OBJECTIVE: To assess the plantar impressions obtained in children during the Jack test, with the aim of quantifying and analyzing their variability in the critical period for plantar foot arch formation. METHOD: A hundred and twenty feet from 60 healthy White children, recruited in an outpatient pediatric clinic, were examined. Our sample included 35 boys and 25 girls, ranging from 2 to 5 years. The Jack test was simulated using a 45o wedge-shaped orthosis applied to the hallux. Bilateral plantar impressions were acquired in the alternate single-foot standing position using a pedigraph. Two plantar impressions were obtained for each foot, with and without the orthosis. The exams were analyzed using the Valenti and Volpon methods. Statistical tests were applied. RESULTS: In all cases, both the Valenti and Volpon indexes decreased as the orthosis was applied. Furthermore, the difference between both indexes with and without the orthosis decreased with age. CONCLUSIONS: It is possible to quantify the Jack test using plantar impressions with the Volpon and Valenti methods. The variability observed in plantar shape tended to decrease after 4 years of age. Finally, the Jack test gradually lost its capability to change plantar impression with age, which reduces its accuracy as a parameter for a good prognosis in longitudinal medial arch formation. Level of Evidence: Level IV, observational descriptive study.
Flatfoot; Anthropometry; Child; Physical examination
