Characterization of the Muscle Electrical Properties in Low Back Pain Patients by Electrical Impedance Myography

OBJECTIVES: This study aims to investigate the electrical properties of lumbar paraspinal muscles (LPM) of patients with acute lower back pain (LBP) and to study a new approach, namely Electrical Impedance Myography (EIM), for reliable, low-cost, non-invasive, and real-time assessment of muscle-strained acute LBP. DESIGN: Patients with muscle-strained acute LBP (n = 30) are compared to a healthy reference group (n = 30). Electrical properties of LPM are studied. BACKGROUND: EIM is a novel technique under development for the assessment of neuromuscular disease. Therefore, it is speculated that EIM can be employed for the assessment of muscle-strained acute LBP. METHODS: Surface electrodes, in 2-electrode configurations, was used to measure the electrical properties of patient's and healthy subject's LPM at six different frequencies (0.02, 25.02, 50.02, 1000.02, 3000.02, and 5000.02 kHz), with the amplitude of the applied voltage limited to 200 mV. Parameters of impedance (Z), extracellular resistance (R(e)), intracellular resistance (R(i)), and the ratio of extracellular resistance to intracellular resistance (R(e)/R(i)) of LBP patient's and healthy subject's LPM were assessed to see if significant difference in values obtained in muscle-strained acute LBP patients existed. RESULTS: Intraclass correlation coefficient (ICC) showed that all measurements (ICC>0.96 for all studying parameters: Z, R(e), R(i), and R(e)/R(i)) had good reliability and validity. Significant differences were found on Z between LBP patient's and healthy subject's LPM at all studying frequencies, with p<0.05 for all frequencies. It was also found that R(e) (p<0.05) and R(e)/R(i) (p<0.05) of LBP patient's LPM was significant smaller than that of healthy subjects while R(i) (p<0.05) of LBP patient's LPM was significant greater than that of healthy subjects. No statistical significant difference was found between the left and right LPM of LBP patients and healthy subjects on the four studying parameters. CONCLUSION: EIM is a promising technique for assessing muscle-strained acute LBP.