Ultrasound imaging distinguishes between normal and weak muscle.

Abstract Chi-Fishman G, Hicks JE, Cintas HM, Sonies BC, Gerber LH. Ultrasound imagining distinguishes between normal and weak muscle. Arch Phys Med Rehabil 2004;85:980–6. Objective To determine whether real-time ultrasound imaging can provide quantitative data that distinguish pathologic from healthy muscle and that correlate with strength measures. Design Nonrandomized matched-pair, repeated-measures design. Setting Ultrasound imaging laboratory, rehabilitation medicine department, government research hospital. Participants Nine patients with stable active or inactive myositis, stratified into 3 groups based on their 10-point manual muscle test (MMT) scores, and 9 age- and gender-matched controls. Interventions Maximal isometric contraction of the rectus femoris muscle in 2 knee-flexion positions (60°, 90°) during simultaneous ultrasound imaging and muscle force dynamometry. Main outcomes measures Changes of the rectus femoris muscle in horizontal (X) and vertical (Y) diameters between relaxed and contracted states, and muscle force measurements. Results The X diameters decreased and the Y diameters increased during isometric contraction in all participants. For each group, average changes in cross-sectional diameters were consistently higher in controls than in patients. Patients with MMT less than 8 differed significantly from controls in both X and Y dimensions. A moderately strong correlation was found between muscle force and the Y diameter during contraction at 60° ( r =.78) and 90° ( r =.67) knee-flexion angles. Conclusions Ultrasonography provided a quantitative measure of change between relaxed and contracted state of muscle, which correlated with muscle force. Ultrasound identified significant differences in cross-sectional diameters between the myopathic and normal muscles sampled and may be useful for measuring muscle response to drug and exercise therapy.