Evaluation of the rule-of-thumb: calculation of the toe allowance for developing feet

The amount of toe allowance (TA, the space in front of the toes) in children's shoes is physiologically important and often estimated by the rule-of-the-parent's-thumb. Besides this, other rules-of-thumb exist mainly based on experiences or footprint analysis. The aim of this study is to scientifically evaluate these rules-of-thumb. TA was calculated as a function of growth rate, foot extension, and walking advance based on three-dimensional (3D) foot scans of 2554 children (6-16 years) during standing and walking. Foot extension was determined as the difference in foot length between static and dynamic weight-bearing, walking advance as movement of the most anterior point of toes, and growth rate as semi-annual foot growth. TA was smaller than all rules-of-thumb and was influenced by gender and foot length. These findings primarily present TA based on 3D foot scans which is important for shoe construction. It is recommended to use 90th percentiles instead of mean values for the construction of TA.