Evidence of Generalized Muscle Stiffness in the Presence of Latent Trigger Points Within Infraspinatus

Shear Wave Elastography for Measuring the Stiffness of Latent Trigger Points and Surrounding Areas in the Infraspinatus Muscle: Intra- and Interexaminer Reliability Analysis

OBJECTIVES

To explore the intra- and interexaminer reliability of shear wave elastograhy (SWE), (an objective alternative to highly subjective procedures with poor inter-rater reliability such as manual palpation) in measuring the stiffness of latent myofascial trigger points (MTrPs) and healthy surrounding areas in the infraspinatus muscle, pressure pain threshold (PPT), interexaminer reliability, and mean differences in SWE and PPTs between MTrPs and control points.

DESIGN

Longitudinal observational study: Intra- and interexaminer reliability study.

SETTING

A university laboratory.

PARTICIPANTS

Forty participants (N=40) with latent MTrPs within the infraspinatus muscle.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

One experienced examiner identified and classified latent MTrPs and selected an asymptomatic control point within the infraspinatus muscle. Later, 2 blinded examiners assessed once the PPTs (blinded to the scores) and acquired 2 SWE images of each location. Reliability estimates were calculated for assessing PPT interexaminer reliability and SWE intra- and interexaminer reliability. PPT and SWE scores were compared by location (MTrP and control) and gender (male/female).

RESULTS

PPTs were significantly lower in MTrPs than control points in males (P=.003) and females (P=.006), and lower in females than males (MTrP P<.001; control point P=.001). Good interexaminer reliability was found for PPTs (intraclass correlation coefficient [ICC]>0.84) and SWE (ICC>0.82). Intraexaminer reliability for SWE was excellent (ICC>0.95) in both the novice and experienced examiners.

CONCLUSIONS

This study demonstrated excellent SWE intraexaminer reliability (ICCs>0.9) and good interexaminer reliability (ICCs>0.82). Although PPT scores indicated significant differences in hyperirritability between latent MTrPs and control points, SWE measurements revealed no significant differences in muscle stiffness.

Measurement properties of shear wave elastography for evaluating rotator cuff muscle stiffness: a systematic review

BACKGROUND

Literature assessing elasticity in rotator cuff (RC) muscles with shear wave elastography (SWE) is growing but little is known about the overall measurement properties. However, this information is crucial before implementation in research or practice. The objective of this review was first, to systematically investigate the evidence regarding reliability and validity of RC muscles SWE. Second, to summarize measurement protocols to support uniformity and standardization of SWE methodology.

METHODS

A literature search was conducted using Medline (PubMed), Web of Science, and Embase. Included studies reported measurement properties of reliability, validity, and/or responsiveness of SWE to evaluate RC muscle stiffness in subjects without and with musculoskeletal shoulder pain. Methodological quality was rated with the Consensus-Based Standards for the Selection of Health Measurement Instruments checklist. The level of evidence (LoE) was determined using a best-evidence synthesis approach.

RESULTS

Forty-two articles were included. Studies assessing reliability (n = 29) had a moderate LoE for positive ratings of intratester reliability for supraspinatus, infraspinatus, and teres minor and intertester reliability for supraspinatus and infraspinatus. A limited LoE for positive ratings was implied for intertester reliability of teres minor and unknown LoE for negative ratings for day-to-day variability of supraspinatus. Studies reporting on convergent validity (n = 13) showed inconsistent correlation between SWE and other outcomes. Studies assessing discriminant validity (n = 18) showed higher SWE in shoulder patients but not in frozen shoulder and RC tears. Studies reporting on responsiveness (n = 10) showed decreased SWE values 1-2 months postoperatie RC repair and after stretching.

CONCLUSION

Although RC muscle SWE measurements showed overall moderate reliability, few studies used appropriate reliability study designs and protocols. The evidence regarding convergent validity, discriminant validity, and responsiveness is inconsistent, underscoring the need to improve measurement procedures and explore day-to-day reliability. SWE is a potentially valuable technique for RC muscle assessment. However, future high-quality methodological research with reliability and validity as a primary focus is needed to better understand its applicability in clinical practice.

