Myofascial Trigger Point Identification in B-Mode Ultrasound: Texture Analysis Versus a Convolutional Neural Network Approach.

Myofascial pain syndrome (MPS) affects 85% of chronic pain sufferers in a specialty pain center. Neck and low-back are commonly affected by MPS. Myofascial trigger points (MTrPs) are characteristic findings of MPS and are palpable tender nodules in the muscles of symptomatic subjects. Mechanical characterization of MTrPs and surrounding tissue can offer important insight about the pathophysiology of the MPS. In this study, we propose an inexpensive technique, based on ultrasound shear wave elastography, to objectively measure mechanical properties of MTrPs and surrounding tissue in the upper trapezius. In an ongoing clinical study, we recruited 34 subjects: 12 healthy controls, 5 with latent (not spontaneously painful) MTrPs and 17 with symptomatic chronic neck pain and active (spontaneously painful) MTrPs. Shear wave elastography was performed on the upper trapezius of all subjects using the Ultrasonix RP system and an external vibrator. Voigt's model was used to estimate shear modulus G and viscosity μ of the interrogated tissue. Preliminary analysis demonstrates that symptomatic muscle tissue in subjects with neck pain is stiffer (G=10.45±11.36 kPa, mean±standard deviation) compared to muscle in control subjects (G=2.08±1.28 kPa) and that muscle tissue with latent MTrPs (μ=14.39±6.41 Pa*s) is more viscous than normal tissue (μ=9.02±3.92 Pa*s) (p<0.05).

Uncovering the biochemical milieu of myofascial trigger points using in vivo microdialysis: An application of muscle pain concepts to myofascial pain syndrome

Chronic non-specific neck pain is a frequent complaint. It is a recognized medical and socioeconomic problem and a frequent cause of job absenteeism. In recent years, case reports about myofascial pain syndrome (MPS) are emerging among patients suffering from pain. MPS is a regional pain syndrome characterized by myofascial trigger points (MTrP) in palpable taut bands of skeletal muscle that refer pain to a distance, and that can cause distant motor and autonomic effects. To assess the prevalence of active and latent MTrPs in subjects suffering from chronic non-specific neck pain. A population-based cross-sectional descriptive study was carried out from January 2012 to December 2014. Three primary healthcare centers in Alcalá de Henares, Madrid (Spain). Two hundred and twenty-four participants diagnosed by their family doctor with chronic non-specific neck pain. Participants were examined by a physical therapist to determine the presence of MPS. Pain descriptions from the subjects and pain body diagrams guided the physical examination. The subjects were not given any information concerning MPS or other muscle pain syndromes. All participants presented with MPS. MTrPs of the trapezius muscles were the most prevalent, in 93.75% of the participants. The most prevalent active MTrPs were located right (82.1%) and left (79%) in the nearly-horizontal fibers of the upper trapezius muscle. Furthermore, active MTrPs in the levator scapulae, multifidi, and splenius cervicis muscles reached a prevalence of 82.14%, 77.68%, and 62.5%, respectively. MPS is a common source of pain in subjects presenting chronic non-specific neck pain.

Quantitative ultrasound using texture analysis of myofascial pain syndrome in the trapezius

ObjectiveCurrently, there is a lack of objective means to quantify myofascial trigger points (MTrPs) and their core features. Our research compares (1) MTrPs and surrounding myofascial tissue using two-dimensional grayscale ultrasound (2DGSUS) and vibration sonoelastography (VSE); (2) the accuracy of both modes in visualizing MTrPs; (3) ‘active’ and ‘latent’ MTrPs, using VSE; and (4) the accuracy of both modes in visualizing deep and superficially located MTrPs.MethodsFifty participants with more than two MTrPs in their quadratus lumborum, longissimus thoracis, piriformis, and gluteus medius muscles were assigned to an active MTrP (low back pain) group or a latent (currently pain free) MTrP group. MTrP identification was based on their essential criteria. An electronic algometer measured repeatedly the tenderness of MTrPs with reference to pressure pain threshold values. A handheld vibrator was applied over MTrPs, while VSE and 2DGSUS readings were taken using an EUB-7500 ultrasound scanner.ResultsThere was a significant difference between MTrP strain and that of the immediately surrounding myofascial tissue, as measured using VSE (P = 0·001). VSE visualized all superficial and deep MTrPs with an accuracy of 100% (for both groups); the blinded results obtained using 2DGSUS achieved 33% and 35% accuracy, respectively. There was no significant difference found between the tissue strain ratios of active and latent MTrPs (P = 0·929).DiscussionSonoelastography can visualize superficial and deep MTrPs, and differentiate them from surrounding myofascial structure through tissue stiffness and echogenicity. VSE was more accurate than 2DGSUS in visualizing and imaging MTrPs.

