Calculation of the Rearfoot Angle Representing Flatfoot from Comparison to the Cavanagh Arch Index

Abstract

A type of flatfoot can be analyzed accurately using the footprint when a human is standing; however, this method cannot be applied when a human is wearing orthotic shoes. This study aims to analyze flatfoot using the rearfoot angle (RFA) measurement. The result is then compared to a footprint measurement known as Cavanagh’s Arch Index (AI). A total of 31 static footprints of the participants consisting of 14 males and 17 females aged 18 to 25 years were collected. According to Cavanagh’s AI as a gold standard, the correlation equation was obtained as RFA = 46.04AI − 6.41 and RFA = 45.32AI − 6.26 for left and right foot, respectively. The correlation coefficient R2 for the left and the right foot is 0.63 and 0.73, respectively. Other statistical analyses using ANOVA and t-tests are presented in this paper. The correlation results obtained from this study are necessary for estimating the reduction in the degree of flatfoot when using orthotic shoes, which is difficult to calculate using the typical AI method from footprint measurements.