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Reference values for gait temporal and loading symmetry of lower-limb amputees can help in refocusing rehabilitation targets

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Background: The literature suggests that optimal levels of gait symmetry might exist for lower-limb amputees. Not only these optimal values are unknown, but we also don't know typical symmetry ratios or which measures of symmetry are essential. Focusing on the symmetries of stance, step, first peak and impulse of the ground reaction force, the aim of this work was to answer to three methodological and three clinical questions. The methodological questions wanted to establish a minimum set of symmetry indexes to study and if there are limitations in their calculations. The clinical questions wanted to establish if typical levels of temporal and loading symmetry exist, and change with the level of amputation and prosthetic components. Methods: Sixty traumatic, K3-K4 amputees were involved in the study: 12 transfemoral mechanical knee users (TFM), 25 C-leg knee users (TFC), and 23 transtibial amputees (TT). Ninety-two percent used the Ossur Variflex foot. Ten healthy subjects were also included. Ground reaction force from both feet were collected with the Novel Pedar-X. Symmetry indexes were calculated and statistically compared with regression analyses and non-parametric analysis of variance among subjects. Results: Stance symmetry can be reported instead of step, but it cannot substitute impulse and first peak symmetry. The first peak cannot always be detected on all amputees. Statistically significant differences exist for stance symmetry among all groups, for impulse symmetry between TFM and TFC/TT, for first peak symmetry between transfemoral amputees altogether and TT. Regarding impulse symmetry, 25% of TFC and 43% of TT had a higher impulse on the prosthetic side. Regarding first peak symmetry, 59% of TF and 30% of TT loaded more the prosthetic side. Conclusions: Typical levels of symmetry for stance, impulse and first peak change with the level of amputation and componentry. Indications exist that C-leg and energy-storage-and-return feet can improve symmetry. Results are suggestive of two mechanisms related to sound side knee osteoarthritis: increased impulse for TF and increased first peak for TT. These results can be useful in clinics to set rehabilitation targets, understand the advancements of a patient during gait retraining, compare and chose components and possibly rehabilitation programs.
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R E S E A R C H Open Access
Reference values for gait temporal and
loading symmetry of lower-limb amputees
can help in refocusing rehabilitation targets
Andrea Giovanni Cutti
*
, Gennaro Verni, Gian Luca Migliore, Amedeo Amoresano and Michele Raggi
From Second World Congress hosted by the American Orthotic & Prosthetic Association (AOPA)
Las Vegas, NV, USA. 06-09 September 2017
Abstract
Background: The literature suggests that optimal levels of gait symmetry might exist for lower-limb amputees.
Not only these optimal values are unknown, but we also dont know typical symmetry ratios or which measures of
symmetry are essential. Focusing on the symmetries of stance, step, first peak and impulse of the ground reaction
force, the aim of this work was to answer to three methodological and three clinical questions. The methodological
questions wanted to establish a minimum set of symmetry indexes to study and if there are limitations in their
calculations. The clinical questions wanted to establish if typical levels of temporal and loading symmetry exist, and
change with the level of amputation and prosthetic components.
Methods: Sixty traumatic, K3-K4 amputees were involved in the study: 12 transfemoral mechanical knee users (TFM),
25 C-leg knee users (TFC), and 23 transtibial amputees (TT). Ninety-two percent used the Ossur Variflex foot. Ten
healthy subjects were also included. Ground reaction force from both feet were collected with the Novel Pedar-X.
Symmetry indexes were calculated and statistically compared with regression analyses and non-parametric analysis
of variance among subjects.
Results: Stance symmetry can be reported instead of step, but it cannot substitute impulse and first peak symmetry.
The first peak cannot always be detected on all amputees. Statistically significant differences exist for stance symmetry
among all groups, for impulse symmetry between TFM and TFC/TT, for first peak symmetry between transfemoral
amputees altogether and TT. Regarding impulse symmetry, 25% of TFC and 43% of TT had a higher impulse on the
prosthetic side. Regarding first peak symmetry, 59% of TF and 30% of TT loaded more the prosthetic side.
Conclusions: Typical levels of symmetry for stance, impulse and first peak change with the level of amputation and
componentry. Indications exist that C-leg and energy-storage-and-return feet can improve symmetry. Results are
suggestive of two mechanisms related to sound side knee osteoarthritis: increased impulse for TF and increased
first peak for TT. These results can be useful in clinics to set rehabilitation targets, understand the advancements
of a patient during gait retraining, compare and chose components and possibly rehabilitation programs.
Keywords: Gait, Ground reaction force, Symmetry, Rehabilitation, Amputees, Prosthesis, Osteoarthritis, C-leg,
Microprocessor controlled knees, Energy storage and return feet
* Correspondence: ag.cutti@inail.it
INAIL Prosthetic Center, Via Rabuina 14, 40054 Vigorso di Budrio, BO, Italy
© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver
(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61
https://doi.org/10.1186/s12984-018-0403-x
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Background
Lower-limb amputees tend to walk asymmetrically when
looking at gait temporal and loading parameters, with
more time spent and load exerted on the intact limb [19].
Temporal asymmetry is typically measured based on step
or stance duration; loading asymmetry based the magni-
tude of the first peak of the vertical ground reaction force
(GRF), and the impulse of GRF [2,3,6,10].
Temporal and loading asymmetries were associated to
several comorbidities [5]: increased falls [11], osteoarth-
ritis of the sound limb [10,1215], osteoporosis of the
contralateral limb [15,16], back pain [1720]. In addition,
walking in public with noticeable asymmetries attracts the
general attention [21], which can be very uncomfortable
for some prosthesis users. With this background, it is not
surprising that a common, almost unquestioned [22], goal
for rehabilitation is to regain a symmetric walking [9,23].
However, the literature does not clearly indicate that
striving for perfect symmetry is really and always the best
option. Already in 1998, Winter & Sienko [1]statedthat
human system with major structural asymmetries in the
neuromuscular skeletal system cannot be optimal when
gait is symmetrical. Rather, a new non-symmetrical opti-
mal is probably being sought by the amputee within the
constraints of his residual system and the mechanics of
his prosthesis. Later in 2005, Schmid and co-workers [3]
compared the center of pressure trajectories under the
sound and prosthetic foot of transfemoral amputees and
concluded that the longer stance on the sound side can be
ascribed to the greater ability of the sound leg to advance
the step and maintain balance until the prosthetic limb
can sustain the body weight. Hof et al. [4] corroborated
this explanation in the theoretical framework of the
extrapolated center of mass[24], concluding that stance
time asymmetry is a sensible adaptationof experienced
transfemoral amputees to improve stability during walking,
to overcome the missing lateral ankle strategy of prosthetic
feet. More recently, Adamczyk & Kuo [8], with a theoret-
ical and experimental approach involving transtibial ampu-
tees, concluded that some asymmetry may be unavoidable
in cases of unilateral limb lossdue to the reduced ankle
plantar flexion of the ankle, with direct consequences on
stance duration, greater collision work at the sound side,
greater work overall, and increased peak force at loading
response [2527]. Imposing symmetry can actually be
detrimental, as also observed by [27,28].
The evidences from the literature, therefore, indicate that
optimal symmetry ratios might exist, to obtain a com-
promise among stability, forward progression, preservation
of body structures and perception of a normal and sym-
metric biped locomotion[21]. Unfortunately, at present
not only optimal symmetry ratios are unknown, but we
also dont know typical symmetry ratios or which measures
of symmetry are essential and which are redundant.
In our opinion, 3 methodological and 3 clinical questions
should be answered to clarify these open issues. The
methodological questions are:
Q1: do all amputees show the typical M-shaped pattern
of the GRF [29], with presence and appropriate timing
of its two peaks? In case of a negative answer, the
measure of loading symmetry based on the first
peak of GRF will be restrict to patients presenting
the M-shaped pattern;
Q2: can we limit the study of temporal symmetry to
stance, leaving out step symmetry? We will give a
positive answer if stance and step symmetries are
very strongly correlated for all amputees, with a
coefficient of determination R
2
> 0.64 [30];
Q3: can we further limit the study of gait symmetry
to just stance symmetry, leaving out loading
symmetry, whose measure requires more
cumbersome and expensive equipment? We will give
a positive answer if stance symmetry is very strongly
correlated (R
2
> 0.64) with the symmetry of the first
peak and impulse of GRF.
The clinical questions are:
Q4: does gait symmetry depend on the level of
amputation? In case of a positive answer, typical
ranges of symmetry should be established, which
can be used to understand how far a new patient is
from well adapted prosthesis users in terms of
percentiles;
Q5: do advanced prosthetic components improve
temporal and loading symmetry? In particular, do
C-leg users have better results than mechanical knee
users of the same mobility level?
Q6: is it always true that amputees overload the
sound side both in terms of first peak and impulse
of GRF, thus contributing to the development of
osteoarthritis?
Unfortunately, at present it is difficult to answer to
these questions based on the available literature, because
there are no studies that considered, at the same time 1)
both temporal and loading asymmetries, 2) both trans-
femoral and transtibial amputees treated at the same
prosthetic & rehabilitation center, 3) mechanical and
electronic knees, 4) energy-storage-and-return feet instead
of the SACH (Solid-Ankle Cushion-Heel) foot. Moreover,
the number of patients included is typically limited to 8,
both for studies on transtibial and transfemoral amputees.
Finally, no studies addressed the correlation between
temporal and loading parameters.
