Myofascial origin of shoulder pain: A literature review

Accepted Manuscript Myofascial origin of shoulder pain: a literature review Stanislav Sergienko , BPT Leonid Kalichman , PT, PhD PII:

S1360-8592(14)00076-X

DOI:

10.1016/j.jbmt.2014.05.004

Reference:

YJBMT 1132

To appear in:

Journal of Bodywork & Movement Therapies

Received Date: 4 February 2014 Revised Date:

4 April 2014

Accepted Date: 28 April 2014

Please cite this article as: Sergienko, S., Kalichman, L., Myofascial origin of shoulder pain: a literature review, Journal of Bodywork & Movement Therapies (2014), doi: 10.1016/j.jbmt.2014.05.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Myofascial origin of shoulder pain: a literature review

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Stanislav Sergienko BPT, Leonid Kalichman PT, PhD*

Department of Physical Therapy, Recanati School for Community Health Professions,

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Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel

*Corresponding author. Leonid Kalichman, Department of Physical Therapy, Recanati

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School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel. Tel: 972-52-2787050;

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Fax: 972-8-6477683. E-mail address: [email protected]

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ACCEPTED MANUSCRIPT ABSTRACT Background: Shoulder pain is a common problem imposing a considerable burden on the affected person and society. Since interventions targeting traditional musculoskeletal

an alternative possible source of shoulder pain.

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conditions are usually only moderately effective, myofascial origin can be suggested as

Objectives: To examine current evidence associated with myofascial origin of shoulder

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pain, with emphasis on diagnosis, prevalence and treatment efficacy.

Methods: PubMed, Google Scholar and PEDro databases were searched from inception

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until December 2013 for terms relating to myofascial pain in the shoulder area. Results: Two studies showed a high reliability of the following diagnostic characteristics during palpation: presence or absence of the taut band, spot tenderness, jump sign, pain recognition and referred pain sensation. Three prevalence studies

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showed a significant greater number of active myofascial trigger points (MTrPs) on the painful shoulder side. Reduced muscle strength, accelerated muscle fatigue, inconsistent muscle activation pattern under load and reduced antagonist reciprocal inhibition were

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found in subjects with latent MTrPs in four observational studies. Six interventional studies demonstrated the effectiveness of dry needling, myofascial manipulation,

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ischemic compression, laser therapy and multimodal treatment. Conclusion: MTrPs in shoulder muscles is a common condition among patients with shoulder complaints and can be reliably diagnosed by palpation. The reviewed interventions seem to be effective in reducing pain, increasing range of motion and improving function of the painful shoulder. KEYWORDS Myofascial pain; Myofascial trigger points; Shoulder pain; Treatment; Review

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ACCEPTED MANUSCRIPT INTRODUCTION Shoulder pain is a common musculoskeletal problem. It is the third most common cause of musculoskeletal consultation in primary care. Approximately 1% of adults annually

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consult a general practitioner with complaints of new shoulder pain (Urwin and others 1998). There are substantial disparities in reported 1-year prevalence of shoulder pain in the general population (4.7-46.7%), strongly influenced by various factors such as

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definition of shoulder disorders, including or excluding limited motion, age, gender and anatomic area (Luime and others 2004; Pope and others 1997). There is no clinical gold

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standard for defining shoulder pain. Shoulder complaints are usually identified as signs and symptoms in the deltoid, upper arm and scapular region, shoulder stiffness and reduced range of motion, often leading to limitations in daily activities (Pope and others 1997). Shoulder pain is widespread and imposes a considerable burden on the affected

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person and society. Swedish insurance data revealed that 18% of disability payments for musculoskeletal disorders was spent on neck and shoulder problems (van der Windt and others 2000). One of the most common causes of shoulder pain is subacromial

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impingement syndrome, comprising rotator cuff tendinopathy or subacromial bursitis. Infections, tumors and neural tissue pathologies are another possibility, but less

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common causes of shoulder pain (Bigliani and Levine 1997; Hawkins and Hobeika 1983; Koester and others 2005; Loitz and others 1999; Mayerhofer and Breitenseher 2004).

Since interventions targeting local subacromial conditions usually provide only

moderately effective treatment of shoulder complaints (Buchbinder and others 2003; Cummins and others 2009; Desmeules and others 2003; Dorrestijn and others 2009; Ekeberg and others 2009; Green and others 2003), alternative possible sources of

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ACCEPTED MANUSCRIPT shoulder pain should be considered. Studies have found a high prevalence of muscles containing active and latent Myofascial Trigger Points (MTrPs) with high local mechanical pain sensitivity and referred pain in patients with chronic non-traumatic

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shoulder pain (Alburquerque-Sendin and others 2013; Bron and others 2011b; Fernandez-de-las-Penas and others 2012; Ge and others 2006; Ge and others 2008).

MTrPs are described as local points, highly sensitive to pressure causing characteristic

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referred sensations, pain, muscle dysfunction and in some cases even sympathetic hyperalgesia (Ge and others 2006; Simons and others 1999).

