Keywords
MB ruler software - intra-rater reliability - inter-rater reliability - photographic
postural assessment
Introduction
“Craniovertebral angle” (CV angle) measurement is a convenient and easy clinical method
for the cervical posture assessment.[1] The angle formed by the intersection of the horizontal line passing through C7 and a line extending from the tragus of the ear to C7 is known as the “CV angle.”[2] This method can be used reliably to assess natural head-neck posture in the sagittal
plane (intra-class correlation coefficient [ICC] = 0.98).[1]
The spinal postural assessment is often necessary in physiotherapy practice and research.
The objective assessment of the spinal posture can be done by methods like X-ray,
3D motion analysis, raster stereography, and photographic postural analysis. The radiographic
assessment is considered the “gold standard” in the literature as it provides clear
images of reference points, but it is not preferred in studies because of the exposure
to radiation. Three-dimension motion analysis is an accurate and reliable method,
but it is not used generally due to the requirement of expensive equipment and laboratory
conditions. The video raster stereography analysis method is reliable and enables
the automatic assessment of spinal motion by multidirectional high-resolution video
recording, but it lacks validity. Many manual methods are available for the postural
assessment like goniometer, flexible ruler, and observational postural analysis by
using the line of gravity. Although manual methods are simple and convenient, they
are subjective. Photographic posture analysis is one of the frequently used, basic,
and observational assessment methods. This approach uses anatomical reference points
for postural angle measurement. The literature supports the clinical use of the photographic
postural assessment because it is a meticulous and objective approach.[3]
The photographic postural evaluation is a convenient and reliable method, with inter-rater
ICC > 0.972 and intra-rater ICC > 0.774.[3] The CV angle can be used reliably to assess cervical posture in the sagittal plane
(ICC = 0.98).[1] Hence, this study was conducted to investigate the inter-rater and intra-rater reliabilities
of MB ruler software using the photographic method to measure the CV angle.
MB ruler is a measuring toolbox, which can be used to measure and track elements on
the computer screen. This software is cost-effective, convenient to use, and easily
available online. It features a triangular ruler (on-screen goniometer) ([Fig. 1]) that helps to detect angles on the image displayed on the computer screen.[4]
Fig. 1 MB ruler software.
MB-Ruler has three instruments for measurements:
-
A triangular ruler to measure distance and angles.
-
A horizontal and vertical ruler with help lines.
-
A screen grid that divides the site in equal rectangles.
All three instruments are often shown and hidden by an easy click.[4]
Method
In this study, “MB-Ruler 5.0 software” (Markus Bader-Software Solutions, triangular
screen ruler) was used. Permission was obtained from the authority for the utilization
of the software.
Ethical Approval and Informed Consent
The ethical approval was obtained from the institutional ethical committee. The written
informed consent documents were signed by the subject before entering the study.
Subjects
A total of 30 physiotherapy students of 20 to 25 years of age, who were asymptomatic,
healthy, and willing to participate were enrolled in the study.
Methodology to Mark the C7 Spinous Process and Tragus of Ear
The spinous processes of C6 and C7 vertebrae are evident. The subject's neck was passively flexed and extended to differentiate
between C6 and C7 vertebrae. The C6 spinous process is mobile, whereas the C7 spinous process remains stable with the movement.[5] This palpation technique was used to identify the C7 spinous process. A body surface sticker was used to mark the C7 spinous process and tragus of the ear.
Methodology to Take Standard Image
A collarless dress was worn by the subject for the photographic session.[1] All subjects were informed to sit comfortably on a high back chair with both feet
flat on the ground, hips and knees positioned at 90 degrees, and buttocks positioned
against the back of the chair. They were instructed to sit as regularly they sit and
place their both hands on the lap.[2] Subject's neck was positioned such that their gaze was fixed on the reference point
in the eye-line on the wall facing the subject.[1] The COOLPIX S6300 camera with 50% zooming power and flash on was used to take images.
The camera was supported on a tripod. The height (distance between the lens of the
camera and floor) was 110 cm, and distance (distance between the lens of the camera
and subject's tragus of the ear) was 150 cm. The height of the camera from flooring,
distance of the camera from the subject, and focus alignment orientation of the camera
were kept constant and assured for each shoot.[1] The camera was placed such that all anatomical markers were visible in the single
image.[6] One standard lateral view image was taken in the sitting position for the measurement
of the CV angle.[2] As per the study done by Niekerk et al, photographs provide accurate and reliable
indicators of the position of the underlying spine.[6]
CV Angle Measurement
The photographs were transferred to the computer via USB data transfer cable and used
for the CV angle assessment.[2]
[6] The CV angle was evaluated by using “MB-Ruler 5.0 Software” ([Fig. 2]).
Fig. 2 Measurement of the CV angle by MB ruler software.
Inter-Rater Reliability
The same single image was individually evaluated by three different observers A, B,
and C as shown in [Table 1]. First day observer A evaluated images for reading A1. Next day observer B evaluated
the same images for reading B1, followed by C1 readings by observer C on the next
day, for the evaluation of inter-rater reliability. In a similar way, A2, B2, and
C2 and A3, B3, and C3 readings were taken on the consecutive days.
Table 1
Evaluation of the CV angle by observer A, B, and C
|
Day
|
Day 1
|
Day 2
|
Day 3
|
Day 4
|
Day 5
|
Day 6
|
Day 7
|
Day 8
|
Day 9
|
|
Reading
|
A1
|
B1
|
C1
|
A2
|
B2
|
C2
|
A3
|
B3
|
C3
|
Intra-Rater Reliability
All three observers repeated the evaluation on the fourth day for test–retest analysis.
