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Original Article

Interrater Reliability of Modified Ashworth Scale

and Modified Tardieu Scale in Children With

Spastic Cerebral Palsy

Winnie Ka Ling Yam, FHKAM (Paediatrics); Milan So Mei Leung, PDipPT

ABSTRACT

Resistance to passive movement in children with spastic cerebral palsy was assessed by two raters using the Modified

Ashworth Scale and the Modified Tardieu Scale. Four muscle groups in the lower limbs were tested using a standardized

procedure. Interrater reliability of the scales was evaluated by the intraclass correlation coefficient. Seventeen children,

with a mean age of 7 years 9 months, were included. Two children were rated twice. The intraclass correlation

coefficients of both scales were low and did not reach the acceptable limit of 0.75. Caution should be used when these

scales are applied. (J Child Neurol 2006;21:1031–1035; DOI 10.2310/7010.2006.00222).

Received May 7, 2005. Received revised Sept 26, 2005, and Nov 13, 2005. Accepted for publication Dec 11, 2005.

From the Departments of Paediatrics and Adolescent Medicine (Dr Yam), and Physiotherapy (Ms Leung) Alice Ho Miu Ling Nethersole Hospital, Hong Kong SAR, China.

Some of our results were presented at the 2004 annual meeting of the Society of Hong Kong Child Neurology and Developmental Paediatrics, Hong Kong and at the 2004 annual meeting of the Hong Kong Paediatric Society, Hong Kong.

Address correspondence to Dr Winnie Ka Ling Yam, Department of Paediatrics and Adolescent Medicine, Alice Ho Miu Ling Nethersole Hospital, Chuen On Road, Tai Po, Hong Kong SAR, China. Tel: 852-2689- 2286; fax: 852-2689-2096; e-mail: [email protected].

Saccadic Adaptation in Children / Salman et al 1031

Numerous modalities of treatment to reduce muscle spasticity

have arisen in recent years. To assess the outcome of these

interventions, accurate and reliable instruments should be used.

The Modified Ashworth Scale and the Modified Tardieu Scale are

two clinical rating scales that are often used for outcome

measurement (Table 1). 1,2

Traditionally, the Modified Ashworth

Scale was widely used, but the Modified Tardieu Scale was

recently proposed as a more reliable clinical tool. 2

The reliability

of the Modified Ashworth Scale has been tested in adults with

stroke, intracranial lesions, and traumatic brain injury. 1,3–5

The

reliability of the Modified Tardieu Scale in adults has not been

reported. For the pediatric population, data on the reliability of

either scale are even more limited and inconclusive. 6–9

Boyd et al

determined the intrarater reliability of these scales in the context

of a randomized clinical trial of botulinum toxin in children. 2

Adductor tone (with the hips and knees flexed and then with the

hips and knees extended) of the placebo group was assessed on

two occasions. Comparison was made between the mean scores

of the Modified Ashworth Scale and the Modified Tardieu Scale

on 16 limbs. No statistical significance was found between the

two means. The authors concluded that there was good

intrarater reliability. Fosang et al tested the reliability of the

two scales on 18 children with cerebral palsy. 7

The hip adductors

(with the hip and the knee in extension), hamstrings, and

gastrocnemius were tested. The interrater reliability, calculated

by the intraclass correlation coefficient, ranged between 0.27

and 0.56 for the Modified Ashworth Scale and 0.55 and 0.74

for the Modified Tardieu Scale. Test–retest reliability, calculated

by the intraclass correlation coefficient, ranged between 0.21

and 0.82 for the Modified Ashworth Scale and 0.38 and 0.93 for

the Modified Tardieu Scale. Using the Wartenberg pendulum

test on the quadriceps of 20 spastic diplegic children, Nordmark

and Andersson showed that there was no significant correla-

tion of parameters in the pendulum test with the Modified

Ashworth Scale. 8

Using three-dimensional movement analysis,

Mackey et al found poor intrarater reliability of the Modified

Tardieu Scale in assessing the biceps of 10 hemiplegic children. 9

In summary, the results on the reliability of both scales remain

equivocal and there is a need for further study to address this

important issue.

Our study aimed at investigating the interrater reliability of

the Modified Ashworth Scale and the Modified Tardieu Scale in

children with cerebral palsy. The importance of our study rested

in providing an opportunity to examine whether Fosang et al’s

results 7

could be replicated. It had been shown that the reliability

of the Modified Ashworth Scale varied between different patient

groups, between different muscle groups, and between different

testing protocols; therefore, our study would clarify whether the

reliability of the Modified Tardieu Scale showed similar

findings. 1,3–5

In contrast to Fonsang et al’s protocol, 7

we believed that the

hip adductors and ankle plantar flexors should be tested in two

positions owing to their anatomic consideration. With the hips

and knees extended, spasticity contributed by the adductor

magnus, adductor longus, adductor brevis, gracilis, and medial

hamstrings would be assessed. With the hips extended and the

knees flexed, contribution from the gracilis and medial ham-

strings could be distinguished from the rest of the hip adductors.

