241
Variations of gait parameters in
Duchenne muscular dvstroDhv
S Khodadadeh, MSc, PhD, M R McClelland, FRCS and J H Patrick, FRCS
The Orthotic Research and Locomotor Assessment Unit, The Robert Jones and Agnes Hunt Orthopaedic Hospital,
Oswestry, Shropshire
The gait parameters (speed, stride length and cadence) of nine boys with Duchenne muscular dystrophy were compared with those of 21
normal boys in the same age range. Diflerences found were due to the altered ability to control their dynamic state and, to a lesser
extent, physical limitations of joint range. This simple method of quantgying gait is proposed as a way in which progression or response
to treatment in muscular dystrophy might be monitored.
The information obtained may alert the clinician to the fact that the progressiue muscle weakness and joint contractures have begun to
cause compensatory mechanisms during walking to,fail.
It is also useful to obtain information on gait in clinical treatment trials as there are very few reliable methods for testing function in
muscular dystrophy.
1 INTRODUCTION
While many authors (1, 2) have commented on the
characteristic waddling gait of children with muscular
dystrophy, there is very little quantitative information
on the changes in their gait parameters compared to
normal children.
Because time and distance are the basic components
of motion, their measurement for each walking cycle
represents the most fundamental description of gait.
The stride length defines the distance moved by the
body during one gait cycle, while the cadence is movement measured in strides per second. The combination
of cadence and stride length determine speed. In
general, to increase speed one increases stride length
rather than cadence as this retains the smoother gait.
Muscular dystrophy children suffer progressive
muscle weakness and joint contracture, both of which
will tend to reduce their maximum walking velocity. By
comparison with the stride length and cadence of
normal boys, it might be possible to understand further
the complexity of change in muscular dystrophy gait
and, perhaps, to suggest a simple way in which progression of the illness might be monitored.
2 SUBJECTS
Twenty-two normal boys, between the ages of 6 and 14
(average age 9 years), were studied. Nine boys with
Duchenne muscular dystrophy aged between 5 and 15
(average age 9 years) who could walk independently
without orthotic stabilization were also studied.
3 METHOD
Each boy was asked to complete two timed walks of a
6.1 metres walkway at three different speeds, slow,
normal and fast, in bare feet. Stride length was measured by dusting their feet liberally with talcum powder
before each walk and measuring the distance between
heel strikes from the subsequent impression left on the
The MS was recemed on 8 June 1990 and wus accepted for publication on 23
October 1990.
H02490 0 IMechE 1990
walkway. The time taken to complete each walk was
recorded, as were the number of strides. From this it
was possible to calculate the walking velocity in metres
per second.
4 THEORY
Although normalization of gait measurements with
respect to body size is regarded as a very significant but
unresolved problem for the standardization of locomotion research (3), a degree of normalization can be
achieved by dividing stride length and velocity by total
body height.
Considering a subject walking with a velocity u,
taking a stride length L, then
L
=
A(u)
where A is not constant. Thus Charteris et aE. (4) made
the assumption that
L
h
where
L = stride length
u = velocity
h = body height
F , is a universal function applying to subjects of all
statures. However, Alexander (5) showed that the equation of Charteris et ul. (4) did not hold across a wide
range of statures as u/h was not dimensionless but had a
dimension of (time)- '.
He proposed that, as gravity has an important influence on walking, u/J(ghj, being dimensionless, was a
more appropriate parameter for such studies (g is the
acceleration due to gravity).
5 RESULTS
The subject was asked to perform a number of practice
walks along the walkway, to accustom him to the somewhat unnatural surroundings of the Gait Laboratory.
Following this each subject made two recorded walks.
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Proc Insln Mech Engrs Vol 204
S KHODADADEH, M R MtCLELLAND AND J H PATRICK
242
Fig. 1 Relationship between normalized stride length and normalized speed
for normal and Duchenne muscular dystrophy boys
Table 1 The mean and standard deviation for normal and Duchenne
muscular dystrophy (DMD)patients
Mean
-___-Fast
Normal
Slow
SD
Mean
SII
Mean
SD
1.34
1.30
0.15
Normal
DMD
Cadence
L/s
094
0.12
0.80
0.20
1.08
1.00
0.09
Normal
Stride
Lh
0.73
0.60
0.09
0.83
0.10
070
0.06
0.10
0.98
DMD
0.80
0.09
0.10
Normal
DMD
Velocity
0.91
0.13
1.21
0.18
0.60
0.10
0.80
0.14
0.20
I 79
u (m/s)
1.30
0.20
0 10
0.30
L,k = strides per second
L = stride length
h = height
u = velocity
mjs = metres per second
SD = standard deviation
When the formula L/h = F(u/d(gh)) is applied to the
normal subjects in this study, the graph obtained correlates well with that of Alexander (5)(Fig 1)
Table 1 shows the mean and standard deviation for
nornial and Duchenne muscular dystrophy boys.