Exploratory Study of Biomechanical Properties and Pain Sensitivity at Back-Shu Points

OBJECTIVES

Hypersensitive acupoints in specific body areas are associated with corresponding internal or visceral disorders. Back-shu points are clinically significant for the diagnosis of visceral organ disease, according to the biomechanical characteristics of the acupoints. In this study, we assessed the biomechanical characteristics and pain sensitivities of five back-shu points linked to five visceral organs in healthy participants.

METHODS

The study included 48 volunteer participants. A myotonometry was used to assess muscle tone and muscle stiffness at five back-shu points associated with visceral organs. Pressure was monitored using a microcontroller and a force sensor. Pain sensitivity was assessed in response to deep pressure pain produced by a constant force.

RESULTS

Substantial differences in muscle tone and stiffness were observed at the five back-shu points; muscle tone was highest at BL15, whereas muscle tone and muscle stiffness were lowest at BL23. Moreover, pain sensitivity was significantly different among the acupoints; pain sensitivity was highest at BL23. There was a significant negative correlation between muscle tone and pain sensitivity.

CONCLUSIONS

We found significant differences in muscle tone, muscle stiffness, and pain sensitivity among five back-shu points associated with visceral organs, which may be attributable to anatomical variations at each point. Our findings suggest that differences at back-shu points should be considered to ensure the accurate diagnosis of visceral disease.

Cervical Multifidus Stiffness Assessment in Individuals with and without Unilateral Chronic Neck Pain: An Inter-Examiner Reliability Study

This study aimed to evaluate the inter-examiner reliability of shear wave elastography (SWE) for measuring cervical multifidus (CM) muscle stiffness in asymptomatic controls and patients with chronic neck pain. A longitudinal observational study was conducted to assess the diagnostic accuracy of a procedure. SWE images, following a detailed procedure previously tested, were acquired by two examiners (one novice and one experienced) to calculate the shear wave speed (SWS) and Young's modulus. The painful side was examined for the experimental cases while the side examined in the control group was selected randomly. Data analyses calculated the intra-class correlation coefficients (ICCs), absolute errors between examiners, standard errors of measurement, and minimal detectable changes. A total of 125 participants were analyzed (n = 54 controls and n = 71 cases). The Young's modulus and SWS measurements obtained by both examiners were comparable within the asymptomatic group (both, p > 0.05) and the chronic neck pain group (both, p > 0.05). Nonetheless, a notable distinction was observed in the absolute error between examiners for shear wave speed measurements among patients with neck pain, where a significant difference was registered (p = 0.045), pointing to a sensitivity in measurement consistency affected by the presence of chronic neck pain. ICCs demonstrated moderate-to-good reliability across both groups, with ICC values for asymptomatic individuals reported as >0.8. Among the chronic neck pain patients, ICC values were slightly lower (>0.780). The study revealed moderate-to-good consistency, highlighting the practicality and generalizability of SWE.

Sensory and emotional responses to deep pressure stimulation at myofascial trigger points: a pilot study

Objective

Although manual pressure, such as that used during a massage, is often associated with pain, it can simultaneously be perceived as pleasant when applied to certain body areas. We hypothesized that stimulation of myofascial trigger points (TPs) leads to simultaneous pain and pleasure. TPs are hyperirritable points located in the taut band of the skeletal muscle.

Method

In this study, we measured the muscle tone, muscle stiffness, and pressure pain threshold of TPs and control points in the left brachioradialis muscle of 48 healthy participants. We also applied deep compression to the two points and collected subjective data on pain, pleasantness, unpleasantness, and relief.

Result

Greater muscle stiffness was observed in the TPs versus control points (t = 6.55, p < 0.001), and the pain threshold was significantly lower in the TPs (t = -6.21, p < 0.001). Unpleasantness ratings after deep compression were significantly lower in the TPs compared with control points (t = -2.68, p < 0.05). Participants experienced greater relief at the TPs compared with control points (t = 2.01, p < 0.05), although the perceived pain did not differ between the two types of points.

Conclusion

We compared the properties of TPs and control points, and found that deep compression at TPs was associated with higher muscle tone and stiffness, lower unpleasantness ratings, and higher relief ratings compared with the control points. These findings suggest that, at least for some TPs, pain and pleasantness are simultaneously elicited by deep pressure stimulation.

