Pain responses in repeated end-range spinal movements and psychological factors in sick-listed patients with low back pain: is there an association?

OBJECTIVE Repeated end-range spinal movements producing specific pain responses (i.e. centralization or non-centralization) may be used for diagnostic and prognostic purposes. However, possible associations between psychological factors and pain responses have been reported. The aim of this study was to investigate the associations between pain responses in repeated end-range spinal movement tests and psychological factors. DESIGN Cross-sectional clinical study. PATIENTS Data from 331 patients sick-listed for 4-12 weeks due to low back pain with or without sciatica. METHODS Initially the patients completed a questionnaire including questions about psychological factors. Then they underwent a standardized physical test procedure and were classified according to centralized or non-centralized pain response. RESULTS Statistically significant associations were found between non-centralization and mental distress (p < 0.009) as well as depressive symptoms (p < 0.049). These associations remained present after adjustment for potential confounders by logistic regression: mental distress odds ratio (OR) 1.16 (95% confidence interval (CI) 1.03-1.30) (p = 0.013), depressive symptoms OR 1.23 (95% CI 1.01-1.51) (p = 0.044). CONCLUSION The pain responses in repeated end-range spinal movements were not independent of psychological factors. Mental distress and depressive symptoms occurred more often among non-centralizers than among centralizers. It is recommended that the possible influence of psychological factors on the result of mechanical testing be accounted for in future studies.