What is the best method for child longitudinal plantar arch assessment and when does arch maturation occur?

BACKGROUND The medial longitudinal arch modifies significantly during growth. Nevertheless, authors differ on the age at which the foot acquires the adult-like shape. The best method to assess this arch in children is also controversial. OBJECTIVES Characterize the longitudinal arch of children between 3 and 10 years and compare the applicability of five evaluation methods. METHODS Plantar prints were acquired from 391 healthy preschools children from the University of Sao Paulo, Brazil. We calculated the arch indexes of: Cavanagh and Rodgers, Chipaux-Smirak, Staheli and the Alfa Angle, and compared them with the feet posture assessment. Non-parametric tests were used to compare among methods and ages. Spearman correlation was used to establish relationships among indexes. RESULTS 3 and 4 years old showed a high prevalence of low arches (36-86%). Between 4 and 5 years old, significant difference was observed for all indexes. The indexes presented good correlation among them, although the proportions of the different arch types were different for each age group (p<0.001). CONCLUSIONS The longitudinal arch acquires an adult-like shape progressively, being statistically notorious the moment of medial longitudinal arch's formation between 4 and 5 years old. The Chipaux-Smirak Index is the best index to assess children's feet; it provides a better classification for lower arches and is easily calculated.