Journal of Rehabilitation Medicine 51-1CompleteIssue | Page 16

Effect of AFOs on tibialis anterior EMG
the sEMG-recordings, 3D gait-analysis was recorded, using a
6-camera Vicon MX13+ motion-analysis system for capturing
marker trajectories. Reflective 25-mm markers were placed
directly on the skin and shoes, according to the modified Helen
Hayes marker-set. Marker trajectories of the foot were used
to manually determine initial contact (IC) and foot-off (FO).
Marker trajectories of the left and right anterior superior iliac
spine along the axis of progression were averaged and used to
calculate walking speed.
Data-processing was performed using custom in-house soft-
ware, developed in Matlab (MathWorks, Natick, MA, USA).
sEMG data were first band-pass filtered with cut-off frequencies
of 25 and 450 Hz. After processing, data were manually checked
for artefacts. If artefacts were found, the specific gait cycle was
removed from the analysis. Subsequently, sEMG data were
rectified and smoothened using a low-pass filter with cut-off
frequency of 10 Hz and split into 4 sub-phases of gait using
foot-events (IC and FO) of both sides: (i) first double support
(DS1), from IC to opposite FO; (ii) single support (SS), from
opposite FO to opposite IC; (iii) second double support (DS2),
from opposite IC to FO; (iv) swing (SW), from FO to IC. Once
the data were segmented into the 4 sub-phases, each sub-phase
was time-normalized to 100%. These time-normalized sub-
phases were used to calculate the area under the curve (AUC)
to express the activity level per sub-phase.
Outcome measures
The primary outcome measure was
TA activity during swing, as the swing
phase is the main sub-phase of gait
in which TA activity is shown during
normal walking to evoke foot-clearance
(2). The secondary outcome measure
was TA activity during the other sub-
phases. Outcomes were calculated for
each of the 4 measurements T1–T4,
with and without AFO. Walking speed
without and with AFO was calculated,
since walking speed is known to affect
EMG (16).
Statistical analysis
SPSS version 19 (IBM SPSS Statistics,
Chicago, IL, USA) was used for data
analysis. The level of significance for
all analyses was set at p < 0.05. No po-
wer calculation was performed, since
relevant data regarding timing of AFO
provision were not available. Because
TA activity per sub-phase did not show
a normal distribution, logarithmic
transformations were performed prior
to statistical testing.
Baseline data, including TA activity
of both groups at T1 without AFO, were
compared using independent samples
t-test/Mann–Whitney U test for con-
tinuous variables and χ 2 test/Fisher’s
exact test for categorical variables, as
appropriate.
Mixed-model repeated measures
analyses were performed, both within-
groups to study whether AFO use affec-
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ted TA muscle activity over a period of 26 weeks, and between-
groups over time, in order to assess a group-by-time interaction.
Both analyses included walking speed as a confounder. The
analyses included data of all 4 measurements (T1, T2, T3, T4).
Since data of 4 measurements was available only without AFO
(the delayed group did not yet use an AFO at T1), the mixed-
model analyses were performed for data without AFOs only.
Between-group effects after 26 weeks were studied comparing
the data of both groups using the independent samples t-test,
both for the without and with AFO condition.
The third objective was to determine whether AFO provision
decreased TA muscle activity when walking with and without
the AFO was compared within a single measurement session. In
order to be able to compare these results with those of previous
studies (mainly including subjects with chronic stroke), data of
the total (early and delayed) group at T4 were included in this
analysis. A paired-samples t-test was used to compare data with
and without AFO.
RESULTS
Baseline
Fig. 1 details the participant flow through the study.
Thirty-three subjects (16 early, 17 delayed) were in-
cluded in the study. Of these, 26 subjects (15 early, 11
Enrollment
Assessed for eligibility
(n=777)
Randomized (n=33)
Stratification on walking ability:
dependent (FAC 0/1/2) (n=21)
independent (FAC 3/4/5) (n=12)
Early (n=16)
FAC 0/1/2 (n=10), FAC 3/4/5 (n=6)
Received allocated intervention (n=16)
Allocated to intervention
Excluded (n=744 )
- Not meeting inclusion criteria (n=734)
- no stroke (n=219)
- multiple strokes/stroke >6wks (n=119)
- no AFO-indication (n=316)
- other (n=80)
- Declined to participate (n=10)
Delayed (n=17)
FAC 0/1/2 (n=11), FAC 3/4/5 (n=6)
Received allocated intervention (n=17)
AFO-provision
Lost to follow-up (n=0)
Missing (n=1)
-no walking ability
EMG-measurement (n=15)
Excluded from analysis (n=1)
-did not complete the study
Analyzed (n=14)
Measurement T1
Lost to follow-up (n=0)
Missing (n=5)
-no walking ability
EMG-measurement (n=12)
Excluded from analysis (n=5)
-did not complete the study
Analyzed (n=7)
AFO-provision
Lost to follow-up (n=1)
-participation took too much effort
Missing (n=0)
EMG-measurement (n=15)
Excluded from analysis (n=0)
Analyzed (n=15)
Lost to follow-up (n=0)
Missing (n=1)
-no lab space available
EMG-measurement (n=14)
Excluded from analysis (n=0)
Analyzed (n=14)
Lost to follow-up (n=0)
Missing (n=0)
EMG-measurement (n=15)
Excluded from analysis (n=0)
Analyzed (n=15)
Measurement T2
Measurement T3
Measurement T4
Lost to follow-up (n=3)
-started AFO-use too soon
-started wearing high mountain shoes
instead of AFO
-no AFO-indication any longer
Missing (n=1)
-measurement not possible
EMG-measurement (n=13)
Excluded from analysis (n=2)
-did not complete the study
Analyzed (n=11)
Lost to follow-up (n=2)
-no suitable shoes for AFO-use provided in time
-hip fracture after fall
Missing (n=1)
- measurement not possible
EMG-measurement (n=11)
Excluded from analysis (n=0)
Analyzed (n=11)
Lost to follow-up (n=0)
Missing (n=1)
- measurement not possible
EMG-measurement (n=11)
Excluded from analysis (n=0)
Analyzed (n=11)
Fig. 1. CONSORT flowchart. The figure shows the participant flow through the study. AFO: ankle-
foot orthosis; FAC: Functional Ambulation Categories.
J Rehabil Med 51, 2019