The aim of this study was to overcome these limita-
tions and answer to questions Q1-Q6 on three groups of
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 30 of 72
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well-adapted, traumatic, K3-K4 amputees: transfemoral
amputees using a restricted set of mechanical knees
(TFM), transfemoral amputees using the C-leg (TFC),
transtibial amputees using energy-storage-and-return feet
(TT). A additional group of healthy control subjects
(Controlsin short), was also included to highlight
general trends.
Methods
Subjects
Sixty K3-K4 lower-limb amputees participated in the
study after signing an informed consent: 12 mechanical
knee users (TFM, 46± 10 y.o.), 25 C-leg users (TFC, 48 ±
13 y.o), 23 transtibial amputees (TT, 44 ± 14 y.o.), with no
statistically significant differences in term of age (ANOVA,
p> 0.62). Ten controls were also included (28 ± 2 y.o.). All
amputees had completed a 3-week, intense gait training
program at the same specialized prosthetic & rehabilitation
center, with the support of the same rehabilitation team.
The clinical center has ISO 9001 treatment pathways for
amputees and provides over 800 transfemoral and 1200
transtibial prostheses every year. Following training, all
patients had been successfully using their prostheses for at
least1monthatthetimeoftesting.
The components provided to patients are summarized
in Table 1. Almost 92% of patients used either the Variflex
or Variflex LP foot. Mechanical knees were selected to
match the activity level of the C-leg, and are consistent
with knees selected for comparison with the C-leg in
previous studies [31,32].
Measurements
After standing still for 10 s, subjects walked along a long
indoor hall at self-selected speed, that was noted. During
this trial, the GRF was measured on each side through
instrumented insoles (Pedar-X, Novel, D), sampling at
100 Hz [33,34].
Data processing
For each subject, GRF data were export to MATLAB.
Based on the 10 sorthostatic posture, body weight was
calculated. Assuming a foot-floor contact threshold at
10% body weight, we detected heel-strike and toe-off
events for the two sides. We isolated the steady state
condition by considering the central 10 strides.
Calculation of temporal symmetry
For each stride, we calculated the step and stance duration.
Then, for each couple of consecutive sound-affected gait
cycles, we calculated the following indexes of symmetry:
Step Symmetry (SPS): Step Duration
SOUND
/ Step
Duration
AFFECTED
Stance Symmetry (SNS): Stance Duration
SOUND
/
Stance Duration
AFFECTED
For Controls, ratios were right over left side. A value
of 1 represents perfect symmetry. For each index of
symmetry, we calculated the subjects median value
over the trial. Finally, we obtained the distribution of
the median values for the two indexes over TFM, TFC,
TT and Controls.
Calculation of loading symmetry
For each gait cycle, the integral over the stance period of
GRF was calculated, i.e. the impulse of GRF, as previously
reported by [2]. Then, for each couple of consecutive
sound-affected gait cycles, we calculated the index of
symmetry:
Impulse Symmetry (IMS): Impulse
SOUND
/
Impulse
AFFECTED
A value of 1 represents perfect symmetry. Right over
left side was used for Controls.
Afterward, the GRF profile of each gait cycle was
checked to verify the presence of the first peak within
the 040% of the gait cycle, and of a second peak within
the 60100%. Subjects reporting both peaks in more
than half of the trials formed the Two-Peakssubgroup.
For the subjects in Two-Peaks we operated as follows.
For each couple of consecutive sound-affected gait cycles,
we calculated the following index:
First Peak Symmetry (P1S): First peak
SOUND
/
First peak
AFFECTED
P1S provides a measure of peak force asymmetry at
loading response, while IMS provides a measure of the
asymmetry in cyclic loading. These are two different
mechanism of osteoarthritis development [10,3537].
For each index of symmetry, we calculated the subjects
median value over the trial. Finally, we obtained the distri-
bution of the median values for the two indexes over
TFM, TFC, TT and Controls.
Table 1 Prosthetic components used and associated quantities
TFM TFC TT
Foot Variflex LP: 10
1C40: 2
Variflex LP: 25 Variflex: 18
Variflex LP: 2
Truestep: 1
Esprit: 1
1C40: 1
Knee TotalKnee 2100: 5
3R60: 2
Mauch: 2
C-leg: 25
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 31 of 72
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Statistical analysis
The distribution of the four indexes of symmetry (SPS,
SNS, IMS and P1S) was checked for normality within
each group (TFM, TFC, TT and Controls) and over all
subjects, both visually with the Normal Probability Plot
and with the Lilliefors test. This last failed for SPS
TFM
and P1S
TT
and there were doubts about IMS in general.
The relationship between SNS and the three indexes
SPS, IMS and P1S was evaluated with regression methods
with the MATLAB Curve Fitting Toolbox. The strength
of the relationship was primarily evaluated in terms of R
2
.
This statistical parameter, multiplied by 100, is usually
interpreted as the variance of yaccounted for by x,
where in this case yis SPS or IMS or P1S, and xis
SNS. In addition, the root-mean-square error (RMSE) of
the residuals was also reported.
Distributions were reported in terms of median and
interquartile range [3], with box plots. For each symmetry
index, the Kruskal-Wallis test (α= 0.05) was adopted to
check for overall statistically significant differences among
TFM, TFC, TTand Controls. In identifying pairwise differ-
ences, the Tukey-Kramer HSDcorrection was applied
within the MATLAB multcomparefunction.
Results
Gait speed was compared among TFM (1.12 ± 0.13 m/s),
TFC (1.17 ± 0.12 m/s), TT (1.23± 0.19 m/s) and Controls
(1.41 ± 0.21 m/s). ANOVA did not show statistically
significant differences among amputees (p=0.14), but
only between Controls and amputees (p= 0.0005).
Further results are reported hereinafter based on their
relevance for questions Q1-Q6.
Question Q1
Figure 1reports the number of subjects in subgroups
Two-Peaks, which decreases from TT (20/23), to TFM
(7/12) to TFC (10/25). The number of TFC with non-
standard GRF is remarkably high (60%); these patients
report a consistent alternativepattern (example provided
in Fig. 1b). Based on these results, the answer to Q1 was
negative and the calculation of the symmetry index P1S
was restricted to the subjects in Two-Peaks.
Question Q2
Figure 2reports the regression analysis for SPS vs SNS
considering the whole set of patients and Controls
(ALLin brief ). R
2
and RMSE values for each group
Fig. 1 aNumber of subjects in subgroup Two-Peaks for TFM (transfemoral mechanical knee users), TFC (transfemoral C-leg users), TT (transtibial
amputees), and Controls: btypical alternative vertical ground reaction force pattern shown by TFC patients not included in Two-Peaks
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 32 of 72
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(TFM, TFC, TT, Controls) and ALL are reported in
Table 2.R
2
was at least 0.70 for all amputees, with
RMSE < 0.042. Therefore, the answer to Q2 was positive
and only SPS was further considered.
Question Q3
Figure 3a and breport the regression analysis for IMS vs
SNS and P1S vs SNS, respectively, for ALL. R
2
and
RMSE values for each group (TFM, TFC, TT, Controls)
and ALL are reported in Table 2. For IMS vs SNS, R
2
was lower than 0.64 for TT, with RMSE > 0.128. For P1S
vs SNS, R
2
was lower than 0.2 for all amputees. Therefore,
the answer to Q3 was negative and IMS, P1S and SPS
were separately considered in all subsequent analyses.
Questions Q4-Q6
Figures 4a,5a and 6a report the distribution of SNS,
IMS and P1S for TFC, TFC, TT and Controls. Numerical
values are reported in Table 3.
For SNS and IMS, the Kruskal-Wallis test showed
statistically significant differences among the medians
of the groups (p< 0.0001) (Figs. 4b and 5b). The pairwise
analyses for:
SNS (Fig. 4c) showed that all amputee groups are
different among each other, supporting a positive
answer for Q4 and Q5;
IMS (Fig. 5c) showed a statistically significant
difference between TFM and all other groups, with
all TFM values > 1 as opposed to TFC and TT. This
supports a partially positive answer to Q4, a positive
answer to Q5 and a negative answer to Q6.
For P1S, the Kruskal-Wallis test reported a statistically
significant difference in the medians among groups
(p= 0.0443) (Fig. 6b). The pairwise comparison did
not show differences (Fig. 6c). This is a very possible
situation for three reasons:
the Kruskal-Wallis and pairwise comparisons try to
negate different hypotheses;
we applied a quite conservative multiple comparison
strategy (HSD);
the statistical power is reduced by the decreased
number of transfemoral amputees (TF) within
Two-Peaks.