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MTrPs may be classified as active or latent. Active MTrPs are characterized by the presence of clinical pain and constant tenderness, preventing full lengthening and leading to weakening of the muscle. Diagnostically, active MTrPs refer to patientrecognized pain upon compression and mediate a local twitch response in muscle fibers

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when adequately stimulated. When compressed, active MTrPs produce referred motor phenomena and often autonomic phenomena, generally in its pain reference zone. In contrast, latent MTrPs are clinically quiescent with respect to spontaneous pain, and are

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painful only when palpated. A latent MTrP may have all the clinical characteristics of active MTrP, always with a taut band that increases muscle tension and restricts range

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of motion (Simons and others 1999). Another contribution of MTrPs to shoulder pain may be related to the weakening

and accelerated fatigability of affected muscles thus altering their activation patterns during shoulder movements (Celik and Yeldan 2011; Ge and others 2012; Ibarra and others 2011; Lucas and others 2010). Subacromial impingement syndrome can be associated with abnormal extrinsic mechanics including faulty posture, altered scapular or glenohumeral kinematics, increased anterior and superior humeral head translations,

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ACCEPTED MANUSCRIPT decreased scapular posterior tipping, external rotation and upward rotation. Hence, weakness or fatigue of the muscles controlling these articulations may play a critical role in the development of subacromial impingement syndrome and shoulder pain

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(Michener and others 2003). Despite the possible importance of a myofascial component, reviews addressing the efficacy of interventions for disorders resulting in shoulder pain, stiffness and

Green and others 2003; Green and others 2005).

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disability rarely mention myofascial pain or MTrP therapy (Green and others 2000;

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The purpose of this review was to examine the current evidence associated with myofascial origin of shoulder pain, with emphasis on diagnosis, prevalence and treatment efficacy.

METHODS

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PubMed, Google Scholar and PEDro databases were searched from inception until December 2013, using a predefined search strategy. Databases were searched for the key words "shoulder", "pain", "myofascial", "trigger point" and various combinations.

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Titles and abstracts of all articles mentioning at least one of the key words were reviewed. Studies of any design or methodological quality, except case reports, dealing

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with MTrPs prevalence in the shoulder area, their effect on shoulder muscle function, clinical diagnosis and any kind of treatment were included. Articles were excluded if they were associated with myofascial pain after surgery, myofascial pain in cancer or fibromyalgia patients, myofascial trigger points not related to shoulder pain, injections or other pharmacological interventions for myofascial pain. Study protocol articles and articles without available full text were also excluded from the review. There were no

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ACCEPTED MANUSCRIPT search limitations or language restrictions. The reference lists of all articles retrieved in full were also searched. The methodological quality of interventional studies was evaluated using the

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PEDro score checklist (http://www.pedro.org.au/). The PEDro scale considers two aspects of trial quality, the "internal validity" of the trial and whether the trial contains

validity" of the trial, or the size of the treatment effect. RESULTS

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sufficient statistical information to make it interpretable. It does not rate the "external

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The search strategy initially revealed 88 papers. Of them, 16 studies met the inclusion criteria and were included in this review.

Evaluation of MTrPs in shoulder muscles

Only two relevant studies dealing with the evaluation of MTrPs in shoulder muscles

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were found. One study investigated the test-retest reliability (three day interval, by the same expert) of MTrP diagnostic characteristics, such as taut band, spot tenderness, jump sign, pain recognition, referred pain and local twitch responses (Al-Shenqiti and

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Oldham 2005). Fifty-eight patients (31 males and 27 females, mean age 48.4 years) with rotator cuff tendonitis participated in the study. Kappa values between testing

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situations for the taut band, spot tenderness, jump sign and pain recognition were 1. Kappa values for referred pain ranged between 0.79 and 0.88 and for the local twitch response between 0.75 and 1, depending on the muscles under investigation. Kappa value for twitch response of supraspinatus and subscapularis could not be calculated as this sign was absent in all patients (Al-Shenqiti and Oldham 2005). In the second observational study, three experienced physical therapists bilaterally palpated the infraspinatus, anterior deltoid, and biceps brachii muscles for a total of 12

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ACCEPTED MANUSCRIPT MTrPs (Bron and others 2007). The raters were blinded as to whether the shoulder of the subject was painful. Forty subjects (16 male and 24 female, 40 ± 11.5 years old) participated in the study, eight were asymptomatic and 32 had unilateral or bilateral

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shoulder pain. The most reliable features of MTrPs were the referred pain sensation and jump sign. The percentage of pair-wise agreement (PA) was ≥ 70% (range 63-93%) for referred pain sensation. For the jump sign, PA was ≥ 70% (range 67-77%). Finding a

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nodule in a taut band (PA = 45-90%) and eliciting a local twitch response (PA = 33-

100%) were shown to be least reliable. The highest inter-tester agreement regarding the

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presence or absence of MTrPs was found in the palpation of infraspinatus muscle (PA = 69-80%) (Bron and others 2007). The summary of studies on evaluation of MTrPs in shoulder muscles is presented in Table 1.

