Referred pain of somatic or neuropathic origin (back pain) (Health factor for workers with an MSD or back pain origin)

Interpretation of the “Referred pain of somatic or neuropathic origin (back pain)” factor

For people with back pain, referred pain of somatic or neuropathic origin negatively influences RTW or sickness absence duration.

Definition of the “Referred pain of somatic or neuropathic origin (back pain)” factor

Short definition: Referred pain are sensations of pain arising from a body region remote from the site of the injury (« Referred Pain, » 2007). In the case of low back pain, referred pain travels down the leg.

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The presence of referred pain negatively influences RTW in workers with back pain (Du Bois et Donceel, 2008; Schultz et al., 2002; Turner et al., 2008). More specifically, pain below the knee is well-known as a poor prognostic factor of pain disability in these workers (Hartvigsen et al., 2018), which explain why the question “Has back pain spread down your leg(s) during the past 2 weeks” was retained by the NIH (National Institute of Health) task force on research standards for chronic low back pain (Deyo et al., 2015).  In fact, back related leg pain manifests as numerous different clinical presentations presenting as a highly heterogenous phenomenon as it can be of somatic or neuropathic origins, or both. Whatever its origin, referred pain represents a more serious condition than when the pain is localized at the site of injury.

For healthcare professionals. Differentiating between somatic and neuropathic back related leg pain is essential to guide treatment, but not an easy task. While low back pain and referred pain of somatic origin are common, referred pain of neuropathic origin is not. Referred pain of somatic origin is produced by noxious stimulation of nerve endings within spinal structures such as discs, zygapophysial joints, or sacroiliac joints and is perceived in regions that share the same segmental innervation as the source (Bogduk, 2009). Since somatic referred pain is not caused by compression of nerve roots, there are no neurological signs. Somatic referred pain expands into wide areas that the patients often find it difficult to define the boundaries. Referred pain of neuropathic origin refers to radicular pain or radiculopathy, which are two related but distinct conditions. Radicular pain is evoked by mechanical stimulation of the dorsal root or its ganglion. Disc herniation is the most common cause, and only if nerve roots are inflamed does mechanical stimulation evoke radicular pain (Bogduk, 2009). The term “sciatica” stems from an era when the mechanisms of referred pain were not understood; the taxonomy of the IASP (International association for the study of pain) recommends replacement by “radicular pain”. Radiculopathy is different from radicular pain and may not be accompanied by pain. The compression of nerve roots by degenerated spinal structures (e.g., herniated discs, facet joints, and/or epidural fat) may lead to radiculopathy that radiates distal to the knee. Radiculopathy is a neurological state in which conduction is blocked along a spinal nerve or its roots, blocking sensory or motor fibers and leading to numbness or weakness (Bogduk, 2009).  There is complete agreement among experts about good clinical indicators of referred pain of neuropathic origin (Mistry, Falla, Noblet, Heneghan et Rushton, 2020), such as pain variously described a burning, electric shock like and/or shooting into leg and pain in association with other neurological symptoms (e.g. pins and needles, numbness, muscle weakness and loss of sensations).

 Bogduk, N. (2009). On the definitions and physiology of back pain, referred pain, and radicular pain. Pain, 147(1-3), 17-19. doi: 10.1016/j.pain.2009.08.020

Deyo, R. A., Dworkin, S. F., Amtmann, D., Andersson, G., Borenstein, D., Carragee, E., . . . Weiner, D. K. (2015). Report of the NIH Task Force on Research Standards for Chronic Low Back Pain. Phys Ther, 95(2), e1-e18. doi: 10.2522/ptj.2015.95.2.e1

Du Bois, M. et Donceel, P. (2008). A screening questionnaire to predict no return to work within 3 months for low back pain claimants. European Spine Journal, 17(3), 380-385. doi: 10.1007/s00586-007-0567-8

Hartvigsen, J., Hancock, M. J., Kongsted, A., Louw, Q., Ferreira, M. L., Genevay, S., . . . Woolf, A. (2018). What low back pain is and why we need to pay attention. The Lancet, 391(10137), 2356-2367. doi: 10.1016/s0140-6736(18)30480-x

Mistry, J., Falla, D., Noblet, T., Heneghan, N. R. et Rushton, A. (2020). Clinical indicators to identify neuropathic pain in low back related leg pain: a modified Delphi study. BMC Musculoskelet Disord, 21(1), 601. doi: 10.1186/s12891-020-03600-y

Referred Pain. (2007). Dans R. F. Schmidt et W. D. Willis (édit.), Encyclopedia of Pain (p. 2106-2107). Berlin, Heidelberg: Springer Berlin Heidelberg.

Schultz, I. Z., Crook, J. M., Berkowitz, J., Meloche, G. R., Milner, R., Zuberbier, O. A. et Meloche, W. (2002). Biopsychosocial multivariate predictive model of occupational low back disability. Spine, 27(23), 2720-2725.

Turner, J., Franklin, G., Fulton-Kehoe, D., Sheppard, L., Stover, B., Wu, R., . . . Wickizer, T. (2008). Early predictors of chronic work disability: a prospective, population-based study of workers with back injuries. Spine, 33(25), 2809-2818.

Tools for measuring the “Referred pain of somatic or neuropathic origin (back pain)” factor