Evaluation of the effectiveness of an ankle-foot orthosis on the walking ability and coordination in patients with Huntington's Disease

Huntington's disease (HD) is an inherited neurodegenerative disorder of the
central nervoussystem. Patients show motoric and cognitive decline and a change
in behaviour. Due to this illnes there will be a decline in the ability to
walk. The characteristic gait of patients with Huntington's disease consists of
lateral side-to-side deviations, difficulties in turning and gait initiation,
imbalance and reduced coordination between limbs. The degree in which the
kinematics is affected varies signifficantly among patients.

To increase the ability to walk conventional physiotherapeutic techniques are
used in patients with HD. In Overduin they recently gained experience in
incorporating an ankle-foot orthosis (AFO) in physiotherapy in patients with
HD. Observations indicate an increase in gait and walkingspeed and a decrease
in involuntary movements. The use of an AFO is, however, not evident in this
group of patients.

In this study the effectiveness of an ankle-foot orthosis on the walking
ability and coordination in patients with Huntington's disease will be
evaluated. Subject will be the question of the clinical relevance of wearing an
AFO according to spatiotemporal parameters of gait and functional
walkingability messured with the Timed up-and-go* test. furthermore the
influence of an AFO on the coordination of movement of patients with HD will be
investigated

First the effects of wearing an AFO on the change in structure of
stridevariability will be evaluated to determine the effects on
movementcoordination. The effect of the AFO on movementcoordination will also
be studied by using alternative methods of analysis from coordinationdynamics
that are recently introduced in the clinical movementanalysis. With this the
degree of fluentness and (ir)regularity of movement (sample entropy a.o.), the
coordination between limbs and the stability of patterns of arm- and legmovents
(the greatest lyapunov exponent a.o.) can be quantified.

This study is an intervention study with crossover design. The patients will
undergo the tests with and without an AFO.
The order of the conditions will be randomized. The researchers will be blinded
for the order of the conditions during the analysis of the data.

The clinical part of this study contains two tests: a ten meter walkingtest at
a personally chosen comfortable walking speed and a *Timed up-and-go* test
[23]. These test will both be performed three times with an AFO and three times
without an AFO. Before the measurement the test will be practised one time
without an AFO and one time with an AFO.
To be able to analyse the pattern of gait the participants will be asked to
walk a minimum of two and a maximum of six minutes (back and forth) at their
preferred speed down a straight corridor (+/- 60 meters long and +/- 2.5 meters
wide). De patients with HD will do this test twice, one time with an AFO and
one time without an AFO.
The pattern of movement during gait will be measured with accelerometers.
Five accelerometers (size: 62 x 41 x 18 mm, weight : 53 grams, McRoberts
Technology, The Hague) will be placed at:
- the pelvis: cranial side of the sacrum, between the spinae iliacae
posterior superior.
- both lower legs: above malleolus lateralis.
- both lower arms: on the dorsal side of the wrist
A footcontactsensor wil be placed in the shoe between the sole and the heel.
The data from the accelerometer and the footcontactsensor will be stored in a
datalogger wich will be attached to the body of the participant. With the
datalogger particular events can be registered, by example the turning points
during the test. With the information from the accelerometer placed at the
pelvis and the information from the footcontactsensor moments of heelcontact
during gait can be identified. By placing accelerometers at the lower
extremities the movements of these parts can be studied during gait.
After every test the participant will be asked about their subjective opinion
as to the difficulty of the test and their feeling of self-confidence during
the test. Two questions are presented using a Likert-schale of 1-5.

The disadvantage for the patient for participating in this study is limited to
the time that is needed to complete the tests. This is estimated at one
morning/afternoon. There are no known risks involved in the methodes used in
this study. The tests are minimal aggravating. Possibly there can be an
increased fall risk. The patient will be accompanied by a researcher who will
walk alongside the patient during the course of the tests.