Prevalence of MTrPs in shoulder muscles and association with symptoms

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The number of MTrPs bilaterally in the infraspinatus muscles was assessed in an observational study of 21 females, 46.3 ± 4.2 years old, with chronic unilateral myofascial shoulder pain (Ge and others 2008). The number of MTrPs was significantly

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greater (p< 0.001) on the painful side (2.45 ± 0.13) than the non-painful side (1.37 ± 0.12). The number of active (2.31 ± 0.13) and latent (2.58 ± 0.13) MTrPs was similar on

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the painful side (P > 0.05), while on the non-painful side, there were only latent MTrPs (2.73 ± 0.13).

Another study evaluated the presence of MTrPs in the shoulder muscles of 72

subjects (22 males and 50 females, 43.9 ± 12.3 years old) with unilateral nontraumatic shoulder pain; the non-affected shoulder was examined as a control (Bron and others 2011b). The median number of muscles with MTrPs per subject was 6 for active and 4 for latent. Active MTrPs were most prevalent in the infraspinatus (77%) and the upper

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ACCEPTED MANUSCRIPT trapezius muscles (58%); latent MTrPs were most prevalent in the teres major (49%) and anterior deltoid muscles (38%). An additional study compared the number of MTrPs bilaterally in 10 shoulder

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muscles in two groups (Alburquerque-Sendin and others 2013). The shoulder impingement syndrome group consisted of 27 patients (13 males and 14 females, 35.6 ± 12.1 years old) with unilateral shoulder pain. The control group consisted of 20 healthy

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right-handed patients (9 males and 11 females, 37.0 ± 11.2 years old). Taking into

account both sides, the impingement group showed a greater number of MTrPs than the

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controls (p=0.01). The total number of muscles with MTrPs was higher on the involved side (4.7 ± 3.1) than on the dominant side in the control group (2.2 ± 2.8) (p=0.017), however no differences were detected with respect to the uninvolved side (3.2 ± 3.0). For latent MTrPs, no differences were found between sides (p>0.05), while the involved

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side presented a higher number (p=0.003) of active MTrPs (3.3 ± 3.0) compared with the uninvolved side (1.1 ± 2.2) (Alburquerque-Sendin and others 2013). Consecutive blue-collar or white-collar workers with chronic pain in the upper

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quadrant were investigated in another study (Fernandez-de-las-Penas and others 2012). In the blue-collar workers group that included 6 males and 10 females, 44 ± 13 years

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old, a mean of 6 ± 3 active and 10 ± 5 latent MTrPs were present. In the white-collar workers group that included 6 male and 13 females, 44 ± 14 years old, it was a mean of 6±4 active and 11±6 latent MTrPs. Active MTrPs in the upper trapezius, infraspinatus, levator scapulae, and extensor carpi radialis brevis muscles were most prevalent in both groups. No significant differences were found for the total number, the number of active or the number of latent MTrPs between groups (all p>0.05). Significant differences in referred pain areas between muscles were found (p<0.001) with the pectoralis major,

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ACCEPTED MANUSCRIPT infraspinatus, upper trapezius, and scalene muscle MTrPs showing the largest referred pain areas (p<0.01) (Fernandez-de-las-Penas and others 2012). The summary of studies on MTrPs prevalence in shoulder muscles is presented in Table 2.

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Effect of MTrPs on shoulder muscles function The study was designed to assess flexion and scaption strength in both shoulders using a hand-held dynamometer (Celik and Yeldan 2011). Group 1 included 28 healthy subjects

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(12 male and 16 female, 24.25 ± 4.9 years old) with at least two latent MTrPs located on the dominant side of the scapular muscles (upper and middle trapezius, supraspinatus,

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serratus anterior and rhomboids major and minor). Group 2 included 23 healthy subjects (18 males and 5 females, 23.52 ± 4.2 years old) without any MTrPs. No significant differences were found in muscle strength between dominant and non-dominant sides in both groups (p>0.05); both sides muscle strength in Group 1 was significantly lower

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than in Group 2 (p<0.05).

Another study recruited 12 healthy volunteers (8 males and 4 females, 27.4 ± 3.6 years old) with no signs or symptoms of musculoskeletal pain (Ge and others 2012).

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Each subject had at least one latent MTrP bilaterally in the upper trapezius muscle. Surface electromyographic (EMG) recordings and intramuscular EMG from latent

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MTrPs and non-MTrPs were obtained from the upper trapezius muscles during sustained isometric contractions. Intramuscular EMG from latent MTrPs showed an early decrease in mean power frequency and a significant decrease at the end of a fatiguing contraction compared with non-MTrPs (p<0.05). Surface EMG from muscle fibers close to latent MTrPs presented with an early increase in normalized root mean square amplitude. The increase was significantly higher than that of non-MTrPs at the end of a sustained isometric contraction (p<0.05). According to these findings, latent

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ACCEPTED MANUSCRIPT MTrPs are associated with an accelerated development of muscle fatigue, simultaneously overloading other active motor units (Ge and others 2012). An observational study employed surface EMGs to measure the timing of muscle

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activation onset of the upper and lower trapezius, serratus anterior, infraspinatus and middle deltoid muscles initially without load and with a light dumbbell in two groups (Lucas and others 2010). The MTrPs group included 28 subjects (16 males and 12

