Classification of large array surface myoelectric potentials from subjects with and without low back pain.

An algorithm was developed and tested for differentiating between the spatial distribution of large arrays of surface electromyographic (LASE) data from subjects with and without low back pain (LBP). The surface EMG data from 62 channels were collected from the low back of 161 healthy and 44 acute (less than 6-weeks) LBP subjects in three minimum stress postural positions including standing, 20 degrees of trunk flexion (at hip joint) and standing with arms extended forward holding a 1.36kg (3lb) weight in each hand. These data were statistically analyzed and the spatial distribution of the root mean square (RMS) values was used in a multivariate quadratic discriminant model to reclassify the healthy and acute LBP subjects. The most predictive results were obtained from the 'flexion' group of experiments and correctly reclassified 95.5% (42/44) of the acute LBP subjects and 99.4% (160/161) of the healthy subjects. The success rate of this reclassification based on surface distribution of myoelectric potentials was found to be better than the reported patient classifications based on a smaller set of electrode pairs using fewer subjects [Peach JP, McGill SM, Classification of low back pain with use of spectral electromyogram parameters. Spine 23(10):1998;1117-23; Roy SH, De Luca CJ, Emley M, Oddsson LI, Buijs RJ, Levins JA, Newcombe DS, Jabre JF. Classification of back muscle impairment based on the surface electromyographic signal. J Rehabil Res Dev 34(4):1997;405-14 [review]]. The results indicated the potential of the model for clinical patient classification.

Large-array surface electromyography in low back pain: a pilot study.

STUDY DESIGN: A large-array surface electromyography device was used to collect data from healthy pain-free persons and from those with acute or chronic low back pain. Images of regional muscle electromyographic activity were assessed visually, and maximum root mean square values were compared statistically. OBJECTIVE: To determine whether data differs by patient type. SUMMARY OF BACKGROUND DATA: Whereas there is a good understanding of the anatomy and psychosocial aspects of low back pain, there is a need to understand better the physiology of low back pain. METHODS: Large-array surface electromyography data were collected from the low back muscles of 201 participants over a 3-month period using a 63-electrode fixed array and a standardized protocol. Color images representing the voltage root mean square difference of each electrode pair were created. Three images from each of three positions (standing upright, standing in 20 degrees of trunk flexion, standing holding weights) were collected from each participant. Serial studies were performed on the acute population over a 6-week follow-up period. RESULTS: Images of regional muscle activity from 92.7% of normal controls (n = 163) showed symmetrical activity. Patients with acute (n = 13) or chronic (n = 25) low back pain had multifocal and/or asymmetrical patterns. Symmetrical patterns returned in the three patients whose acute pain resolved during the study. Maximum root mean square values were higher among patients with acute (P = 0.03) and chronic (P = 0.04) pain than among control subjects. CONCLUSIONS: Large-array surface electromyography produced data from patients with back pain that differed from data on subjects without back pain. This method may be useful in evaluating patients with low back pain.