Article

Hinged ankle-foot orthoses are prescribed routinely for the treatment of ankle
joint deficits, despite the conflicting outcomes and the little evidence on their
functional efficacy. In particular, the axis of rotation of the hinge is
positioned disregarding the physiological position and orientation. A
multi-segment model was utilized to assess in vivo the effect of different
positions for this axis on the kinematics of foot joints. A special custom-made
hinged orthosis was manufactured via standard procedures for a young healthy
volunteer. Four locations for the mechanical axis were obtained by a number of
holes where two nuts and bolts were inserted to form the hinge: a standard
position well above the malleoli, at the level of the medial malleolus, at the
level of the lateral malleolus, and the physiological between the two malleoli.
The shank and foot were instrumented with 15 reflective markers according to a
standard protocol, and level walking was collected barefoot and with the orthosis
in the four mechanical conditions. The spatio-temporal parameters observed in the
physiological axis condition were the closest to normal barefoot walking. As
expected, ankle joint rotation was limited to the sagittal plane. When the
physiological axis was in place, rotations of the ankle out-of-sagittal planes,
and of all other foot joints in the three anatomical planes, were found to be
those most similar to the natural barefoot condition. These preliminary measures
of intersegmental kinematics in a foot within an ankle-foot orthosis showed that
only a physiological location for the ankle mechanical hinge can result in
natural motion at the remaining joints and planes.
CI - Copyright (c) 2014 Elsevier B.V. All rights reserved.

Langue : ANGLAIS