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females, 33.9 ± 11.4 years old) with at least one latent MTrP in the scapular positioning muscles on the dominant side, but not in the infraspinatus or middle deltoid. The control

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group included 14 subjects (7 males and 7 females, 35.6 ± 8.6 years old) with no latent MTrPs in any of the test muscles. The control group displayed a relatively stable sequence of muscle activation significantly different in timing and variability to that of the latent MTrPs group in all muscles except the middle deltoid (all p<0.05). The latent

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MTrPs group muscle activation pattern under load was inconsistent, the only common feature being early activation of the infraspinatus (Lucas and others 2010). Intramuscular and surface EMG activity between antagonist muscles was

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investigated in another study (Ibarra and others 2011). Fourteen healthy asymptomatic subjects (12 males and 2 females, 26 ± 6.9 years old) participated in a 2-trial study in

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which latent and non-MTrP were detected by palpation in the posterior deltoid muscle. This experiment consisted of 2 sessions with an intramuscular EMG needle electrode inserted into either a latent MTrP or a non-MTrP in the posterior deltoid muscle on the dominant side. The intramuscular EMG activity, but not surface EMG activity in the antagonist muscle, was significantly higher at rest and during shoulder flexion with latent MTrPs than non-MTrPs (p<0.05), signifying reduced antagonist reciprocal

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ACCEPTED MANUSCRIPT inhibition (Ibarra and others 2011). The summary of studies on the effect of MTrPs on shoulder muscles function is presented in Table 3. Treatment of MTrPs in shoulder muscles

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The search strategy revealed six studies dealing with myofascial pain treatment in the shoulder area. Characteristics and results of the reviewed intervention studies are shown in Tables 4 and 5, respectively.

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In a single-blinded within-subject design study, 14 patients with bilateral shoulder pain and active MTrPs in the infraspinatus muscles were evaluated (Hsieh and others

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2007). An MTrP in the infraspinatus muscle on a randomly selected side was dry needled; the contralateral side MTrPs was untreated and used as a control. Shoulder pain intensity was assessed by the Visual Analogue Scale (VAS). Internal rotation active and passive range of motion and pressure pain threshold (PPT) of the MTrPs was

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measured on both sides before and immediately after dry needling. All outcome measures significantly improved only on the treated side (p<0.01). Another study designed as a cross-over randomized control trial (RCT) evaluated

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the effect of 15 ischemic compression (IC) sessions on shoulder MTrPs in 59 patients with chronic shoulder pain (Hains and others 2010). A validated 13-question Shoulder

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Pain and Disability Index (SPADI) questionnaire was used to measure shoulder pain and functional impairment. After the first 15 treatments, the experimental group demonstrated a significant reduction in the SPADI score compared with the control group (p<0.05). The control group subjects also significantly reduced their SPADI scores after the cross-over (p<0.001). Another RCT assessed the effectiveness of multimodal treatment of MTrPs in patients with chronic shoulder pain (Bron and others 2011a). Thirty-four experimental

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ACCEPTED MANUSCRIPT group subjects received a 12 week treatment program. Manual compression of the MTrPs, manual stretching of the muscles and intermittent cold application with stretching was performed once a week by a physical therapist. Patients were instructed

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to perform muscle-stretching and relaxation exercises at home and received ergonomic recommendations and advice as to maintaining good posture. Thirty-one control group subjects remained on the waiting list for 3 months. Compared with the controls after 12

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weeks of treatment, the intervention group showed significant improvement according to the Disabilities of Arm, Shoulder and Hand (DASH) score and VAS (all p<0.05)

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(Bron and others 2011a).

The effectiveness of low-level laser therapy in treating shoulder MTrPs was evaluated in another RCT (Yamany and Salim 2011). Forty patients with unilateral shoulder pain and at least three MTrPs in the deltoid and/or upper trapezius muscles

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were randomly assigned into active and placebo laser groups. The subjects received 12 treatment sessions during a 4 week period, 3 sessions a week. A stretching and strengthening exercise program was performed daily under

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supervision in a clinic and at home for all patients in both groups. After 4 weeks of treatment, VAS and active range of motion significantly improved in both groups. PPT

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significantly increased only in the active laser group (all p < 0.0001). Compared with the placebo group, the active laser group made significant improvements in all outcomes (all p < 0.01) (Yamany and Salim 2011). A quasi-experimental study was designed to evaluate the effect of three fascial

manipulation sessions on chronic posterior brachial pain in 28 patients (Day and others 2009). Fascial manipulation involves applying local deep friction to specific areas over the deep fascia, identified as centers of coordination (Stecco 2004). The densification of

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ACCEPTED MANUSCRIPT fascia (lack of gliding between layers of fascia and between fascia and adjacent structures) was assumed to be associated with myofascial pain (Stecco and others 2013). VAS measurement of pain prior to the first session and after the third session was

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compared with a follow-up evaluation at three months. A mean pain reduction of 57% was obtained after the third session (p<0.0001) and remained without significant

changes (p>0.05) when reassessed after a three month follow-up (Day and others

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2009).