If spasticity of the gracilis and medial hamstrings was present,

the hips could not be abducted to a wider range than that

achieved with the knees extended. For the ankle plantar flexors,

spasticity contributed by the gastrocnemius would be assessed

when the knee was extended, whereas the soleus would be

assessed when the knee was flexed. The gracilis, medial

Table 1. Modified Ashworth Scale and Modified Tardieu Scale

Grade Description

Modified Ashworth Scale 0 No increase in muscle tone 1 Slight increase in muscle tone, manifested by a catch, followed by minimal resistance at the end of range of motion when the part

is moved in flexion or extension/abduction or adduction, etc 1+ Slight increase in muscle tone, manifested by a catch, followed by minimal resistance throughout the remainder (less than half) of

the range of motion 2 More marked increase in muscle tone through most of the range of motion, but the affected part is easily moved 3 Considerable increase in muscle tone; passive movement is difficult 4 Affected part is rigid in flexion or extension (eg, abduction or adduction)

Modified Tardieu Scale Quality of muscle reaction 0 No resistance throughout the course of the passive movement 1 Slight resistance through the course of passive movement; no clear ‘‘catch’’ at a precise angle 2 Clear catch at a precise angle, interrupting the passive movement, followed by release 3 Fatiguable clonus (, 10 s when maintaining the pressure) appearing at a precise angle 4 Unfatiguable clonus (.10 s when maintaining the pressure) at a precise angle 5 Joint immovable

Joint angles Measure relative to the position of minimal stretch of the muscle (corresponding to angle zero) for all joints except the hip, where it is relative

to the resting anatomic position (eg, angle zero corresponds to the ankle at 90 deg and the hip at midline) R1 Angle of muscle reaction R2 Angle of full range of motion (passive range of motion)

Definition of velocities used V1 As slow as possible (slower than the natural drop of the limb segment under gravity) V2 Speed of the limb segment falling under gravity V3 As fast as possible (faster than the rate of the natural drop of the limb segment under gravity)

Adapted from Bohannon and Smith and Boyd et al.1,2

1032 Journal of Child Neurology / Volume 21, Number 12, December 2006

hamstrings, and gastrocnemius muscles crossed two joints,

whereas the other hip adductors and soleus muscles crossed

only one joint. Muscles that crossed two joints were particularly

prone to development of spasticity and contracture.

Differentiating the contributions of spasticity from the different

muscle groups enabled subsequent interventions to target the

appropriate muscles. Therefore, we believed that these muscles

groups should be tested individually.

Fosang et al tested the interrater reliability of the Modified

Ashworth Scale score, the Modified Tardieu Scale score, and R2.

We believed that the interrater reliability of R1 and R2 2 R1

should also be examined because of their important clinical

implications. It had been proposed that when the muscle was

stretched to the R1 position, muscle spasticity came into action.

When the muscle was stretched to the R2 position, the

viscoelasticity of the soft tissues and joints and the component

of contracture might come into play. Thus, the R2 2 R1 value

indicated the level of spasticity in the joint. 9

Botulinum toxin

injection might be useful in children with a large R2 2 R1 because

there was a higher degree of spasticity. On the other hand, surgical

intervention might be more appropriate in those with a small R2 2

R1 because of the higher degree of contracture.

The reasons for the low reliability in other studies included

low variability or a limited range of scores, extraneous factors,

and scoring methods. 4

In designing our study protocol, these

factors were specifically attended to so as to minimize the effects.

METHOD

Participants

Children were recruited from the departments of Physiotherapy and

Paediatrics and Adolescent Medicine in Alice Ho Miu Ling Nethersole

Hospital, Hong Kong. Convenience sampling was used. Children with

spastic cerebral palsy were included. Different topographic distributions

(hemiplegia, diplegia, monoplegia, triplegia, and quadriplegia) of cerebral

palsy were allowed. This ensured that a wide range of muscle tone was

included for evaluation of both ends of the scales. Children were excluded if

they suffered from other types of cerebral palsy (such as dyskinetic, ataxic,

and mixed types) or if parental consent could not be obtained. The Ethics

Committee of the Hospital Authority, Hong Kong, approved the study.

