Original article
Biochemicals Associated With Pain and Inflammation are Elevated in Sites Near to and Remote From Active Myofascial Trigger Points

https://doi.org/10.1016/j.apmr.2007.10.018Get rights and content

Abstract

Shah JP, Danoff JV, Desai MJ, Parikh S, Nakamura LY, Phillips TM, Gerber LH. Biochemicals associated with pain and inflammation are elevated in sites near to and remote from active myofascial trigger points.

Objectives

To investigate the biochemical milieu of the upper trapezius muscle in subjects with active, latent, or absent myofascial trigger points (MTPs) and to contrast this with that of the noninvolved gastrocnemius muscle.

Design

We used a microanalytic technique, including needle insertions at standardized locations in subjects identified as active (having neck pain and MTP), latent (no neck pain but with MTP), or normal (no neck pain, no MTP). We followed a predetermined sampling schedule; first in the trapezius muscle and then in normal gastrocnemius muscle, to measure pH, bradykinin, substance P, calcitonin gene-related peptide, tumor necrosis factor alpha, interleukin 1β (IL-1β), IL-6, IL-8, serotonin, and norepinephrine, using immunocapillary electrophoresis and capillary electrochromatography. Pressure algometry was obtained. We compared analyte concentrations among groups with 2-way repeated-measures analysis of variance.

Setting

A biomedical research facility.

Participants

Nine healthy volunteer subjects.

Interventions

Not applicable.

Main Outcome Measures

Preselected analyte concentrations.

Results

Within the trapezius muscle, concentrations for all analytes were higher in active subjects than in latent or normal subjects (P<.002); pH was lower (P<.03). At needle insertion, analyte concentrations in the trapezius for the active group were always higher (pH not different) than concentrations in the gastrocnemius muscle. At all times within the gastrocnemius, the active group had higher concentrations of all analytes than did subjects in the latent and normal groups (P<.05); pH was lower (P<.01).

Conclusions

We have shown the feasibility of continuous, in vivo recovery of small molecules from soft tissue without harmful effects. Subjects with active MTPs in the trapezius muscle have a biochemical milieu of selected inflammatory mediators, neuropeptides, cytokines, and catecholamines different from subjects with latent or absent MTPs in their trapezius. These concentrations also differ quantitatively from a remote, uninvolved site in the gastrocnemius muscle. The milieu of the gastrocnemius in subjects with active MTPs in the trapezius differs from subjects without active MTPs.

Section snippets

Participants

Subjects were recruited from members of the staff of the clinical center at the National Institutes of Health (NIH). All subjects underwent a thorough musculoskeletal evaluation so as to rule out potential causes of their symptoms other than MTPs in the upper trapezius muscle. Exclusion criteria included a history of the following conditions: fibromyalgia, cervical or lumbar radiculopathy, other pain syndromes, or cancer. Subjects with knee pain, pathology or infection, previous injection

Results

Subjects in the active group reported greater pain levels (P<.001) on the VAS than did subjects in the latent and normal groups. The active group also had a lower PPT in both the trapezius and gastrocnemius muscles, which would indicate a greater sensitivity to direct pressure. The PPT differences were not significant, however.

In comparing data from subjects previously sampled6 with the subjects in this study, we found close agreement of biochemical concentrations. Figure 2 shows, as examples,

Discussion

We have confirmed that biochemicals associated with pain and inflammation are elevated in soft tissue in the vicinity of active MTPs. The concentrations of these biochemicals, including protons (equivalent to inverse pH), bradykinin, SP, CGRP, TNF-α, IL-1β, 5-HT, and norepinephrine differentiate the active group from the latent and normal groups. Two additional analytes not previously sampled, IL-6 and IL-8, were also significantly higher in the active group.

We have also shown that the

Conclusions

Our microdialysis system, utilizing samples of less than 1μL, is capable of continuous, near real-time, in vivo recovery of molecules 75kDa and smaller directly from the soft tissue environment without harmful effects on subjects.

There is a unique biochemical milieu of substances associated with pain and inflammation in the vicinity of an active MTP in the upper trapezius that includes elevated concentrations of protons, SP, CGRP, bradykinin, TNF-α, IL-1β, IL-6, IL-8, 5-HT, and norepinephrine.

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Supported by the Intramural Research Program, National Institutes of Health (NIH), the Clinical Center and Office of the Director, NIH.

A commercial party having a direct financial interest in the results of the research supporting this article has conferred or will confer a financial benefit upon the author or 1 or more of the authors. Shah, Danoff, Phillips, and Gerber have filed a patent application for the device used in this study.

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