The Lumbodorsal Fascia as a Potential Source of Low Back Pain: A Narrative Review

Abstract

The lumbodorsal fascia (LF) has been proposed to represent a possible source of idiopathic low back pain. In fact, histological studies have demonstrated the presence of nociceptive free nerve endings within the LF, which, furthermore, appear to exhibit morphological changes in patients with chronic low back pain. However, it is unclear how these characteristics relate to the aetiology of the pain. In vivo elicitation of back pain via experimental stimulation of the LF suggests that dorsal horn neurons react by increasing their excitability. Such sensitization of fascia-related dorsal horn neurons, in turn, could be related to microinjuries and/or inflammation in the LF. Despite available data point towards a significant role of the LF in low back pain, further studies are needed to better understand the involved neurophysiological dynamics.

Figure 1

The current literature supports a potential nociceptive function of LF in the aetiology of low back pain. This graph represents two of several possible scenarios in respective cases of fascia generated low back pain. (1) Microinjuries and/or inflammation and resulting irritation of nociceptive nerve endings in lumbar fascia may directly induce back pain, accompanied with a sensitization of fascial nociceptors. In a second pathway (2) tissue deformation due to injury and/or immobility may impair proprioceptive signalling. This induces a sensitization of fascial nociceptors wide, which then alters the functioning of related polymodal neurons in the spinal cord to respond more strongly to potential nociceptive signalling, even to gentle stimulation. Combinations of both pathways are of course also possible. Figure partially based on Langevin & Sherman [25].

Figure 2

In a third scenario for fascia generated low back pain (3) irritation of other tissues—such as muscle fibers, facet joint capsules, spinal nerve roots, or the annulus fibrosus of the discs—could elicit an increased sensitivity in the LF innervated by the same segment of the spinal cord. The increased sensitivity of fascial nerve endings would then lead to nociceptive signalling, even in response to gentle stimulation. A combination with the pathways described in Figure 1 is also possible. Figure partially based on Langevin & Sherman [25].

Figure 3

Example of a histological section taken of the posterior layer of LF at the level of L2. Arrows indicate fibers containing alpha-smooth muscle actin, an immunohistochemical marker for myofibroblasts, which is stained in red. Nuclei are stained dark blue. Although nothing is known about the presence of low back pain in this donor, the high density of myofibroblasts in this tissue is notable and is reminiscent of comparable histological sections in fascial pathologies such as Frozen Shoulder (Bunker et al. 1995). A high density of these contractile cells is usually only seen in fibrotic pathologies and/or in tissue conditions with an increased injury repair activity. Length of image 225 μm.