Fig. 2 Step symmetry index (SPS) vs Stance symmetry index (SNS). Each dot represents one subject. Subjects of the same group feature the same
color (see legend in the plot). The purple parabolic line is the regression line for ALL subjects together. The equation of the fitting is reported on
the right, with the fitting quality parameters R
2
(coefficient of determination) and RMSE (Root Mean Squared Error)
Table 2 Quality of fit of the regressions for step (SPS), impulse
(IMS) and first peak symmetry (P1S) indexes vs stance symmetry
index (SNS)
SPS vs SNS IMS vs SNS P1S vs SNS
R
2
RMSE R
2
RMSE R
2
RMSE
TFM 0,97 0,042 0,81 0,137 0,06 0,154
TFC 0,81 0,042 0,69 0,090 0,04 0,177
TT 0,70 0,036 0,37 0,128 0,20 0,289
CONTROLS 0,51 0,017 0,47 0,040 0,05 0,038
ALL 0,95 0,037 0,79 0,103 0,00 0,247
The coefficient of determination (R
2
), and the Root Mean Squared Error (RMSE)
are reported for every group (TFM transfemoral mechanical knee users, TFC
transfemoral C-leg users, TT transtibial amputees, Controls), and for all subjects
altogether (ALL). Bold: R
2
> 0.64, Regular: 0.36 < R
2
< 0.64, Italic: R
2
< 0.36 [30]
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 33 of 72
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For this reason, we grouped subjects per level of ampu-
tation (TFM and TFC together), and results are reported
in Fig. 7a. The Kruskal-Wallis test now shows a stronger
significance among groups (p= 0.0186) and the pairwise
analysis shows a statistically significant difference between
TF and TT. The variability in P1S is much higher in am-
putees than in Controls (Bartletts test for equal variances,
p= 0.001). These results support a negative answer to Q6.
Discussion
In this study, we addressed three methodological and
three clinical questions regarding the temporal and loading
symmetry of transfemoral amputees (both mechanical and
C-leg users) and transtibial amputees, to support in the
development of more targeted rehabilitation goals, that are
particularly needed [9,38].
As a general consideration, the self-selected walking
speed was not statistically different among amputees,
despite a slight increase in the median from TFM, to
TFC, to TT toward Controls. Absolute values compare
well with previously reported data [2,7,39].
For the sake of clarity, results are discussed below for
each question, in comparison with the available literature
whenever possible.
Question Q1
Question Q1 asked if all amputees show the typical
M-shaped pattern of the GRF, with presence and
Fig. 3 aImpulse symmetry index (IMS) vs Stance symmetry index (SNS) and bFirst peak symmetry index (P1S) vs SNS. Each dot represents a
subject. Subjects of the same group feature the same color (see legend in the plot). In (a), the purple parabolic line is the regression line for ALL
subjects together. The equation of the fitting is reported on the right, with the fitting quality parameters R
2
(coefficient of determination) and
RMSE (Root Mean Squared Error). No valid regression was found for P1S vs SNS. TFM: transfemoral mechanical knee users, TFC: transfemoral C-leg
users, TT: transtibial amputees
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 34 of 72
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appropriate timing of its two peaks. Results support a
negative answer.
As previously noted, this is particularly evident for TFC,
who presented a consistent alternativepattern: after a
steep rise (initial contact/loading response), GRF shows a
further (almost) monotonical increase (midstance), after
which it drops (terminal stance/pre-swing). TFM falling
out of Two-Peaks did not present this pattern, and were
typically not included in Two-Peaks due to a delayed P1
after 40% of the stance phase. Since no kinematic and
Fig. 4 aBox plot for the stance symmetry index (SNS) over the groups; bResults of the Kruskal-Wallis test; cPairwise comparisons:
non-overlapping lines indicate a statistically significant difference. TFM: transfemoral mechanical knee users, TFC: transfemoral C-leg
users, TT: transtibial amputees
Fig. 5 aBox plot for the impulse symmetry index (IMS) over the groups; bResults of the Kruskal-Wallis test; cPairwise comparisons: non-overlapping
lines indicate a statistically significant difference. TFM: transfemoral mechanical knee users, TFC: transfemoral C-leg users, TT: transtibial amputees
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 35 of 72
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kinetic data were collected, we can just speculate that this
TFC pattern is the combined effect of:
the Variflex behavior, with strong energy storage in
loading response [25,26];
C-leg knee flexion in loading response [40];
theconfidencegainedbythisgroupofamputees
on the capacity of the C-leg to sustain them at
heel-strike and loading response, with no need to
force extension.
The ultimate effect for this pattern is a soft landing
on the prosthetic side, which might increase comfort
[32]. These speculations require future experimental
confirmations, but match well with previous evidences
that only a fraction of transfemoral amputees can fully
rely on C-leg stability despite knee flexion during early
stance [32,40]. This might be the effect of a specialized
rehabilitation.
Question Q2
Question Q2 asked if we can limit the study of temporal
symmetry to stance leaving out step symmetry. Results
support a positive answer.
The regression of SPS vs SNS for each group and for
ALL was quadratic, with excellent fits.
SNS explained from 70 to 97% of the variance in SPS
data in amputees (R
2
, as reported in Table 2). Even for
Controls, who feature a very small peak-to-peak SNS
(.97 to 1.01), the explained SPS variance is 50% with a
RMSE as small as 0.017.
Fig. 6 aBox plot for the first peak symmetry index (P1S) over the groups; bResults of the Kruskal-Wallis test; cPairwise comparisons: non-
overlapping lines indicate a statistically significant difference. TFM: transfemoral mechanical knee users, TFC: transfemoral C-leg users, TT:
transtibial amputees
Table 3 Numerical values for the indexes of symmetry SNS (stance), IMS (impulse) and P1S (first peak)
SNS IMS P1S
Median 25th 75th IQR Median 25th 75th IQR Median 25th 75th IQR
TFM 1,22 1,20 1,29 0,09 1,32 1,20 1,55 0,36 0,91 0,90 1,06 0,16
TFC 1,11 1,05 1,15 0,09 1,16 1,00 1,24 0,24 0,98 0,80 1,04 0,24
TF 0,94 0,87 1,05 0,18
TT 1,03 1,00 1,06 0,06 1,02 0,96 1,13 0,17 1,07 0,98 1,24 0,26
CONTROLS 1,02 0,98 1,01 0,03 0,95 0,91 0,99 0,09 0,98 0,94 0,99 0,05
For each group, the median is reported together with the 25th, 75th and interquartile range (IQR). TFM transfemoral mechanical knee users, TFC transfemoral C-
leg users, TF transfemoral, TT transtibial amputees
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 36 of 72
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This is the first time that the SPS vs SNS regression is
reported in the literature and that a quadratic relationship
is described. The nonlinear fit is not surprising, because
SPS is non-linearly related to the interplay of 1) the
sounds and affected side stance durations and 2) the two
double support durations. The quadratic fit stresses the
importance of stance time symmetry, since it influences
step asymmetry by a factor 2.
Question Q3
Question Q3 asked if the study of gait symmetry can be
limited to just stance temporal symmetry, leaving out
loading symmetry. Results support a negative answer.
When IMS vs SNS was examined considering the full
set of subjects, a quadratic fit emerged: SNS explained
as much as 79% of the variance in IMS. This is the first
time this relationship is examined and reported. Since
IMS is the integral of GRF over the stance phase, it is
not surprising that IMS and SNS are related: a high
stance time asymmetry is a leading factor for a high
impulse asymmetry. However, GRF magnitude does
not linearly increase with time, and has a shape which
can differ between the sound and affected side. When
all these elements become part of a ratio, it is not
surprising that the relation between IMS and SNS can
be non-linear.
This conclusion is valid for TFM and TFC at group
level too, given the R
2
> 0.64. However, this is just
partially true for TT, because R
2
decreases to 0.37 and
the RMSE is high (0.128): reporting SNS and not IMS
can be misleading. This different evidence for TT can
be ascribed to two factors only:
The improvement in SNS asymmetry (1.03, IQR
0.06) compared to TFM (1.22, IQR 0.09) and TFC
(1.11, IQR 0.09) (Table 3);
A greater asymmetry in GRF magnitude between
sides. This is supported by the evidences for P1S, as
reported in Fig. 7. Further discussions are postponed
to Q6 below.
An adequate regression for P1S vs SNS was not found
for none of the groups and ALL: the two indexes must
measure different construct and therefore they must be
separately reported.
Question Q4
Question Q4 asked if gait symmetry depends on the
level of amputation. Results support a positive answer.
With reference to SNS, all amputee groups had statisti-
cally different median values. All TF spend more time on
the sound side: TFM have the highest asymmetry (median
asymmetry of 22%), which is twofold the TFCs(11%).As
canbeseeninFig.4, this is also true for 75% of TT, which
means that ¼ of TT do spend more time on the affected
side. This was never clearly reported in the literature. The
TT asymmetry (3%) is 4 times less than TFC. Controls, in
median, have a perfect symmetry, with a IQR of just 3%.
Fig. 7 aBox plot for the first peak symmetry index (P1S) after grouping all transfemoral amputee together (TF); bResults of the Kruskal-Wallis
test; cPairwise comparisons: non-overlapping lines indicate a statistically significant difference. TF: transfemoral amputees, TT: transtibial amputees
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 37 of 72
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
The SNS median for TFC (1.11) compares well with
the median SNS that can be calculated from the results
reported in [3] (1.09). Furthermore, our results can be
compared with the study of Nolan et al. [2], that involved
4 transfemoral and 4 transtibial amputees using a single
hinge knee and a SACH foot. Once appropriately converted
to our indexes, Nolans results are reported in Table 4.
Results, can also be compared with Bateni et al. [41], which
reported a mean stance asymmetry for TT of about 7%
(calculated as the ratio of the mean between sides).
Compared to these studies, our SNS values are lower.
In particular, 63% of TT and 20% of TFC have a SNS
lower than ±5%, which makes them unperceived by
others as impairedwalkers with regard to temporal
symmetry [21]. This is not surprising given the different
prosthetic components used and the fact that our
patients followed a specialized rehabilitation training.
Our SNS results for TT are also in very good agree-
ment with results reported by Jarvis et al. [38]for
young veterans (median 1.04, IQR = 0.03). For TFC,
our SNS is higher (1.11 compared to 0.98) but the IQR
is much smaller (0.09 compared to 0.20). This remarks
that the training for transfemoral amputees is more
challenging.
