Development and Validation of a Subject-Specific Coupled Model for Foot and Sports Shoe Complex: A Pilot Computational Study

Abstract

Nowadays, footwear serves an essential role in improving athletic performance and decreasing the risk of unexpected injuries in sports games. Finite element (FE) modeling is a powerful tool to reveal the biomechanical interactions between foot and footwear, and establishing a coupled foot-shoe model is the prerequisite. The purpose of this pilot study was to develop and validate a 3D FE coupled model of the foot and sports shoe complex during balanced standing. All major foot and shoe structures were constructed based on the participant's medical CT images, and 3D gait analysis was conducted to define the loading and boundary conditions. Sensitivity analysis was applied to determine the optimum material property for shoe sole. Both the plantar and shoe sole areas were further divided into four regions for model validation, and the Bland-Altman method was used for consistency analysis between methods. The simulated peak plantar and sole pressure distribution showed good consistency with experimental pressure data, and the prediction errors were all less than 10% during balanced standing with only two exceptions (medial and lateral forefoot regions). Meanwhile, the Bland-Altman analysis demonstrated a good agreement between the two approaches. The sensitivity analysis suggested that shoe sole with Young's modulus of 2.739 MPa presented the greatest consistency with the measured data in our scenario. The established model could be used for investing the complex biomechanical interactions between the foot and sports shoe and optimizing footwear design, after it has been fully validated in the subsequent works under different conditions.

Keywords: balanced standing; biomechanics; contact interaction; finite element modeling; foot; model validation; sports shoe.

Figure 1

Three-dimensional finite element model of the foot and sports shoe complex. The model started from the reconstruction of each solid part of the foot and shoe, and then, the main two parts (foot and shoe) were assembled together to form the finial structure, which includes foot bone, cartilage, ligament, plantar fascia, soft tissue, shoe upper, and shoe sole.

Figure 2

The application of boundary and loading conditions: (A) the heading angles of foot in sagittal and coronal plane were further calculated based on the Euler angles of foot rigid body coordinate system with respect to the global coordinate system; (B) the foot-plate system approach used to simulate the interaction between the foot, shoe, and ground, μ1 represents the friction coefficient between the shoe sole and plate while μ2 represents the friction coefficient between the foot and shoe upper.

Figure 3

The subdivided regions and comparison between predicted pressure distribution and experimental pressure data: (A) plantar region and (B) sole region; both the plantar and sole areas were further divided into four specific regions, including medial forefoot (MFF), lateral forefoot (LFF), midfoot (MF), and hindfoot (HF) for foot model, medial fore-sole (MFS), lateral fore-sole (LFS), medial hind-sole (MHS), and lateral hind-sole (LHS) for shoe model.

Figure 4

Bland–Altman plot of experimental and simulated pressure data. Different colored circles represent different regions. As shown in the figure legend, the black one represents the plantar regions, while the other five represent the sole regions with different material properties.