EFFECT OF VARYING ARCH HEIGHT WITH AND WITHOUT THE PLANTAR FASCIA ON THE MECHANICAL-PROPERTIES OF THE FOOT

A biomechanical model was used to calculate the mechanical properties of the foot at a load of 683 newtons, while changing arch height with and without the plantar fascia. An increase in arch height from 20 mm to 60 mm decreased predicted vertical displacement of the foot from 11 .8 mm to 5.5 mm with the plantar fascia intact and from 13.5 mm to 7.5 mm without the plantar fascia. The amount of horizontal elongation de creased from 8.6 mm to 8.4 mm with the plantar fascia and increased fr om 9.8 mm to 11.7 mm without. A 60-mm arch height yielded a 40% increa se in horizontal elongation and a 36% increase in vertical displacemen t when the plantar fascia was cut, whereas a 20-mm arch height yielded a 13% increase in horizontal elongation and a 14% increase in vertica l displacement. A change in arch height from 20 mm to 60 mm increased stiffness of the foot with and without the plantar fascia.