Abstract
Flatfoot is one of the most common foot pathology for children. This study aims to investigate the prevalence of flatfoot for Taiwanese children, the anthropometric database of children with and without flatfoot, as well as the effect of the two different types of commonly used orthoses on objective and subjective responses.Two experiments are included. In the first stage, the prevalence of flatfoot and the anthropometric database of school children in Taiwan have been established. A total of 1024 school children (549 boys and 475 girls) with age 5 to 13 years old participated in this study. Fifteen foot dimensions were measured using a 3D coordinate measuring probe, digital tape measure and Harris mat imprint. The results show that the prevalence of flatfoot for 5 to 13 years old children was 28% with a decreasing trend with age. The prevalence of flatfoot was 35% in boys and 20% in girls. The percent of overweight and obese children was 20%. Obese children have a higher frequency of flatfoot, greater foot dimensions, and less change in foot breadth between weight-bearing and non-weight-bearing conditions than normal weight children. Children with flatfoot have lower foot height and greater foot length change than children with normal feet.In the second stage, through the laboratory experiments, the effect of different orthotic design on the kinematics, kinetics and muscle activity of lower extremity, as well as the rating of perceived exertion were evaluated. Two groups of children with age of 5 to 11 years old were recruited: nine children with flatfoot (arch index above 0.3) and twelve children with normal foot. Flatfoot group has four experiment conditions: the barefoot, shoe-only, Supra-Malleolar Orthosis (SMO), and University of California Biomechanics Laboratory (UCBL) orthosis conditions; while normal foot group has only two experiment conditions: barefoot and shoe-only conditions.The findings show that children with flatfoot tend to walk with the greater joint motions and higher muscle activities of lower extremity, as well as lower vertical ground reaction force (GRF) and longer durations of the first peak forces of vertical and medical-lateral GRFs than those of normal foot children. For the orthotic evaluation, the results indicate that both the SMO and UCBL orthoses can successfully reduce the joint motion of knee and ankle, the mean muscle activity of tibialis anterior, as well as facilitate the occurrence of the first medial-lateral GRF. In addition, the SMO can further reduce the range of hip flexion and increase the vertical GRF. Although the SMO has more positive impact on gait performance than the UCBL orthosis, but it will cause higher discomfort in ankle and lateral forefoot areas. Therefore, the comfort of SMO should be improved, so that it would become more suitable for flatfoot children to use.