Validity and reliability of a novel subtalar joint axis of rotation locator measurement device

Main outcome measures Variables that were measured in this study were as follows: 1) Inclination of STJ AoR in the sagittal plane measured by radiographic images (Median MDXP-40 Inc, Korea) of the foot in the sagittal plane. In order to collect radiological images of the foot, subjects stood with a tandem position and the STJ was placed in neutral position. Sagittal plane inclination of the STJ AoR were further analyzed using ViewRex (TechHeim, Korea) per McClay‘s method [1]; 2) Inclination of the STJ AoR in the sagittal plane was measured by the locator; 3) Inclination of the STJ AoR in the transverse plane was measured by the locator. The anterior and posterior exit point were determined per Kirby’s method [2]. Once the locator was aligned along two points, (anterior medial and posterior lateral exit point) a Digital Mini Protractor (WWC-TE Bevel Box, USA) was used to measure inclination angle. Pearson correlation was used to analyze the relationship of validity between radiographs and the locator measuring the STJ sagittal plane inclination. Intra Correlation Coefficient (ICC) was used to analyze day-to-day reliability of the locator.