Measuring Shear Wave Velocity in Adult Skeletal Muscle with Ultrasound 2-D Shear Wave Elastography: A Scoping Review

Ultrasound 2-D shear wave elastography (US 2D-SWE) is a non-invasive, cost-effective tool for quantifying tissue stiffness. Amidst growing interest in US 2D-SWE for musculoskeletal research, it has been recommended that shear wave velocity (SWV) should be reported instead of elastic moduli to avoid introducing unwanted error into the data. This scoping review examined the evolving use of US 2D-SWE to measure SWV in skeletal muscle and identified strengths and weaknesses to guide future research. We searched electronic databases and key review reference lists to identify articles published between January 2000 and May 2021. Two reviewers assessed the eligibility of records during title/abstract and full-text screening, and one reviewer extracted and coded the data. Sixty-six studies met the eligibility criteria, of which 58 were published in 2017 or later. We found a striking lack of consensus regarding the effects of age and sex on skeletal muscle SWV, and widely variable reliability values. Substantial differences in methodology between studies suggest a pressing need for developing standardized, validated scanning protocols. This scoping review illustrates the breadth of application for US 2D-SWE in musculoskeletal research, and the data synthesis exposed several notable inconsistencies and gaps in current literature that warrant consideration in future studies.

Myofascial Pain Syndrome: A Nociceptive Condition Comorbid with Neuropathic or Nociplastic Pain

Myofascial pain syndrome is featured by the presence of myofascial trigger points (TrPs). Whether TrPs are primary or secondary phenomena or if they relate to central or peripheral nervous system disorders is controversial. Referred pain, a cardinal sign of TrPs, is a central phenomenon driven by peripheral input. In 2021, the International Association for the Study of Pain (IASP) proposed a clinical criteria and grading system for classifying patients with pain on nociceptive, neuropathic, or nociplastic phenotypes. Myofascial TrP pain has been traditionally categorized as a nociceptive phenotype; however, increasing evidence supports that this condition could be present in patients with predominantly nociplastic pain, particularly when it is associated with an underlying medical condition. The clinical response of some therapeutic approaches for managing TrPs remains unclear. Accordingly, the ability to classify myofascial TrP pain into one of these phenotypes would likely be critical for producing more successful clinical treatment outcomes by a precision medicine approach. This consensus paper presents evidence supporting the possibility of subgrouping individuals with myofascial TrP pain into nociceptive, nociplastic, or mixed-type phenotype. It is concluded that myofascial pain caused by TrPs is primarily a nociceptive pain condition, is unlikely to be classified as neuropathic or nociplastic, but can be present in patients with predominantly neuropathic or nociplastic pain. In the latter cases, management of the predominant central pain problem should be a major treatment goal, but the peripheral drive from TrPs should not be ignored, since TrP treatment has been shown to reduce sensitization-associated symptomatology in nociplastic pain conditions, e.g., fibromyalgia.

Changes in stiffness at active myofascial trigger points of the upper trapezius after dry needling in patients with chronic neck pain: a randomized controlled trial

BACKGROUND/OBJECTIVE

Since, to our knowledge, the effects of dry needling (DN) on active myofascial trigger point (MTrP) stiffness have not been analyzed previously with shear wave elastography (SWE), our aim was to compare the effects of a single session of DN and sham DN applied to the most active MTrP located in the upper trapezius muscle on clinical outcomes.

METHODS

A randomized, double-blinded sham-controlled trial was conducted; 60 patients were randomized into an experimental (DN) or sham (sham DN) group. Baseline data including sociodemographic and clinical characteristics were collected. SWE and pain pressure thresholds (PPTs) at the MTrP and a control point located 3 cm laterally were the main outcomes assessed before and 10 min after the interventions.

RESULTS

Patients receiving DN interventions experienced greater increases in the control point PPTs immediately after receiving the intervention compared with sham DN (p < 0.05), but no differences were found for the MTrP (p > 0.05). Post-intervention PPT improvements were found at both locations for both groups (p < 0.01). No significant changes for either MTrP or control locations were found for SWE outcomes in either group (all ps > 0.05). No significant within-group SWE differences were found in the DN or sham DN groups (p > 0.05).

