William Ledoux, Ph.D.
VA Center of Excellence for Limb Loss Prevention and Prosthetic
Engineering
E-mail: wrledoux@u...
TITLE:
"The Concept of Foot Type"
ABSTRACT:
The human foot is a complex machine that performs varying
functions: it provides
proprioception, it serves as a sensory organ (transducing temperature
and pressure), and it is
instrumental in maintaining a platform for balance. Feet come in varied
shapes and sizes, but
most can be categorized into one of three groups or foot types: pes
cavus (high arch),
neutrally aligned and pes planus (low arch). Mechanically, the
foot is the load-bearing
interface between the body and the environment during locomotion and
quiet stance. It serves
as a flexible "mobile adaptor" when the foot first comes in contact
with the ground and as a
rigid lever arm when the foot propels the body forward. It is our
overarching hypothesis that
foot structure (i.e., the shape of the bones and their relative
positions) affects foot
function (i.e., the motion of the bones of the foot and the pressure
beneath the foot).
Our group has explored the effect of foot type on foot function by
studying pes cavus,
neutrally aligned, asymptomatic pes planus and symptomatic pes planus
feet; two pes planus
groups were included because many people with flat feet have no
pain. Our completed research
has shown that three-dimensional (3D) static foot alignment as
determined from computed
tomography (CT) scans differs among foot types, and that plantar
pressure and static hindfoot
alignment differs among foot types. Furthermore, our current
research involves studying the
effect of foot type by: 1) quantifying quasi-static joint motion as
determined from multiple,
controlled magnetic resonance imaging (MRI) scans, 2) determining the
range of motion of foot
bones with externally mounted motion sensors as the foot progresses
through circumduction, and
3) measuring simplified foot bone motion during gait (i.e., the foot
and ankle are modeled as 6
rigid bodies) using retro-reflective kinematic markers.