Sir,
Standing height is one of the most commonly used anthropometric parameters for the determination of longitudinal growth. It also helps in identification of people in medicolegal cases. However, measurement of height is difficult in individuals who cannot stand due to musculoskeletal disorder or with amputated lower limbs. For those cases, arm span can be used to estimate the height by developed regression equations. Several methods for arm span measurement have been reported in previous studies [1–4]. Those methods and their potential errors are listed in Table 1. Two major difficulties in arm span measurement are shown in Fig. 1a and b.
Table 1.
Potential errors in measurement of arm span length by currently available methods
| Posture | Subject in position during measurement | Measurement | Potential errora |
|---|---|---|---|
| Erect; back on wall [1] | Yes | Measuring tape passes in front of the body | Arc; hypotenuse |
| Erect; back on wall [2] | Yes | Measuring tape passes on the back of the body | Hypotenuse |
| Erect [3] | Yes | Measuring tape across the back of the body | Hypotenuse |
| Erect; back on wall [3] | No | Marked two points on wall is measured | Hypotenuse |
| Erect; back on horizontal lined material [3, 4] | No | Marked two points on horizontal line is measured | Horizontal lines may not be perfect |
aFor brief description of arc and hypotenuse error, see Fig. 1
Fig. 1.
Potential errors in arm span length measurement—a if two arms are not placed on the same horizontal line, “hypotenuse error” occurs, b if measured with the subject in position, “arc error” occurs (illustrations are not according to proportion)
We intended to develop a portable tool which would be devoid of current errors for arm span measurement. Furthermore, we aimed to make it with possible minimal cost.
We printed one vinyl banner (commonly known as flex printing) of 6′ × 8′ size with numbered and colored horizontal lines at 1 cm interval as shown in Fig. 2. Then, three spirit levels were fixed on the banner at the upper part. We named it “FlexTool” as we made it with a material which is popularly known as “flex” and the tool is a flexible and portable one. It can be hanged on any wall with proper leveling for measurement of arm span in erect posture. The lower end of the FlexTool should be set 2′ above the floor to get 8′ × 8′ coverage. This tool can be kept flat on a floor to measure arm span in supine or prone position. In this case, the hypotenuse error (Fig. 1a) is not there, hence leveling is not required. The marked horizontal line is sufficient to prevent any error.
Fig. 2.
A schematic of FlexTool showing its length and width, spirit level, and numbered horizontal lines
For measurement in the erect posture, the subject stands with her/his back on the FlexTool (set against a wall), heels approximated together, and arms stretched maximally with the arm making an angle of 90° with the body. Tips of the fingers with maximum length (commonly, middle finger) are positioned on the same numbered horizontal line. A chalk powdered card is taken to mark the point of the tip of the fingers. Then, the subject leaves the position and the length between marked points is measured by a measuring tape.
This low-cost FlexTool can be made in any resource-limited settings with minimal cost. It can be used to measure arm span in both standing and laying down position without any prevalent errors faced with other methods. However, its practical superiority in the measurement of arm span is a topic of further research. In addition, being relatively flimsy in nature, vinyl banner may get damaged with frequent folding and unfolding. Any clinician or the institution should consider both the advantages and disadvantages of the tool before adaptation.
Author contributions
HM: concept and design, literature search, development of the tool, drafting of manuscript. SM: literature search, development of the tool, editing and revising the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Ethical standard statement
This article does not contain any studies with human or animal subjects performed by the any of the authors.
Informed consent
For this type of study informed consent is not required.
References
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