A Descriptive Study of the Centralization Phenomenon

STUDY DESIGN: Occurrence and treatment responses associated with the centralization phenomenon were analyzed prospectively in 289 patients with acute neck and back pain with or without referred spinal symptoms. OBJECTIVES: To document symptom changes to mechanical assessment during initial evaluation and during consecutive visits. Using standard operational definitions, patients were categorized reliably into three inclusive and mutually exclusive pain pattern groups: centralization, noncentralization, and partial reduction. It was hypothesized that the occurrence of centralization would be less than previously reported and that the centralization group would have better treatment results. SUMMARY OF BACKGROUND DATA: Centralization has been reported to occur with high frequency during mechanical assessments of patients with acute spinal syndromes. When centralization is observed, a favorable treatment result is expected. Because centralization has not been defined consistently in the literature, the true prevalence and treatment responses associated with centralization have not been confirmed. METHODS: Consecutive patients with neck or back pain syndromes and referred to outpatient physical therapy services were categorized into three pain pattern groups by experienced therapists trained in the McKenzie system. Changes in distal pain location were scored and documented before and after each visit. Maximal pain intensity over 24 hours, perceived functional status, and number of treatment visits were compared between groups. RESULTS: Patients could be categorized reliably according to movement signs and symptoms. The centralization pain pattern group had significantly fewer visits than the other two groups (P < 0.001). Pain intensity rating and perceived function were different between the centralization and noncentralization groups (P < 0.001). There was no difference in treatment response between the centralization and partial-reduction groups (P = 0.306). Prevalence of patients assigned to the three groups was 30.8% in the centralization group, 23.2% in noncentralization, and 46% in the partial-reduction group. CONCLUSION: Categorization by changes in pain location to mechanical assessment and treatment allowed identification of patients with improved treatment outcomes and facilitated planning of conservative treatment of patients with acute spinal pain syndromes. If a proximal change in pain location is not observed by the seventh treatment visit, the results of this study support additional medical evaluation for physical or nonphysical factors that could be delaying quick resolution of the acute episode.