Correlates of myoelectric asymmetry detected in low back pain patients using hand-held post-style surface electromyography

Paraspinal surface electromyographic (SEMG) scanning, utilizing post-style hand-held electrodes, was conducted to determine the usefulness of the technique as an assessment for myoelectric indicators of low back pain (LBP). A secondary objective was to correlate myoelectric abnormalities with other known outcome measures of the manipulable lesion.

Blinded SEMG assessments with the patients standing upright, fully flexed and extended at the trunk, and measures of pressure pain thresholds (PPT) were made after four tests administered by another examiner.

The research was conducted on patients in a private chiropractic practice.

A convenience sample of 10 of the practitioner's most acute LBP patients without neurological deficit were asked to participate and none refused. Six patients without recent LBP volunteered as controls.

Preset myoelectric indicators included: thoracolumbar asymmetry (T-L/A: first seen in an earlier pilot study), loss of flexion/relaxation (F/R) at L3, contralateral responsivity (increased myoelectric activity opposite the side of leg pain) and right/left asymmetry (R-L/A) at L3.

Significant differences between groups were seen in T-L/A (p = .04) and R-L/A [data averaged from three postures (p = .04)], and robust group differences were seen in F/R (p = .011 right; p = .026 left). Contralateral responsivity was not significant. Loss of F/R was the only indicator that correlated with diminished PPT (r = .52 right; r = .46 left) and with Oswestry disability (r = .42), and that negatively correlated, as expected, with straight leg raising (r = -.50 right; r = -.74 left).

Results support use of the technique to detect muscle dysfunction related to LBP. Further research of SEMG correlations with measures of the manipulable lesion is warranted.