CONCLUSION

A single session of DN or sham DN applied to active MTrPs located in the upper trapezius muscle produced no detectable changes in stiffness at the MTrP or control locations. Real DN induced an immediate analgesic response at both MTrP and control locations, while sham DN induced an immediate MTrP response.

TRIAL REGISTRATION NUMBER

NCT04832074 (ClinicalTrials.gov).

Scoping review and interpretation of myofascial pain/fibromyalgia syndrome: An attempt to assemble a medical puzzle

BACKGROUND

Myofascial Pain Syndrome (MPS) is a common, overlooked, and underdiagnosed condition and has significant burden. MPS is often dismissed by clinicians while patients remain in pain for years. MPS can evolve into fibromyalgia, however, effective treatments for both are lacking due to absence of a clear mechanism. Many studies focus on central sensitization. Therefore, the purpose of this scoping review is to systematically search cross-disciplinary empirical studies of MPS, focusing on mechanical aspects, and suggest an organic mechanism explaining how it might evolve into fibromyalgia. Hopefully, it will advance our understanding of this disease.

METHODS

Systematically searched multiple phrases in MEDLINE, EMBASE, COCHRANE, PEDro, and medRxiv, majority with no time limit. Inclusion/exclusion based on title and abstract, then full text inspection. Additional literature added on relevant side topics. Review follows PRISMA-ScR guidelines. PROSPERO yet to adapt registration for scoping reviews.

FINDINGS

799 records included. Fascia can adapt to various states by reversibly changing biomechanical and physical properties. Trigger points, tension, and pain are a hallmark of MPS. Myofibroblasts play a role in sustained myofascial tension. Tension can propagate in fascia, possibly supporting a tensegrity framework. Movement and mechanical interventions treat and prevent MPS, while living sedentarily predisposes to MPS and recurrence.

CONCLUSIONS

MPS can be seen as a pathological state of imbalance in a natural process; manifesting from the inherent properties of the fascia, triggered by a disrupted biomechanical interplay. MPS might evolve into fibromyalgia through deranged myofibroblasts in connective tissue ("fascial armoring"). Movement is an underemployed requisite in modern lifestyle. Lifestyle is linked to pain and suffering. The mechanism of needling is suggested to be more mechanical than currently thought. A "global percutaneous needle fasciotomy" that respects tensegrity principles may treat MPS/fibromyalgia more effectively. "Functional-somatic syndromes" can be seen as one entity (myofibroblast-generated-tensegrity-tension), sharing a common rheuma-psycho-neurological mechanism.

Assessment of Myofascial Trigger Points via Imaging: A Systematic Review

ABSTRACT

This study systematically reviewed the published literature on the objective characterization of myofascial pain syndrome and myofascial trigger points using imaging methods. PubMed, Embase, Ovid, and the Cochrane Library databases were used, whereas citation searching was conducted in Scopus. Citations were restricted to those published in English and in peer-reviewed journals between 2000 and 2021. Of 1762 abstracts screened, 69 articles underwent full-text review, and 33 were included. Imaging data assessing myofascial trigger points or myofascial pain syndrome were extracted, and important qualitative and quantitative information on general study methodologies, study populations, sample sizes, and myofascial trigger point/myofascial pain syndrome evaluation were tabulated. Methodological quality of eligible studies was assessed based on the Quality Assessment of Diagnostic Accuracy Studies criteria. Biomechanical properties and blood flow of active and latent myofascial trigger points assessed via imaging were found to be quantifiably distinct from those of healthy tissue. Although these studies show promise, more studies are needed. Future studies should focus on assessing diagnostic test accuracy and testing the reproducibility of results to establish the best performing methods. Increasing methodological consistency would further motivate implementing imaging methods in larger clinical studies. Considering the evidence on efficacy, cost, ease of use and time constraints, ultrasound-based methods are currently the imaging modalities of choice for myofascial pain syndrome/myofascial trigger point assessment.

Is early diagnosis of myofascial pain syndrome possible with the detection of latent trigger points by shear wave elastography?