When looking at IMS, the TFM median was statisti-
cally different from TFC and TT: TFM asymmetry is
twice that of TFC and 16 times TTs. The comparison
with Nolan et al. [2] is striking: our TFM had an impulse
asymmetry which is half Nolans; for TT it is 10 times
less. This result points, again, in the direction of the
benefits of energy-storage-and-return feet and more
advanced knees. Improvement in loading asymmetry with
energy-storage-and-return feet and feet with improved
roll-over shape has been previously reported in [25,27,42],
and match well with simulation studies [8].
Finally, P1S results show statistically significant differ-
ences between TF and TT (Fig. 7). About 59% of TF have
a higher peak on the prosthetic side. Our results agree with
Castro et al., which did not report an increased peak GRF
on the sound side, but rather an increase in the GRF im-
pulse. TT clearly show an asymmetric loading with higher
values for the sound side (70% of patients), but 3 times less
than that reported by Nolan and co-workers. As previously
reported, it is reasonable to ascribe this improvement
to the use of energy-storage-and-return feet compared
to SACH [27,43].
Question Q5
Question Q5 asked if advanced prosthetic components
improve temporal and loading symmetry, and if C-leg
users have better results than mechanical knee users of
the same mobility level. Results support a positive answer.
Results have been partially discussed while addressing
Q1 and Q4 and can be summarized stating that TFC were
statistically different from TFM for SNS and IMS. Results
for IMS bring TFC to undistinguishable results to TT.
Also, the C-leg in combination with Variflex triggers a
new GRF pattern that possibly ensures an increased
comfort during walking (Question Q1). This requires fur-
ther experimental confirmations.
Petersen et al. [44] have previously reported about
SNS in C-leg users compared to TFM. However, that
study was not able to prove a statistically significant
improvement but just a trend, probably due to the
small number of subjects included (5) with different
amputation etiologies. Our results confirm that trend,
with statistically significant differences. More generally,
a considerable body of knowledge is available about
the positive effects of the C-leg on amputeesmobility
[31,4547], gait kinematic [3240], kinetic [39]and
step-length symmetry [32]. Our findings match well
with this general trend toward improved symmetries.
As discussed in Q4, the comparison of the literature
with our results for TT suggests a possible positive effect
of energy-storage-and-return feet in comparison with
SACH, for all the indexes of symmetry.
Question Q6
Question Q6 asked if it is always true that amputees
overload the sound side both in terms of first peak and
impulse of GRF, thus contributing to the development of
osteoarthritis. Results support a negative answer.
As previously discussed about Q4, if we focus on IMS,
100% of TFM overload the sound side. This percentage
decreases to 75% of TFC and 57% of TT. If we look at
P1S, 41% TF load more the sound side. However, this
percentage rises to 70% for TT. Based on these different
percentages of TT and TF for IMS and P1S, it could be
argued that two different mechanisms might be related
to knee osteoarthritis for the two groups: peak overload
for TT (measured by P1S), and extended duration of force
action (impulse) for TF (measured by IMS). Given the
higher prevalence of knee osteoarthritis in TF compared
to TT [5,10], it might be speculated that the second
mechanism is more detrimental than the first.
Table 4 Results from Nolan et al. [2], converted to the indexes
of symmetry used in this study. SNS (stance), IMS (impulse) and
P1S (first peak)
SNS IMS P1S
TFM 1,27 1,69 1,22
TT 1,05 1,36 1,25
CONTROLS 1,03 1,08 1,08
Having named Nthe indexes in [2], the new values follow from this
equation: New =(2+N)/(2-N)
TFM transfemoral mechanical knee users, TT transtibial amputees
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 38 of 72
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Conclusions
In the Introduction, we posed three methodological
and three clinical questions regarding the gait temporal
and loading symmetry of lower-limb amputees. Based
on the results collected on traumatic, K3-K4, transfemoral
(mechanical knees and C-leg users) and transtibial patients
successfully fit and trained in using their prosthesis, we
can answer as follows.
The three methodological questions wanted to establish
a minimum set of symmetry indexes to study and if there
are limitations in their calculations. First, the first peak of
the vertical ground reaction force at loading response
cannot be clearly identified in all amputees, and the
calculation of its index of symmetry was limited to patients
with the typical M-Shaped pattern of the ground reaction
force. Second, the analysis of temporal symmetry can be
limited to stance, leaving out step symmetry. Third, stance,
impulse and first peak symmetries should be separately
reported.
The three clinical questions wanted to establish if typical
levels of temporal and loading symmetry exist and change
with the level of amputation and prosthetic components.
First, the symmetries of stance, impulse and first peak are all
influenced by the level of amputation. In particular, the time
spent on the sound side decreases significantly from transfe-
moral mechanical knee users, to C-leg users, to transtibial
patients. The impulse on the sound side decreases signifi-
cantly from mechanical knee users to C-leg and transtibial
patients. Transtibial patients have a higher first peak at load-
ing response on their sound side, while most transfemoral
patients do not. Second, advanced prosthetic component
seem to positively influence the temporal and loading sym-
metry. In particular, the C-leg in combination with the Vari-
flex foot improves stance, impulse symmetry and for about
60% of patients smooths the first peak at loading response.
About 20% of C-leg users have a stance asymmetry which is
below the level of perceived impaired gait, compared to 0%
of mechanical knee users. For transtibial patients, compari-
sons of our results with the literature point toward an
improvement of all indexes of symmetry, possibly due to the
use of energy-storage-and-return feet instead of SACH feet.
Third, it is not always true that amputees overload the
sound side. Percentagewise, transfemoral amputees tend to
overload the sound side with increased impulse, while TT
with increased peak GRF. This might be suggestive of two
separate mechanisms for the onset of knee osteoarthritis.
We think that our results can be exploited in the clinical
routine. First, clinicians can use our results to set reason-
able targets for rehabilitation. Specifically, they can
compare the level of symmetry of a new patient with
the ranges provided, and put the patients performance
and advancements during rehabilitation in perspective.
Moreover, technical and healthcare professionals might
use our findings to compare the effect of different
prosthetic components and potentially the effect of dif-
ferent rehabilitation programs. Second,itisoftenre-
quired by payers (e.g. insurances, public healthcare
services, or patients), to justify the use of advanced
prosthetic components. We think that our results sup-
port the use of C-leg and energy-storage-and-return feet
on K3-K4 traumatic patients: thanks to the improvement
in temporal and loading symmetry compared to mechan-
ical knees and SACH foot, these components can poten-
tially have a positive effect on the asymmetry-related
comorbidities analyzed in the Introduction and de-
crease social stigma. Further research is required to ex-
tend these results to other groups of patients, such as
K2 and non-traumatic amputees. Finally,ourresults
might suggest possible strategies to mitigate knee
osteoarthritis of the sound side. Pending further re-
search, transfemoral amputees might take advantage of
prosthetic components with an improved knee-foot co-
ordination to specifically tackle stance time asymmetry.
Transtibial patients might benefit from improved socket
construction that does not limit knee extension, and pros-
thetic feet with improved push-off, roll-over shape and
range of motion to reduce the first peak at loading
response.
Abbreviations
GRF: Vertical component of the ground reaction force; IMS: Impulse
symmetry index; P1S: Symmetry index of the first peak of the ground
reaction force; SNS: Stance duration symmetry index; SPS: Step duration
symmetry index; TF: Transfemoral amputees; TFC: Transfemoral amputees
using a C-leg knee (Ottobock, D); TFM: Transfemoral amputees using a
mechanical knee; TT: Transtibial amputees
Funding
This research was conducted with internal institutional funds of INAIL. The
publication cost of this article was funded by the American Orthotic &
Prosthetic Association (AOPA).
Availability of data and materials
All data generated or analysed during this study are included in this
published article.
About this supplement
This article has been published as part of Journal of NeuroEngineering and
Rehabilitation Volume 15 Supplement 1, 2018: Advancements in Prosthetics
and Orthotics: Selected articles from the Second World Congress hosted by
the American Orthotic & Prosthetic Association (AOPA). The full contents of the
supplement are available online at https://jneuroengrehab.biomedcentral.com/
articles/supplements/volume-15-supplement-1.
Authorscontributions
AGC, MR and GV designed the experiment. MR and AGC collected and
processed the data. All Authors contributed to data analysis and manuscript
preparation. All authors read and approved the final manuscript.
Ethics approval and consent to participate
The Centro Protesi institutional scientific committee approved the study.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 39 of 72
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published maps and institutional affiliations.
Published: 5 September 2018
References
1. Winter DA, Sienko SE. Biomechanics of below-knee amputee gait. J
Biomech. 1988;21(5):3617.
2. Nolan L, Wit A, Dudziñski K, Lees A, Lake M, Wychowañski M. Adjustments
in gait symmetry with walking speed in trans-femoral and trans-tibial
amputees. Gait Posture. 2003;17(2):14251.
3. Schmid M, Beltrami G, Zambarbieri D, Verni G. Centre of pressure
displacements in trans-femoral amputees during gait. Gait Posture. 2005;
21(3):25562.
4. Hof AL, van Bockel RM, Schoppen T, Postema K. Control of lateral balance in
walking. Experimental findings in normal subjects and above-knee
amputees. Gait Posture. 2007;25(2):2508.
