Electrical Impedance Myography in the Assessment of Disuse Atrophy

Objective: To quantify disuse atrophy using electrical impedance myography (EIM), a noninvasive technique that we have used successfully to study neurogenic and myopathic atrophy. Design: We performed EIM of the tibialis anterior of subjects with disuse atrophy secondary to cast immobilization and in their contralateral normal leg. Subjects were studied shortly after cast removal and again several weeks to months after the cast was removed and normal mobility was restored. Setting: Outpatient neurology and orthopedic practices at a tertiary care medical center. Participants: Otherwise healthy Subjects (N = 10) with unilateral leg fracture. Interventions: Not applicable. Main Outcome Measures: Resistance, reactance, and phase measured at 50kHz. Results: The main EIM outcome parameter, phase at 50kHz, was lower in the immobilized leg in 9 of 10 cases. Additionally, when normal mobility was restored, the phase of the casted leg increased relative to its initial measurement in all 10 cases, while it increased inconsistently in the contralateral leg. Conclusions: EIM may be a powerful tool for the assessment of disuse atrophy.