Assessing muscle compliance in stroke with the Myotonometer

Background This study explores changes of the intrinsic biomechanical property in the biceps brachii muscle after a hemispheric stroke using the Myotonometry technique. Methods Nineteen subjects with chronic hemiplegia participated in the study. Myotonometer was used to measure tissue displacement when compression force was applied at 8 levels from 2.45 N to 19.6 N. Muscle displacement and compliance were determined and averaged over multiple trials. Findings Statistical analysis indicated a significant decrease in muscle displacement and compliance in the spastic muscles compared with the contralateral side (muscle displacements: spastic: 4.51 (0.31) mm, contralateral: 5.74 (0.37) mm, p < 0.005; compliance: spastic: 0.17 (0.011) mm/N, contralateral: 0.22 (0.014) mm/N, p < 0.005). Correlation analysis, however, did not show any association between clinical assessments and myotonometric measurement (p > 0.1). Interpretation Alterations of muscle compliance in the spastic side reflect changes in the contractile or intrinsic mechanical properties after a stroke. Findings of the study have demonstrated high sensitivity and effectiveness of the Myotonometer in assessing muscle compliance changes.