A cohort study assessed the short-term effect of IC for MTrPs on muscle strength,

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mobility, pain sensitivity, and disability in office workers and the effect on disability and general pain at 6-month follow-up (Cagnie and others 2013). Nineteen subjects completed the study and were included for the analyses. All the participants were righthanded office workers performing at least 4 hours of computer work and were

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answering the following criteria: (1) neck/shoulder pain or discomfort of > 30 days during the last year in the neck or shoulder region, (2) pain frequency of at least once a week, and (3) an intensity of pain of at least 2 on a scale from 0 to 10.

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Outcome measures were general neck and shoulder complaints on a Numeric Rating Scale (NRS), Neck Disability Index (NDI), passive neck flexion-extension and

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side flexion measured by inclinometer, neck and shoulder muscle strength measured by dynamometer, and PPT assessed by NRS and algometry. Subjects were tested at baseline (pre-control), after a control period of no treatment of 4 weeks (post-control), and after 4-week intervention training (post-treatment). At 6-month follow-up general neck/shoulder pain and disability were reassessed. All the subjects received 8 sessions of treatment (4 weeks, 2 times a week), consisting of IC on the 4 most painful MTrPs selected during the first testing session. IC

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ACCEPTED MANUSCRIPT consisted of pressure that was gradually increased until the subject experienced his/her highest tolerable pain and was sustained for one minute. The results showed a statistically significant decrease in general neck/shoulder

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pain at post-treatment (p =0.001) and at 6-month follow-up (p = 0.003) compared with pre-control and post-control. There was no significant main effect for NDI scores. PPP increased at post-treatment in all 4 treated MTrPs (p <0.001). There was a significant

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treatment (p<0.05) (Cagnie and others 2013).

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increase in range of motion and muscle strength from pre-control/post-control to post-

DISCUSSION

Two studies assessed the reliability of MTrPs clinical diagnosis in the shoulder region focusing on diagnostic characteristics during palpation. High reliability of presence or

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absence of the taut band, spot tenderness, jump sign, pain recognition and referred pain sensation demonstrated that MTrP palpation is a useful and reliable tool in diagnosing myofascial pain in patients with non-traumatic shoulder pain (Al-Shenqiti and Oldham

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2005; Bron and others 2007).

Prevalence studies have shown a significant greater number of active MTrPs on

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the painful shoulder side. In contrast, no significant difference was found in the number of latent MTrPs between painful and non-painful shoulder muscles. Active MTrPs were most prevalent in the infraspinatus, upper trapezius and levator scapulae muscles (Alburquerque-Sendin and others 2013; Bron and others 2011b; Ge and others 2008). Surprisingly, no significant difference was found in the total number of shoulder MTrPs between white-collar and blue-collar workers (Fernandez-de-las-Penas and others

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ACCEPTED MANUSCRIPT 2012). Obviously, type of work is not a key factor in upper quadrant MTrPs development. Other contributing factors should be investigated in future studies. The effect of MTrPs on shoulder muscle function was evaluated in four

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observational studies. Reduced muscle strength, accelerated muscle fatigue and simultaneous overloading active motor units were found in subjects with latent MTrPs (Celik and Yeldan 2011; Ge and others 2012). In addition, two EMG studies assessing

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the interaction between shoulder muscles and latent MTrP showed an inconsistent

muscle activation pattern under load and reduced antagonist reciprocal inhibition (Ibarra

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and others 2011; Lucas and others 2010). These findings may have an important clinical implication for diagnosis and treatment of disorders associated with abnormal shoulder muscle function, i.e. subacromial or subcoracoid impingement syndromes, rotator cuff or biceps tendinopathy, etc.

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The association between prevalence of active MTrPs and shoulder pain and the influence of MTrPs on shoulder muscle function emphasizes the importance of evaluating myofascial pain in every case of shoulder pain. We feel that myofascial pain

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evaluation should become routine when evaluating shoulder pain. Reviewed studies on the treatment of shoulder myofascial pain, demonstrated the

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effectiveness of dry needling, myofascial manipulation, IC, laser therapy and multimodal treatment that included manual MTrPs compression, manual muscles stretching, cold application, home exercises and ergonomic recommendations. Most studies used VAS of pain intensity as an outcome measure, usually combined with range of motion, functional scales or PPT (Bron and others 2011a; Day and others 2009; Hains and others 2010; Hsieh and others 2007; Yamany and Salim 2011). Since significant electromyographic changes were found in muscles affected by MTrPs (Ge

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ACCEPTED MANUSCRIPT and others 2012; Ibarra and others 2011; Lucas and others 2010), EMG recordings could be used as additional quantitative outcome measure in future MTrPs treatment studies.

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CONCLUSIONS Presence of MTrPs in shoulder muscles is a common condition among patients with

shoulder complaints. Therefore, the myofascial component should be considered as a

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possible primary or secondary source of shoulder pain during clinical examination.

The reviewed interventions for shoulder muscle MTrPs seem to be effective in

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reducing pain, increasing range of motion and improving function of the painful shoulder. Additional studies are needed to identify the contributing factors and causes of MTrPs development in the shoulder area in order to establish preventive strategies for

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these conditions.