Purpose

The aim of the study was to investigate the contribution of shear wave elastography to the diagnosis of myo-fascial pain syndrome (MPS) of the upper part of the trapezius.

Material and methods

Ethical committee approval was obtained for the study. Thirty volunteer women with trigger points in the upper part of the trapezius muscle and 30 healthy women with a similar age distribution were included in the study. The patient group performed a self-stretching exercise program for 4 weeks. No intervention was applied to the control group. Muscle stiffness values of both groups were evaluated with shear wave elastography (SWE), and pain levels of all volunteers were evaluated by the Visual Analogue Scale at the beginning and the end of the study. The statistical analyses were performed using SPSS version 18.0.

Results

There was a significant decrease after the treatment in terms of upper trapezius muscle stiffness and the pain levels in the patient group (p < 0.001 and p < 0.001). In the patient group, there was a moderate correlation between the decrease in the pain level and the reductions in muscle stiffness (r = 0.595). In control group, there was no significant difference in terms of both muscle stiffness and pain levels before and after treatment (p > 0.05).

Conclusions

SWE is a reliable method for detecting latent trigger points in MPS, and it can be used for evaluating the response to treatment.

Effects of Dry Needling on Muscle Stiffness in Latent Myofascial Trigger Points: A Randomized Controlled Trial

The aim of this study was to analyze the effects of dry needling (DN) in upper trapezius latent trigger points (LTrPs) on muscle stiffness. A total of 51 recreational physically active subjects with LTrPs in the upper trapezius volunteered to participate and were randomly divided into a DN-group (n = 27) and a sham-DN group (n = 24). Volunteers received 1-session of DN or placebo treatment. Muscle stiffness, measured with strain and shear-wave elastography, pressure pain threshold (PPT), post-needling soreness, and muscle thickness were evaluated before treatment, and at 30-min, 24-hours, and 72-hours follow-up after treatment. The DN-group showed lower values from baseline for muscle stiffness measured with shear-wave elastrography at 24-hours (from 44.44 ± 15.97 to 35.78 ± 11.65 kpa; P < .01) and at 72-hours (35.04 ± 12.61 kpa; P < .01) and with strain elastography at 72-hours (from 1.75 ± 0.50 to 1.36 ± 0.40 AU; P < .01). The DN-group showed higher values of PPT than the sham-DN group at 72-hours (4.23 ± 0.75 vs. 5.19 ± 1.16 kg/cm²; P < .05). There was a progressive decrease in post-needling soreness compared to pain during needling of 33.13 ± 21.31% at 30-min, 80.92 ± 10.06% at 24-hours, and a total decrease in post-needling soreness in all participants at 72-hours. DN therapy is effective in reducing short-term muscle stiffness and increasing the PPT in volunteers with LTrPs in the upper trapezius after a treatment session. PERSPECTIVE: This study found that one session of DN intervention in latent trigger points of the upper trapezius muscle reduced muscle stiffness and the pressure pain threshold for the dry needling group compared to the sham dry needling group.

Criteria Used for the Diagnosis of Myofascial Trigger Points in Clinical Trials on Physical Therapy: Updated Systematic Review

OBJECTIVE

The objective of this study was to conduct an updated systematic review of diagnostic criteria for myofascial trigger points (MTrPs) used in clinical trials of physical therapy interventions from 2007 to 2019.

METHODS

MEDLINE and Physiotherapy Evidence Database (PEDro) were searched using the following MeSH keywords: "trigger points," "trigger point," "myofascial trigger point," "myofascial trigger points," "myofascial pain," and "myofascial pain syndrome." The MeSH keywords were combined by using Boolean operators "OR"/"AND." All physiotherapy clinical trials including patients with musculoskeletal conditions characterized by at least 1 active MTrP or latent MTrP in any body area were selected. We pooled data from an individual criterion and criteria combinations used to diagnose MTrPs. The protocol was developed in accordance with the PRISMA-P guidelines.

