UBC Theses and Dissertations
Psychophysiological correlates of low back pain Wilfling, Francis Joseph
Low Back Pain (LBP) is extremely common and is perhaps the single most socially-costly medical disorder. Yet, very little is known about the etiology of LBP, and current treatments for the disorder are thus correspondingly ineffective. The research reported here was designed to test a general psychophysiological model of the etiology of psychosomatic disorders, applied to LBP and lumbar intervertebral disc degeneration by way of established biomechanical principles. The general model was proposed by Sternbach (1966) who hypothesized that, in the event of repeated, excessive environmental stress, that body part which is the most psychophysiologically responsive will break down. This process is promoted by the lack of normal homeostatic restraints, restraints which are often found lacking in neurotic individuals (Alexander, 1972; Goldstein, 1972). In specific application of the Sternbach model to the LBP condition, it was hypothesized that electromyographic stress responses of abnormal magnitude and duration are evident in the posterior lumbar and abdominal oblique muscles of LBP subjects. On the basis of well researched biomechanical and pathophysiological mechanisms, reviewed in this paper, such muscle response abnormalities would be expected to give rise to LBP and to hasten degeneration of the lumbar intervertebral discs. Asymptomatic subjects with a minimal history of LBP, when compared to normal Control subjects without such a history, were in fact not found to exhibit the critical characteristics of the Sternbach model. The LBP subjects were not more neurotic than members of the general population, and in response to various stressors, neither their posterior lumbar muscles nor their abdominal oblique muscles showed activity that was of excessive magnitude or duration. Two unexpected findings, however, provided new information which can be incorporated into established biomechanical processes which, in additive or synergistic fashion, would be expected to contribute to the occurrence of LBP and lumbar intervertebral disc degeneration. First, it was found that the LBP subjects showed less activity in the posterior lumbar muscles than did the Control subjects. This finding is discussed in the context of established biomechanical principles of spinal stabilization and in terms of pathophysiological processes of intervertebral disc degeneration resulting from shear forces acting on the poorly stabilized spine. Second, it was found that during the occurrence of psychological and physical stressors, LBP subjects did not restrict their respiration rate as much as did Control subjects. This finding is discussed in terms of the hydraulic abdominal "balloon effect" which, if decreased, could be expected to expose the lumbar spine to destructive forces and trauma, producing LBP and lumbar intervertebral disc degeneration. Possible causes for the apparent psychophysiological anomalies found in LBP subjects and possible corrective procedures to overcome them are discussed, and suggestions for further research are given.
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