Psychological, electromyographic, and neurochemial aspects of chronic low back pain: Can a biopsychosocial model be confirmed?

Objectives: Previous studies have suggested that there are psychological, physiological, and biochemical factors contributing to chronic low back pain [CLBP]. No previous study has related these factors, though biopsychosocial models of pain are widely hypothesized. The current study aimed to determine psychological, electromyographic, and biochemical components involved in CLBP patients and compare these with a matched healthy normal control [HNC] group. Methods: Twenty-three chronic low back pain patients and 23 matched non-pain controls completed a psychological questionnaire derived from the Minnesota Multiphasic Personality Inventory. Static and dynamic electromyographic analysis of the lumbar paraspinals was performed. Additionally saliva samples were taken from a matched group of pain and thirty-eight HNC subjects and analyzed for the neuropeptides substance P [SP] and neurokinin A [NKA]. Results: Chronic low back pain patients were found to show a significantly higher frequency of depression, hypochondriasis, hysteria, and psychasthenia [P < 0.001]. Significantly increased paraspinal activity and asymmetry as compared with the matched HNC group was found [P < 0.05]. A significantly increased level of SP [P < 0.05] as compared with the HNC group was also found, though no significant difference was found for NKA. A correlation matrix found there to be a significant correlation between the psychological variables for both groups [P < 0.01], the electromyography results for both groups [P < 0.05], and between SP and NKA [P < 0.05] for both groups. However, no correlation between variables from the separate categories were found. Conclusions: Although there were several limitations to this cross-sectional study, these measures are interpreted as supporting a possible model of CLBP which incorporates psychological, biomechanical, and biochemical components. However, the relationship between these components is undetermined. Further, individuals may be affected differently by the particular components.