Application of surface electromyography topography in low back pain rehabilitation

Abstract

The management of low back pain (LBP) has long been a challenge as it is a highly prevalent disease worldwide due to the lack of an apparent etiology and a conclusive therapeutic treatment. Heterogeneous groups of LBP patients with diverse medical backgrounds also complicate the problem. A clinical threshold is demanded to match the patients and treatments appropriately in order to maximize the treatment success rate. Besides, the assessments of disability and pain perception due to LBP made by self-evaluated questionnaires in current clinical setting are highly susceptible to subjective feeling and the memory of patients. LBP and spasm are closely related but little is known for the underlying physiology, especially the musculature of LBP patients with spasm. These problems exacerbate the difficulty in LBP rehabilitation further. Surface electromyography (sEMG) topography is a cutting- edge technology to assess the lumbar muscle in vivo non-invasively by illustrating the distribution of global muscle activity visually. sEMG topography has the potential application as an objective assessment tool for LBP rehabilitation. In present study, sEMG topography was used to address 1) the prognostic value of sEMG topography on LBP rehabilitation, 2) the establishment and validation of a clinical classification threshold for identification of LBP patients who are responsive to exercise therapy and 3) the investigation of sEMG topography in accordance with the physiological outcomes (functional disability, pain perception and spasm). Forty-five healthy subjects and fifty patients with chronic non-specific LBP were enrolled to the study. sEMG test was conducted to every subject under the motions of lumbar flexion and extension in order to gather the myoelectric signals by a 16-channel sEMG. Various sEMG topographic parameters (sEMG parameters) were developed for quantitative analysis of sEMG topography. They were Root-Mean-Square-Difference of Relative Area (RMSD RA), Relative Width (RMSD RW) and Relative Height (RMSD RH) at flexion and extension. Results showed that sEMG parameters were of significant prognostic value for LBP patients towards exercise therapy. A clinical threshold of 0.21 was proposed and validated based on the geometric calculation of RMSD RA and RMSD RW at flexion and extension. The threshold was substantiated to increase the success rate of exercise therapy from 46% to 86% when the value measured by sEMG topography was below 0.21. sEMG parameters were found significantly associated with disability and pain perception in a positive manner. Severer disability and pain perception were represented by larger values of sEMG parameters. sEMG topography demonstrated symmetric patterns for patients with or without spasms on bilateral sides of lumbar muscles. The symmetry in sEMG topography evinced the consistency of the musculature of bilateral lumbar muscles while the lost of symmetry might indicate malfunction of lumbar muscles unilaterally. To conclude, this study corroborated versatile roles of sEMG topography in LBP rehabilitation as a prognosis, clinical threshold, and objective measurement. The findings of this study have paved the way of sEMG topography for future application in clinical setting. A study of larger scale would be recommended to complement the present findings.