5. Gailey R, Allen K, Castles J, Kucharik J, Roeder M. Review of secondary
physical conditions associated with lower-limb amputation and long-term
prosthesis use. J Rehabil Res Dev. 2008;45(1):1529.
6. Castro MP, Soares D, Mendes E, Machado L. Plantar pressures and ground
reaction forces during walking of individuals with unilateral transfemoral
amputation. PM&R. 2014;6(8):698707.
7. Wezenberg D, Cutti AG, Bruno A, Houdijk H. Differentiation between solid-
ankle cushioned heel and energy storage and return prosthetic foot based
on step-to-step transition cost. J Rehabil Res Dev. 2014;51(10):157990.
8. Adamczyk PG, Kuo AD. Mechanisms of gait asymmetry due to push-off
deficiency in unilateral amputees. IEEE Trans Neural Syst Rehabil Eng. 2015;
23(5):77685.
9. Highsmith MJ, Andrews CR, Millman C, Fuller A, Kahle JT, Klenow TD, Lewis KL,
Bradley RC, Orriola JJ. Gait training interventions for lower extremity amputees:
a systematic literature review. Technol Innov. 2016;18(23):99113.
10. Morgenroth DC, Gellhorn AC, Suri P. Osteoarthritis in the disabled
population: a mechanical perspective. PM&R. 2012;4(5 Suppl):S207.
11. Vanicek N, Strike S, McNaughton L, Polman R. Gait patterns in transtibial
amputee fallers vs. non-fallers: biomechanical differences during level
walking. Gait Posture. 2009;29(3):41520.
12. Norvell DC, Czerniecki JM, Reiber GE, Maynard C, Pecoraro JA, Weiss NS. The
prevalence of knee pain and symptomatic knee osteoarthritis among
veteran traumatic amputees and nonamputees. Arch Phys Med Rehabil.
2005;86:48793.
13. Struyf PA, van Heugten CM, Hitters MW, Smeets RJ. The prevalence of
osteoarthritis of the intact hip and knee among traumatic leg amputees.
Arch Phys Med Rehabil. 2009;90:4406.
14. Lemaire ED, Fisher FR. Osteoarthritis and elderly amputee gait. Arch Phys
Med Rehabil. 1994;75(10):10949.
15. Burke MJ, Roman V, Wright V. Bone and joint changes in lower limb
amputees. Ann Rheum Dis. 1978;37(3):2524.
16. Rush PJ, Wong JS, Kirsh J, Devlin M. Osteopenia in patients with above knee
amputation. Arch Phys Med Rehabil. 1994;75(1):1125.
17. Shojaei I, Hendershot BD, Wolf EJ, Bazrgari B. Persons with unilateral
transfemoral amputation experience larger spinal loads during level-ground
walking compared to able-bodied individuals. Clin Biomech (Bristol, Avon).
2016;32:15763. https://doi.org/10.1016/j.clinbiomech.2015.11.018.
18. Yoder AJ, Petrella AJ, Silverman AK. Trunk-pelvis motion, joint loads, and
muscle forces during walking with a transtibial amputation. Gait Posture.
2015;41(3):75762.
19. Russell Esposito E, Wilken JM. The relationship between pelvis-trunk
coordination and low back pain in individuals with transfemoral
amputations. Gait Posture. 2014;40(4):6406.
20. Rabuffetti M, Recalcati M, Ferrarin M. Trans-femoral amputee gait: socket-
pelvis constraints and compensation strategies. Prosthetics Orthot Int. 2005;
29(2):18392.
21. HandžićI, Reed KB. Perception of gait patterns that deviate from normal
and symmetric biped locomotion. Front Psychol. 2015;6:199.
22. Marinakis GN. Interlimb symmetry of traumatic unilateral transtibial
amputees wearing two different prosthetic feet in the early rehabilitation
stage. J Rehabil Res Dev. 2004;41(4):58190.
23. Esquenazi A. Gait analysis in lower-limb amputation and prosthetic
rehabilitation. Phys Med Rehabil Clin N Am. 2014;25(1):15367.
24. Hof AL. The extrapolated center of massconcept suggests a simple control
of balance in walking. Hum Mov Sci. 2008;27(1):11225.
25. Powers MC, Torburn L, Perry J, Ayyappa E. Influence of prosthetic foot
design on sound limb loading in adults with unilateral below-knee
amputations. Arch Phys Med Rehabil. 1994;75(7):8259.
26. Snyder RD, Powers CM, Fountain C, Perry J. The effect of five prosthetic feet
on the gait and loading of the sound limb in dysvascular below-knee
amputees. J Rehabil Res Dev. 1995;32:30915.
27. Hansen AH, Meier MR, Sessoms PH, Childress DS. The effects of prosthetic
foot roll-over shape arc length on the gait of trans-tibial prosthesis users.
Prosthetics Orthot Int. 2006;30(3):28699.
28. Gard SA. Use of quantitative gait analysis for the evaluation of prosthetic
walking performance. J Prosthet Orthot. 2006;18(6):P93P104.
29. Perry J, Burnfield J. Gait analysis: normal and pathological function:
Thorofare: SALCK Inc.; 2010.
30. Evans JD. Straightforward statistics for the behavioral sciences. Pacific Grove:
Brooks/Cole Publishing; 1996.
31. Cutti AG, Lettieri E, Del Maestro M, Radaelli G, Luchetti M, Verni G, Masella C.
Stratified cost-utility analysis of C-leg versus mechanical knees: findings
from an Italian sample of transfemoral amputees. Prosthetics Orthot Int.
2017;41(3):22736.
32. Segal AD, Orendurff MS, Klute GK, McDowell ML, Pecoraro JA, Shofer J,
Czerniecki JM. Kinematic and kinetic comparisons of transfemoral amputee
gait using C-leg and Mauch SNS prosthetic knees. J Rehabil Res Dev. 2006;
43(7):85770.
33. Putti AB, Arnold GP, Cochrane L, Abboud RJ. The Pedar in-shoe system:
repeatability and normal pressure values. Gait Posture. 2007;25(3):4015.
34. Hurkmans HL, Bussmann JB, Benda E, Verhaar JA, Stam HJ. Accuracy and
repeatability of the Pedar Mobile system in long-term vertical force
measurements. Gait Posture. 2006;23(1):11825.
35. Dekel S, Weissman SL. Joint changes after overuse and peak overloading of
rabbit knees in vivo. Acta Orthop Scand. 1978;49(6):51928.
36. Guilak F. Biomechanical factors in osteoarthritis. Best Pract Res Clin
Rheumatol. 2011;25(6):81523.
37. Buckwalter JA, Anderson DD, Brown TD, Tochigi Y, Martin JA. The roles of
mechanical stresses in the pathogenesis of osteoarthritis: implications for
treatment of joint injuries. Cartilage. 2013;4(4):28694.
38. Jarvis HL, Bennett AN, Twiste M, Phillip RD, Etherington J, Baker R. Temporal
spatial and metabolic measures of walking in highly functional individuals
with lower limb amputations. Arch Phys Med Rehabil. 2016;98(7):138999.
39. Kaufman KR, Frittoli S, Frigo CA. Gait asymmetry of transfemoral amputees
using mechanical and microprocessor-controlled prosthetic knees. Clin
Biomech (Bristol, Avon). 2012;27(5):4605.
40. Kaufman KR, Levine JA, Brey RH, Iverson BK, McCrady SK, Padgett DJ, Joyner MJ.
Gait and balance of transfemoral amputees using passive mechanical and
microprocessor-controlled prosthetic knees. Gait Posture. 2007;26(4):48993.
41. Bateni H, Olney SJ. Kinematic and kinetic variations of below-knee amputee
gait. J Prosthet Orthot. 2004;14(1):210.
42. Underwood HA, Tokuno CD, Eng JJ. A comparison of two prosthetic feet on
the multi-joint and multi-plane kinetic gait compensations in individuals with a
unilateral trans-tibial amputation. Clin Biomech (Bristol, Avon). 2004;19:60916.
43. Lehmann JF, Price R, Boswell-Bessette S, Dralle A, Questad K, deLateur BJ.
Comprehensive analysis of energy storing prosthetic feet: flex foot and Seattle
foot versus standard SACH foot. Arch Phys Med Rehabil. 1993;74(11):122531.
44. Petersen AO, Comins J, Alkjær T. Assessment of gait symmetry in
transfemoral amputees using C-leg compared with 3R60 prosthetic knees. J
Prosthet Orthot. 2010;22(2):10612.
45. Hahn A, Lang M. Effects of mobility grade, age, and etiology on functional
benefit and safety of subjects evaluated in more than 1200 C-leg trial
fittings in Germany. J Prosthet Orthot. 2015;27(3):8694.
46. Hafner BJ, Willingham LL, Buell NC, Allyn KJ, Smith DG. Evaluation of
function, performance, and preference as transfemoral amputees transition
from mechanical to microprocessor control of the prosthetic knee. Arch
Phys Med Rehabil. 2007;88(2):20717. Erratum in: Arch Phys Med Rehabil.
2007 Apr;88(4):544
47. Highsmith MJ, Kahle JT, Bongiorni DR, Sutton BS, Groer S, Kaufman KR. Safety,
energy efficiency, and cost efficacy of the C-leg for transfemoral amputees: a
review of the literature. Prosthetics Orthot Int. 2010;34(4):36277.
