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      Characteristics of Myofascial Pain Syndrome of the Infraspinatus Muscle

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          To report the characteristics of myofascial trigger points (MTrPs) in the infraspinatus muscle and evaluate the therapeutic effect of trigger-point injections.


          Medical records of 297 patients (221 women; age, 53.9±11.3 years) with MTrPs in the infraspinatus muscle were reviewed retrospectively. Because there were 83 patients with MTrPs in both infraspinatus muscles, the characteristics of total 380 infraspinatus muscles with MTrPs (214 one side, 83 both sides) were investigated. Specific characteristics collected included chief complaint area, referred pain pattern, the number of local twitch responses, and distribution of MTrPs in the muscle. For statistical analysis, the paired t-test was used to compare a visual analogue scale (VAS) before and 2 weeks after the first injection.


          The most common chief complaint area of MTrPs in the infraspinatus muscle was the scapular area. The most common pattern of referred pain was the anterolateral aspect of the arm (above the elbow). Active MTrPs were multiple rather than single in the infraspinatus muscle. MTrPs were frequently in the center of the muscle. Trigger-point injection of the infraspinatus muscle significantly decreased the pain intensity. Mean VAS score decreased significantly after the first injection compared to the baseline (7.11 vs. 3.74; p<0.001).


          Characteristics of MTrPs and the therapeutic effects of trigger-point injections of the infraspinatus muscle were assessed. These findings could provide clinicians with useful information in diagnosing and treating myofascial pain syndrome of the infraspinatus muscle.

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          Most cited references 30

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          Review of enigmatic MTrPs as a common cause of enigmatic musculoskeletal pain and dysfunction.

           G Simons (2004)
          This article explores how myofascial trigger points (MTrPs) may relate to musculoskeletal dysfunction (MSD) in the workplace and what might be done about it. The cause of much MSD and pain is often enigmatic to modern medicine and very costly, just as the cause of MTrPs has been elusive for the past century, despite an extensive literature that is confusing because of restricted regional approaches and a seemingly endless variety of names. MTrPs are activated by acute or persistent muscle overload, which is characteristic of MSD in the workplace. MTrPs can involve any, and sometimes many, of the skeletal muscles in the body and are a major, complex cause of musculoskeletal pain. The clinical and etiological characteristics of MTrPs have been underexplored by investigators, leading to undertraining of health care professionals, underappreciation of their clinical importance. MTrPs have no gold standard diagnostic criterion, and no routinely available laboratory or imaging test. MTrPs require a specific non-routine examination and muscle-specific treatment for prompt relief when acute, and also resolution of perpetuating factors when chronic. After identifying a critical false assumption, electrodiagnostic studies are now making encouraging progress toward clarifying the etiology of MTrPs based on the 5- or 6-step positive-feedback model of the integrated hypothesis. Specific research needs are noted. MTrPs are treatable and they deserve increased attention and consideration by research investigators and clinicians.
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            Pathophysiologic and electrophysiologic mechanisms of myofascial trigger points.

            To review recent clinical and basic science studies on myofascial trigger points (MTrPs) to facilitate a better understanding of the mechanism of an MTrP. English literature in the last 15 years regarding scientific investigations on MTrPs in either humans or animals. Research works, especially electrophysiologic studies, related to the pathophysiology of MTrP. (1) Studies on an animal model have found that a myofascial trigger spot (MTrS) in a taut band of rabbit skeletal muscle fibers is similar to a human MTrP in many aspects. (2) An MTrP or an MTrS contains multiple minute loci that are closely related to nerve fibers and motor endplates. (3) Both referred pain and local twitch response (characteristics of MTrPs) are related to the spinal cord mechanism. (4) The taut band of skeletal muscle fibers (which contains an MTrP or an MTrS in the endplate zone) is probably related to excessive release of acetylcholine in abnormal endplates. The pathogenesis of an MTrP appears to be related to integrative mechanisms in the spinal cord in response to sensitized nerve fibers associated with abnormal endplates.
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              Lidocaine injection versus dry needling to myofascial trigger point. The importance of the local twitch response.

               C Hong (2015)
              This study was designed to investigate the effects of injection with a local anesthetic agent or dry needling into a myofascial trigger point (TrP) of the upper trapezius muscle in 58 patients. Trigger point injections with 0.5% lidocaine were given to 26 patients (Group I), and dry needling was performed on TrPs in 15 patients (Group II). Local twitch responses (LTRs) were elicited during multiple needle insertions in both Groups I and II. In another 17 patients, no LTR was elicited during TrP injection with lidocaine (9 patients, group Ia) or dry needling (8 patients, group IIa). Improvement was assessed by measuring the subjective pain intensity, the pain threshold of the TrP and the range of motion of the cervical spine. Significant improvement occurred immediately after injection into the patients in both group I and group II. In Groups Ia and Ib, there was little change in pain, tenderness or tightness after injection. Within 2-8 h after injection or dry needling, soreness (different from patients' original myofascial pain) developed in 42% of the patients in group I and in 100% of the patients in group II. Patients treated with dry needling had postinjection soreness of significantly greater intensity and longer duration than those treated with lidocaine injection. The author concludes that it is essential to elicit LTRs during injection to obtain an immediately desirable effect. TrP injection with 0.5% lidocaine is recommended, because it reduces the intensity and duration of postinjection soreness compared with that produced by dry needling.

                Author and article information

                Ann Rehabil Med
                Ann Rehabil Med
                Annals of Rehabilitation Medicine
                Korean Academy of Rehabilitation Medicine
                August 2017
                31 August 2017
                : 41
                : 4
                : 573-581
                [1 ]Department of Rehabilitation Medicine and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine & Severance Hospital, Seoul, Korea.
                [2 ]Department of Physical Medicine and Rehabilitation, National Health Insurance Service Ilsan Hospital, Goyang, Korea.
                [3 ]Department of Physical and Rehabilitation Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
                Author notes
                Corresponding author: Sang Chul Lee. Department of Rehabilitation Medicine and Research Institute of Rehabilitation Medicine, Yonsei University College of Medicine & Severance Hospital, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea. Tel: +82-2-2228-3711, Fax: +82-2-363-2795, bettertomo@
                Copyright © 2017 by Korean Academy of Rehabilitation Medicine

                This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Original Article


                pain, injections, trigger points, infraspinatus, myofascial pain syndromes


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