A constitutive model for the mechanical characterization of the plantar fascia.
ABSTRACT A constitutive model is proposed to describe the mechanical behavior of the plantar fascia. The mechanical characterization of the plantar fascia regards the role in the foot biomechanics and it is involved in many alterations of its functional behavior, both of mechanical and nonmechanical origin. The structural conformation of the plantar fascia in its middle part is characterized by the presence of collagen fibers reinforcing the tissue along a preferential orientation, which is that supporting the major loading. According to this anatomical evidence, the tissue is described by developing an isotropic fiber-reinforced constitutive model and since the elastic response of the fascia is here considered, the constitutive model is based on the theory of hyperelasticity. The model is consistent with a kinematical description of large strains mechanical behavior, which is typical of soft tissues. A fitting procedure of the constitutive model is implemented making use of experimental curves taken from the literature and referring to specimens of human plantar fascia. A satisfactory fitting of the tensile behavior of the plantar fascia has been performed, showing that the model correctly interprets the mechanical behavior of the tissue in the light of comparison to experimental data at disposal. A critical analysis of the model with respect to the problem of the identification of the constitutive parameters is proposed as the basis for planning a future experimental investigation of mechanical behavior of the plantar fascia.
Article: A biomechanical model of the foot.[show abstract] [hide abstract]
ABSTRACT: The foot is modeled as a statically indeterminate structure supporting its load at the heads of the five metatarsals and the tuberosity of the calcaneous. The distribution of support is determined through an analysis of the deformations caused in the structure as a result of the forces at these locations. The analysis includes the effect of the plantar aponeurosis and takes into account the deformation of the metatarsals and bending of the joints. A parametric study is presented to illustrate the behavior of the solution under a broad range of conditions.Journal of Biomechanics 02/1986; 19(12):989-1001. · 2.72 Impact Factor
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ABSTRACT: Structurally the foot is equivalent to a twisted plate. The hindpart is located in the sagittal plane and the forepart in the transverse plane. The transition induced by the twist creates the transverse and the longitudinal arches. Under vertical loading of the foot plate by the tibiotalar column, compressive forces are created on the dorsum and tensile forces on the plantar aspect of the foot plate. The plantar aponeurosis acting as a tie-rod when under tension relieves the tensile forces from the plantar aspect of the foot plate. The increased tension in the plantar aponeurosis in the weightbearing position of the foot occurs with anterior flexion of the leg or with hyperextension of the toes. In the plantigrade position when vertical loading and external rotation are simultaneously applied by the tibiotalar column on the foot, the hindfoot and the midfoot are supinated, and the forefoot is pronated. The medial longitudinal arch is higher, the foot is shorter, and the plantar aponeurosis is relaxed. The foot is then more flexible. With vertical loading and simultaneous internal rotation, the hindfoot and the midfoot are pronated, and the forefoot is supinated. The medial longitudinal arch is lower, the foot is longer, and the plantar aponeurosis is tense. The foot is then more rigid and a better lever arm. Demonstrations are presented both in living and in anatomic dissections.Foot & ankle 09/1987; 8(1):4-18.
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ABSTRACT: Material properties of the plantar aponeurosis were determined by a two-dimensional video tracking method to simultaneously measure the aponeurosis deformation. Failure loads averaged 1189 +/- 244 N and were higher in men. Average stiffness of the intact fascia was 203.7 +/- 50.5 N/mm at a loading rate of 11.12 N/sec and it did not vary significantly for the loading rates of 11.12 to 1112 N/sec. The high tensile loads required for failure were consistent with clinical and biomechanical studies and indicated the importance of the aponeurosis in foot function and arch stability.Foot & Ankle International 11/1994; 15(10):557-60. · 1.47 Impact Factor