Method:
(1) Make a footprint of the patient on firm paper, graph paper or cardboard.
(2) A line is drawn from the heel to the farthest point on the pad of the foot at base of the second toe.
(3) The line is divided into 3 equal segments one third the length of the total line (involves placing 2 points)
(4) A perpendicular line is drawn through the original line at each of the 2 points.
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Portion of Footprint
|
Zone
|
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pad of the foot
|
C
|
|
middle portion
|
B
|
|
heel
|
A
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(5) The relative area of the footprint in each zone is then measured.
(5a) One method is to cut the paper on which the footprint is taken and weighing each zone. This method is simple but requires careful cutting and an accurate scale.
(5b) Morphometry can be used with point counting.
(5c) If the footprint is taken on graph paper, the number of squares can be counted.
arch index =
= (area for zone B) / (total area for all 3 zones)
Interpretation:
• The index in a person with a normal arch is from about 0.21 to 0.26.
• A high arch is associated with a low index value, while a flat arch will have a high value.
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Arch Index (AI)
|
Arch Type
|
|
<= 0.21
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high arch
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|
0.211 to 0.259
|
normal arch
|
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>= 0.26
|
flat arch
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