Feasibility study of a smart ankle foot orthosis in people with paretic ankle muscles

Many different pathologies such as spina bifida, hereditary motor and sensory
neuropathy, and multiple sclerosis may result in ankle muscle paresis. People
with paretic ankle muscles are unable to actively dorsiflex and/or plantarflex
their ankle. Active dorsiflexion moment is necessary for toe clearance (and
thus prevent falls) during the swing phase of gait[1]. Active plantarflexion
moment is necessary to provide push-off (and thus maintain a normal comfortable
walking speed) during the stance phase of gait[1]. To improve walking, people
with paretic ankle muscles often use an AFO.

The use of conventional AFOs also comes with some disadvantages. Conventional
AFOs generally limit ankle ROM[2], introducing additional problems in
activities in which more ankle ROM is necessary than allowed for by the AFO.
Examples of such activities are hill locomotion, stair locomotion and standing
up from/ sitting down on a chair[3].
Also for level walking, more ankle ROM is needed than allowed for by current
AFOs. Normal gait consists of a stance and a swing phase. Stance phase consists
of three rockers. During the heel rocker the ankle gradually plantarflexes
until the foot is flat on the floor. If plantarflexion motion is diminished as
a result of current AFO use, also stability is reduced[1]. During the ankle
rocker the ankle dorsiflexes. Current AFOs hamper ankle dorsiflexion and
thereby either prevent the tibia to rotate in the ankle forward or tibial
progression may happen to fast. During the forefoot rocker, the ankle
plantarflexes creating a plantarflexion moment. With current AFOs,
plantarflexion motion is not possible and only limited plantarflexion moment is
generated, impairing the push off, compared to norm-values[4]. As a result
comfortable walking speed is lower in people with plantarflexor paresis using
current AFOs when compared to norm-values[4]-[6]. During swing phase, the ankle
dorsiflexes to enable toe clearance. Since current AFOs limit ankle ROM, this
is beneficial for swing as it prevents foot drop during swing.

A smart AFO was designed that provides more normal ankle moments compared to
current AFOs and allows normal ankle ROM. This novel AFO stores energy in a
mechanical spring during the ankle rocker and uses this energy to assist
push-off during the forefoot rocker. Walking should thereby improve and also
hill locomotion, stair locomotion and standing up from/ sitting down on a chair
should be easier.

The objective of this feasibility study is compare the smart AFO + standardized
shoes to subjects* own AFO + own shoes. Subjects* experiences with the orthotic
devices will be evaluated and points for improvement will be asked. Subjects*
performance with the smart AFO will be compared to performance with their own
AFO. This is to evaluate if the smart AFO provides more normal ankle moments
and allows more normal ankle ROM during level, uphill and downhill walking. The
objective is also to evaluate if hill locomotion, stair locomotion and standing
up from/ sitting down on a chair is easier with the smart AFO. This study is
necessary to continue the development of the smart AFO to improve the quality
of life of people with paretic ankle muscles using AFOs.

Feasibility study with cross-over design and random sequence generation.
Subjects will be recruited between February 2015 and February 2016 (dependent
on the technical approval of the smart AFO and the availability of subjects).
The study will be performed at the Rehabilitation department of the University
Medical Center Groningen, location Beatrixoord, Haren, Netherlands. Testing
will be done with the Gait Real-time Analysis Interactive Lab (GRAIL, Figure
4). The GRAIL is an instrument that is used for regular walking and balance
training purposes and can be used to record kinematic and kinetic gait
variables. Walking on the treadmill of the GRAIL is not more fatiguing than
normal walking. The treadmill of the GRAIL can automatically adapt itself to
the comfortable walking speed of a person. As in daily use, the GRAIL will be
controlled and monitored by a certified operator. Subjects are at all times
allowed to use the hand rails of the GRAIL. During testing, a standard walking
environment will be displayed on the screen of the GRAIL. All subjects will be
secured by a safety vest that is part of the standard GRAIL equipment (see
Figure 4).

All subjects walk and perform activities in random order with the smart AFO +
standardized shoes and with their own AFO + own shoes. Walking tests consist of
(in random order): walking on a lever surface and walking up and down hill.
Activities consist of (in random order): walking stairs, and standing up and
sitting down on a chair.
Subject experience with the AFOs and suggestions for improvement will be
measured by a self-developed questionnaire.

Only immediate effects of the orthotic devices will be measured. Time span for
a subject will be 2:30hrs. Subjects will walk at a self-selected speed on a
treadmill that is also used for regular training purposes. Besides level and
hill walking (both on the same treadmill), subjects walk up and down a three
steps standardized staircase and stand up from/ sit down on a standardized
chair. The smart AFO should improve both patients* gait and the execution of
activities.
In this study a smart medical device (the smart AFO) will be evaluated. We
expect no risk of potential issues of concern for the subjects. This study can
only start after the approval of the organisation responsible for evaluating
new medical devices within the UMCG. The smart AFO will be under evaluation
here at the beginning of January 2015. As soon as approval is obtained this
approval form will be delivered at the UMCG METc desk.