• Akihiro Kawano, Taiichiro Yanagizono, Ichiro Kadouchi, Tetsuya Umezaki, and Etsuo Chosa.
• Division of Orthopedic Surgery, Miyazaki Prefecture Center for Disabled Children, Miyazaki 889-1601, Japan. Electronic address: a-kawano@wc4.so-net.ne.jp.
• J Orthop Sci. 2018 Mar 1; 23 (2): 389-393.

BackgroundBotulinum toxin A treatment involves injecting botulinum toxin A to relax muscle spasticity. Using ultrasonography, this study examined changes in the muscle architecture before and after treatment to evaluate the influence of botulinum toxin A injection on muscles.MethodsThe participants included 18 children (mean age, 6.2 years) with cerebral palsy who were treated with botulinum toxin A for lower extremity spasticity and 27 healthy children (mean age, 6.4 years) as a control group. In all cases, botulinum toxin A was injected into the gastrocnemius muscle. The muscle length, muscle width, and pennation angle (which indicates the degree of muscle fiber tone), were measured using B-mode ultrasonography before and 12 weeks after injection.ResultsThe muscle length and muscle width were shorter in the cerebral palsy group than in the control group. The pennation angle in the cerebral palsy group significantly decreased after injection from 28.2 ± 3.6° to 25.8 ± 2.5° in the resting position of the ankle and from 18.6 ± 2.8° to 15.9 ± 1.7° in the maximum dorsiflexion position of the ankle. In the control group, the pennation angle was 25.9 ± 3.2° in the resting position of the ankle and 15.1 ± 2.5° in the maximum dorsiflexion position of the ankle. The rate of increase of fascicle length during passive movement from the resting position of the ankle to the maximum dorsiflexion position was 143.9% in the cerebral palsy group, which was significantly less than the value of 157.7% in the control group. After botulinum toxin A treatment, the rate of increase of fascicle length in the cerebral palsy group increased to 155.1%.ConclusionsThe decrease in the pennation angle after botulinum toxin A treatment is considered to be the result of a reduction of spasticity and subsequent structural changes in flaccid muscle fibers.Copyright © 2017 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

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