Identification of Myofascial Trigger Point Using the Combination of Texture Analysis in B-Mode Ultrasound with Machine Learning Classifiers.

Myofascial pain syndrome is a chronic pain disorder characterized by myofascial trigger points (MTrPs). Quantitative ultrasound (US) techniques can be used to discriminate MTrPs from healthy muscle. In this study, 90 B-mode US images of upper trapezius muscles were collected from 63 participants (left and/or right side(s)). Four texture feature approaches (individually and a combination of them) were employed that focused on identifying spots, and edges were used to explore the discrimination between the three groups: active MTrPs (n = 30), latent MTrPs (n = 30), and healthy muscle (n = 30). Machine learning (ML) and one-way analysis of variance were used to investigate the discrimination ability of the different approaches. Statistically significant results were seen in almost all examined features for each texture feature approach, but, in contrast, ML techniques struggled to produce robust discrimination. The ML techniques showed that two texture features (i.e., correlation and mean) within the combination of texture features were most important in classifying the three groups. This discrepancy between traditional statistical analysis and ML techniques prompts the need for further investigation of texture-based approaches in US for the discrimination of MTrPs.

Ultrasound Imaging and Guidance for Cervical Myofascial Pain: A Narrative Review.

Cervical myofascial pain is a very common clinical condition in the daily practice of musculoskeletal physicians. Physical examination is currently the cornerstone for evaluating the cervical muscles and identifying the eventual presence of myofascial trigger points. Herein, the role of ultrasound assessment in precisely localizing them is progressively mounting in the pertinent literature. Moreover, using ultrasound, not only the muscle tissue but also the fascial and neural elements can be accurately located/evaluated. Indeed, several potential pain generators, in addition to paraspinal muscles, can be involved in the clinical scenario of cervical myofascial pain syndrome. In this article, the authors extensively reviewed the sonographic approach for cervical myofascial pain in order to better diagnose or guide different procedures that can be performed in the clinical practice of musculoskeletal physicians.

The importance of myofascial trigger points in chronic neck pain: An ultrasonography preliminary study.

BACKGROUND: Ultrasonographic evaluation of trigger points detected by physical examination in patients with myofascial pain syndrome is being used more frequently in clinical care. However, the sonographic appearance of trigger points, in association with pain and disability, has not been adequately described. OBJECTIVE: To reveal the presence of trigger points with ultrasonography in those with myofascial pain syndrome and to determine if ultrasound images can help discriminate between demographic and disease characteristics. METHODS: Fifty-two participants with chronic neck pain (NP) were in this cross-sectional study. The pain intensity was evaluated using a 0-10 cm visual analog scale (VAS). The neck disability index measured the NP-induced disability status of the participants. Ultrasonography was used to measure the thicknesses of the paraspinal muscles and the presence of hypoechoic areas within these muscles. RESULTS: There was a positive correlation between the VAS scores of the participants and the ultrasonographic detection of myofascial trigger points (MTPs) in the multifidus and middle trapezius muscles (right/left r = .30, p = .027; r = .29, p = .029; r = .32, p = .009, r = .30, p = .011, respectively). These features correlated with the disability levels of the participants and the MTPs on both the right and left sides of the splenius, multifidus, upper trapezius, and middle trapezius (r = .32, p = .028; r = .38, p = .013, r = .25, p = .027; r = .33, p = .016; r = .25, p = .025, r = .32, p = .018, r = .28, p = .013, r = .29, p = .016, respectively). A significant correlation was present between the detection of MTP at ultrasonography and decreased muscle thickness in the relevant muscles (between p = .001 and p = .034). CONCLUSION: The detection of MTPs with ultrasonography is associated with the severity of pain and disability in those with chronic NP. Features on ultrasound include hypoechoic changes within muscle and reduced muscle thickness associated with MTPs.

Assessment of Concordance between Chairside Ultrasonography and Digital Palpation in Detecting Myofascial Trigger Points in Masticatory Myofascial Pain Syndrome.

