Development of knowledge-based criteria for designing foot orthoses.

摘要

Diabetes, especially for those with peripheral neuropathy, are susceptible for developing plantar foot ulcers, which frequently lead to hospitalization and limb amputations. Diabetic ulceration and plantar foot pain are correlated with abnormally high plantar foot pressures, which can be successfully treated by a foot orthosis, helping to correct foot abnormalities and to relieve and redistribute elevated plantar pressures.;Owing to the complexity of the ankle-foot structures and experimental difficulties, experimental studies on foot orthosis were often restricted to subjective assessments, gross joint motions and plantar pressure distribution. Computational modeling, such as the finite element (FE) method provide an efficient approach to predict the load distribution between the foot and different supports, which offer additional information such as the internal stress and strain of the ankle-foot complex.;In this study, a 3D FE model of the human foot and ankle was developed from reconstruction of MR images from the right foot of a male adult subject. The developed FE model, which took into consideration the nonlinearities from material properties, large deformations and interfacial slip/friction conditions consisted of 28 bony structures, 72 ligaments and the plantar fascia embedded in a volume of encapsulated soft tissue. The biomechanical effects of tissue stiffness, muscular reaction, surgical and orthotic performances on the ankle-foot complex were investigated. Experimental measurements on cadavers and on the subject who underwent the MR scanning were obtained to validate the FE predictions in terms of plantar pressure, foot arch and joint motion, plantar fascia and ligamentous strains under different weight-bearing and orthotic conditions of the foot.;The FE analysis predicted that custom-molded shape was a more important design factor in reducing peak plantar pressure than the stiffness of orthotic material. Besides the use of an arch-supporting foot orthosis, insole stiffness was found to be the second most important factor for peak pressure reduction. Other design factors contributed to a lesser extent in peak pressure reduction in the order of insole thickness, midsole stiffness and midsole thickness. The developed FE model allows efficient parametric evaluations of different design parameters of orthosis without the prerequisite of fabricated orthosis and replicating patient trials.