Immediate effects of dynamic- and static-based custom insoles on structural alignment, pressure distribution and subjective comfort in paediatric flexible flatfoot

Background Customised insoles for paediatric flexible flatfoot are typically designed using static foot postures, which may fail to reflect the dynamic mechanical demands of gait. This study explored an alternative method, evaluating whether dynamically modelled insoles, captured during active locomotion, can effectively provide optimized kinematic control and plantar load distribution while maintaining ergonomic comfort as compared to traditional static designs. Methods Two insoles were customised for 15 children (8–10 years) with flexible flatfeet: a static-based insole (SI), modelled during seated great toe dorsiflexion, and a dynamic-based insole (DI), modelled from the active arch profile during walking. Assessments included geometric characteristics (arch height and medial longitudinal arch [MLA] angle), rearfoot angle (RFA), peak plantar pressure (PPP), and subjective ergonomic comfort. Results DI exhibited a significantly greater arch height and MLA angle than SI. Kinematically, both designs reduced severe RFA misalignments, with DI demonstrating more consistent bilateral kinematic control. Kinetically, both functioned as effective total-contact devices, attenuating pressure peaks at the heel and lateral forefoot. Notably, despite the more pronounced structural contour of DI, participants reported high subjective comfort scores that were statistically equivalent to SI. Conclusion Both SI and DI effectively improved rearfoot eversion and reduced localized pressures without compromising subjective comfort. Specifically, the dynamic approach achieved greater total-contact load redistribution across the MLA.