INTRODUCTION: Masticatory myofascial pain is a musculoligamentous syndrome that can mimic odontogenic pain. Pain referral to odontogenic structures can be traced to hyperirritated myofascial trigger points (MTrPs). This pragmatic study evaluated the concordance between ultrasonography and palpation in detecting MTrPs in the masseter and temporalis muscles. METHODS: Fifty-seven patients suspected to have temporomandibular disorder were included. MTrPs were palpated manually by expert clinicians. Ultrasonography was then performed by a blind sonographer. The quantity of MTrPs and the involved muscle sections, the pain occurrence, and the location of the MTrPs within the muscle sections were compared using the mean difference (MD) and concordance statistics (Cohen κ and the interclass correlation coefficient [ICC]) as applicable. RESULTS: Ultrasonography located MTrPs as 2.1 ± 1.3 mm2 hypoechoic nodules at a depth of 7 ± 3.3 mm. Ultrasonography moderately agreed with palpation on the quantity of MTrPs per patient (MD = 1; 95% confidence interval [CI], 0.06-1.9; ICC = 0.56; 95% CI, 0.32-0.72). Palpation detected marginally more involved muscle sections per patient (MD = 0.7; 95% CI, 0.06-1.34.05; ICC = 0.64; 95% CI, 0.44-0.77) with more pain occurrence per patient (MD = 1.4; 95% CI, 0.56-2.28; ICC = 0.13; 95% CI, -0.26 to 0.41). There was a discordance in the location of the MTrPs within the muscle sections per patient (κ = -0.46; 95% CI, -0.77 to -0.14). CONCLUSIONS: Ultrasonography and palpation concurred moderately to substantially on the quantity of MTrPs and the involved muscle sections but disagreed on the location of the MTrPs within the muscle sections. Ultrasonography has the potential as a chairside diagnostic aid to help clinicians determine an accurate diagnosis, enhance patient experience during examination, and avoid unnecessary treatments that can mitigate the risk of iatrogenic damage.

From Histoanatomy to Sonography in Myofascial Pain Syndrome: A EURO-MUSCULUS/USPRM Approach.

ABSTRACT: Myofascial pain is a common clinical condition, whereby accurate physical examination is usually considered as the cornerstone to identify/diagnose the "trigger point complex," that is, the characteristic finding of this syndrome. Considering the emerging role of ultrasound examination as the natural extension of physical assessment for musculoskeletal disorders, we briefly revise the histological/anatomical features of trigger points and propose a standardized, multistep sonographic approach to myofascial pain. We also imply that the integrated clinical-ultrasound evaluation could be considered as a potential tool to discriminate different phases/subsets of this challenging pathology.

Ultrasound-guided 3-in-1 trigger point injection for treating myofascial pain syndrome in muscles of the lateral scapular area: a case report.

BACKGROUND: Myofascial pain syndrome (MPS) is a common cause of musculoskeletal pain. MPS in the muscles of the lateral scapula frequently develops due to poor sitting posture (rounded shoulders and cervical kyphosis) in the office as well as long working hours. Herein, we introduce the use of the trigger point injection (TPI) technique in three muscles (i.e., the deltoid, infraspinatus, and teres major muscles) with the same sonographic view for the purpose of treating MPS in the lateral scapular area. CASE DESCRIPTION: A 48-year-old woman presented to our hospital complaining of dull pain in the right lateral scapular area that had persisted for 4 months. The numeric rating scale (NRS) pain score was 5. After confirming taut bands and tenderness in the muscles of the right lateral scapular area, we diagnosed the patient with MPS within the deltoid, infraspinatus, and teres major muscles. Under ultrasound (US) guidance, a mixed solution of 1 mL of 2% lidocaine and 2 mL of normal saline was injected layer by layer into the three muscles within the same sonographic view. At the 1-month follow-up (F/U) visit, the patient reported only slight initial pain (NRS score, 1). CONCLUSIONS: Thus, we recommend our US-guided 3-in-1 technique for performing TPI to treat MPS in the muscles of the lateral scapular area.

