Foot Dimension Assessment: Reliability and Agreement of Manual, Pedobarographic, and Handheld 3D Scanning Methods

Background: Accurate assessment of foot morphology is essential in sports medicine, orthopaedics, and footwear design. Manual examination remains common but may lack accuracy and reproducibility. Alternative techniques, such as pedobarography and handheld 3D scanning, may offer more objective and reliable data, given that their reliability and agreement with established methods are confirmed. Methods: Twenty-six healthy adults (age 25.8 ± 4.7 years; BMI 24.1 ± 2.0 kg/m²) were investigated. Foot dimensions were assessed via manual examination, pedobarography, and handheld 3D scanning, each performed in random order by two independent investigators on two separate occasions. Relative and absolute intra-rater reliability were analysed using intraclass correlation coefficients (ICC), the change in the mean of repeated measurements (bias), limits of agreement (LoA), and the typical error (TE). Inter-method agreement was evaluated using Lin's concordance correlation coefficients (CCC), mean bias, and LoA to assess interchangeability as well as systematic bias. Results: Good-to-excellent relative and absolute intra-rater reliability was found for the distance-related foot dimensions across all methods, except for heel width assessed via pedobarography (small bias but wide LoA and high TE). Relative and absolute reliability of the angular parameters assessed via pedobarography and 3D scanning ranged from poor to excellent. Inter-method agreement between manual examination, pedobarography, and 3D scanning appeared low when considering all three agreement indices (i.e., CCC, mean bias, and LoA). The largest discrepancies were observed for heel width and arch-related measures. Conclusions: All three methods seem reliable for assessing distance-related foot dimensions. However, limited agreement among the three methodological approaches indicates that they cannot be used interchangeably without standardisation.