Reliability of the Modified Ashworth Scale in the assessment of plantar flexor muscle spasticity in patients with traumatic brain injury

Although the Modified Ashworth Scale (MAS) is commonly used to assess the severity of muscle spasticity for ankle plantarflexors, its reliability has only been established for elbow muscles. Interrater reliability, intrarater reliability and temporal (between-days) reliability were examined in this study. Also, interrater reliability for use of the scale with plantarflexors was compared with reported results from the measurement of elbow flexors. Thirty adult volunteers with traumatic brain injuries participated. There were 20 men and 10 women; the mean age was 28.3 years (SD = 10.8). Two physical therapists used the MAS to score the subjects independently Measurements were repeated to yield multiple scores for intrarater reliability assessment. Twenty-one of the subjects returned individually on separate days to be measured again, so that temporal reliability could be assessed. Spearman's correlation coefficients were 0.73 for interrater reliability 0.74 and 0.55 for intrarater reliability, and 0.82 for temporal reliability. Overall, reliability of the MAS for assessing plantarflexor spasticity in patients with traumatic brain injury was found to be minimally adequate to support its continued use. However, interrater reliability was less than that which has been reported for elbow flexors, and intrarater reliability findings were mixed.