Raters

Two raters, including a pediatrician (rater 1) and a physiotherapist (rater

2), scored each child. Both raters had more than 10 years of experience in

handling children with cerebral palsy and were familiar with both scales.

To ensure adherence to the methodology, a meeting was held before

commencement of the study to clarify the procedure and to distribute

written guidelines. The two scales and instructions were also included in

the recording form so that raters might refer to them. However, no

extensive training or standardization was done to resemble the usual

clinical practice in which the scales would be used.

Instrument and Testing Position

The Modified Ashworth Scale and the Modified Tardieu Scale were used.

The Modified Ashworth Scale is a 6-point rating scale for gauging muscle

resistance to passive movement. 10

The Modified Tardieu Scale is another

6-point rating scale for describing the quality of muscle reaction. In

addition, two angles (R1 and R2) were determined in the Modified

Tardieu Scale. The angle of muscle reaction (R1) was defined as the point

in the joint range in which a velocity-dependent ‘‘catch’’ or clonus was felt

during a quick stretch of the muscle. The angle of full range of motion

(R2) was equivalent to the passive range of motion. The difference

between the two angles (R2 2 R1) represented the dynamic component. 9

Both R1 and R2 were measured relative to the neutral position or resting

anatomic position of the joints. The neutral position at the ankle joint

(corresponding to angle zero) was the position with the ankle at 90

degrees to the lower leg. A negative value would be given if the ankle

could not be dorsiflexed beyond angle zero. The resting anatomic

position at the hip joint was defined as the thigh being at zero degrees to

the trunk. A negative value would be given if the hip could not be

abducted beyond the resting position. The limbs were moved as fast as

possible in obtaining R1 and moved slowly to its end range in obtaining

R2.

Four muscle groups in each lower limb were tested. These included

hip adductors with the knee extended, hip adductors with the knee

flexed, ankle plantar flexors with the knee extended, and ankle plantar

flexors with the knee flexed. Starting positions and velocities adopted in

testing the muscles were standardized (Table 2). The head of the child

was maintained neutral to avoid eliciting asymmetric tonic neck reflex.

This abnormal reflex, which was common in children with cerebral palsy,

might interfere with the muscle tone. The adductors were tested with

both hips and knees in full extension. Then the adductors were tested

with the hips in full extension and the knees in 90-degree flexion. The legs

were moved from the neutral position to the maximal abducted position

without any concomitant pelvic movement. To minimize any pelvic

movement, both lower limbs were moved together. The ankle plantar

flexors with the knee extended were tested by moving the ankle from

maximal plantar flexion to maximal dorsiflexion. The ankle plantar

flexors were tested again with the knee flexed. The hindfoot was

maintained in the neutral position to avoid calcaneal valgus or varus. The

raters moved the limbs three times to grade the tone and the joint ranges.

Data on the Modified Ashworth Scale score, Modified Tardieu Scale

score, and two Modified Tardieu Scale angles (R1 and R2) were collected

for each muscle group. Both lower limbs of each child were assessed.

Procedure

When the children came for their physical therapy session, they were

invited to participate in the study if they fulfilled the inclusion criteria.

Assessment was done by the two raters during the same 2-hour physical

therapy session of the child. The raters performed the assessment

independently, and there was at least a 5-minute rest between the two

assessments. The order of assessment and the sequence of muscle testing

by the two raters were random. Testing was performed when the child

Table 2. Starting Joint Positions and Velocities

Muscle Group Starting Joint Position Velocity

Hip adductors, knee flexed Hips extended, knees flexed by 90 deg V3 for R1 Hip adductors, knee extended Hips and knees extended V1 for R2 Ankle plantar flexors, knee extended Knee fully extended Ankle plantar flexors, knee flexed Knee flexed by 90 deg

Interrater Reliability of Modified Ashworth and Tardieu Scales in Spastic Cerebral Palsy / Yam and Leung 1033

was emotionally stable because muscle tone might be affected by fear or

anxiety. The results were entered into a separate recording sheet for each

rater so that each rater determined the result without being aware of the

results from the other rater.

