Poster 86: Local Biochemical Milieu Response to Microdialysis Needle Advancement in the Upper Trapezius Muscle in Normal, Latent, and Active Myofascial Trigger Points

Abstract

Objective: To observe temporal changes of selected biochemical markers in response to microdialysis needle advancement (MNA). Design: Prospective, controlled. Setting: Biomedical research hospital. Participants: 9 subjects were equally distributed among 3 groups based on trapezius findings: normals (no neck pain or myofascial trigger points [MTP]); latents (no neck pain but MTP present); and actives (neck pain and MTP present). Intervention: Samples were obtained at regular intervals for 9 minutes after MNA. Main Outcome Measures: Intergroup and intragroup comparison of marker slopes post-MNA (5−9min) and at profile tail (10−14min). Selected markers include bradykinin, serotonin, norepinephrine, interleukin (IL)-1β, substance P (SP), calcitonin gene-related peptide (CGRP), tumor necrosis factor alpha (TNF-α), IL-6, IL-8, and IL-12. Results: Time-dependent profiles of each marker were characterized by a distinct curve. Levels peaked at approximately 5 minutes then descended, but not all markers returned to baseline. For post-MNA, each marker concentration, except IL-12, descended. There were intergroup slope differences between actives versus latents and normals for all markers except IL-6 and IL-8 (P<.05). For the profile tail, intergroup slope differences were found between actives versus latents and normals for bradykinin, serotonin, SP, CGRP, IL-1β, and TNF-α (P<.05). In actives, bradykinin and serotonin increased whereas other markers remained stable or continued to decline. Conclusions: Marker peaks temporally corresponded with MNA. The post-MNA marker decline suggests a possible biochemical basis for dry-needling MTPs. Intergroup differences post-MNA and at profile tail in actives differ biochemically from latents and normals. This is consistent with previous studies. Bradykinin, serotonin, and CGRP increased at profile tail in actives only, suggesting they may play a role in the maintenance of active MTPs. Additionally, the elevation in bradykinin suggests muscle injury may distinguish actives from latents and normals. Among cytokines, TNF-α peaked higher and declined slower in actives versus latents and normals, suggesting a greater role in myofascial pain.