Quantitative surface electromyography topography for low back pain assessment

Abstract

Muscle function impairment was found to be low back pain (LBP)-associated. This paper proposed a new assessment tool using surface electromyography (sEMG) topography, which can visualize the sEMG activity in back muscle during dynamic motion. This study was aimed to quantity the pattern features of dynamic sEMG topography from in-vivo lumbar flexion-extension test in healthy subjects and low back pain (LBP) patients, to investigate the potential use of this technique in LBP assessment. SEMG signals were recorded in 100 normal subjects and 14 LBP patients by applying surface EMG electrode array on the low back muscles during forward bending. Rootmean-square (RMS) was calculated, while the topographies of RMS distribution were constructed by cubic spline interpolation. The highest 20% RMS value region of the topography was defined as high activity. The area, width and width/height ratio of high activity were calculated and compared between normal and LBP. SEMG topographies in normal subjects showed symmetrical muscle activities, while LBP patients did not come up with regular patterns. The high activity region on LBP patients showed significantly larger area (p<0.03), width (p<0.01) and width-to-height ratio (p<0.05) than normal subjects. The alternation of pattern in high activity region suggested imbalanced lumbar muscle contraction which might imply abnormal postural coordination strategies in LBP patients. The sEMG topographic morphology was found to be significantly different between LBP patients and normal subjects. This study provides a quantitative and objective approach to investigate muscle function.