Elsevier

Physiotherapy

Volume 99, Issue 3, September 2013, Pages 212-220
Physiotherapy

Preliminary evidence for the features of non-reducible discogenic low back pain: survey of an international physiotherapy expert panel with the Delphi technique

https://doi.org/10.1016/j.physio.2012.09.007Get rights and content

Abstract

Objectives

The lumbar intervertebral disc is a known source of low back pain (LBP). Various clinical features of discogenic pain have been proposed, but none have been validated. Several subgroups of discogenic pain have been hypothesised, with non-reducible discogenic pain (NRDP) proposed as a relevant clinical subgroup. The objectives of this study were to obtain consensus from an expert panel on the features of discogenic low back pain, the existence of subgroups of discogenic LBP, particularly NRDP, and the associated features of NRDP.

Design

Three-round Delphi survey.

Participants

Twenty-one international physiotherapists with expertise in LBP.

Methods

Panellists listed and ranked features that they believed to be indicative of discogenic pain and NRDP. On completion of Round 3, features with ≥50% agreement between panellists were deemed to have reached consensus.

Results

After three rounds, 10 features of discogenic LBP were identified. Nineteen of the panellists believed that NRDP was a subgroup of discogenic LBP, and nine features of NRDP were identified.

Conclusion

This study provides preliminary validation for the features associated with discogenic LBP. It also provides evidence supporting the existence and features of NRDP as a separate clinical subgroup of discogenic LBP.

Introduction

Low back pain (LBP) is a major problem around the world, with prevalence at epidemic proportions [1], [2]. Randomised controlled trials investigating the efficacy of treatments for LBP have failed to show consistent effects, potentially due to the inclusion of heterogeneous samples [3], [4]. As a result, the identification of LBP subgroups has been identified as a high research priority [3], [4], [5], [6].

A common clinical feature of LBP is centralisation, defined as the proximal movement and/or abolition of distal symptoms originating from the spine in response to the application of mechanical loading strategies (MLS), such as repeated movements [7], [8], [9]. The mechanism underpinning this response has been described as a ‘reduction’ of a painful and abnormally displaced nucleus pulposus to a more central and less pain-provoking position within the lumbar disc [10], [11], [12]. Reducible discogenic pain (RDP) can therefore be defined as a subgroup of LBP where signs/symptoms respond positively and predictably to MLS.

Significant evidence exists supporting the validity of clinical features for RDP. Large surveys have shown that primary care practitioners believe RDP is a prevalent condition that responds to MLS as a form of treatment [13], [14], [15]. Centralisation as a clinical marker of RDP has been identified in a systematic review as a predictor of positive outcomes in pain, function, return to work and decreased healthcare usage [8]. A recent clinical trial using MLS on specific subgroups reported positive effect sizes that were clinically meaningful [positive likelihood ratio of 7.8 for >30% reduction of Roland–Morris Disability Questionnaire, 95% confidence interval (CI) 2.6 to 23.3] [16]. Another recent systematic review demonstrated evidence for the diagnostic accuracy of centralisation in predicting the results of lumbar discography (positive likelihood ratio 2.8, 95% CI 1.4 to 5.3) [17]. Based on this literature, RDP as a subgroup of LBP has good face, concurrent and predictive validity. However, aside from centralisation, the clinical features believed to be associated with RDP by practitioners [13] and some researchers [12], [18] have not been validated.

Non-reducible discogenic pain (NRDP) has been described as discogenic pain without focal herniation/nerve root compression that does not respond to MLS [12], [18], [19]. Inflammatory processes in the disrupted annulus fibrosis [20] or an incompetent annulus/non-functional hydrostatic mechanism [11] have been proposed as possible mechanisms leading to the non-predictable nuclear migration observed during MLS [21]. However, there is minimal research on the clinical features of NRDP.

Further research on the features of different types of discogenic pain can be justified based on the literature described above. On this basis, the opinions of international physiotherapists with extensive knowledge in LBP were sought with the following research questions:

  • What are the features that expert physiotherapists believe to be indicative of discogenic LBP?

  • Do experts believe that subgroups of discogenic LBP, other than RDP, exist?

  • What are the features that experts believe to be indicative of NRDP?

Section snippets

Methods

Following approval by the Human Research Ethics Committee at the University of Melbourne, study information and a questionnaire were emailed to potential panellists. They were invited to provide informed consent and participate by answering the questionnaire items.

Results

Eighty-eight potential panellists were emailed with an invitation to participate in this study (14 university coordinators, 30 McKenzie therapists and 44 researchers), and the first seven consenting experts from each source were recruited. Table 2 shows the reasons for non-participation of potential panellists. Demographics and experience of the recruited panellists are listed in Table 3.

A summary of the Delphi rounds is provided in Fig. 2. Five experts were unable to participate in all rounds

Discussion

This study aimed to identify and provide preliminary evidence for features indicative of discogenic pain and NRDP. The majority of panellists agreed that centralisation was indicative of discogenic pain, which is consistent with large practitioner surveys [13] and data on predictive [8] and concurrent validity [17].

Clinicians believe that there may be features indicative of discogenic pain other than centralisation [13]. All features that reached consensus in the present study have been

Acknowledgements

The authors wish to thank the expert physiotherapists who sustained their contribution as members of the panel.

Ethical approval: University of Melbourne Human Research Ethics Committee (Ref. No. 0710082).

Conflict of interest: None declared.

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