Five movement based classification schemes were identified and, from a broad perspective, the theoretical basis and key elements can be generalised into two main approaches. One approach (MDT, TBC, and PBC) is initially guided by evaluation of the response to loading the spine in different directions, and the other (MSI and OCS) is guided by identification of strategies of modified movement along with a process of diagnostics. Inter-tester reliability across schemes varies depending upon the subgroup and level of training, with ranges from 'poor to fair' (PBC), 'moderate' (MDT, TBC, OCS), 'substantial' (MSI), and 'excellent' (OCS).
Several areas of convergence and divergence were identified between schemes. Most share a common clinical reasoning strategy to classify patients into subgroups based on relevance of a specific movement direction to the symptoms in order to direct intervention and predict outcomes. The MDT, TBC and PBC schemes also offer categories for patients who do not fit into a directional preference. MDT, TBC, and PBC schemes converge in their use of repeated spinal movements to investigate the phenomenon of centralisation of pain, but diverge in their relative emphasis on this parameter, the inclusion of additional assessment options, and differences in the recommended treatments. The MSI and OCS schemes share the use of modification of painful movement to aid allocation to a subgroup, but they diverge in their emphasis on impairments, the specific clinical tests used, and the relative emphasis on neurophysiologic and psychosocial factors. Differences between classification philosophies and strategies are greater than similarities. Disparity clearly exists between pursuit of a pathoanatomical source of pain (PBC) versus the disengagement from this model (all other schemes). The MDT scheme places emphasis on ignoring known structural pathology and assesses initial pain response to movement in an effort to determine if the centralisation phenomenon can be elicited. The MSI scheme would consider this an inappropriate strategy for a spinal stenosis condition and the TBC scheme would more likely cease provocative movement testing to determine if manipulation or stabilisation exercises would be of benefit. MDT, TBC, MSI, and OCS schemes are designed around a preferred treatment strategy for each subgroup; however, the PBC scheme deliberately avoids selection of treatment.
Diversity exists across schemes in the extent of their consideration of the biopsychosocial framework. In regards to the psychosocial aspects of LBP, the current emphasis in the majority of schemes (MDT, PBC, and TBC) has been to focus on "magnified illness behaviour" [121
] and the "fear-avoidance" [111
] model to assess the influence of psychological factors in LBP. The OCS scheme appears to integrate a wider psychological spectrum of the attention, cognitive, beliefs and behavioural aspect of LBP. This viewpoint is based on previous OCS studies, which have used the Tampa Scale for Kinesiophobia [122
], Örebro Musculoskeletal Pain Screening Questionnaire, Hopkins Symptoms Check List, and FABQ [87
], in addition to the scheme's emphasis on incorporating a biopsychosocial model. There is currently a divergence in opinion on how to address psychosocial aspects of LBP. MDT and PBC schemes preferentially treat the mechanical dysfunction regardless of psychological presentation, with the intention that improvement in symptoms may positively affect the psychological domain [123
]. The TBC scheme focuses on one behavioural dimension of pain to guide assessment. The OCS scheme attempts to address the cognitive and behavioural aspects of LBP. Future research could explore which approach best reduces persistent or recurrent pain, or if additional psycho-social dimensions should be assessed (i.e., happiness [124
], optimism [125
], self-efficacy [126
], stress hardiness [127
], sense of coherence [128
], treatment expectancy [129
], life satisfaction [130
], mindfulness [131
]) from both patient and practitioner [132
Further diversity exists across schemes in the extent of their consideration of the neurophysiological aspects of pain within the biopsychosocial framework. Although the MDT scheme acknowledges a "chronic pain state" category, the definition of this subgroup pertains primarily to dominance of psychological factors and less on pain systems theory. For example, if a mechanical approach did not decrease fear avoidance, then a graded exercise intervention would be applied. The PBC scheme may hold a broader perspective of altered sensory features, by including "abnormal pain state" and "adverse neural tension" categories. The OCS scheme separates pain systems into "centrally mediated" and "peripherally mediated" subgroups, although operational criteria require development. How these subgroups relate to a proposed neuropathic pain grading system [117
] remains unknown.
Clinical trials are required to validate the use of subgrouping in low back pain. Although additional work is required to determine the optimal sequence of trials to be conducted, at minimum randomised controlled trials are required to determine whether classification of patients on the basis of these schemes leads to better outcomes for people with low back pain. Additional trials are necessary which investigate the relative importance of different aspects of the schemes for treatment outcome (e.g. consideration of movement vs. psychological perspectives).