Stability and variability of prosthetic walking: The relation between the variability and stability of the gait pattern of amputees.

Learning to walk with a prosthesis is not an easy task. In order to adequately
train this walking ability, it is of interest for patients and therapists to
monitor changes their walking performance. These changes are difficult to
monitor subjectively. Hence it is useful to use objective measures. Evaluation
of walking ability can be done in terms of walking speed, symmetry or energy
cost. However, also stability of the walking pattern will be an important
outcome parameter.
Frequently, stability is measured based on the variability of the walking
pattern in terms of standard deviation or coefficient of variance. Recent
studies, however, have shown that the assumption underlying these conventional
outcome measures, i.e. that the steps during walking are independent of each
other, is not valid. Therefore, a possible structure and regularity in the
variability is ignored. It was additionally shown that new (non-linear)
approaches could better discriminate between the variability of different
groups (for instance patients vs. healthy people or old vs. young people).
Different pathologies have been studied based on these new approaches of
variability and stability, however walking with a limb prosthesis has not
deserved any attention. In this study the dynamics prosthetic of walking will
be analyzed in order to find an adequate measure for monitoring the stability
of walking.

In this study the differences in variability and stability of people walking
with and without a limb prosthesis will be investigated. In addition, it will
be studied which of the employed outcome measures will discriminate best
between both groups. Finally, the relation between variability and stability of
walking in general will be analyzed.

Subjects perform four six-minutes walk under four conditions: 1) indoor, 2)
indoor with cognitive dual task, 3) outdoor on regular surface, 4) outdoor on
irregular surface. During walking the acceleration of the trunk will be
measured using an ambulant accelerometer, worn around the pelvis. Walking
velocity will be measured on several parts of the track. All tests for the
subjects with a prosthesis will be performed at self selected walking speed.
The control group, without prosthesis, will perform each condition twice; at
self selected speed and at the speed of the matched prosthetic user. All tests
will be performed at and around the Heliomare rehabilitation center

Burden and risk for the subjects will be low. Subjects will walk indoor on
regular surface and outdoor on normal pavement and somewhat irregular pavement.
In none of the conditions serious obstacles are met. The conditions do not
deviate from the circumstances people meet in their normal daily life. The
experimenter will always be close by, to assist when necessary.