Cutti et al. Journal of NeuroEngineering and Rehabilitation 2018, 15(Suppl 1):61 Page 40 of 72
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... For example, ground force impulse is significantly different in children with cerebral palsy and hemiparetic stroke survivors than in control groups (Balasubramanian et al., 2007;White et al., 2005). Impulse differences are also seen between individuals with transfemoral and transtibial amputations, and inter-limb IA has been noted to improve with use of more advanced prosthetic technology (Cutti et al., 2018;Zmitrewicz et al., 2006). ...
... In contrast, clinical literature suggests notable differences in ground reaction forces between limbs during walking in stroke survivors (Allen et al., 2011;Balasubramanian et al., 2007;C.-L. Chen et al., 2001), and other clinical populations (Cutti et al., 2018;White et al., 2005;Zmitrewicz et al., 2006), indicating that the perturbation applied herein may not have been disruptive enough to be detected by IA. Therefore, we would conclude that IA may be better suited for detecting more severe gait pathology and less well suited for mild to moderate gait impairments. ...
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... The testing paradigm for LLA for both feedback strategies (BV, UV) consisted of increasing participants' baseline STSR toward STSR = 1.0 (targeted STSR). Previous studies have reported baseline STSR values ranging from 0.70 -1.0 for LLA, depending on the level of amputation and type of prosthesis [13], [16], [29]. STSR converging toward a value of 1 indicates gait symmetry improvement, whereas STSR diverging from 1 indicates asymmetry [3]. ...
... As hypothesized, all participants were able to significantly improve their stance time symmetry ratio (STSR) using A recent study showed that mean STSR values for LLA can range considerably (from 0.78 ± 0.08 to 0. 97 ± 0.03) depending on the level of amputation and type of prosthetic knee (e.g., mechanical versus microprocessor prosthetic knee) [29]. TFA typically present with higher asymmetry caused by greater underlying physiological differences. ...
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Full-text available
Individuals with lower-limb amputation (LLA) often exhibit atypical gait patterns and asymmetries. These patterns can be corrected using biofeedback (BFB). Real-time BFB strategies have demonstrated to be effective to various degrees in BFB systems. However, no studies have evaluated the use of corrective vibrotactile BFB strategies to improve temporal gait symmetry of LLA. The aim of this study was to evaluate a wearable vibrotactile BFB system to improve stance time symmetry ratio (STSR) of LLA, and compare two corrective BFB strategies that activate either one or two vibrating motors at two different frequency and amplitude levels, based on a pre-set STSR target. Gait patterns of five unilateral LLA were assessed with and without BFB. Spatiotemporal and kinematic gait parameters were measured and assessed using a wearable motion capture system. Usability and workload were assessed using the System Usability Scale and NASA Task Load Index questionnaires, respectively. Results showed that participants significantly (p<0.001) improved STSR with BFB; however, this coincided with a reduction in gait speed and cadence compared to walking without feedback. Knee and hip flexion angles improved and changes in other parameters were variable. Immediate post-test retention effects were observed, suggesting that gait changes due to BFB were preserved for at least a short-time after feedback was withdrawn. System usability was found to be acceptable while using BFB. The outcomes of this study provide new insights into the development and implementation of clinically practical and viable BFB systems. Future work should focus on assessing the long-term use and retention effects of BFB outside controlled-laboratory conditions.
... It appears that the strategy may involve moving towards a more symmetrical gait to enable the amputee to walk longer by reducing energy expenditure. Possible impacts of this symmetrization include prosthesis alignment adjustment or prosthetic knee improvement, as well as a reduction-based approach to train the patient in load transfer to improve symmetry [5]. When an amputee faces challenging situations (uneven terrain, uphill or downhill slopes, etc.), they tend to decrease their speed and increase their asymmetry [15]. ...
Article
Purpose The continued development of microprocessor-based knee prostheses has improved the independence of people with a femoral amputation in many environments. This study aimed to describe the effect of slopes on kinematic joint variables and segmental asymmetry. Methods Ten individuals with transfemoral amputation fitted with microprocessor-controlled knees performed 5 sessions of treadmill walking at their preferred speed in an immersive virtual environment in 5 incline conditions (Level, 3° and 6° Uphill, and 3° and 6° Downhill). The Human Body Model was used to quantify kinematic joint variables from motion capture system data. The perimeter-to-area method was used to determine the symmetry ratio of the trajectory of the leg segments in the sagittal plane Results There was a significant effect of the Uphill conditions on step length and width on the intact side and on all kinematic joint variables on both sides, although the changes differed according to the phase of the gait cycle. The segmental symmetry index was significantly modified in all slope conditions compared with Level. Conclusions Kinematic joint variables are affected by slopes; the effect was greater for the Uphill than Downhill conditions compared with the Level condition. The perimeter-to-area symmetry ratio differed from the Level condition for all slope conditions. These results indicate that, although microprocessor knees improve the autonomy of prosthesis users, work is required to improve their capacity of adaptation to varied terrain to reduce kinematic asymmetry.
... In the present study, knee OA was more prevalent in 87 TTA (66.4%) followed by 33 TFA (25.2%) with the same percentage using trans-tibial and trans-femoral prostheses, respectively. This seems to be consistent with literature revealing that symmetry for the first peak; stance and impulse vary with amputation level and are related to intact knee OA [28]. However, some prosthetic feet, such as energy storing and return (ESAR) prosthetic feet may not result in any significant difference in joint kinematics and hence may not affect joint contact forces, which may be responsible for OA in other cases on the intact side [29]. ...
Article
Background Patients with transfemoral amputation experience socket-related problems and musculoskeletal overuse injuries, both of which are exacerbated by asymmetric joint loading and alignment. Bone-anchored limbs are a promising alternative to treat chronic socket-related problems by directly attaching the prosthesis to the residual limb through an osseointegrated implant; however, it remains unknown how changes in alignment facilitated through a bone-anchored limb relate to loading asymmetry. Questions/purposes What is the association between femur-pelvis alignment and hip loading asymmetry during walking before and 12 months after transfemoral bone-anchored limb implantation? Methods Between 2019 and 2022, we performed 66 bone-anchored limb implantation surgeries on 63 individuals with chronic socket-related problems. Of those, we considered those with unilateral transfemoral amputation as potentially eligible for this study. Based on that, 67% (42 of 63) were eligible, a further 55% (23 of 42) were excluded because they had incomplete datasets either at baseline (such as an inability to ambulate with a socket prosthesis) or did not complete the 12-month follow-up data collection. This resulted in 19 participants being included in this retrospective longitudinal analysis (9 males and 10 females, mean ± age 51 ± 11 years, mean BMI 28 ± 4 kg/m2). As part of standard clinical care, hip-to-ankle radiographs and motion capture data during overground walking were collected at two timepoints: 2 days before (preimplantation) and 12 months after bone-anchored limb implantation (postimplantation). Femur-pelvis skeletal alignment was measured from the radiographs (femoral abduction angle, residual femur length ratio, and pelvic obliquity). Symmetry indices of hip internal hip moment impulses (flexion/extension, abduction/adduction, internal/external rotation) were calculated from the motion capture data. Differences in alignment and internal joint moment impulse symmetry indices were compared across timepoints using paired t-tests with self-selecting walking speed as a covariate. Associations between skeletal alignment and hip moment impulse symmetry indices were computed at both timepoints using Spearman rank correlation with 5000 bootstrapped resamples. Results Twelve months after bone-anchored limb implantation, a comparison of preimplantation and postimplantation measurements showed reductions in the femoral abduction angle (-8° ± 10° versus 3° ± 4°, mean difference 11° [95% confidence interval (CI) 7° to 16°]; p < 0.001) and the residual femur length ratio (57% ± 15% versus 48% ± 11%, mean difference -9% [95% CI -12% to -5%]; p < 0.001). Additionally, a comparison of preimplantation and postimplantation calculations showed that the internal hip moment symmetry was improved in the sagittal and frontal planes (flexion symmetry index: 30 ± 23 versus 11 ± 19, mean symmetry index difference -19 [95% CI -31 to -6]; p = 0.03; extension symmetry index: 114 ± 70 versus 95 ± 63, mean symmetry index difference -19 [95% CI -42 to 4]; p = 0.03; abduction symmetry index: -54 ± 55 versus -41 ± 45, mean symmetry index difference 13 [95% CI -15 to 40]; p = 0.03). A larger length ratio of the residual limb relative to the intact limb was moderately associated with hip moment impulse symmetry in all three anatomical planes of motions both before and 12 months after transfemoral bone-anchored limb implantation, with strong associations observed between postimplantation hip extension and external rotation moment impulse symmetry (extension: ρ = -0.50 [95% CI -0.72 to -0.07]; p = 0.03; internal rotation: ρ = 0.64 [95% CI 0.25 to 0.85]; p = 0.004). Conclusion The associations between residual femur length and hip loading symmetry in patients with transfemoral bone-anchored limbs suggest that those with shorter residual limbs will demonstrate more asymmetric joint loading when using a bone-anchored limb. Thus, these findings could potentially be used to better inform targeted interventions based on residual limb morphology, including continued gait training in rehabilitation to promote joint loading symmetry and surgical considerations surrounding limb length changes in those with shorter limbs. Future studies might also examine joint loading symmetry during other activities of daily living after bone-anchored limb implantation to further expand knowledge of how residual limb anthropometry is associated musculoskeletal health after bone-anchored limb implantation. Level of Evidence Level III, therapeutic study.
