Analysis of Automatically Extracted Hallux Valgus Angles Using Markerless 3D Foot Scans From North America, Europe and Asia

Abstract Background The forefoot is the foot most affected part by ill-fitting shoes. Footwear fitting standards have the measurements of length, width and arch length. Toe shape has not yet been used in footwear measurement. This study aims at investigating the variation in toe shape, as measured by the hallux valgus angle. Methods An automatic and reproducible hallux valgus angle measuring method using 3D foot scans with no palpation markers is proposed and applied to about half a million samples collected across North America, Europe and Asia. The measuring method is robust, it can detect the medial contour along the proximal phalanx even in extreme cases. Results The hallux valgus angle has a normal distribution with long tails on both sides in the general population. In the three regions (North America, Europe, Asia), the mean and standard deviation of this angle are 9° ± 6°, 8 ° ± 6°, 12° ± 6° for males and 11 ° ± 7°, 12 ° ± 7°, 16° ± 7° for females. Conclusions The hallux valgus angle has a broad distribution in the general population. Females have larger hallux valgus angle than males, and people from Asia have larger hallux valgus angle than people from North America and Europe.