A biomechanical model of the foot: the role of muscles, tendons, and ligaments.

A biomechanical model of the foot is developed and analyzed to determine the distribution of support under the metatarsal heads, the tension in the plantar aponeurosis, and the bending moment at each of the joints of the foot. This model is an extension of our earlier work to include the role of muscles, tendons, and ligaments. Two cases are presented: in the first the center of gravity of the body is over the mid foot, and in the second, the center of gravity is anterior, over the metatarsals, and no support is provided by the heel. The model shows the extent to which the muscles reduce the force in the supporting ligaments at each of the joints and decrease the tension in the plantar aponeurosis, and that this effect is more pronounced when the center of gravity of the body is moved forward

A biomechanical model of the foot: the role of muscles, tendons, and ligaments.

A biomechanical model of the foot is developed and analyzed to determine the distribution of support under the metatarsal heads, the tension in the plantar aponeurosis, and the bending moment at each of the joints of the foot. This model is an extension of our earlier work to include the role of muscles, tendons, and ligaments. Two cases are presented: in the first the center of gravity of the body is over the mid foot, and in the second, the center of gravity is anterior, over the metatarsals, and no support is provided by the heel. The model shows the extent to which the muscles reduce the force in the supporting ligaments at each of the joints and decrease the tension in the plantar aponeurosis, and that this effect is more pronounced when the center of gravity of the body is moved forward

Analysis of Stress in the Metatarsals.

Shear and normal stresses throughout the second, third, fourth and fifth metatarsals under various loading conditions were determined mathematically using standard techniques from the theory of mechanics of solids. Anatomical data was obtained by CAT scanning the foot of a 20-year-old man at 5 mm increments. For each segment, the horizontal and vertical co-ordinates of points were determined along the outer and inner surfaces of the bone cross sections. Using this data, the stress was calculated throughout each cross-section for a load applied at the metatarsal head in the frontal plane at every 15° interval between the horizontal and the vertical directions. Maximum tensile stress occurred in the second metatarsal in the cross-sections 3.0 cm and 4.0 cm from the proximal end, and were the result of a vertical load. The maximum tensile stress in the third metatarsal occurred in the cross section 3.5 cm from the proximal end, as a result of a horizontal load applied on the lateral side. A similar loading produced the maximum tensile stress in the fourth metatarsal, at a distance of 3.0 cm from the proximal end. The maximum tensile stress in the fifth metatarsal occurred 3.5 cm from the proximal end, as a result of a load applied on the lateral side in a direction slightly inclined to the horizontal. The findings of this study closely relate to the incidence and location of metatarsal stress fractures

Subtalar Pronation--relationship to the Medial Longitudinal Arch Loading in the Normal Foot.

A three-dimensional biomechanical model was used to calculate the mechanical response of the foot to a load of 683 Newtons with the subtalar joint in the neutral position, at five degrees of pronation, and at five degrees of supination. Pronation causes the forefoot to evert, increasing the load borne by the first metatarsal. This results in a 47% increase in the moment about the talonavicular joint and a 58% increase in the moment about the navicular-medial cuneiform joint. Subtalar joint supination causes the forefoot to invert and results in a 55% increase in the moment about the calcaneal-cuboid joint