Preliminary evidence for the features of non-reducible discogenic low back pain: survey of an international physiotherapy expert panel with the Delphi technique
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.
References (58)
- et al.
The centralisation phenomenon of spinal symptoms – a systematic review
Man Ther
(2004) - et al.
The role of repeated end-range/pain response assessment in the management of symptomatic lumbar discs
Spine J
(2003) - et al.
Healing of a painful intervertebral disc should not be confused with reversing disc degeneration: implications for physical therapies for discogenic back pain
Clin Biomech
(2010) - et al.
Posture and the compressive strength of the lumbar spine
Clin Biomech
(1994) - et al.
Mechanical or inflammatory low back pain. What are the potential signs and symptoms?
Man Ther
(2009) - et al.
Clinical indicators of ‘nociceptive’, ‘peripheral neuropathic’ and ‘central’ mechanisms of musculoskeletal pain. A Delphi survey of expert clinicians
Man Ther
(2010) - et al.
Delphi as a method to establish consensus for diagnostic criteria
J Clin Epidemiol
(2003) - et al.
Physical therapy for acute low back pain: associations with subsequent healthcare costs
Spine
(2008) The prevalence of low back pain: a systematic review of the literature from 1966 to 1998
J Spinal Disord
(2000)- et al.
Subgrouping patients with low back pain: evolution of a classification approach to physical therapy
J Orthop Sports Phys Ther
(2007)