Abstract
BACKGROUND: Flatfoot (Pes Planus), often regarded as a physiological deviation in children, is of concern to parents because there is no test to predict the development of foot arch. This study aimed to use a new diagnostic flatfoot criterion to determine 1) how the footprint index changes during the development of foot arches, 2) what factors can predict a foot arch development, and 3) whether foot arch development could be a process of body growth. METHODS: 572 children were enrolled in a prospective longitudinal study of anthropometrical parameters and physical fitness twice at age of 6.7 and 8.2 years. The bimodal frequency distribution of the Chippaux-Smirak index (CSI) of the footprint was used to define flatfoot as CSI <0.58 and non-flatfoot as CSI >0.61. Body measurements and physical fitness tests were compared between children with flatfeet who developed foot arches and children who did not. RESULTS: Of 263 children with flatfeet, the CSI significantly changed from 0.72 to 0.46 in 70 children who developed foot arches over 1.5 years and the others had minimal change in the index. Children with foot arch development had a lower initial CSI, improved boys' performance in one-leg balance, and less increase in girls' body height than children who remained flatfooted, whereas sex and weight were similar in both groups. CONCLUSION: This longitudinal study with the bimodal distribution of the CSI investigated how the development of foot arch advances in children around age 7. A significant and unique pattern in change of the CSI suggests involvement of a maturational stage in foot arch development. Along with the improved performance in one-leg balance, the unidirectional transition from flatfoot to non-flatfoot is associated with improvement in motor control of the ankle. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR-OCS-14004300).