Abstract
Lower stiffness of the medial longitudinal arch is reportedly a risk factor for lower
leg disorders. The plantar aponeurosis is considered essential to maintaining the
medial longitudinal arch. It is therefore expected that medial longitudinal arch stiffness
is influenced by plantar aponeurosis stiffness. However, this has not been experimentally
demonstrated. We examined the relationship between the plantar aponeurosis stiffness
and medial longitudinal arch stiffness in humans in vivo. Thirty young subjects participated
in this study. The navicular height and shear wave velocity (an index of stiffness)
of the plantar aponeurosis were measured in supine and single-leg standing positions,
using B-mode ultrasonography and shear wave elastography, respectively. The medial
longitudinal arch stiffness was calculated based on body weight, foot length, and
the difference in navicular height between the supine and single-leg standing conditions
(i. e., navicular drop). Shear wave velocity of the plantar aponeurosis in the supine
and single-leg standing positions was not significantly correlated to medial longitudinal
arch stiffness (spine: r=−0.14, P=0.45 standing: r=−0.16, P=0.41). The findings suggest
that the medial longitudinal arch stiffness would be strongly influenced by the stiffness
of foot structures other than the plantar aponeurosis.
Key words
plantar fasciitis - shear wave elastography - ultrasonography - plantar fascia