The myofascial pain syndrome (MPS) is considered the most common musculoskeletal condition. The lumbopelvic pain (LPP) is established as one of the most prevalent musculoskeletal disorders. Nevertheless, previous research has not yet studied the contractibility changes by tensiomyography between myofascial trigger point (MTrP) types and normal tissue. Therefore, the aim of this study was to determine the tensiomyography, sonoelastography, and pressure pain threshold (PPT) differences between the palpation area of active and latent MTrPs with regards to control points in the lumbar erector spinae muscles of subjects with LPP. A cross-sectional descriptive study was performed. A convenience sample of 60 points (20 active MTrPs, 20 latent MTrPs, and 20 control points) was registered bilaterally in the lumbar erector spinae muscles from subjects with nonspecific LPP. The palpation order of active MTrPs, latent MTrPs, or control points was randomized for each side. The outcome assessors were blinded to the order or point type. The outcome measurements order for each point was sonoelastography manual strain index, tensiomyography, and PPT, separated by 15 minutes. Five contractile objective parameters were: maximal radial displacement (Dm), contraction time (Tc), sustain time (Ts), delay time (Td), and half-relaxation time (Tr). Tensiomyography parameters did not show any statistically significant difference (P > 0.05) between active MTrPs, latent MTrPs, and control points. Nevertheless, PPT and sonoelastography showed statistically significant differences (P < 0.05) between all point types, except for active and latent MTrPs PPT comparison (P = 0.091). Regarding the active MTrPs, a moderate positive correlation was observed between PPT and Dm (P = 0.047; τB = 0.450). Considering the control points, a moderate positive correlation was shown between sonoelastography and Td (P = 0.044; τB = 0.328). The tensiomyography contractile properties did not seem to show differences, while the sonoelastography and mechanosensitivity presented a higher stiffness and a lower PPT, respectively, between the palpation area of active and latent MTrPs with regards to control points in the lumbar erector spinae muscles of subjects with LPP. Considering the correlations, further research is needed regarding the muscle contractile properties modifications under MPS treatments, especially Dm in active MTrPs and Td in normal sites.

Myofascial Trigger Points, Pain, Disability, and Sleep Quality in Individuals With Mechanical Neck Pain

Myofascial trigger points (MTrPs) are palpable painful nodules that can develop in skeletal muscle and are associated with myofascial pain syndrome (MPS), a common chronic pain condition. Symptomatic MTrPs are often a therapeutic target for management of MPS, but the pathophysiology of MTrPs are poorly understood, and the diagnostic criteria lack reliability. Based on the results of our previous studies involving ultrasound imaging of MTrPs, we hypothesized that muscle containing MTrPs has heterogeneous fiber orientation within the affected zone and surrounding areas compared to palpably normal muscle. For this study, we sought to utilize the known variation of shear speed with muscle fiber orientation as a method for determining anisotropy in muscle fibers. We developed a standardized method to acquire shear wave elastography images at different transducer orientations in the upper trapezius muscle of subjects with chronic neck pain (>3 months). The images were aligned with palpable MTrPs using a custom transducer holder with a fixed imaging window. The variation of the shear wave speed of the muscle as a function of the transducer angle was used as a surrogate for muscle fiber orientation. The asymmetry of the fiber orientation was then determined and compared between active (spontaneously-painful) MTrPs, latent (not spontaneously-painful) MTrPs, and normal muscle tissue. Preliminary results from this study showed a statistically significant increase in asymmetry of fiber orientation between active (12.36 ± 7.96° N=14) and normal sites (5.75 ± 4.92° N=8; p<0.027). Our data suggest that disruption of fiber architecture may be an important feature that distinguishes active MTrPs from normal muscle tissue.

The most common cause of chronic musculoskeletal pain is chronic myofascial pain syndrome (MPS). MPS often presents with increased muscle stiffness, and the myofascial trigger point (MTrP). Imaging modalities have been used to identify the MTrP, but their role in the detection and diagnosis of MPS remains unclear. The purpose of this review was to identify evidence in literature for the use of imaging in the role of classifying and explaining the physiology of MTrPs. Since few imaging techniques have been performed on MTrPs, we explored the imaging techniques that can effectively image complex skeletal muscle microstructure, and how they could be used. As part of a scoping review, we conducted a systematic search from three medical databases (CINAHL, EMBASE and MEDLINE) from year to year to analyze past MTrP imaging, as well as analyzing imaging techniques performed on the microstructure of muscle. Previously, ultrasound has been used to differentiate active, latent MTrPs, but these studies do not adequately address their underlying anatomical structure. MRI remains the standard method of imaging skeletal muscle. The existing MRI literature suggests that the DTI technique can quantify muscle injury, strain, and structure. However, theoretically, HARDI and DKI techniques seem to provide more information for complex structural areas, although these modalities have a disadvantage of longer scan times and have not been widely used on skeletal muscle. Our review suggests that DTI is the most effective imaging modality that has been used to define the microstructure of muscle and hence, could be optimal to image the MTrP. HARDI and DKI are techniques with theoretical potential for analysis of muscle, which may provide more detailed information representative of finer muscle structural features. Future research utilizing MRI techniques to image muscle are necessary to provide a more robust means of imaging skeletal muscle and the MTrP.

