Dose-Dependent Pain and Pain Radiation after Chemical Stimulation of the Thoracolumbar Fascia and Multifidus Muscle: A Single-Blinded, Cross-Over Study Revealing a Higher Impact of Fascia Stimulation

Abstract

Acute low back pain can be experimentally induced by injections of hypertonic saline into deep tissues of the back, such as fascia and muscle. The current study investigated the dose-dependency of peak-pain and spatial extent of concomitant radiating pain following 50, 200 and 800 μL bolus injections of hypertonic saline (5.8%) into the thoracolumbar fascia and multifidus muscle, since data on dose-dependency is lacking in humans. Sixteen healthy subjects rated (11 female, 5 male; 23.3 ± 3.1 years, mean ± SD) intensity and spatial extent of pain. Injections into the fascia resulted in significantly higher peak-pain (+86%, p < 0.001), longer pain durations (p < 0.05), and larger pain areas (+65%, p < 0.02) and were less variable than intramuscular injections. Peak-pain ratings and pain areas were 2–3-fold higher/larger for 200 μL vs. 50 μL. In contrast, peak pain increased only marginally at 800 μL by additional 20%, while pain areas did not increase further at all in both, fascia and muscle. Thus, higher injection volumes did also not compensate the lower sensitivity of muscle. Peak-pain ratings and pain areas correlated between fascia and muscle (r = 0.530, p < 0.001 and r = 0.337, p < 0.02, respectively). Peak-pain ratings and pain areas correlated overall (r = 0.490, p < 0.0001), but a weak correlation remained when the impact of between-tissue differences and different injection volumes were singled out (partial r = 0.261, p < 0.01). This study shows dose-dependent pain responses of deep tissues where an injection volume of 200 μL of hypertonic saline is deemed an adequate stimulus for tissue differentiation. We suggest that pain radiation is not simply an effect of increased peripheral input but may afford an individual disposition for the pain radiation response. Substantially higher pain-sensitivity and wider pain areas support fascia as an important contributor to non-specific low back pain.

Differential Sensitization of Muscle versus Fascia in Individuals with Low Back Pain

“…They found that the injection of hypertonic saline into the deep fascia induced a longer pain duration and higher peak pain as compared with injection of the muscle and subcutaneous tissues. A recent study demonstrated similar results [ 26 ]. Hoheisel et al used a rat model of chemical sensitization of the thoracolumbar fascia and demonstrated increased concentration of nociceptor fibers in the fascia [ 27 ] and increased dorsal horn nociceptive activity [ 25 ] following chemical sensitization.…”

“…Previous studies investigating the differential effect of hypertonic saline injection into the deep fascia vs. muscles demonstrated that, in the short term, fascia sensitization resulted in significant increases in pain in the area under the curve, which was attributable mostly to longer pain duration and less to higher pain intensity [ 25 , 26 ]. However, these studies were conducted in healthy individuals, and thus sensitization of fascia and muscle in myofascial pain patients cannot be inferred.…”

The association between adverse childhood experiences and peripartal pain experience

“…To capture which areas of a participant's body were affected by a respective pain, pain drawings (see Refs. 45, 114) were used for back pain, pelvic pain, and peak labor pain.…”

“…To capture which areas of a participant's body were affected by a respective pain, pain drawings (see Refs. 45,114) were used for back pain, pelvic pain, and peak labor pain. Participants were asked to mark all pain-affected areas, which they had previously described in the SES.…”

Molecular Mechanisms Underlying the Pain-Relieving Effects of Extracorporeal Shock Wave Therapy: A Focus on Fascia Nociceptors

“…In recent years, some papers discussed strong morphological and functional evidence for a nociceptive capacity of deep fascia and thus its contribution to various painful musculoskeletal conditions [ 58 , 60 , 61 , 62 , 63 , 64 ]. Clinical trials on healthy human volunteers demonstrated that electrical high-frequency stimulation of TLF or injection of pain-inducing substances into the TLF evokes long-term potentiation-like pain amplification while generating pain sensations that are more intense and unpleasant when compared to subcutaneous and muscular tissue [ 58 , 104 , 105 , 106 , 107 ].…”