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ACCEPTED MANUSCRIPT ACKNOWLEDGEMENTS

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The authors thank Mrs Phyllis Curchack Kornspan for her editorial services.

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Green S, Buchbinder R, Glazier R, Forbes A. 2000. Interventions for shoulder pain.

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Green S, Buchbinder R, Hetrick S. 2003. Physiotherapy interventions for shoulder pain. Cochrane Database Syst Rev(2):CD004258.

Green S, Buchbinder R, Hetrick S. 2005. Acupuncture for shoulder pain. Cochrane Database Syst Rev(2):CD005319.

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Hains G, Descarreaux M, Hains F. 2010. Chronic shoulder pain of myofascial origin: a randomized clinical trial using ischemic compression therapy. J Manipulative Physiol Ther 33(5):362-9.

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Hawkins RJ, Hobeika PE. 1983. Impingement syndrome in the athletic shoulder. Clin Sports Med 2(2):391-405.

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Hsieh YL, Kao MJ, Kuan TS, Chen SM, Chen JT, Hong CZ. 2007. Dry needling to a key myofascial trigger point may reduce the irritability of satellite MTrPs. Am J Phys Med Rehabil 86(5):397-403.

Ibarra JM, Ge HY, Wang C, Martinez Vizcaino V, Graven-Nielsen T, Arendt-Nielsen L. 2011. Latent myofascial trigger points are associated with an increased antagonistic muscle activity during agonist muscle contraction. J Pain 12(12):1282-8.

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ACCEPTED MANUSCRIPT Koester MC, George MS, Kuhn JE. 2005 .Shoulder impingement syndrome. Am J Med 118(5):452-5. Loitz D, Loitz S, Reilmann H. 1999. [The subacromial-syndrome. Diagnosis,

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Luime JJ, Koes BW, Hendriksen IJ, Burdorf A, Verhagen AP, Miedema HS, Verhaar

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Mayerhofer ME, Breitenseher MJ. 2004. [Impingement syndrome of the shoulder]. Radiologe 44(6):569-77.

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Michener LA, McClure PW ,Karduna AR. 2003. Anatomical and biomechanical mechanisms of subacromial impingement syndrome. Clin Biomech (Bristol, Avon) 18(5):369-79.

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Pope DP, Croft PR, Pritchard CM, Silman AJ. 1997. Prevalence of shoulder pain in the community: the influence of case definition. Ann Rheum Dis 56(5):308-12.

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Simons DG, Travell JG, Simons LS. 1999. Travell and Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore, MD: Williams & Wilkins.

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ACCEPTED MANUSCRIPT community: the comparative prevalence of symptoms at different anatomical sites, and the relation to social deprivation. Ann Rheum Dis 57(11):649-55. van der Windt DA, Thomas E, Pope DP, de Winter AF, Macfarlane GJ, Bouter LM,

review. Occup Environ Med 57(7):433-42.

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Silman AJ. 20 .00Occupational risk factors for shoulder pain: a systematic

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Myofascial Trigger Points of Shoulder Pain. World Applied Sciences Journal

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1.758-764:(6)2

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Table 1. Summary of studies on evaluation of MTrPs in shoulder muscles. Design

Participants

Shenqiti

test-retest

rotator cuff

reliability, three

tendonitis

Mean

(male/female)

age

58 (31/27)

48.4

& Oldham day interval, by the

8 asymptomatic and

reliability between

32 with unilateral or

three experienced

bilateral shoulder

physical therapists

pain

TE D

2007

Inter-tester

40 (16/24)

40 ± 11.5

EP

Bron et al

same expert

AC C

2005

Kappa value

M AN U

Al-

N

SC

Inclusion Criteria

Outcome

Results

RI PT

Study

Kappa values for the taut band, spot tenderness,

jump

sign

and

pain

recognition were 1. Kappa values for referred pain ranged between 0.79 and 0.88 and for the local twitch response between 0.75 and 1

Percentage of

The most reliable features of MTrPs

pair-wise

diagnosis were referred pain sensation

agreement

(PA ≥ 70%, range 63-93%) and jump

(PA)

sign (PA ≥ 70%, range 67-77%)

PA - Percentage of pair-wise agreement, MTrPs – myofascial trigger points.

23

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Table 2. Summary of MTrPs prevalence in shoulder muscles studies. Participants N

Mean

(male/female)

age

Chronic unilateral

21

46.3 ±

The number of

shoulder pain

(0/21)

4.2

MTrPs bilaterally in

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Ge et al 2008

Results

nontraumatic

(22/50)

shoulder pain

43.9 ± 12.3

0.001) on the painful side (2.45 ± 0.13) than the non-

the infraspinatus

painful side (1.37 ± 0.12). The number of active

muscles

(2.31 ± 0.13) and latent (2.58 ± 0.13) MTrPs was

TE D

72

EP

unilateral

AC C

Bron et al 2011

The number of MTrPs was significantly greater (p<

SC

Inclusion Criteria

Outcome

RI PT

Study

similar on the painful side (P > 0.05), while on the non-painful side only latent MTrPs were found (2.73 ± 0.13)