Quantitative Shear Wave Speed Assessment for Muscles With the Diagnosis of Taut Bands and/or Myofascial Trigger Points Using Probe Oscillation Shear Wave Elastography: A Pilot Study.

OBJECTIVE: To use probe oscillation shear wave elastography (PROSE) with two vibration sources to generate two shear waves in the imaging plane to quantitatively assess the shear wave speeds (SWSs) of muscles with and without the diagnosis of taut bands (TB) and/or myofascial trigger points (MTrPs). METHODS: Thirty-three patients were scanned with the PROSE technique. Shear waves were generated through continuous vibration of the ultrasound probe, while the shear wave motions were detected using the same probe. SWSs for the sides with and without TBs and/or MTrPs were computed and compared. The pressure pain thresholds (PPTs) were measured as an indicator of maximum pain tolerance of patients. The statistical differences between the SWSs with and without TBs and/or MTrPs with different PPT values were analyzed using the nonparametric Wilcoxon rank-sum test. RESULTS: The mean SWSs for the sides with TBs and/or MTrPs are faster than that of the contralateral side without TBs and/or MTrPs. A significant difference was observed between mean SWSs with and without TBs and/or MTrPs without any information of PPT, with rank-sum test P < .005. Additionally, with the information of PPT, a significant difference was observed between mean SWSs for the sides with and without TBs and/or MTrPs, for PPT values between 0 and 50 N/cm2 (P < .005), but for PPT values between 50 and 90 N/cm2 , it was difficult to differentiate mean SWSs with and without TBs and/or MTrPs. CONCLUSION: Our preliminary results show that SWSs measured from patients had a significant difference between the mean SWSs with and without TBs and/or MTrPs.

New application of multimodal ultrasound imaging for identification of myofascial trigger points in the trapezius muscle.

BACKGROUND: The study aimed to quantify the characteristics of trapezius myofascial trigger points (MTrPs) using shear wave elastography (SWE) and contrast-enhanced ultrasound (CEUS) and explore the application value of the new ultrasound techniques in identifying MTrPs. METHODS: Forty patients participated in this study. MTrPs in the trapezius muscle were determined by palpation, and SWE and CEUS were used to quantify the focal and adjacent areas. The elastic modulus values and CEUS parameters between the focal area of MTrPs and adjacent areas were evaluated and compared. Pathological biopsy was performed according to the above two methods, and the pathological tissues were observed by Masson staining, immunohistochemistry and electron microscope. RESULTS: The elastic modulus values were significantly higher for the focal area of MTrPs compared to those for adjacent areas (P<0.05). There were statistically significant differences in MTrP parameters, including peak intensity, mean transit time, and area between the focal and adjacent areas (P<0.05). Masson staining showed that there were inflammatory cell infiltration dominated by lymphocytes in the vascular wall. Electron microscopy showed a large number of fibroblast proliferation, lamellar collagen proliferation and lysosomal deposition; immunohistochemical results: the expression of CD3+, CD4+, CD8+, CD68+, mhc-1+, dys+, CD8 was more than that of CD20 (F=4.385, P=0.036). CONCLUSIONS: Combined use of SWE and CEUS provides a new detection approach for quantitative identification of MTrPs in the trapezius muscle, which has high application value and is a method worthy of wider use in clinical practice.

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.

Interrater and Intrarater Reliability and Minimum Detectable Change of Ultrasound for Active Myofascial Trigger Points in Upper Trapezius Muscle in Individuals With Shoulder Pain.