RESULTS

Of 478 possibly relevant publications, 198 met the inclusion criteria. Of these 198 studies, 129 studies (65.1%) stated specifically the diagnostic criteria used for MTrPs in the main text, 56 studies (28.3%) failed to report any method whereby MTrP was diagnosed, and 13 studies (6.6%) adopted expert-based definitions for MTrPs without specification. Of 129 studies, the 6 criteria applied most commonly were: "spot tenderness" (n=125, 96.9%), "referred pain" (95, 73.6%), "local twitch response" (63, 48.8%), pain recognition (59, 45.7%), limited range of motion" (29, 22.5%), and "jump sign" (10, 7.8%). Twenty-three combinations of diagnostic criteria were identified. The most frequently used combination was "spot tenderness," "referred pain," and "local twitch response" (n=28 studies, 22%).

CONCLUSIONS

A number of the included studies failed in properly reporting the MTrP diagnostic criteria. Moreover, high variability in the use of MTrP diagnostic was also observed. Spot tenderness, referred pain, and local twitch response were the 3 most popular criteria (and the most frequently used combination). A lack of transparency in the reporting of MTrP diagnostic criteria is present in the literature.

REGISTRY

This systematic review was registered under the Centre for Reviews and Dissemination, PROSPERO number: CRD42018087420.

Effect of manual compressive therapy on latent myofascial trigger point pressure pain thresholds

OBJECTIVE

This study compared the effects of 90 s of manual compressive therapy (MCT) on latent myofascial trigger points (LTPs) for 3 sessions per week for 4 weeks to determine changes in individual pressure pain threshold (PPT). A total of 30 (15 males, 15 females; age = 22 ± 4 y/o, height = 175 ± 18 cm, weight = 162.5 ± 57.5 kg) symptomatic subjects with LTPs volunteered for the study.

METHODS

PPT was measured at baseline and pre- and post-treatment for all 12 sessions with a pressure algometer across the 4-week treatment time frame. The MCT was applied to the control group on their LTP at pressure intended to provide a sham condition (1/10 on verbalized analog scale (VAS)). Two experimental groups had MCT applied either directly on the LTP (d-TP) or in close-proximity to their LTP (cp-TP) at moderate pressure (7/10 on VAS).

RESULTS

There was a significant increase in PPT from the first through twelfth treatment sessions (p < 0.001, partial η² = 0.914). A significant increase in PPTs between treatment groups was acutely observed from pre- to post-therapy tests (p = 0.001, partial η² = 0.146). The differences between pre- versus post-treatment PPT measures indicated significant differences (d-TP vs. control, p < 0.001; cp-TP vs. control, p = 0.007). No differences were observed between experimental groups (p = 0.215).

CONCLUSIONS

PPT continued to increase after several weeks of MCT when applied directly on or within 2.5 cm of an identified LTP compared to control.

Ultrasound elastography findings in piriformis muscle syndrome

Background:

Piriformis muscle syndrome (PMS) is relatively less known and underestimated because it is confused with other clinical pathological conditions. Delays in its diagnosis may lead to chronic somatic dysfunction and muscle weakness.

Objective:

Here, we aimed to evaluate the diagnostic performance of the ultrasound elastography (UE) as an easy, less-invasive, and cost-effective method for early diagnosis of PMS.

Materials and Methods:

Twenty-eight cases clinically diagnosed as PMS at the outpatient clinic were evaluated by UE. The elastographic strain ratio was calculated by dividing the strain value of the subcutaneous fat tissue by the mean stress value of the muscle beneath. The diagnostic performances of the strain rate measures were compared using the receiver operating characteristic curve analysis.

Results:

Twenty-one (N = 21) cases were female, and seven (N = 7) of the cases were male. The mean age was 45 years (ranged 24–62 years). The strain rates of piriformis muscle (PM) and gluteus maximus (GM) muscles were significantly higher on the PMS-diagnosed side (P < 0.001). The cutoff value of UE strain ratio for the PM and GM were 0.878 [95% confidence interval (CI) 0.774–0.981] and 0.768 (95% CI 0.622–0.913), respectively, and the sensitivity and specificity values were, respectively, 80.95% and 85.71% for the PM, and they were, respectively, 85.71% and 66.67% for the GM.

Conclusion:

We showed that the muscle elasticity and tissue hardening increased on the problematic side both on PM and GM. UE may provide early diagnosis of PMS, thereby increasing the possibility of treatment with less invasive methods.