Two-Dimensional Hindfoot Model for Plantar Pressure Prediction

Objective: High plantar pressures have been associated with foot ulceration in patients with diabetes. Treatment usually includes an in-shoe intervention designed to reduce plantar pressure under the heel by using insoles. Finite element (FE) analysis provides an efficient computational framework to investigate the performance of different insoles for optimal pressure reduction. The aim of this study is to design a patient-specific, two-dimensional (2D) FE model of a diabetic hindfoot. Method: A 2D FE model of the hindfoot was developed from reconstruction of magnetic resonance images (Simpleware ScanIP-ScanFE, v.5.0 and Rhinoceros v.4.0). Finite element software ABAQUS was used to perform the numerical stress analyses. A diabetes subject [age 72 years; body mass index (BMI) 25.1 kg/m2] and a healthy subject (age 28 years; BMI 20.2 kg/m2) were acquired. The foot biomechanics analysis was carried out. Vertical ground reaction forces (Bertec), taken from the midstance phase of the gait, were applied to the FE model. Validation of the pressure state was achieved by comparing model predictions of contact pressure distribution with experimental plantar pressure measures (Imagortesi). Result: A nonlinear 2D FE hindfoot model was developed and meshed with quadratic elements. The measured and model-predicted peak plantar pressures of the diabetes subject were, respectively, 682.32 and 602.82 KPa. The values for the healthy subject were 483.63 KPa for the measured peak plantar pressure and 428.63 KPa for the simulated one. The model-predicted structural response of the heel pad was in agreement with experimental results within 10% of error. Conclusion: The proposed model will be useful to simulate the different insole material and their contribution in decreasing the plantar pressures.