A search to identify RCTs investigating neural mobilization yielded 11 studies that met the inclusion criteria for this review. Analyses of these studies, using the criteria of Linton and van Tulder
11, indicated that 8 of the 11 studies
8,24–28,30,32 concluded a positive benefit from using neural mobilization in the treatment of altered neurodynamics or neurodynamic dysfunction. Three of the 11 studies
10,29,31 concluded a neutral benefit, which suggests that neural mobilization was no more beneficial than standard treatment or no treatment. Nine of the 11 studies
8,10,25–28,30–32 reviewed demonstrated moderate methodological quality; the two remaining studies
24,29 yielded limited methodological quality. Studies exhibited weaknesses in random allocation, intention to treat, concealed allocation, and blinding; consequently, our ability to review and assess the therapeutic efficacy of neural mobilization for treatment of altered neurodynamics through evaluation of appropriate randomized controlled trials was substantially limited.
Methodological weaknesses can lead to over- or underestimations of actual outcomes. For example, blinding can significantly eliminate bias and confounding, and is essential in maintaining the robustness of an RCT. Blinding is difficult for use in studies involving manual therapy
33,34, although in this review only 9 of the 11 studies blinded the raters. Some have argued that blinding for use in manual therapy studies is useful
34, although it is arguable that non-masked raters could bias outcome findings.
The outcome measures used by the RCTs in this review also lacked homogeneity. A battery of different scales was used, and findings are not transferable across populations. One method used to standardize measures of success is the use of a minimal clinically important different score (MCID). MCID relates to the smallest change in a clinical outcome measure, which correlates to a person feeling “slightly better” than the initially recorded state
33. Findings can be dichotomized into success or failure. In research that analyzes the therapeutic benefit of an intervention, the MCID is an important statistic, as it represents a level of therapeutic benefit significant enough to change clinical practice
34. MCIDs are population- and pathology-specific, and they require analysis to determine a properly computed value. To our knowledge, all or a majority of the outcome scales used have not been evaluated for an MCID for the population examined in our study.
Due to the heterogeneity in respect to the neural mobilization interventions used in these RCTs, it is difficult to make general conclusions regarding neural mobilization as a general therapeutic tool. Over all, six different categories or types of neural mobilization treatments were identified (Table
5). Of these, there was limited evidence to support the use of active nerve and flexor tendon gliding exercises of the forearm
24,26,30, cervical contralateral glides
8,28,32, and Upper Limb Tension Test 2b (ULTT2b) mobilization
29,31 in the treatment of altered neurodynamics or neurodynamic dysfunction. There was inconclusive evidence to support the use of slump stretches
27 and combinations of neural mobilization techniques
10,25 in the treatment of altered neurodynamics or neurodynamic dysfunction.
Future studies are needed and a larger, more comprehensive body of work is required before conclusive evidence is available. We found only 10 RCTs met the inclusion criteria for this systematic review. Unfortunately, all studies were clinically heterogeneous in that each looked at a number of different pathologies and different types of neural mobilization. This made quantitative analysis of therapeutic efficacy impossible. As Reid and Rivett
21 have stated, direct quantitative comparison, within the realms of systematic review, is very difficult when pathologies, interventions, and outcome measures are heterogeneous. For example, even for this review there were a number of studies that looked at neural mobilization in treatment for lateral epicondylalgia
29,32, carpal tunnel syndrome
24,26,30,31, and cervicobrachial pain
8,25,28. The specific neural mobilization intervention differed between studies, making, in these cases, the treatments too heterogeneous for statistical pooling.
With respect to the clinical implications of these findings, it is interesting to note that generally all the RCTs that looked at neural mobilization for upper quadrant (i.e., cervical spine, shoulder girdle, and upper limb) problems, with the exception of one study
25, concluded that there was limited evidence for therapeutic efficacy. This is in direct contrast to studies that examined neural mobilization for lower quadrant (i.e., lumbar spine, pelvic girdle, and lower limb) problems
10,25,27 in that all provided inconclusive evidence for therapeutic efficacy. From a more specific pathological perspective, for neural mobilization of cervical nerve roots, three papers supported the use of cervical contralateral glide mobilization. For neural mobilization of the median nerve in people with carpal tunnel syndrome, three papers supported the use of active nerve and flexor tendon gliding exercises of the forearm
24,26,30.
Future Research
Considering the results of the extensive literature search carried out for this review, there is an obvious paucity of research concerning the therapeutic use of neural mobilization. Not only is there a lack in quantity of such research, upon dissection of the scarce research that is available, there is also a lack of quality. Future research should look not only at similar pathologies but also at similar neural mobilization techniques.
Another key feature of these studies is that only clinical outcome measures were used. In the introduction, we discussed the biomechanical, physiological, and morphological theories underlying neural mobilization. One of the key theories for using neural mobilization is to exploit the mechanical effect that this form of mobilization has on the neural tissue and its mechanical interface. It is possible to use objective
in-vivo measurements of neural movement (i.e., glide, slide, stretch, etc.) via real-time diagnostic ultrasound. It will be important to eventually substantiate clinical improvements with objective measurement of neural movement. For example, recent unpublished data have demonstrated that it is possible to visualize and quantify, with reasonable reliability, sciatic nerve movement during neural mobilization
35. As it has been postulated that an improvement in nerve mobility may explain any perceived benefits of neural mobilization, it would be relevant to make a comparison of clinical measures with objective measures (e.g., ROM and neural mobility) in an
in-vivo situation in studies that examine neural mobilization. Such a comparison may give clues as to whether neural mobilization is more likely to impose a mechanical effect or a neurophysiological effect on the nervous system.
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