The influence of contractures and variation in measurement stretching velocity on the reliability of the Modified Ashworth Scale in patients with severe brain injury

Objective: To determine the influence of contractures and different stretching velocities on the reliability of the Modified Ashworth Scale (MAS) in patients with severe brain injury and impaired consciousness. Design: Cross-section observational study. Setting: A rehabilitation centre for adult persons with neurological disorders. Subjects: Fifty patients with impaired consciousness due to severe cerebral damage of various aetiologies. Measurement protocol: Three experienced and trained medical professionals rated each patient in a randomized order once daily for two consecutive days. Shoulder, elbow, wrist, knee and ankle spasticity were assessed by the use of the MAS with different stretching velocities. The presence of contractures was assessed by a goniometer. Main outcome measures: Retest and inter-rater reliability (k(w) = weighted kappa) of the MAS. Results: The retest reliability of the MAS was good (shoulder joints (k(w) 0.74), elbow joints (k(w) 0.74), wrist joints (k(w) 0.72), knee joints (k(w) 0.72), ankle joints (k(w) 0.77)) and the inter-rater reliability was moderate (shoulder joints (k(w) 0.49), elbow joints (k(w) 0.52), wrist joints (k(w) 0.51), knee joints (k(w) 0.54) ankle joints (k(w) 0.49)). The presence of contractures significantly influenced the reliability of MAS in shoulder and wrist joints. No influence of stretching velocity on the reliability of the MAS was found. Conclusion: In patients with impaired consciousness due to severe brain injury the MAS has good retest, but only limited inter-rater, reliability. The presence of contractures may influence reliability of the MAS, but stretching velocity does not.