and intra-rater correlations (0.783–0.829) [11], indicating high reliability. Also, the correlations between the flexicurve angle and the Cobb measurement in thoracic kyphosis (0.72) and lumbar lordosis (0.60) were relatively high. As both the reliability and validity are high, flexicurve kyphosis angle is considered to be a useful tool in the clinical setting.
Comparisons between the flexicurve and other methods have been reported. Greendale and colleagues performed a validation study among flexicurve kyphosis index, kyphosis angle, and Debrunner kyphometer and concluded that all these three methods showed high reliability and validity [12]. Barrett et al. performed a validation study between flexicurve and manual inclinometer, which demonstrated that not only the flexicurve kyphosis index and kyphosis angle but also the manual inclinometer showed high reliability [17]. All these reports support the clinical benefit of the flexicurve as well as Debrunner kyphometer and inclinometer.
Debrunner Kyphometer
The Debrunner kyphometer is a protractor with a 1-degree scale at the end of two double, parallel arms connected to blocks covering the two spinous processes each (Fig. 3.6). This protractor gives the angle of kyphosis when the blocks are placed at the upper and lower limits of the thoracic spine. The upper foot of the upper arm block is placed directly on the C7 spinous process, and the lower foot of the lower arm block is placed on the T12 spinous process, thus the upper block being at C7–T1 level and the lower block at T11–T12 level. Locating these spinous processes needs some skills. The C7 spinous process is the first prominence at the lower part of the neck by palpation. The T12 spinous process can be counted from the T8 spinous process, which is located at the inferior angle of the scapula, or from the L4 spinous process, which intersects a line drawn between the superior borders of the iliac crests. However, it is difficult to palpate these spinous processes in obese subjects. Therefore, those with advanced training may be able to find the landmarks more easily, whereas it may be more difficult for the novice testers. This device was originally invented to measure the thoracic kyphosis, but it can also be used to measure the lumbar lordosis, or the motion of the thoracic spine and lumbar spine [19]. When measuring the lumbar lordosis, the upper block is placed at T11–T12 level and the lower block at S1–S2 level. Both the reliability and validity of Debrunner kyphometer are reported to be high [7, 18, 19]. The ICC of 0.68 indicates reasonable agreement [18], whereas the kappa values of 0.84 (interobserver agreement) and 0.92 (intraobserver agreement) [18] or the ICC of 0.91–0.94 [19] indicate high reliability. The regression coefficient of 0.76 between the Cobb measurement and kyphometer measurement indicates relatively high validity [7].