The presence of

The median number of muscles with MTrPs per

MTrPs in the

subject was 6 for active and 4 for latent. Active

shoulder muscles

MTrPs were most prevalent in the infraspinatus (77%) and the upper trapezius muscles (58%); latent MTrPs were most prevalent in the teres major (49%) and anterior deltoid muscles (38%)

24

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shoulder

27

35.6 ±

The number of

The impingement group showed a greater number of

Sendin et al

impingement

(13/14)

12.1

MTrPs bilaterally in

MTrPs than the controls (p=0.01). The total number

2013

syndrome with

shoulder muscles in

of muscles with MTrPs was higher on the involved

unilateral shoulder

two groups

control group (2.2 ± 2.8) (p=0.017), no differences

37.0 ±

handed patients

(9/11)

11.2

16

las-Penas et al

workers with

(6/10)

2012

chronic pain in the

44 ±

EP

blue-collar

13

AC C

Fernandez-de-

white-collar workers with

19

were detected with respect to the uninvolved side

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20

TE D

healthy right-

upper quadrant

side (4.7 ± 3.1) than on the dominant side in the

SC

pain

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Alburquerque-

44 ±

(3.2 ± 3.0). For latent MTrPs, no differences were found between sides (p>0.05), while the involved side presented a higher number (p=0.003) of active MTrPs (3.3 ± 3.0) compared with the uninvolved side (1.1 ± 2.2)

The number of

A mean of 6 ± 3 active and 10 ± 5 latent MTrPs were

active and latent

present in the blue-collar workers group, compared to

MTrPs in both

6±4 active and 11±6 latent MTrPs in the white-collar

groups.

group. No significant differences were found for the

The referred pain

total number, the number of active or the number of

areas (drawn on

latent MTrPs between groups (all p>0.05).

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(6/13)

14

upper quadrant

anatomic maps,

Significant differences in referred pain areas between

digitized, and

muscles were found (p<0.001) with the pectoralis

measured)

major, infraspinatus, upper trapezius, and scalene

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chronic pain in the

muscle MTrPs showing the largest referred pain

SC

areas (p<0.01).

AC C

EP

TE D

M AN U

MTrPs – myofascial trigger points.

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Table 3. Summary of studies on the effect of MTrPs on shoulder muscles function. Participants Inclusion Criteria

Outcome N

Mean

(male/female)

age

Results

RI PT

Study

Healthy subjects with ≥

28

24.25

flexion and scaption strength in

Yeldan

latent MTrPs located on

(12/16)

± 4.9

both shoulders using a hand-

2011

the dominant side of the

M AN U

SC

Celik &

held dynamometer

scapular muscles 23

23.52

without any MTrPs

(18/5)

± 4.2

Ge et al

Healthy volunteers with

12

2012

≥one latent MTrP

(8/4)

trapezius muscle

muscle strength between dominant and nondominant sides in both groups (p>0.05). Both sides muscle strength in group with MTrPs was significantly lower than in group without MTrPs (p<0.05).

27.4 ± Surface and intramuscular EMG Intramuscular EMG from latent MTrPs from latent MTrPs and non-

showed an early decrease in mean power

EP

3.6

MTrPs from the upper trapezius frequency and a significant decrease at the

AC C

bilaterally in the upper

TE D

Healthy subjects

No significant differences were found in

muscles during sustained isometric contractions

end of a fatiguing contraction compared with non-MTrPs (p<0.05). Surface EMG from muscle fibers close to latent MTrPs presented with an early

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increase in normalized root mean square amplitude. The increase was significantly

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higher than that of non-MTrPs at the end of a sustained isometric contraction (p<0.05)

≥ One latent MTrP in

28

33.9 ±

Timing of muscle activation

al 2010

the scapular positioning

(16/12)

11.4

onset of the upper and lower

M AN U

SC

Lucas et

muscles on the

trapezius, serratus anterior,

dominant side 14 (7/7)

MTrPs

35.6 ±

muscles with and without light

8.6

load

Healthy asymptomatic

14

26 ±

and

subjects

(12/2)

6.9

significantly

of

muscle

different

in

activation

timing

and

in all muscles except the middle deltoid (all p<0.05)

activity of latent MTrP or a

surface EMG activity in the antagonist

non-MTrP in posterior deltoid

muscle, was significantly higher at rest and

muscle (antagonist) during

during shoulder flexion with latent MTrPs

AC C

2011)

sequence

Intramuscular and surface EMG The intramuscular EMG activity, but not

EP

(Ibarra

others

stable

infraspinatus and middle deltoid variability to that of the latent MTrPs group

TE D

Controls with no latent

The control group displayed a relatively

shoulder flexion

than non-MTrPs (p<0.05)

MTrPs – myofascial trigger points, EMG – electromyography.

