Diagnosing Muscle Atrophy by Use of a Comprehensive Method of Assessing the Elastic Properties of Muscle During Passive Stretching.

The purpose of this study was to apply a new method for quantitatively assessing atrophied muscles by use of sonoelastography. B-mode sonography and shear-wave elastography of the gastrocnemius muscle (GM) were performed on 12 patients and 32 healthy control volunteers during passive stretching induced by ankle rotation from 40° plantar flexion to 30° dorsiflexion. The GM length and corresponding elastic moduli were measured consecutively per frame. The elastic modulus-length curve was created by plotting the elastic modulus against the GM length during passive stretching. Three physiologically significant parameters-slack elasticity modulus (), slack length (), and passive elastic coefficient ()-were estimated from the measured elasticity modulus-length curve to quantify the elastic properties of the GM. All results showed a smooth exponential curve. In the state of relaxation, atrophied GM was softer than GM of healthy control subjects. However, when the muscles were passively stretched from a state of slack to tension, was significantly greater for the patients with atrophied GMs than for the control subjects. Furthermore, the diagnostic accuracy of for muscle atrophy was greater than that of . Increased elastic stiffness may be considered a positive finding for the characterization of muscle atrophy. Because of its high diagnostic accuracy and reproducibility, the elastic modulus-length curve can provide new insights into the diagnosis of muscle disease and allows monitoring of muscle function in rehabilitation.