OBJECTIVE: We sought to investigate the interrater and intrarater reliability of ultrasound and the minimum detectable change (MDC) for the trigger points (TrPs) active in the upper trapezius (UT) muscle in individuals with shoulder pain. METHODS: Forty individuals with shoulder pain were investigated for the presence of active TrPs in the UT muscle by means of ultrasound for the parameters of gray scale, muscle thickness of UT muscle at rest, and contraction and area of TrPs. The intrarater reliability was performed on 2 days, and interrater reliability on the same day. For the gray scale, the reliability was evaluated using the kappa coefficient (κ), while the other parameters were measured by the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and MDC. RESULTS: For the gray scale, the intrarater agreement was almost perfect (κ = 1.00) and the interrater agreement was substantial (κ = 0.75). The intrarater and interrater reliability were excellent for most of the parameters, except for the area of TrPs (intrarater: ICC = 0.71, substantial; interrater: ICC = 0.52, substantial). The MDC for intrarater reliability varied between 0.04 and 0.05 (SEM% between 2.4% and 38.87%), and that for interrater reliability ranged from 0.05 to 0.07 (SEM% between 3.18% and 55.10%), with a higher value for area. CONCLUSION: Parameters such as gray scale, resting muscle thickness, and muscle contraction of the UT muscle, obtained through ultrasound, showed excellent intrarater and interrater reliability with low SEM%. The intrarater and interrater reliability for the area deserves a caveat regarding their use.

Myofascial Trigger Points Therapy Modifies Thermal Map of Gluteal Region.

BACKGROUND: Thermal imaging may be effectively used in musculoskeletal system diagnostics and therapy evaluation; thus, it may be successfully applied in myofascial trigger points assessment. OBJECTIVE: Investigation of thermal pattern changes after myofascial trigger points progressive compression therapy in healthy males and females. METHODS: The study included 30 healthy people (15 females and 15 males) with age range 19-34 years (mean age: 23.1 ± 4.21). Thermograms of myofascial trigger points were taken pre- and posttherapy and consecutively in the 15th and 30th minutes. Pain reproducible by palpation intensity was assessed with numeric rating scale. RESULTS: Progressive compression therapy leads to myofascial trigger points temperature (p=0.02) and surface (p=0.02) and surface (p=0.02) and surface (p=0.02) and surface (. CONCLUSIONS: The study indicates that myofascial trigger points reaction to applied therapy spreads in time and space and depends on participants' sex.

The relative risk to the femoral nerve as a function of patient positioning: potential implications for trigger point dry needling of the iliacus muscle.

Objectives: Prudent dry needling techniques are commonly practiced with the intent to avoid large neurovascular structures, thereby minimizing potential excessive bleeding and neural injury. Patient position is one factor thought to affect the size of the safe zone during dry needling of some muscles. This study aimed to compare the size of the needle safe zone of the iliacus muscle during two different patient positions using ultrasound imaging. Methods: The distance from the anterior inferior iliac spine (AIIS) to the posterior pole of the femoral nerve was measured in 25 healthy participants (11 male, 14 female, mean age = 40) in both supine and sidelying positions using a Chison Eco1 musculoskeletal ultrasound unit. The average distance was calculated for each position and a two-tailed, paired t-test (α < 0.05) was used to examine the difference between positions. Results: The mean distance from the AIIS to the posterior pole of the femoral nerve was statistically greater with participants in the sidelying position (mean[SD] = 35.7 [6.2] mm) than in the supine position (mean[SD] = 32.1 [7.3] mm, p < .001). Discussion: Although more study is needed, these results suggest that patient positioning is one of several potential variables that should be considered in the optimization of patient safety/relative risk when performing trigger point dry needling. Level of Evidence: Level 4 (Pre-Post Test).

Ultrasound imaging of the upper trapezius muscle for safer myofascial trigger point injections: a case report.

Chronic myofascial pain of the cervical spine and shoulders is commonplace in clinical practice and is often related to adverse posture during work conditions in our lifestyle. The diagnosis is clinical and injections of the neck/shoulder muscles, especially the upper trapezius, are commonly performed in a blinded way. The anatomy of the posterior compartment of the neck is complicated, and several neurovascular structures are located nearby the trapezius and levator scapulae muscles in the inter-fascial planes. In this case of ours, we describe in details the sono-anatomy of the lower neck and propose a posterior ultrasound-guided real-time in-plane approach to inject the muscle belly of the upper trapezius, i.e. avoiding the superficial and deep branches of the transverse cervical artery and the spinal accessory nerve.