Data Analysis

Measurements by different raters on the same child at the same time

were used to determine the interrater reliability. The interrater reliability

was calculated for the Modified Ashworth Scale scores, Modified Tardieu

Scale scores, and R1, R2, and R2 2 R1. For nominal and ordinal data,

such as the Modified Ashworth Scale score and the Modified Tardieu

Scale score, reliability should be tested with kappa statistics. Quadratic

weighing for kappa statistics was commonly recommended. When such a

weighting system was used, the weighted kappa would be equivalent to

the intraclass correlation coefficient. 11

For continuous data, such as R1,

R2, and R2 2 R1, the reliability should be tested with the intraclass

correlation coefficient. 12

Therefore, the intraclass correlation coefficient

was chosen as the test statistic. Data were analyzed using SPSS (SPSS

Inc, Chicago, IL). The two-way mixed-consistency model of intraclass

correlation coefficient was used. The intraclass correlation coefficient

reflected both the degree of correspondence and the degree of agreement

between the ratings. The closer the intraclass correlation coefficient

result was to 1, the better the agreement was between raters. Good

reliability was generally defined as an intraclass correlation coefficient $

0.75. 12

RESULTS

Seventeen children with a mean age of 7 years 9 months (range 3

years 6 months–15 years 11 months) were included. Seven of the

children were male, and 10 were female. Eleven children had

spastic diplegic cerebral palsy, two had left hemiplegic cerebral

palsy, and four had triplegic cerebral palsy. Nine of the children

belonged to level I in the Gross Motor Function Classification

System, five to level II, and three to level III. Two children were

rated twice. These second ratings were done 1 week after the

first and after botulinum toxin had been given. Because the

current study involved interrater reliability only, the second

ratings for these two children were also included for analysis.

The Modified Ashworth Scale and Modified Tardieu Scale scores

were distributed across the entire scales (Table 3). Exception

was for the hip adductors, for which the scores were

concentrated near the lower end. No child reported any pain

during the testing procedure.

The results for the interrater reliability are shown in Table 4.

Intraclass correlation coefficients for the Modified Ashworth

Scale ranged between 0.41 and 0.73, whereas those for the

Modified Tardieu Scale ranged between 0.22 and 0.71. Intraclass

correlation coefficients for R1 ranged between 0.37 and 0.71, for

R2 between 0.17 and 0.74, and for R2 2 R1 between 0.40 and 0.69.

DISCUSSION

Although Fosang et al concluded that the interrater reliability of

the Modified Tardieu Scale was better than that of the Modified

Ashworth Scale, none of the interrater intraclass correlation

coefficients (of the Modified Ashworth Scale score or the

Modified Tardieu Scale score) in their study reached the

acceptable level of 0.75. 7

Our results showed a similar finding.

The interrater intraclass correlation coefficients of passive range

of motion (equivalent to R2 in our study) ranged between 0.63

and 0.78 for hip abduction, popliteal angle, and ankle dorsiflex-

ion in Fosang et al’s study. We did not test the popliteal angle in

our study, but the interrater intraclass correlation coefficients of

R1, R2, and R2 2 R1 for hip adductors or ankle plantar flexors

did not reach 0.75.

Some common reasons for low interrater reliability were

specifically addressed in our study. Our results in Table 3 did not

support a limited range of scores as a reason for low reliability.

Extraneous factors, such as the emotional status of the child or

pain, could contribute to the variability. 10

The emotional

instability of the child had been eliminated by specific instruc-

tions in our testing procedure, and no child reported any pain. To

improve scoring methods, strict standardization of the position

and procedure was used in our study. The starting limb position,

neutral positioning of the head, and the number and velocity of

testing movement were specified to reduce variability arising

from reflex excitability and viscoelasticity of soft tissues and

joints. 10

However, it would be interesting to undertake further

studies to see if another standardization (eg, preceding activities,

interval between testing movements, force used, external

standardization with three-dimensional movement analysis)

Table 3. Score Distribution of the Modified Ashworth Scale and the Modified Tardieu Scale

Grade

Hip Add, KF Hip Add, KE Ankle PF, KE Ankle PF, KF

Rater 1 Rater 2 Rater 1 Rater 2 Rater 1 Rater 2 Rater 1 Rater 2

Modified Ashworth Scale 0 20 17 19 15 13 18 7 10 1 4 6 2 7 1 3 5 14 1+ 1 2 0 0 1 0 3 0 2 5 11 5 14 3 2 10 3 3 8 2 12 2 9 8 10 9 4 0 0 0 0 11 7 3 2

Modified Tardieu Scale 0 20 17 19 15 14 14 8 10 1 2 8 0 11 0 5 1 1 2 16 13 19 12 11 10 14 16 3 0 0 0 0 3 0 11 7 4 0 0 0 0 1 6 4 4 5 0 0 0 0 9 3 0 0

Hip Add 5 hip adductors; KE 5 knee extended; KF 5 knee flexed; PF 5 plantar flexors.

1034 Journal of Child Neurology / Volume 21, Number 12, December 2006

might improve the reliability. 4,13

To resemble the clinical setting,

we distributed written guidelines and included the scales and

instructions in the recording forms. Further studies should be

performed to identify what type of training to raters might

increase the interrater reliability of the scale.