Similar calculations for the children with Ihchcnne
rnuscular dystrophy showed lhcm to lie below and
almost parallel to thc normal curve having a slower
preferred walking speed and a shorter stride length for a
given velocity.
Keference to Tablc 2 shows that the maximum velocity of thcse boys I S also greatl! reduced. This indicalc\
Table 2
Uaxrrniin: mean \eIocitq and standard deviation 01 Duchenne muscular dystrophy and normal buys
DMD
1.30
SD
0.20
1.1-1 7
that at higher walking speed Duchenne boys are unable
to alter their stride length in a normal fashion Thus
thcv increase their walking speed mainly b) increasing
their cadencc
6 DISCUSSION
The maximum stride length that a subject can take is
restricted b) a number of factors including pelvic rotation. knee extension and body progression over the
anklc rocker, a. described by Rose et al. (61. It 1s less
apparent that limited extension of the hip produces a
reduction in itep length of the other leg and hcncc of
stride length (6) With a slight equinus and kick of
hypercxtension a: the knee the step might be lengthened
to aliow a prxnary heel-strike. In other cases with more
marked eyumus. the disadvantage of long step\, in
terms of reduced stability, may outweigh this advantage.
Most of the muscular dystropy children in this study
had combinations of mild deformities at the hip
(maximum 5 1- knee (maximum 10 ) and ankle
(maximurn 10 1. Logically these would all have an additive effect in reducing their maximum stride length
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VARIATIONS OF GAIT PARAMETERS IN DUCHENNE MUSCULAR DYSTROPHY
With short strides, the centre of mass is less displaced
both in the vertical and in the horizontal direction.
Short strides are therefore, in any case, less tiresome
and less risky than long strides (7). They are an adaptive
change to the disease that a Duchenne muscular dystrophy boy instinctively makes.
Further, Kirtley et al. (8) showed a significant correlation between increasing walking speed and increasing
size of knee flexing moment in the first half of the stance
phase in normal subjects. Since quadriceps weakness is
a feature of Duchenne muscular dystrophy boys, this
will have a limiting effect upon the length of their stride.
Indeed, we know that they learn to control and reduce
the flexing moments around the knee by adopting an
equinus gait (9). Hence, not only are there possible limitations to their stride length but also their walking
speed is governed by the degree of control they can
produce with their weak muscles. It seems likely that
their mode of walking is a compromise between energy
consumption and dynamic stability.
With time, increasing stiffness and joint contractures
will lead to further changes in stride length and velocity
adaptations until the stage is reached when the child
can no longer walk without intervention, either in the
form of surgery and/or orthosis. The possibility exists,
therefore, that monitoring these changing dynamic
aspects of gait in boys with Duchenne muscular dystrophy will provide an indication of how near they are
to losing their ability to walk.
7 CONCLUSION
Children with Duchenne muscular dystrophy have gait
parameters that differ from the normal. They are unable
243
to achieve similar velocities due to physical limitations
of stride length and this is measurable by the simple
method described.
The long-term follow-up of stride length and cadence
could provide a simple means of monitoring the disease
progression in an out-patient clinic. Assessment of
various treatments, whether orthotic or surgical,
medical or physiotherapy, can then be studied and the
effects measured.
REFERENCES
Siegel, I. M., Miller, J. E. and Ray, R. D. Subcutaneous lower limb
tenotomy in the treatment of pseudohypertrophic muscular dystrophy. J. Bone J t Surg., 1968,50A(7), 1437-1443.
Spencer, G. E. and Vignos, P. J. Bracing for ambulation in childhood progressive muscular dystrophy. J . Bone J t Surg., 1962,
44A(2), 234242.
Inman, V. T., Ralston, H. J. and Todd, R. F. Human walking, 1981
(Williams and Wilkins, Baltimore and London).
Charteris, J., Wall, J. C. and Nottrodt, J. W. Pliocene hominid
gait: new interpretations based on available footprint data from
laetoli. Am. 1.Phys. Anthrop., 1982,58, 133-144.
Alexander, R. McN. Stride length and speed for adults, children
and fossil hominids. Am. J . Phys. Anthrop., 1984, 63, 23-27.
Rose, G. K., Butler, P. and Stallard, J. Gait. Principles, biomechanics
and assessment, 1982, p. 55 (ORLAU Publishing, Oswestry,
Shropshire).
Larsson, Lars-Erik Neurocontrol of gait in progressive neuromuscular diseases. In Recent achievements in restoratiue neurology,
Vol. 2, Progressive neurornusculur diseases (Eds Dimitrijevic,
Kakulas and Vrbova), 1986 (Karger, Basel).
Kirtley, C., Jefferson, R. and Whittle, M. The effect of walking
speed on gait parameters. Annual report of the OTford Orthopaedic
Engineering Centre, December 1984, pp. 14-16.
Khodadadeh, S., McClelland, M. R., Patrick, J. H., Edwards, R. H.
T. and Evans, G . A. Knee moments in Duchenne muscular dystrophy. The Lancet, 6 September 1986, pp. 544-545.
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