Optimization of pressure relief in gradient lattice orthotic insoles based on plantar pressure-rod diameter mapping.

OBJECTIVE: Traditional orthotic insoles exhibit limited mechanical adaptability, making them insufficient for addressing individualized foot correction requirements. Although gradient lattice structures show promise in enhancing mechanical compatibility, their regional modulus regulation lacks a reliable theoretical foundation, thereby significantly hindering performance optimization and clinical translation of such insoles. This study aims to optimize the structural design of orthotic insoles and systematically evaluate their pressure-relieving performance through computational modeling and comparative analysis. APPROACH: First, a quantitative relationship between elastic modulus and relative density is established through mechanical analysis of lattice unit structures. Subsequently, this relationship is employed to construct a foot pressure-to-rod diameter mapping model, enabling precise regional modulus customization in the insole by modulating lattice unit density. Finally, finite element simulations are conducted to systematically compare the pressure-relief performance of six distinct structural insole designs and evaluate their effectiveness in optimizing plantar pressure distribution. MAIN RESULTS: The results show that the full-contact continuous positive gradient octst-S lattice orthopedic insoles designed using the proposed method have a 61.09% reduction in peak plantar pressure compared to flat insoles. These improvements lead to a more uniform pressure distribution and effective mitigation of local stress concentration. SIGNIFICANCE: This study establishes a quantitative foundation for modulus regulation in gradient lattice orthotic insoles. The developed mapping relationship offers a scalable design strategy and can be readily applied to other functional or medical assistive devices requiring regionally tailored mechanical properties. Keywords: Gradient lattice；Modulus regulation；Mapping model for sole pressure-rod diameter.