Large Array EMG Monitoring Of Lumbar Region Muscle Action In Discogenic Low Back Pain
This project explored the use of large array surface electromyography (LASE) as a technique for assessing the patterns of muscular activity under standardized loading conditions in patients with lumbar disc related pain and healthy subjects. Specifically, the project evaluated quantitative parameters of visually observed patterns of muscle action proposed to clinically discriminate between groups. If such correlates exist, then, this work may lead to technology assessment for sensitivity and specificity as a diagnostic procedure. Solutions to the issues for determining the effects of low back pain (LBP) on force and moment generation in the spine as well as its effect on the paraspinal muscle activity were sought in three stages. First, a biomechanical model was developed to calculate the passive forces and moments of the total subject population, which included 38 subjects (20 healthy and 18 LBP). The model also allowed for the assessment of the active forces and moments generated by the paraspinal muscles. Second, LASE recordings were collected from each subject using three standardized postures, upright, weighted (holding 5 lb weights in hand), and 20 degrees lumbar flexion at the hip. The LASE recordings were used to create a single muscle equivalent, root mean square myoelectric signal (RMS-MES) model that evaluated muscle activation levels during the standardized tasks. Such a model must be able, to partition passive and active load components acting on the lumbar spine and to estimate equivalent muscle loads from activity observed during the given tasks. Finally, a novel RMS contour surface map was constructed as a means to quantify regional muscle behavior. A first parameter for testing differences between subject groups used symmetry/eccentricity. Results confirmed that an increase in paraspinal muscle activity is directly related to the force generation of the muscles for both groups while performing the standardized tasks. However, the LBP group demonstrated a disproportionately greater increase in muscle force generation when subjected to the monotonically increasing loads than did the healthy subjects. Additionally, a stepwise logistic model was used to identify important parameter differences between the two groups. It may be fruitful for future work to examine other quantitative characteristics of RMS surface maps to differentiate the behavior of muscle activity. In contrast to small area surface electromyography, LASE may provide additional information for classifying type and severity of low back injury leading to the development of more successful treatment methods.