Quantitative Analysis of Intrinsic Muscle Stiffness in Biceps Brachii of Post-stroke Patients

Introduction. Due to the subjective characteristic of the scales used for evaluation of spasticity, the interest in the tools that can objectively quantify the possible altered components in the spastic muscles have grown. A candidate parameter for muscle stiffness assessment is the shear modulus (mu), quantified using the supersonic shear imaging (SSI). The objective of study is to compare the measure of stiffness estimated by mu in the biceps brachii of the spastic upper limb and of the contralateral side as a control, in patients with chronic stroke. Methods. A cross-sectional study was carried out with patients after stroke (n = 10, mean age 51.7 +/- 12.9 years, 6 men). All images were acquired with an Aixplorer (R) V.9 ultrasound device with the elbow at full extension and the probe over the biceps brachii of both sides. After verifying the normal distribution, the paired t-test parametric test was applied (p < 0.05). Results. All volunteers but one presented larger mu values in the spastic upper limb compared to control. The paired t-test revealed a significant difference, when the average of the measurements where compared (spastic upper limb = 27.04 kPa; control = 14.81 kPa; p = 0.004). Conclusions. Our results, suggest that the mu parameter obtained through SSI elastography is potentially related to muscle stiffness, being a quantitative measure of spasticity.