The Centralization Phenomenon: Prevalence and Predictive Value

A recent research report in JOSPT investigates the centralization phenomenon including its prevalence among cervical and lumbar cases, and its relationship to treatment outcomes. In keeping with the spirit of standardizing and refining our methods and language, this article is definitely a step in the right direction.

In this study, centralization is characterized as "spinal pain and referred symptoms that are progressively abolished in a distal-to-proximal direction in response to therapeutic loading or movement strategies". Werneke points out that despite being a fairly well-defined concept, varied methods of classifying centralization lead to significant difficulty in comparing treatment outcomes. The objectives of the study were:

• Determine the association between age, symptom chronicity, and prevalence of centralization among cases of nonspecific cervical and low-back pain
• Determine if classifying patients into centralization and noncentralization subgroups can predict functional status, pain, and numbers of visits at discharge
• Compare clinically meaningful changes between patients placed in either the centralization or noncentralization subgroups.

The study examined 418 adults between the ages of 19-91 years of age (mean age of 58 and SD of 17 years). Two therapists performed a standardized examination, and patients were classified as either centralizing or noncentralizing. Patients in both groups were assessed for changes in functional status and pain reports. The authors discovered some very interesting findings:

• The prevalence of centralization was only 17% for the entire population
• The highest prevalence of centralization was seen in patients between 18-44 years of age at 30-32%.
• The lowest prevalence of centralization was seen in patients between 65-74 years (8-14%%) and over 75 years of age (0-1%)
• Patients with acute symptoms had higher rates of centralization (23-28%) compared to those with chronic symptoms (6 -11%)
• A higher percentage of patients who centralized had minimally clinically important differences (MCID) in functional status and/or pain intensity than noncentralizing patients.

The authors conclude that centralization was useful but declined in significance for older and more chronic patients. Secondly the use of an operational definition of centralization had predictive ability and associated with pain and functional outcomes in this study. Lastly, the use of centralization could improve clinical classification and assessment of outcomes.

This was yet another fine example of the positive direction our profession is moving with respect to research. It certainly doesn't provide all the answers we need to manage this population, but it provides a good foundation for further investigation into perhaps standardizing our treatment methods as well. As always, I welcome any thoughts or questions!

Werneke, M.W. (2008). Centralization: Prevalence and Effect on Treatment Outcomes Using a Standard Operational Definition and Measurement Method. Journal of Orthopaedic and Sports Physical Therapy DOI: 10.2519/jospt.2008.2596