Abnormal Biomechanical Conditions of the Foot in Child with Down Syndrome During Standing: A Finite Element Study

Background: Down syndrome children have a high incidence of pes planus. Pain follows and does harm to their daily life. To well manage their foot pain, it’s necessary to know the mechanism of the pain from the aspect of biomechanics. The purpose of this study was to characterize the abnormal biomechanical conditions of foot in Down syndrome children during standing, comparing to the normal control children by finite element method. Methods: Two participants aged 5 were recruited in this study that are a Down syndrome child with pes planus and a normal control child. Two three-dimension finite element foot models were constructed from CT of the two participants, each of which include bones, ligaments, plantar fascia, cartilages, epiphyseal plates and an encapsulated soft tissue. The plantar pressure during standing and anthropometric data were collected from the same participants for model validation and simulation. Results: The abnormal alignment of the transverse tarsal joint showed in Down syndrome child. The contact pressure in Down syndrome child was higher in tibiotalar joint, compared with the normal control child. The tensile force of spring, plantar calcaneocuboid ligaments in Down syndrome child was approximately 9 folds and 58 folds greater than normal control child, respectively. In Down syndrome child contact force of the talonavicular joint was 0.05 times the body weight and calcaneocuboid joint was near zero, whereas the value in normal control child was 0.11 and 0.01 respectively. Conclusion: The Down syndrome child showed abnormal biomechanical conditions in foot in terms of joints contact pressure, tensile force of ligament around transverse tarsal joint and contact force transmission through transverse tarsal joint. These abnormal biomechanical conditions resulted from pes planus are the potential factors that may cause their foot pain. Conservative interventions should be considered at their early age to eliminate negative effect of these potential factors.