Quantitative magnetic resonance imaging of the upper trapezius muscles - assessment of myofascial trigger points in patients with migraine.

BACKGROUND: Research in migraine points towards central-peripheral complexity with a widespread pattern of structures involved. Migraine-associated neck and shoulder muscle pain has clinically been conceptualized as myofascial trigger points (mTrPs). However, concepts remain controversial, and the identification of mTrPs is mostly restricted to manual palpation in clinical routine. This study investigates a more objective, quantitative assessment of mTrPs by means of magnetic resonance imaging (MRI) with T2 mapping. METHODS: Ten subjects (nine females, 25.6 ± 5.2 years) with a diagnosis of migraine according to ICHD-3 underwent bilateral manual palpation of the upper trapezius muscles to localize mTrPs. Capsules were attached to the skin adjacent to the palpated mTrPs for marking. MRI of the neck and shoulder region was performed at 3 T, including a T2-prepared, three-dimensional (3D) turbo spin echo (TSE) sequence. The T2-prepared 3D TSE sequence was used to generate T2 maps, followed by manual placement of regions of interest (ROIs) covering the trapezius muscles of both sides and signal alterations attributable to mTrPs. RESULTS: The trapezius muscles showed an average T2 value of 27.7 ± 1.4 ms for the right and an average T2 value of 28.7 ± 1.0 ms for the left side (p = 0.1055). Concerning signal alterations in T2 maps attributed to mTrPs, nine values were obtained for the right (32.3 ± 2.5 ms) and left side (33.0 ± 1.5 ms), respectively (p = 0.0781). When comparing the T2 values of the trapezius muscles to the T2 values extracted from the signal alterations attributed to the mTrPs of the ipsilateral side, we observed a statistically significant difference (p = 0.0039). T2 hyperintensities according to visual image inspection were only reported in four subjects for the right and in two subjects for the left side. CONCLUSIONS: Our approach enables the identification of mTrPs and their quantification in terms of T2 mapping even in the absence of qualitative signal alterations. Thus, it (1) might potentially challenge the current gold-standard method of physical examination of mTrPs, (2) could allow for more targeted and objectively verifiable interventions, and (3) could add valuable models to understand better central-peripheral mechanisms in migraine.

Novel method to measure active myofascial trigger point stiffness using ultrasound imaging.

INTRODUCTION: Myofascial trigger points (MTrPs) are one of the most common and important causes of musculoskeletal pain. Ultrasound is a useful modality in examining musculoskeletal disorders. By applying compressive stress and observing changes in ultrasound images, the elastic modulus (Young's modulus) can be calculated. Our objective was to develop a novel method to distinguish MTrPs from normal tissues. METHODS: A total of 29 subjects with MTrP in the sternocleidomastoid muscle were assessed. A force gauge was attached to a transducer to obtain stress levels. To obtain strain, images were recorded in both with stress and without stress states. By dividing the stress level by the measured strain, the elastic modulus was determined. RESULTS: Elastic modulus in MTrPs and the normal part of the muscle were measured to be 13379.57 ± 1069.75Pa and 7078.24 ± 482.92Pa, respectively (P = 0.001). This indicated that MTrPs were stiffer than normal parts of the muscle. CONCLUSION: This study presents a new method for the quantitative measurement of the elastic modulus of MTrP, thereby distinguishing MTrPs from normal adjacent muscular tissue, with more simplicity and lower cost, compared to other ultrasound methods.

