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

Abstract

ObjectivesThis 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.DesignPatients with muscle-strained acute LBP (n = 30) are compared to a healthy reference group (n = 30). Electrical properties of LPM are studied.BackgroundEIM 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.MethodsSurface 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 (Re), intracellular resistance (Ri), and the ratio of extracellular resistance to intracellular resistance (Re/Ri) 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.ResultsIntraclass correlation coefficient (ICC) showed that all measurements (ICC>0.96 for all studying parameters: Z, Re, Ri, and Re/Ri) 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 Re (p<0.05) and Re/Ri (p<0.05) of LBP patient's LPM was significant smaller than that of healthy subjects while Ri (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.ConclusionEIM is a promising technique for assessing muscle-strained acute LBP.

EIS measurements for characterization of muscular tissue by means of equivalent electrical parameters

“…In addition, also the values of R 0 were estimated since it is directly linked to the extra-cellular resistance [7,13,14].…”

“…The lower limit eliminates EMG surface signal [19], the upper limit is to elicit a part of b region [14] in order to probe both properties of cell and cell suspension [21]. The linear frequency sweep was of 10 points to limit the time length of the test and hence to avoid subjects' fatigue [11,19,22] (each test takes about 1 min).…”

“…In biomedical engineering, it is common to model systems and particular electrical measurement of biological tissues by means of equivalent electrical circuits which provide a simplified description of the properties of the measured organs [6,13,14]. An opportune choice of the model makes possible to correlate the circuit elements to underlying physical and physiological processes [7,13].…”

“…An opportune choice of the model makes possible to correlate the circuit elements to underlying physical and physiological processes [7,13]. Muscular tissue, such as any other biological tissue, is formed by cells whose structure can be represented by considering extra cellular fluids (blood and interstitial fluid), cell membrane and intra cellular components [14]. From the electrical point of view, intra and extracellular media can be considered as a liquid electrolyte (represented by a resistive component) and the cell membrane, being characterized by a double layer of lipids, behaves as a capacitor [6,7].…”

Miografía por impedancia eléctrica

“…En dolor lumbar agudo, se han detectado cambios, especialmente a bajas frecuencias, con disminución de la resistencia extracelular (Re) a nivel de los músculos paraespinales lumbares, secundario al edema (que aumenta el espacio extracelular), permitiendo una diferenciación confiable entre sujetos sanos y sujetos con patología lumbar aguda 37 . En lesiones musculares agudas, la acumulación de líquido por el edema postraumático y el daño de las membranas celulares origina una disminución de la resistencia (R) y de la reactancia (Xc) musculares, parámetros que recuperan los valores pre-lesión cuando se documenta la recuperación total del tejido por ecografía 26 .…”