Abstract:
This study explored the use of a coupled Finite Element (FE) analysis and optimization technique as a biomechanical tool to predict in-shoe pressures and evaluate the effectiveness of a therapeutic intervention. The primary objective was to examine how a metatarsal (MT) pad, when placed inside a shoe, affects peak pressures on the metatarsal head (MTH) region during the initiation of late stance. Researchers created a sophisticated 3D FE model of the forefoot, a shoe, and an MT pad, assigning biomechanically-appropriate material properties such as hyperfoam for footwear and incompressible hyperelastic properties for soft tissues.
The methodology involved first capturing experimental barefoot plantar pressures and ground reaction forces (GRF) from a subject. These experimental data were used to validate a barefoot FE model through an optimization process that adjusted bone and foot orientation to match predicted pressures with measured pressures. A similar optimization was then applied to the in-shoe model (with and without the MT pad) to align reaction moments with those calculated in the barefoot simulation, using a kinematic constraint to manage the foot-shoe interaction. The results showed that while there was a discrepancy between the absolute pressure values of the in-shoe model and the experiment (520 kPa vs. 277 kPa at MTH2), the model successfully predicted the trend of pressure reduction. Specifically, the inclusion of an MT pad reduced the model's peak MTH2 pressure by 18%, a result that aligns with previous experimental findings. The study concludes that this biomechanical modeling approach is a viable method for designing and assessing therapeutic footwear interventions, like MT pads, using barefoot data as a foundation, thereby reducing the need for extensive physical experimentation.
