Describing the medial longitudinal arch using footprint indices and a clinical grading system

The current literature is not clear regarding the best method of determining medial longitudinal arch (MLA) height. Differences in MLA height can significantly alter lower extremity biomechanics; therefore, an accurate and reproducible assessment of arch height is essential for clinical evaluation and future research. The goal of this project was to determine the reliability of common arch height measurement techniques.

Foot length, truncated foot length, navicular height, dorsal height, and footprint indices were obtained from healthy volunteers using a mirrored foot photograph box (MFPB). Between-rater and between-day reliability was determined using the interclass correlation coefficient, and the Pearson correlation coefficient was used to determine if any of the footprint parameters correlated with navicular height or normalized navicular height.

The most reliable footprint measurement was the footprint index, followed by the Staheli index, Chippaux-Smirak Index, arch index, truncated arch index, and arch length index. The correlation of footprint measurements to normalized navicular height ranged from 0.585 to 0.648.

Historically, the height of the navicular is considered to be the best approximation of MLA height. The results of this study indicate that the footprint indices are highly correlated with navicular height, indicating that both navicular height measurements and footprint measurements are valid measures of MLA height. Multiple methods exist for measuring the height of the MLA; therefore, it is important to develop a standard set of measurements to be used when foot type is used as a variable in research studies or when making a clinical diagnosis.