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

OBJECTIVE: To evaluate stiffness of infraspinatus muscle tissue, both with and without latent trigger points, using ultrasound shear wave elastography (SWE). The primary hypothesis is that muscle with a latent trigger point will demonstrate a discrete region of increased shear wave speed. The secondary hypothesis is that shear wave speed (SWS) in the region with the trigger point will be higher in patients compared with controls, and will be similar between the two groups in the uninvolved regions. DESIGN: Case-control. SETTING: Hospital-based outpatient physical therapy center. PARTICIPANTS: Convenience sample (N=18) of patients (6 female, 3 male, mean age=44) (range=31-61y) diagnosed with latent trigger points in infraspinatus and matched controls without trigger points. MAIN OUTCOME MEASURES: Shear wave speed (m/s). RESULTS: SWS of the latent trigger point (mean=4.09±SD1.4 m/s) did not differ from the adjacent muscle tissue (3.92±1.6 m/s, P>.05), but was elevated compared to corresponding tissue in controls (2.8±0.75 m/s, P=.02). SWS was generally greater in patients' uninvolved tissue (3.83±1.6 m/s) when compared to corresponding tissue in controls (2.62±0.2 m/s, P=.05). CONCLUSION: Although discrete regions of increased SWS corresponding to the trigger point were not observed in patients, evidence of generally increased muscle stiffness in infraspinatus was exhibited compared to healthy controls. Further study of additional muscles with SWE is warranted.

The shear wave elastic modulus and the increased nuclear factor kappa B (NF-kB/p65) and cyclooxygenase-2 (COX-2) expression in the area of myofascial trigger points activated in a rat model by blunt trauma to the vastus medialis.

We aimed to elucidate the increased inflammatory cytokines expression such as nuclear factor kappa B (NF-kB/p65), cyclooxygenase-2 (COX-2), and voltage-gated calcium channels (VGCC) in the area of activated myofascial trigger points (MTrPs) in a rat model by blunt trauma to the vastus medialis and to evaluate the feasibility of a quantitative analysis of muscle elastic modulus using shear wave elastography (SWE). Twelve 7-week-old male SD rats were divided into normal (NM, n = 6) and model groups (MO, n = 6). In the MO group, MTrPs were activated with a blunt strike to the left vastus medialis and subsequent eccentric exercise for 8 weeks. After 4 weeks of rest, the elastic modulus in the focal site was evaluated using SWE. Electromyography (EMG) data were collected at MTrPs and muscle tissues were evaluated for expression of nuclear factor kappa B (NF-kB/p65), cyclooxygenase-2 (COX-2) protein, and voltage-gated calcium channels (VGCC). The number of the palpable taut bands; EMG frequency and amplitude; elastic modulus values; and NFkB/p65, COX-2, and VGCC expression levels were significantly higher for the left focal area in the MO group compared to those for the NM group (p's < 0.05). These findings suggest that elastic modulus measurement using ultrasound SWE may be effective in evaluating MPS. In addition, increased COX-2, NFkB/p65, and VGCC expression may expand the integrated hypothesis of trigger points.

Effect of ischemic compression for cervicogenic headache and elastic behavior of active trigger point in the sternocleidomastoid muscle using ultrasound imaging.

OBJECTIVES: To investigate the effect of ischemic compression on clinical outcomes of a cervicogenic headache and elastic behavior of myofascial trigger points. DESIGN: Randomized, controlled trial. SETTING: Outpatient headache clinic. SUBJECTS: 19 subjects with a cervicogenic headache originating from myofascial trigger point within the sternocleidomastoid muscle. INTERVENTIONS: Subjects were randomized in treatment group (n = 9) and control group (n = 10). Subjects in the treatment group received 4 sessions of ischemic compression in the myofascial trigger point region. MAIN MEASURES: Headache intensity, frequency, and duration, trigger point elastic modulus, trigger point area, pressure tolerance, and pressure pain threshold were assessed before and after treatment. RESULTS: Subjects in the treatment group compared with those in control group showed significant improvements in headache intensity (P = 0.002), headache frequency (P = 0.005), headache duration (P = 0.015), pressure tolerance (P < 0.001), pressure pain threshold (P = 0.039), and myofascial trigger point area (P = 0.017). Changes in myofascial trigger point elastic modulus did not reach a significant level (P > 0.05). CONCLUSION: The improvements in outcome measures suggest that ischemic compression may be effective in subjects with a cervicogenic headache associated with a myofascial trigger point in the sternocleidomastoid muscle. Data suggests that biomechanical properties of MTrP and severity of headache symptoms are not directly linked, and other mechanisms could be more influential in contributing to symptoms.