Article
The purpose of this paper is to undertake a systematic review on various mechanical design considerations, simulation and optimization techniques as well as the clinical applications of energy storing and return (ESAR) prosthetic feet used in amputee rehabilitation. Methodological databases including PubMed, EMBASE, and SCOPUS were searched till July 2022, and the retrieved records were evaluated for relevance. The design, mechanism, materials used, mechanical and simulation techniques and clinical applications of ESAR foot used in developed and developing nations were reviewed. 61 articles met the inclusion criteria out of total 577 studies. A wide variety of design matrices for energy- storing feet was found, but the clinical relevance of its design parameters is uncommon. Definitive factors on technical and clinical characteristics were derived and included in the summary tables. To modify existing foot failure mechanisms, material selection and multiple experiments must be improved. Gait analysis and International Organization for Standardization (ISO) mechanical testing standards of energy-storing feet were the methods for integrating clinical experimentation with numerical results. To meet technological requirements, various frameworks simulate finite element models of the energy-storing foot, whereas clinical investigations involving gait analysis require proper insight. Analysis of structural behavior under varying loads and its effect on studies of functional gait are limited. For optimal functional performance, durability and affordability, more research and technological advancements are required to characterize materials and standardize prosthetic foot protocols.
Article
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Gait symmetry is one of the most informative aspects describing the quality of gait. Many indices have been proposed to quantify gait symmetry. Among them, indices focusing on the comparison of the two body sides (e.g., Symmetry Angle, SA) and indices based on the analysis of the locomotor act as a whole, dealing with the body center of mass (e.g., Symmetry Index, SIBCoM) or lower trunk accelerometry (e.g., improved Harmonic Ratio, iHR) have been proposed. Remarkably, the relationship between these indices has received little attention so far, as well as the influence of gait speed on their values. The aim of this study is to investigate this relationship by comparing the SA, SIBCoM, and iHR, and to explore the effect of walking speed on these indices. Ten healthy adults walked for 60 s on a treadmill at seven different speeds (from 0.28 to 1.95 m s⁻¹) and simulate an asymmetric gait (ASYM) at 0.83 m s⁻¹. Marker-based trajectories were recorded, and the body center of mass 3D trajectory was obtained. Simultaneously, lower trunk 3D linear accelerations were collected using a triaxial accelerometer. SIBCoM, iHR, and SA were calculated for each stride, each anatomical direction, and each condition. Perfect symmetry was never displayed in any axes and any indices. Significant differences existed between SIBCoM, and iHR in all anatomical directions (p < 0.0001). The walking speed significantly affected SIBCoM and iHR values in anteroposterior and craniocaudal directions, but not in mediolateral. Conversely, no walking speed effect was found for SA (p = 0.28). All three indices significantly discriminated between ASYM and the corresponding walking condition (p < 0.05). Gait symmetry may differ significantly according to the data source, mathematical approach, and walking speed. Healthy individuals display an asymmetrical gait and acknowledging this aspect is crucial when establishing rehabilitation objectives and assessing the quality of gait in the clinical setting.
Article
Background Despite the demonstrated greater efficacy of microprocessor knees (MPK) over mechanical knees (MK), the latter is still widely used by persons with transfemoral amputation. Besides motivations related to local insurance policies, quality of life (QoL) and satisfaction with the prosthesis play a key role in user preference. Objective The aim of this study is to compare QoL and satisfaction in a large sample of MPK and MK users and to assess how these outcomes are explained by clinical and demographic characteristics. Study Design Retrospective study. Methods The study was conducted on 75 MPK and 60 MK users. Quality of life was assessed using the EuroQoL Five Dimensions and the EuroQoL Visual Analog Scale questionnaires. Satisfaction was assessed with the Satisfaction with Prosthesis questionnaire. All 3 instruments were self-administered. Univariate and multivariate regression analyses were conducted thereafter. Results The difference in satisfaction between MPK and MK users was not statistically significant. Significant differences were observed instead for QoL. From the univariate regression analysis, 6 factors were significant predictors of QoL and satisfaction. On multivariate analysis, the number of significant factors was reduced to 3, namely knee type, age at the first prosthesis, and experience with prosthesis. Type of knee and age at the first prosthesis significantly predicted QoL scores, explaining 12% of EuroQoL Five Dimensions and 25% of EuroQoL Visual Analog Scale variances. Age at the first prosthesis and experience with prosthesis predicted Satisfaction with Prosthesis scores in the multivariate model, explaining 25% of the variance. Conclusions MPK affects QoL but not satisfaction, which is positively driven by patients’ experience with prosthesis and negatively affected by the age at the time of the first prosthesis.
Article
Background: Individuals with unilateral transfemoral amputation walk with increased levels of asymmetry, and this is associated with reduced gait efficiency, back pain and overuse of the intact limb. This study investigated the effect of walking with a unilateral absence of loading response knee flexion on the symmetry of anterior-posterior kinetics and centre of mass accelerations. Methods: A retrospective cohort study design was used, assessing three-dimensional gait data from individuals with unilateral transfemoral amputation (n = 56). The anterior-posterior gait variables analysed included; peak ground reaction forces, impulse, centre of mass acceleration, as well as rate of vertical ground reaction force increase in early stance. With respect to these variables, this study assessed the symmetry between intact and prosthetic limbs, compared intact limbs against a healthy unimpaired control group, and evaluated effect on symmetry of microprocessor controlled knee provision. Findings: Significant between-limb asymmetries were found between intact and prosthetic limbs across all variables (p < 0.0001). Intact limbs showed excessive loading when compared with control group limbs after speed normalisation across all variables (p < 0.0001). No improvement in kinetic symmetry following microprocessor controlled knee provision was found. Interpretation: The gait asymmetries for individuals with transfemoral amputation identified in this study suggest that more should be done by developers to address the resultant overloading of the intact limb, as this is thought to have negative long-term effects. The provision of microprocessor controlled knees did not appear to improve the asymmetries faced by individuals with transfemoral amputation, and clinicians should be aware of this when managing patient expectations.
Article
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Lower extremity (LE) amputation patients who use prostheses have gait asymmetries and altered limb loading and movement strategies when ambulating. Subsequent secondary conditions are believed to be associated with gait deviations and lead to long-term complications that impact function and quality of life as a result. The purpose of this study was to systematically review the literature to determine the strength of evidence supporting gait training interventions and to formulate evidence statements to guide practice and research related to therapeutic gait training for lower extremity amputees. A systematic review of three databases was conducted followed by evaluation of evidence and synthesis of empirical evidence statements (EES). Eighteen manuscripts were included in the review, which covered two areas of gait training interventions: 1) overground and 2) treadmill-based. Eight EESs were synthesized. Four addressed overground gait training, one covered treadmill training, and three statements addressed both forms of therapy. Due to the gait asymmetries, altered biomechanics, and related secondary consequences associated with LE amputation, gait training interventions are needed along with study of their efficacy. Overground training with verbal or other auditory, manual, and psychological awareness interventions was found to be effective at improving gait. Similarly, treadmill-based training was found to be effective: 1) as a supplement to overground training; 2) independently when augmented with visual feedback and/or body weight support; or 3) as part of a home exercise plan. Gait training approaches studied improved multiple areas of gait, including sagittal and coronal biomechanics, spatiotemporal measures, and distance walked.
Article
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Decreased push-off power by the prosthetic foot and inadequate roll-over shape of the foot have been shown to increase the energy dissipated during the step-to-step transition in human walking. The aim of this study was to determine whether energy storage and return (ESAR) feet are able to reduce the mechanical energy dissipated during the step-to-step transition. Fifteen males with a unilateral lower-limb amputation walked with their prescribed ESAR foot (Vari-Flex, Ossur; Reykjavik, Iceland) and with a solid-ankle cushioned heel foot (SACH) (1D10, Ottobock; Duderstadt, Germany), while ground reaction forces and kinematics were recorded. The positive mechanical work on the center of mass performed by the trailing prosthetic limb was larger (33%, p = 0.01) and the negative work performed by the leading intact limb was lower (13%, p = 0.04) when walking with the ESAR foot compared with the SACH foot. The reduced step-to-step transition cost coincided with a higher mechanical push-off power generated by the ESAR foot and an extended forward progression of the center of pressure under the prosthetic ESAR foot. Results can explain the proposed improvement in walking economy with this kind of energy storing and return prosthetic foot.
Article
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This study examines the range of gait patterns that are perceived as healthy and human-like with the goal of understanding how much asymmetry is allowable in a gait pattern before other people start to notice a gait impairment. Specifically, this study explores if certain abnormal walking patterns can be dismissed as unimpaired or not uncanny. Altering gait biomechanics is generally done in the fields of prosthetics and rehabilitation, however the perception of gait is often neglected. Although a certain gait can be functional, it may not be considered as normal by observers. On the other hand, an abnormally perceived gait may be more practical or necessary in some situations, such as limping after an injury or stroke and when wearing a prosthesis. This research will help to find the balance between the form and function of gait. Gait patterns are synthetically created using a passive dynamic walker (PDW) model that allows gait patterns to be systematically changed without the confounding influence from human sensorimotor feedback during walking. This standardized method allows the perception of specific changes in gait to be studied. The PDW model was used to produce walking patterns that showed a degree of abnormality in gait cadence, knee height, step length, and swing time created by changing the foot roll-over-shape, knee damping, knee location, and leg masses. The gait patterns were shown to participants who rated them according to separate scales of impairment and uncanniness. The results indicate that some pathological and asymmetric gait patterns are perceived as unimpaired and normal. Step time and step length asymmetries less than 5%, small knee location differences, and gait cadence changes of 25% do not result in a change in perception. The results also show that the parameters of a pathologically or uncanny perceived gait can be beneficially altered by increasing other independent parameters, in some sense masking the initial pathology.