In summary, the interrater reliability of the Modified

Ashworth Scale and the Modified Tardieu Scale was low.

Caution should be used in applying these scales in the

assessment of lower limb muscle tone for children with cerebral

palsy. As these scales remained important in the clinical setting,

further studies should be undertaken to identify ways to improve

their reliability. These scales might remain useful if intrarater

reliability could be documented. 10

References

1. Bohannon RW, Smith MB: Interrater reliability of a modified Ashworth scale of muscle spasticity. Phys Ther 1987;67:206–207.

2. Boyd RN, Barwood SA, Ballieu CE, Granham HK: Validity of a clinical measure of spasticity in children with cerebral palsy in a double-blinded randomized controlled clinical trial, abstract. Dev Med Child Neurol 1998;40(Suppl 78):7.

3. Allison SC, Abraham LD, Petersen CL: Reliability of the Modified Ashworth Scale in the assessment of plantarflexor muscle spasticity in patients with traumatic brain injury. Int J Rehabil Res 1996;19:67–78.

4. Blackburn M, van Vliet P, Mockett SP: Reliability of measure- ments obtained with the Modified Ashworth Scale in the lower extremities of people with stroke. Phys Ther 2002;82:25–34.

5. Gregson JM, Leathley M, Moore AP, et al: Reliability of the Tone Assessment Scale and the Modified Ashworth Scale as clinical

tools for assessing poststroke spasticity. Arch Phys Med Rehabil 1999;80:1013–1016.

6. Boyd RN, Graham HK: Objective measurement of clinical findings in the use of botulinum toxin type A for the management of children with cerebral palsy. Eur J Neurol 1999;6(Suppl 4): S23–S35.

7. Fosang AL, Galea MP, McCoy AT, et al: Measures of muscle and joint performance in the lower limb of children with cerebral palsy. Dev Med Child Neurol 2003;45:664–670.

8. Nordmark E, Andersson G: Wartenberg pendulum test: Objective quantification of muscle tone in children with spastic diplegia undergoing selective dorsal rhizotomy. Dev Med Child Neurol 2002;44:26–33.

9. Mackey AH, Walt SE, Lobb G, Stoot NS: Intraobserver reliability of the Modified Tardieu Scale in the upper limb of children with hemiplegia. Dev Med Child Neurol 2004;46: 267–272.

10. Pandyan AD, Johnson GR, Price CIM, et al: A review of the properties and limitations of the Ashworth and Modified Ashworth scales as measures of spasticity. Clin Rehabil 1999; 13:373–383.

11. Streiner DL, Norman GR: Reliability, in Streiner DL, Norman GR (eds): Health Measurement Scales: A Practical Guide to Their Development and Use, New York, Oxford University Press, 1991, 79–96.

12. Portney LG, Watkins MP: Statistical measures of reliability, in Portney LG, Watkins MP (eds): Foundations of Clinical Research: Applications to Practice, Upper Saddle River, NJ, Prentice-Hall, 2000, 557–586.

13. Smith AW, Jamshidi M, Lo SK: Clinical measurement of muscle tone using a velocity-corrected modified Ashworth scale. Am J Phys Med Rehabil 2002;81:202–206.

Table 4. Interrater Agreement on the Modified Ashworth Scale and the Modified Tardieu Scale

Intraclass Correlation Coefficient (95% Confidence Interval)

Muscle Group Modified Ashworth Scale Modified Tardieu Scale R1 R2 R2 2 R1

Hip adductors, knee flexed

0.41 (0.11–0.64) 0.66 (0.44–0.81) 0.71 (0.51–0.84) 0.74 (0.55–0.85) 0.53 (0.26–0.72)

Hip adductors, knee extended

0.73 (0.54–0.85) 0.71 (0.51–0.84) 0.71 (0.50–0.84) 0.53 (0.25–0.72) 0.69 (0.48–0.83)

Ankle plantar flexors, knee extended

0.56 (0.30–0.74) 0.22 (20.11–0.50) 0.55 (0.29–0.74) 0.17 (20.15–0.46) 0.40 (0.09–0.63)

Ankle plantar flexors, knee flexed

0.46 (0.16–0.67) 0.44 (0.15–0.67) 0.37 (0.06–0.61) 0.36 (0.05–0.61) 0.53 (0.26–0.73)

R1 5 angle of muscle reaction; R2 5 angle of full range of motion.

Interrater Reliability of Modified Ashworth and Tardieu Scales in Spastic Cerebral Palsy / Yam and Leung 1035