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Table 4. Characteristics of the reviewed shoulder myofascial pain treatment studies. Experimental Group Mean

Inclusion

(male/female)

Age

Criteria

14 (8/6)

Intervention

60.2±13.2 Bilateral

1 session of

The same 14

subjects from the

shoulder pain +

MTrP dry

2007

Infraspinatus

needling

M AN U

et al

MTrPs

3 sessions of

et al

posterior

fascial

2009

brachial pain 41 (21/20)

26.7

46.5±8.8

Shoulder pain

TE D

Chronic

Hains

28 (13/15)

for at least the

2010

past 3 months

AC C

et al

Age

Inclusion

Intervention

Criteria

60.2±13.2 Bilateral shoulder pain +

treatment group

Infraspinatus

used as a control

MTrPs

-

-

18 (5/13)

45.6±7.4

-

-

-

manipulation

15 sessions of

Shoulder pain

15 sessions of

ischemic

for at least the

ischemic

compression on

past 3 months

compression on

EP

Day

N (male/female)

RI PT

Hsieh

N

SC

Study

Control Group

shoulder muscle

cervical muscle

MTrPs (once a

MTrPs (once a

week)

week)

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Table 4. Characteristics of the reviewed shoulder myofascial pain treatment studies (cont).

al

(13/21)

42.8±11.7

2011

Unilateral

12 week program of

31

nontraumatic

manual MTrPs

shoulder pain for

compression and muscles

at least 6 months

stretching, cold

45.0±13.2 Unilateral

(8/23)

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34

SC

Bron et

application, stretching and

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relaxation exercises at

Remained on

nontraumatic

the waiting list

shoulder pain

for 3 months

for at least 6 months

home, ergonomic

recommendations

(12/8)

2011

32.6±2.79

Unilateral

12 sessions of laser during

shoulder pain with at least three

20

34.8±7.22 Unilateral

12 sessions of

a 4 week period, combined (10/10)

shoulder pain

placebo laser

with an exercise program

with at least

during a 4

three MTrPs

week period,

AC C

MTrPs

TE D

et al

20

EP

Yamany

combined with an exercise program

Cagnie

19

39.47±8.32 Office workers

8 sessions of IC during a 4

-

-

-

-

30

ACCEPTED MANUSCRIPT

2013

(3/16)

with mild neck

week period, applied on 4

and shoulder

most painful MTrPs

complaints for

identified during

more than 30 days examination

SC

during the last

RI PT

et al

AC C

EP

TE D

MTrPs – myofascial trigger points; IC – ischemic compression

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year

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Table 5. Results of the reviewed should myofascial pain treatment studies.

5/10

al 2007

Outcome

Short Term

Long Term (Follow-up)

Shoulder IR AROM

Increase in treatment side (p <0.01)

-

Shoulder IR PROM

Increase in treatment side (p <0.01)

-

SC

Hsieh et

PEDro

Infraspinatus MTrPs PPT Increase in treatment side (p <0.01)

M AN U

Study

RI PT

Findings

-

Reduction in treatment side (p<0.001)

Pain intensity by VAS

Mean pain reduction of 57% after 3rd

The benefit did not significantly change at the

2009

session (p<0.0001)

three month follow-up (p>0.05)

Hains et

Reduction in experimental group SPADI

Reduction in experimental group SPADI scores

scores compared with controls (p<0.05)

after 6 months (p<0.001). Reduction in control

9/10

SPADI score

EP

al 2010

3/10

-

group SPADI scores after crossover (p<0.001)

AC C

Day et al

TE D

Pain intensity by VAS

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Table 5. Results of the reviewed should myofascial pain treatment studies (cont). DASH score

group compared with controls (p<0.05)

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2011

6/10 VAS score for current pain,

Reduction in experimental group VAS scores

average and most severe

compared with the controls (all p<0.05)

et al 2011

VAS

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pain during the past 7 days Yamany

-

-

SC

Bron et al

Functional improvement in experimental

VAS and AROM significantly improved in

8/10 Shoulder Flex/Abd AROM

both groups, PPT significantly increased only in the active laser group (all p < 0.0001)

PPT

-

TE D

Compared with placebo, the active laser group showed significant improvements in all

General neck/shoulder

et al

complaints by NRS

NRS significantly decreased at post treatment

AC C

Cagnie

EP

outcomes (all p < 0.01) At 6-month follow-up NRS was still

(p = 0.001) compared with

significantly lower compared with

precontrol/postcontrol

precontrol/postcontrol (p = 0.003)

NDI

No significant difference (p = 0.079)

No significant difference (p = 0.079)

Cervical PROM

Significant increase in flexion-extension

2013

-

33

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(p = 0.003) and side flexion (p ≤ .001) compared with precontrol/postcontrol Significant increase in PPT compared with precontrol/postcontrol (p<0.001)

All strength scores significantly increased

-

-

SC

Muscle Strength

RI PT

PPT

(p<0.05)

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compared with precontrol /postcontrol

IR AROM - Internal Rotation Active Range of Motion; IR PROM - Internal Rotation Passive Range of Motion; PPT - Pressure Pain Threshold; VAS - Visual Analog Sale; SPADI - The Shoulder Pain and Disability Index; DASH - The Disabilities of Arm, Shoulder and

EP AC C

NDI - Neck Disability Index.

TE D

Hand; Flex/Abd AROM - Flexion/Abduction Active Range of Motion; MTrPs – myofascial trigger points; NRS - Numeric Rating Scale;

34