Review articleCentralization and directional preference: A systematic review
Introduction
The treatment of back and neck pain remains controversial. Recent research has highlighted the value of reliable examination findings that can be used to predict response to different treatments (Long et al., 2004; Childs et al., 2004; Hicks et al., 2005; Long et al., 2008). Clinically induced symptom responses have been used to determine treatment; with spinal loads being used to induce lasting changes in the site or intensity of symptoms to determine prognosis and management. Such responses are intrinsic to a number of spinal classification or management systems (Fritz et al., 2003; McKenzie and May, 2003; Petersen et al., 2003; Murphy and Hurwitz, 2007; Tuttle, 2009). Probably the most researched clinically induced symptom response is centralization, which has been defined as the abolition of distal and spinal pain in response to repeated movements or sustained postures (McKenzie and May, 2003). Centralization has been the subject of 2 systematic reviews within the last decade, both of which were positive about its usefulness as a prognostic indicator (Aina et al., 2004; Chorti et al., 2009). The first of these reviews is no longer contemporary, and the second was on the prognostic value of symptom responses in general; only half of the 18 studies dealt specifically with centralization.
An associated, but separate phenomenon is that of directional preference, which has been defined as the repeated movement which induces centralization or abolition of symptoms, but also a decrease in symptom severity, and/or a positive mechanical response, such as an increase in range of movement (McKenzie and May, 2003). Movements in the opposite direction may cause these symptoms and signs to worsen. A finding of directional preference at baseline has been shown to predict a significantly better response to directional preference exercises than non-specific exercises (Long et al., 2004, 2008). A number of classification systems use this phenomenon, though not always termed as such, as a part of their assessment and management process (Fritz et al., 2003; McKenzie and May, 2003; Petersen et al., 2003; Van Dillen et al., 2003; Murphy and Hurwitz, 2007; Tuttle, 2009; Hall et al., 2009).
Thus given the apparent usefulness of the centralization phenomenon in predicting outcomes, and the value of directional preference in directing management strategy, it seemed appropriate to conduct a new systematic review. The aim of the present study was to systematically review the literature relating to all aspects of centralization and directional preference.
Section snippets
Study selection
Any full-text study that reported some aspect of centralization or directional preference, in adults reporting spinal pain (low back or neck pain) with or without radiating symptoms. As we knew different types of study design were to be included we restricted qualitative evaluation of study methods to the prognostic studies, for which clear cut quality criteria exist (Hudak et al., 1996). To the authors' knowledge the first paper on centralization was published in 1990.
Data sources and searches
A search was made of
Study selection and characteristics of studies
1416 titles and abstracts were screened, 131 full articles were reviewed, and 62 articles were finally included (see Fig. 1). The majority of studies related to centralization; only 8 related to directional preference (Delitto et al., 1993; Erhard et al., 1994; Snook et al., 1998; Fritz et al., 2003; Long et al., 2004; May, 2006; Hefford, 2008; Long et al., 2008; Werneke et al., 2011). The majority involved patients with back pain, only 5 involved patients with neck pain (Tuttle, 2005; Tuttle
Discussion
This is the largest review to date on centralization, and the first to attempt to review data on directional preference. The literature on centralization has expanded considerably since the first review (Aina et al., 2004). This current review found that the occurrence of centralization was less than reported previously, but still represented a substantial proportion of the neck and back pain populations that were included. There was an indication that centralization was more common in acute
Conclusion
Centralization and directional preference appear to be well accepted concepts commonly encountered by clinicians examining patients with back and neck pain, of a specific or non-specific nature, and have been reported in at least 62 studies, most of which deal with centralization. This review attempted to summarise the data from these studies. Centralization is generally, but not universally associated with a good prognosis, but this effect declines in certain sub-groups. The evidence for
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