That chronic low back pain (CLBP) is associated with functional and structural changes in the central nervous system is difficult to dispute and subject to wide-ranging ongoing research (Moseley and Flor, 2012, Omori et al., 2013, Vrana et al., 2016), especially in the field of neuroimaging and neurophysiology (Henry et al., 2011). There are many proposed and emerging therapeutic approaches in the literature (such as sensorimotor retraining) targeted at a normalisation of those central nervous system alterations in patients with CLBP (Daffada et al., 2015, Linder et al., 2016, Luomajoki et al., 2016, Wand et al., 2011a).
To move this area of research forward there is a need for good quality, clinically applicable assessment techniques/outcome measures of cortical reorganisation. Such measures might help to identify those patients, whose persistent pain is associated with central nervous system alterations and would be most likely to benefit from such sensorimotor interventions (keeping in mind, of course, that evidence of a causal relationship between cortical changes and pain is lacking). In addition, we need good outcome measures to assess the effectiveness of such interventions.
In daily clinical practice, we need to tackle this without having access to, and knowledge of, sophisticated and expensive brain imaging and neurophysiological assessment approaches. Here, clinical sensorimotor measurement instruments (SMIs) such as two-point discrimination, graphesthesia, lumbopelvic movement control tests, laterality judgement, body image drawings or specialised questionnaires, such as the Fremantle Back Awareness Questionnaire (FreBAQ) (Adamczyk et al., 2018, Bray and Moseley, 2011, Luomajoki and Moseley, 2011, Nishigami et al., 2015, Wand et al., 2011b, Wand, 2014) come into play. These measurement instruments could be used as clinically feasible proxy measures of cortical reorganization. However, before these SMIs can be recommended they need to demonstrate good clinimetric properties.
An important property of an assessment instrument is that it demonstrates good reliability (De Vet et al., 2011). The instrument should, to a great extent, provide information about the patient’s actual state or change following an intervention, e.g. a specialised sensorimotor intervention (Atkinson and Nevill, 1998). Without having demonstrated sufficient reliability, an assessment instrument should be treated with great caution. Additionally, the assessment instrument needs to demonstrate validity – it truly measures what it purports to measure.
In the case of SMIs, the demonstration of validity is somewhat challenging. Usually, one could assess an instrument’s validity by comparing it to a well-established and trusted instrument (criterion validity) (De Vet et al., 2011). To assess cortical activity, direct assessment to a gold standard would require expensive specialist equipment and highly skilled technical staff, such as functional magnetic resonance imaging (fMRI) and Electroencephalography (EEG). Alternatively, one could assess different aspects of validity e.g. comparing SMI results to those of another instrument, claiming to measure the same construct (convergent validity) (Mokkink et al., 2009) and/or to provide its ability to distinguish between people having or not having the dysfunction/condition under investigation (known-groups validity) respectively (De Vet et al., 2011).
We recently conducted a systematic review to investigate the reliability and validity of simple SMIs in people with CLBP (Ehrenbrusthoff et al., 2018). The review was undertaken using the COSMIN guidelines (Mokkink et al., 2009). Databases were systematically searched and revealed ten studies, covering six SMIs with findings for reliability and validity. The methodological quality of these studies ranged from poor to good, with only one study rated as good. One main reason for downgrading the methodological quality of the studies was the small sample sizes. Two-point discrimination, laterality judgement and movement control tests had moderate evidence supporting their ability to distinguish between healthy people and those with CLBP, hence they demonstrated a degree of known-groups validity. There was insufficient evidence to assess the reliability or convergent validity of the SMIs revealed by the search.
Hence, the reliability of these SMIs still needs to be established. As mentioned above, without having demonstrated sufficient reliability, the validity data alone need to be interpreted cautiously. Thus, the clinical use of the SMIs to guide our daily clinical decisions should be undertaken with caution. More research into the clinimetric properties of simple clinical SMIs is warranted and such studies should be mindful of the need for adequate sample sizes. Such work might give us the tools to better understand the clinical implications of the cortical changes that occur in patients with CLBP and help us to develop and test new sensorimotor treatment strategies to target these cortical changes.
About Katja Ehrenbrusthoff
Katja is physiotherapist, specialised manual therapist and research fellow at the Hochschule fuer Gesundheit (hsg), Bochum, Germany. She has a Masters in Advanced Clinical Practice from Teesside University (TU), Middlesbrough, GB and also works clinically with patients with musculoskeletal disorders in a physiotherapy practice. This research is part of her PhD project, which is a collaborative project of TU and hsg Bochum. Her PhD focuses on the assessment of sensorimotor dysfunction in people with chronic low back pain under supervision of Dr Cormac Ryan and Prof Denis Martin from TU and Prof. Dr. Christian Grüneberg from hsg Bochum.
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