The centralization phenomenon and fear-avoidance beliefs as prognostic factors for acute low back pain: a preliminary investigation involving patients classified for specific exercise.

STUDY DESIGN: Secondary analysis of a prospective cohort of patients with acute low back pain (LBP).

OBJECTIVES: To determine if the centralization phenomenon and fear-avoidance beliefs predict measurement of pain and disability 6 months after entering the study.

BACKGROUND: The centralization phenomenon and fear-avoidance are predictive of future pain and disability. However, previous prognostic studies have not routinely included both measures in homogenous subgroups of patients with acute LBP.

METHODS AND MEASURES: Patients completed self-report questionnaires and were evaluated and treated with treatment-based classification guidelines. Only the patients classified for specific exercise were included in this analysis (n = 28). Measures of disability and pain intensity were reassessed at 6 months by mail. Separate hierarchical regression models predicted measures of disability and pain intensity with the centralization phenomenon, fear-avoidance beliefs, and prespecified covariates.

RESULTS: There were no significant differences in duration of symptoms, fear-avoidance beliefs, and history of LBP based on the centralization phenomenon (P > .05). Patients reporting the centralization phenomenon were significantly more likely to have leg pain (P < .01). A regression model including initial disability, the centralization phenomenon, and fear-avoidance beliefs about work significantly predicted 6-month disability, explaining 49% of the total variance (P < .001). A regression model that included initial pain intensity and the centralization phenomenon significantly predicted 6-month pain intensity, explaining 29% of the total variance (P < .016). These factors also appeared to be clinically meaningful predictors of outcome, but lacked precision for immediate use in clinical settings. The following covariates were not included in the final regression models: presence of leg pain, history of LBP, and duration of LBP.

CONCLUSIONS: Baseline elevation in fear-avoidance beliefs about work and lack of centralization phenomenon predicted higher disability. Baseline lack of centralization phenomenon predicted higher pain intensity. These results can only be generalized to patients with acute LBP classified for specific exercise. It will be necessary to independently validate these prediction models before they can be implemented in clinical settings.