First day observer A took A1 readings, on the fourth day the same observer took A2
reading, and on the seventh day A3 reading. B1, B2, and B3 readings were taken by
observer B on day two, five, and eight. In similar ways, reading C1, C2, and C3 were
taken by observer C on day three, six, and nine, respectively ([Table 1]).[1]
Results
Data were analyzed using SPSS 25 ([Table 2]). The statistical significance was set at p < 0.05. The outcome measure used is the CV angle.
Table 2
Statistical analysis
|
Intra-class correlation
|
95% Confidence interval
|
|
Observer
|
|
Lower bound
|
Upper bound
|
|
Observers A vs. B
|
0.92
|
0.83
|
0.96
|
|
Observers A vs. C
|
1.00
|
1.00
|
1.00
|
|
Observers B vs. C
|
0.92
|
0.83
|
0.96
|
|
Observers A1 vs. A2
|
1.00
|
1.00
|
1.00
|
|
Observers A1 vs. A3
|
1.00
|
1.00
|
1.00
|
|
Observers A2 vs. A3
|
1.00
|
1.00
|
1.00
|
|
Observers B1 vs. B2
|
0.92
|
0.83
|
0.96
|
|
Observers B1 vs. B3
|
0.92
|
0.82
|
0.96
|
|
Observers B2 vs. B3
|
1.00
|
1.00
|
1.00
|
|
Observers C1 vs. C2
|
1.00
|
1.00
|
1.00
|
|
Observers C2 vs. C3
|
1.00
|
1.00
|
1.00
|
|
Observers C2 vs. C3
|
1.00
|
1.00
|
1.00
|
The demographic details of the subjects are mentioned in [Tables 3] and [4].
Table 3
Age distribution (years)
|
Mean
|
22.90
|
|
SD
|
1.66
|
|
Min
|
20
|
|
Max
|
25
|
Table 4
Gender distribution (numbers)
|
Number
|
Percent
|
|
Female
|
19
|
63.3
|
|
Male
|
11
|
36.7
|
In this study, 30 volunteer students (11 boys and 19 girls) in the age range of 20
to 25 years were involved. The CV angle was evaluated by MB ruler software by three
different observers. It was found that the CV angles measured by MB ruler software
in the present study were reliable and repeatable ([Graph 1], [2], and [3]).
Graph 1 Intra-rater reliability observer A.
Graph 2 Intra-rater reliability observer B.
Graph 3 Intra-rater reliability observer C.
Cronbach's α coefficient value of intra-rater (0.999) and inter-rater (0.892) reliabilities
is observed to be high ([Table 5]); thus, “MB ruler software” is reliable for assessing the CV angle.
Table 5
Cronbach's α coefficient
|
Cronbach's α coefficient value of intra-rater reliability
|
0.999
|
|
Cronbach's α coefficient value of inter-rater reliability
|
0.892
|
Discussion
In the present study, the inter-rater and intra-rater reliabilities of the MB ruler
software using the photographic method for the evaluation of the CV angle were investigated
with 30 samples and it has been found to be reliable. For the evaluation of the CV
angle, the inter-rater (ICC > 0.999) and intra-rater (ICC > 0.892) reliabilities of
the MB ruler software were observed to be in the range of very good to excellent.
In this study, inter-rater and intra-rater ICC classifications were made based on
the study done by Ferreira et al as mentioned in [Table 6].[7]
Table 6
ICC values with interpretation
|
ICC value
|
Interpretation
|
|
<0.70
|
Non-acceptable
|
|
0.71 < ICC < 0.79
|
Acceptable
|
|
0.80 < ICC < 0.89
|
Very good
|
|
ICC > 0.90
|
Excellent
|
Abbreviation: ICC, intra-class correlation coefficient.
In the literature, there are handful of reliability studies on the spinal angle measurements,
which utilized various methods in different age groups, as mentioned in [Table 7].
Table 7
Reliability studies of different spinal angle measurement methods
|
Author
|
Publication year
|
Methodology
|
Subjects gender and age
|
Sample size
|
ICC
|
|
Mcevoy et al.[9]
|
2005
|
Photographic posture assessment
|
boys and girls 5–12 years
|
38
|
≥0.93
|
|
Perry et al.[10]
|
2009
|
Photographic posture assessment
|
male and female aged 13–17 years
|
22
|
Interrater 0.40–0.75
Interrater 0.75–0.90
|
|
Pusic et al.11
|
2010
|
Manual & automatic measurement in photographic posture analysis
|
males between 10–13 years
|
273
|
Automatic 0.81–0.92
manual 0.80–0.91
|
Abbreviation: ICC, intra-class correlation coefficient.
The existing postural assessment methods are subjective. The objective and reliable
approaches are expensive, require special training, or equipment. On the contrary,
the photographic postural assessment is an economical and simple method of posture
evaluation. MB ruler software that can be used for photographic postural analysis
is low cost, advantageous in terms of easy availability and application, and often
used in research studies; hence, finding its reliability was important.[3]
It was found that the CV angles evaluated by MB ruler software in this study were
reliable and repeatable. As this study has proven the reliability of the MB ruler
software, it can be used for the clinical and research work to evaluate postural angles.
The essential component of the current study was that an easily accessible MB ruler
software was used for the assessment of the angles. The limitation of the study was
the small sample size; future study can be done on a large group.
Conclusion
MB ruler software has good intra-rater (ICC = 0.999) and inter-rater (ICC = 0.892)
reliabilities; hence, it can be used for various postural assessments with photographic
methods in the clinical and research works.
