Centralization Phenomenon as a Prognostic Factor for Chronic Low Back Pain and Disability

STUDY DESIGN: Two hundred twenty-three consecutive adults with acute low back pain with or without referred spinal symptoms were treated conservatively and followed prospectively for 1 year. OBJECTIVES: To investigate the predictive value of centralization phenomenon (CP) with psychosocial variables previously identified as important risk factors for patients with acute onset of nonserious or nonspecific low back pain who subsequently develop chronic pain or disability. SUMMARY OF BACKGROUND DATA: Psychosocial factors have been shown to be predictors of chronic disability, but measures from physical examination rarely predict chronic behavior. The authors of the present study investigated whether dynamic assessment of changes in clinical measures during treatment could be used to classify patients and predict occurrence of chronic pain or disability. METHODS: Patients with acute symptoms and no history of surgery were treated by five physical therapists trained in McKenzie evaluation/treatment methods. Seventy-three percent were receiving workers' compensation benefits. At initial evaluation and discharge, 23 independent variables were assessed representing psychosocial, clinical, and demographic factors. Pain location changes to repeated trunk movements were assessed at every visit. Patients were placed in two groups: 1) those with pain that did not centralize and 2) those who completely centralized or demonstrated partial reduction of pain location with time. Treatment was individualized and based on McKenzie methods. Patients were contacted at 12 months after discharge, and dependent variables of pain intensity, return to work status, sick leave at work, activity interference at home, and continued use of health care were assessed. RESULTS: Nine independent variables influenced pain symptoms or disability. Pain pattern classification (noncentralization) and leg pain at intake were the strongest predictive variables of chronicity. CONCLUSION: Dynamic assessment of change in anatomic pain location during treatment and leg pain at intake were predictors of developing chronic pain and disability.