Article
Objective: To record the temporal spatial parameters and metabolic energy expenditure during walking of individuals with amputation, walking with advanced prostheses, and after completion of comprehensive rehabilitation compared with able-bodied persons. Design: Cross-sectional. Setting: Multidisciplinary comprehensive rehabilitation center. Participants: Severely injured UK military personnel with amputation and subsequent completion of their rehabilitation program (n=30; unilateral transtibial: n=10, unilateral transfemoral: n=10, and bilateral transfemoral: n=10) were compared with able-bodied persons (n=10) with similar age, height, and mass (P>.537). Total number of participants (N = 40). Interventions: Not applicable. Main outcome measures: Temporal spatial and metabolic energy expenditure data were captured during walking on level ground at a self-selected speed. Results: The individuals with amputation were all men, with a mean age of 29±4 years and a mean New Injury Severity Score of 31±16. Walking speed, stride length, step length, and cadence of individuals with a unilateral transtibial or transfemoral amputation were comparable with able-bodied persons, and only individuals with a bilateral transfemoral amputation had a significantly slower walking speed (1.12m/s, P=.025) and reduced cadence (96 steps per minute, P=.026). Oxygen cost for individuals with a unilateral transtibial amputation (0.15mL/kg/m) was the same as for able-bodied persons (0.15mL/kg/m) and significantly increased by 20% (0.18mL/kg/m, P=.023) for unilateral transfemoral amputation and by 60% (0.24mL/kg/m, P<.001) for bilateral transfemoral individuals with amputation. Conclusions: The scientific literature reports a wide range of gait and metabolic energy expenditure across individuals with amputation. The results of this study indicate that individuals with amputation have a gait pattern which is highly functional and efficient. This is comparable with a small number of studies reporting similar outcomes for individuals with a unilateral transtibial amputation, but the results from this study are better than those on individuals with transfemoral amputations reported elsewhere, despite comparison with populations wearing similar prosthetic componentry. Those studies that do report similar outcomes have included individuals who have been provided with a comprehensive rehabilitation program. This suggests that such a program may be as important as, or even more important than, prosthetic component selection in improving metabolic energy expenditure. The data are made available as a benchmark for what is achievable in the rehabilitation of some individuals with amputations, but agreeably may not be possible for all amputees to achieve.
Article
Background: The fitting rate of the C-Leg electronic knee (Otto-Bock, D) has increased steadily over the last 15 years. Current cost-utility studies, however, have not considered the patients' characteristics. Objectives: To complete a cost-utility analysis involving C-Leg and mechanical knee users; "age at the time of enrollment," "age at the time of first prosthesis," and "experience with the current type of prosthesis" are assumed as non-nested stratification parameters. Study design: Cohort retrospective. Methods: In all, 70 C-Leg and 57 mechanical knee users were selected. For each stratification criteria, we evaluated the cost-utility of C-Leg versus mechanical knees by computing the incremental cost-utility ratio, that is, the ratio of the "difference in cost" and the "difference in utility" of the two technologies. Cost consisted of acquisition, maintenance, transportation, and lodging expenses. Utility was measured in terms of quality-adjusted life years, computed on the basis of participants' answers to the EQ-5D questionnaire. Results: Patients over 40 years at the time of first prosthesis were the only group featuring an incremental cost-utility ratio (88,779 €/quality-adjusted life year) above the National Institute for Health and Care Excellence practical cost-utility threshold (54,120 €/quality-adjusted live year): C-Leg users experience a significant improvement of "mobility," but limited outcomes on "usual activities," "self-care," "depression/anxiety," and reduction of "pain/discomfort." Conclusion: The stratified cost-utility results have relevant clinical implications and provide useful information for practitioners in tailoring interventions. Clinical relevance: A cost-utility analysis that considered patients characteristics provided insights on the "affordability" of C-Leg compared to mechanical knees. In particular, results suggest that C-Leg has a significant impact on "mobility" for first-time prosthetic users over 40 years, but implementation of specific low-cost physical/psychosocial interventions is required to retun within cost-utility thresholds.
Article
Background: Persons with lower limb amputation walk with increased and asymmetric trunk motion; a characteristic that is likely to impose distinct demands on trunk muscles to maintain equilibrium and stability of the spine. However, trunk muscle responses to such changes in net mechanical demands, and the resultant effects on spinal loads, have yet to be determined in this population. Methods: Building on a prior study, trunk and pelvic kinematics collected during level-ground walking from 40 males (20 with unilateral transfemoral amputation and 20 matched controls) were used as inputs to a kinematics-driven, nonlinear finite element model of the lower back to estimate forces in 10 global (attached to thorax) and 46 local (attached to lumbar vertebrae) trunk muscles, as well as compression, lateral, and antero-posterior shear forces at all spinal levels. Findings: Trunk muscle force and spinal load maxima corresponded with heel strike and toe off events, and among persons with amputation, were respectively 10-40% and 17-95% larger during intact vs. prosthetic stance, as well as 6-80% and 26-60% larger during intact stance relative to controls. Interpretation: During gait, larger spinal loads with transfemoral amputation appear to be the result of a complex pattern of trunk muscle recruitment, particularly involving co-activation of antagonistic muscles during intact limb stance; a period when these individuals are confident and likely to use the trunk to assist with forward progression. Given the repetitive nature of walking, repeated exposure to such elevated loading likely increases the risk for low back pain in this population.
Article
Introduction: Mobility grade (MG) rating is often used to indicate or contraindicate the use of a microprocessor-controlled prosthetic knee component for individuals with transfemoral (TF) limb loss. Methods: A retrospective cross-sectional analysis of a cohort that underwent a C-Leg or C-Leg compact trial fitting was conducted. Data were retrieved on standardized questionnaires from 445 prosthetic fitting centers. Utilization of functional benefits as assessed by both subjects and their practitioners was obtained on either 5-point Likert scales or corresponding measures. Correlations of functional benefits with age, MG, and amputation etiology were tested. Responders were defined as subjects receiving ratings within the top 40% of the respective scale. A logistic multiple regression model was used to calculate effect sizes. Results: Data on 1223 subjects (mean age, 55.6 years; predominantly male [83%]) were investigated. Eighty-eight percent of the trial fittings were conducted in a single day. The cohort was stratified based on age (21-40 years, 13.7%; 41-60 years, 44.1%; >60 years, 38.2%), MG (MOBIS: MG2, 38.4%; MG3, 39.2%; MG4, 6.5%), and amputation etiology (vascular disease including diabetes [24%] and other [76%]). Subjects showed a high potential to change MG after having been fitted with a C-Leg (MG2-MG3, 50%; MG3-MG4, 22%). The number of reported falls was high; 82% reported at least one fall in the past 12 months, 49% reported multiple falling in this period. The utilization of functional benefit (responsiveness) was related to safety (83%), relief of sound limb (95%), capability to divide attention (94%), gait pattern harmonization (95%), variation of gait speed (93%), overall reduction in walking effort (88%), and reduction in walking aids (23%). Kendall τ detected either none or weak correlations of functional benefit with age, MG, or amputation etiology. The multiple regression model calculated predictive power of the stratifiers to range between 0.7% and 9%. Conclusions: Responders are not limited to specific age groups, MGs, or amputation etiologies. The utilization of functional benefits is not correlated with age, MG, or etiology of the amputation nor do any of these factors possess any relevant predictive power. Rather, the responsiveness is highly independent of age, MG, and amputation etiology. Furthermore, it seems that technology itself substantially influences MG rating. Therefore, we find it important that the potential benefits of an microprocessor-controlled knee (MPK) are assessed on an individual basis. The present study suggests that a prediction of an individual's capability to utilize the functional benefits of C-Leg solely on grounds of the aforementioned factors or their interdependencies is hard to argue.
Article
This is my review of the textbook, not the textbook itself. ResearchGate keeps crediting me with citations to the textbook.
Article
People with unilateral, transtibial amputation (TTA) have an increased prevalence of chronic low back pain (LBP) relative to able-bodied people. However, a definitive cause of increased LBP susceptibility has not been determined. The purpose of this work was to compare dynamic trunk-pelvis biomechanics between people with (n=6) and without (n=6) unilateral TTA during walking using a computational modeling approach. A generic, muscle-actuated whole body model was scaled to each participant, and experimental walking data were used in a static optimization framework to calculate trunk-pelvis motion, L4L5 joint contact forces, and muscle forces within the trunk-pelvis region. Results included several significant between-group differences in trunk-pelvis biomechanics during different phases of the gait cycle. Most significant was greater lateral bending toward the residual side during residual single-limb stance (p<0.01), concurrent with an elevated L4L5 joint contact force (p=0.02) and greater muscle force from the intact-side obliques (p<0.01) in people with TTA relative to able-bodied people. During both double-limb support phases, people with TTA also had a greater range of axial trunk rotation away from the leading limb, concurrent with greater ranges of muscle forces in the erector spinae and obliques. In addition, a greater range of force (p=0.03) in residual-side psoas was found during early residual limb swing in people with TTA. Repeated exposure to atypical motion and joint/muscle loading in people with TTA may contribute to the development of secondary musculoskeletal disorders, including chronic, mechanical LBP. Copyright © 2015 Elsevier B.V. All rights reserved.