Penetration and shared nodes between muscles, tendons and the plantar aponeurosis mesh elements in finite element models of the foot may cause inappropriate structural behavior of the tissues. Penetration between tissues caused using separate mesh without motion constraints or contacts can change the loading direction because of an inadequate mesh displacement. Shared nodes between mesh elements create bonded areas in the model, causing progressive or complete loss of load transmitted by tissue. This paper compares by the finite element method the structural behavior of the foot model in cases where a shared mesh has been used versus a separated mesh with sliding contacts between some important tissues. A very detailed finite element model of the foot and ankle that simulates the muscles, tendons and plantar aponeurosis with real geometry has been used for the research. The analysis showed that the use of a separate mesh with sliding contacts and a better characterization of the mechanical behavior of the soft tissues increased the mean of the absolute values of stress by 83.3% and displacement by 17.4% compared with a shared mesh. These increases mean an improvement of muscle and tendon behavior in the foot model. Additionally, a better quantitative and qualitative distribution of plantar pressure was also observed.

Background: Plantar pressure distribution is a valuable tool for studying how the ground reaction forces are transmitted from the feet to the body and for detecting abnormalities in foot biomechanics. Objectives: The objective of this study was to determine the effect of the foot type (normal foot, flatfoot, and cavus foot) on plantar pressure distribution in healthy Mexican men and women aged from 3 to 74 years. Methods: A database of the plantar pressure distribution under dynamic and static conditions for both feet was studied using descriptive statistics, regression analysis, and statistical factorial design. The database contained images of the soles of the feet and pressure distribution of 996 persons between 3 and 74 years old (53.9% females and 46.1% males). Two different conditions were evaluated; the first was in a static condition, and the second was during walking. The Chippaux–Smirak Index (CSI) was used to classify the type of feet. Results: In the left foot, a linear regression analysis of the soles of the feet shows that the prevalence of flatfoot (p-value = 3.45 × E⁻⁵) decreased with age, while the normal foot (p-value = 7.39 × E⁻⁵) increased. When people are standing (static), the hindfoot (55.64 ± 18.80%) presents more pressure than the forefoot (45.18 ± 19.50%), while in dynamic, the forefoot (55.95 ± 13.36%) supports more pressure than the hindfoot (44.05 ± 13.36%). Similar behavior occurs in the right foot. A statistical factorial design ANOVA shows that the plantar pressure in the forefoot and hindfoot regions is significantly different (p < 0.05). Conclusions: The prevalence of flatfoot decreased with age, while the proportion of normal foot type increased. Under static conditions, the hindfoot bore more load than the forefoot, whereas under dynamic conditions, the forefoot bore more load than the hindfoot. This research contributes to generating a comprehensive database of reference values of the plantar pressure of different foot types in a Mexican population; this will be useful to podiatrists, clinicians, and physiotherapists for the analysis or treatment of abnormal foot postures.