Interrater Reliability of
a
Modified Ashworth Scale of
Muscle Spasticity
RICHARD W. BOHANNON
and MELISSA B. SMITH
We undertook this investigation to determine the interrater reliability of manual
tests of elbow flexor muscle spasticity graded on a modified Ashworth scale. We
each independently graded the elbow flexor muscle spasticity of 30 patients with
intracranial lesions. We agreed on 86.7% of our ratings. The Kendall's tau
correlation between our grades was .847 (p < .001). Thus, the relationship
between the raters' judgments was significant and the reliability was good.
Although the results were limited to the elbow flexor muscle group, we believe
them to be positive enough to encourage further trials of the modified Ashworth
scale for grading spasticity.
Key
Words:
Elbow,
Muscle
spasticity,
Physical
therapy.
Spasticity, defined herein
as a
velocity-dependent response
of muscle
to
passive stretching,1,2
may be
among
the
most
commonly acknowledged sequelae
of
central nervous system
lesions.3 Although
the
role actually played
by
spasticity
in
motor dysfunction4 may
be
less than that suggested
by
some
authors,5,6 antagonistic muscle spasticity
can
limit
the
force
demonstrated
by an
agonist muscle during voluntary move-
ment.7,8
One
of
the methods that has been proposed
for
measuring
muscle spasticity involves manually moving
a
limb through
the range
of
motion
to
passively stretch specific muscle
groups. Ashworth has described
a
five-point ordinal scale
for
grading the resistance encountered during such passive muscle
stretching.9 Ashworth's scale grades spasticity
as
follows:
0 =
normal muscle tone;
1 =
slight increase
in
muscle tone,
"catch" when limb moved;
2 =
more marked increase
in
muscle tone, but limb easily
flexed;
3
=
considerable increase
in musle tone;
and 4 =
limb rigid
in
flexion
or
extension.
As
Ashworth's scale assigns grades
to a
manually determined
resistance
of
muscle
to
passive stretching,
it
measures spas-
ticity as defined herein. The scale, therefore, has face validity,
in addition
to
some of the other characteristics recommended
for ordinal scales by MacKenzie and Charlson.10 Our previous
experience with
the
scale revealed that many
of
our patients
with hemiplegia demonstrated levels
of
spasticity defined
by
the grades at the lower end of the Ashworth scale and that the
Ashworth grade
of
" 1"
was
indiscrete.
To
render
the
scale
more discrete, we added the grade
"
1
+" and slightly modified
the definitions (Tab.
1).
These modifications resulted
in a
scale that conforms even more precisely than
the
Ashworth
scale
to
the guidelines
of
MacKenzie and Charlson.10
Although Ashworth's subjective scale
has
been used clini-
cally
to
examine
the
efficacy
of
Lioresal®*11
and of
electrical
stimulation12
in
the treatment
of
spasticity, we were unaware
of
any
studies that verify
the
reliability
of
manual tests
of
spasticity graded with the Ashworth scale. Lacking such veri-
fication and wishing to test the reliability
of
our own modifi-
cation
of
the scale, we undertook this study. The purpose
of
this study
was to
determine
the
interrater reliability
of a
manual test
of
elbow
flexor muscle group spasticity using the
modified Ashworth scale.
Our
expectation was that
two
cli-
nicians,
who
regularly
use the
test, could measure spasticity
reliably using the modified scale.
METHOD
Patients
Thirty patients
(17
men and
13
women) participated in this
study. Their mean
age
was 59.3
±
17.6 years (range,
19-81
years).
All of
the patients
had
lesions involving
the
central
nervous system.
One
patient
had
multiple sclerosis,
5 had
closed head injuries,
and 24 had
cerebrovascular accidents.
The paretic
or
weaker side
of
each patient (as determined by
hand-held dynamometry) was tested. Consequently,
the
left
side was tested
in
half
of
the patients,
and the
right side was
tested
in
the other
half.
All rehabilitation patients were tested
routinely during their initial assessment;
the
patients
who
participated
in
this study were the first 30 patients who could
follow instructions adequately.
All of the
patients granted
informed consent before testing.
Procedure
Each patient was tested first
by
his
or
her therapist (one
of
the authors)
and
then
by the
other author. Testing was con-
ducted with each patient positioned supine
on a
padded
mat
table.
We
extended
the
patient's elbow from
a
position
of
maximal possible flexion
to
maximal possible extension over
a duration
of
about
one
second (by counting "one thousand
Mr. Bohannon
is
Chief,
Department
of
Physical Therapy, Southeastern
Regional Rehabilitation Center, Cape Fear Valley Medical Center,
PO Box
2000,
Owen
Dr,
Fayetteville,
NC
28302 (USA).
Ms.
Smith is Senior Physical Therapist, Southeastern Regional Rehabilitation
Center.
This article
was
submitted November
14, 1985; was
with
the
authors
for
revision four weeks;
and was
accepted April
30, 1986.
Potential Conflict
of
Interest:
4.
* Geigy Pharmaceuticals,
Div of
CIBA-GEIGY Corp, Ardsley,
NY
10502.
206 PHYSICAL THERAPY