Objective-The objective of this study is to assess the discriminative ability of textural analyses to assist in the differentiation of the myofascial trigger point (MTrP) region from normal regions of skeletal muscle. Also, to measure the ability to reliably differentiate between three clinically relevant groups: healthy asymptomatic, latent MTrPs, and active MTrP. Methods-18 and 19 patients were identified with having active and latent MTrPs in the trapezius muscle, respectively. We included 24 healthy volunteers. Images were obtained by research personnel, who were blinded with respect to the clinical status of the study participant. Histograms provided first-order parameters associated with image grayscale. Haralick, Galloway, and histogram-related features were used in texture analysis. Blob analysis was conducted on the regions of interest (ROIs). Principal component analysis (PCA) was performed followed by multivariate analysis of variance (MANOVA) to determine the statistical significance of the features. Results-92 texture features were analyzed for factorability using Bartlett's test of sphericity, which was significant. The Kaiser-Meyer-Olkin measure of sampling adequacy was 0.94. PCA demonstrated rotated eigenvalues of the first eight components (each comprised of multiple texture features) explained 94.92% of the cumulative variance in the ultrasound image characteristics. The 24 features identified by PCA were included in the MANOVA as dependent variables, and the presence of a latent or active MTrP or healthy muscle were independent variables. Conclusion-Texture analysis techniques can discriminate between the three clinically relevant groups.

Myofascial pain syndrome (MPS) affects 85% of chronic pain sufferers in a specialty pain center. Neck and low-back are commonly affected by MPS. Myofascial trigger points (MTrPs) are characteristic findings of MPS and are palpable tender nodules in the muscles of symptomatic subjects. Mechanical characterization of MTrPs and surrounding tissue can offer important insight about the pathophysiology of the MPS, which is currently poorly understood. In this study, we propose an inexpensive technique, based on ultrasound shear wave elastography, to objectively measure mechanical properties of MTrPs and surrounding tissue in the upper trapezius. In an ongoing clinical study, we recruited 34 subjects: 12 healthy controls, 10 with not spontaneously painful MTrPs (latent) and 12 with symptomatic chronic neck pain (&amp;gt;3 months) and active (spontaneously painful) MTrPs. Shear wave elastography was performed on the upper trapezius of all subjects using the Ultrasonix RP system and an external vibrator. Voigt’ s model was used to estimate shear modulus G and viscosity μ of the interrogated tissue. Preliminary analysis demonstrates that symptomatic muscle tissue in subjects with neck pain is stiffer (G = 8.40 ± 8.31 kPa, mean ± standard deviation) compared to muscle in control subjects (G = 2.86 ± 2.48 kPa) (p &amp;lt; 0.05), and that active MTrPs are more viscous (μ = 17.10 ± 9.46 Pa*s) than surrounding tissue (μ = 10.59 ± 5.96 Pa*s). Latent MTrPs (μ = 24.31 ± 12.72 Pa*s) and surrounding tissue (μ = 20.09 ± 7.48 Pa*s) are more viscous than normal tissue (μ = 10.96 ± 4.17 Pa*s).

BackgroundShoulder pain is reported to be highly prevalent and tends to be recurrent or persistent despite medical treatment. The pathophysiological mechanisms of shoulder pain are poorly understood. Furthermore, there is little evidence supporting the effectiveness of current treatment protocols. Although myofascial trigger points (MTrPs) are rarely mentioned in relation to shoulder pain, they may present an alternative underlying mechanism, which would provide new treatment targets through MTrP inactivation. While previous research has demonstrated that trained physiotherapists can reliably identify MTrPs in patients with shoulder pain, the percentage of patients who actually have MTrPs remains unclear. The aim of this observational study was to assess the prevalence of muscles with MTrPs and the association between MTrPs and the severity of pain and functioning in patients with chronic non-traumatic unilateral shoulder pain.MethodsAn observational study was conducted. Subjects were recruited from patients participating in a controlled trial studying the effectiveness of physical therapy on patients with unilateral non-traumatic shoulder pain. Sociodemographic and patient-reported symptom scores, including the Disabilities of the Arm, Shoulder, and Hand (DASH) Questionnaire, and Visual Analogue Scales for Pain were compared with other studies. To test for differences in age, gender distribution, and education level between the current study population and the populations from Dutch shoulder studies, the one sample T-test was used. One observer examined all subjects (n = 72) for the presence of MTrPs. Frequency distributions, means, medians, standard deviations, and 95% confidence intervals were calculated for descriptive purposes. The Spearman's rank-order correlation (ρ) was used to test for association between variables.ResultsMTrPs were identified in all subjects. The median number of muscles with MTrPs per subject was 6 (active MTrPs) and 4 (latent MTrPs). Active MTrPs were most prevalent in the infraspinatus (77%) and the upper trapezius muscles (58%), whereas latent MTrPs were most prevalent in the teres major (49%) and anterior deltoid muscles (38%). The number of muscles with active MTrPs was only moderately correlated with the DASH score.ConclusionThe prevalence of muscles containing active and latent MTrPs in a sample of patients with chronic non-traumatic shoulder pain was high.

A Systematic Comparison Between Subjects With No Pain and Pain Associated With Active Myofascial Trigger Points

Myofascial pain syndrome (MPS) is a common, yet poorly understood, acute and chronic pain condition. MPS is characterized by local and referred pain associated with hyperirritable nodules known as myofascial trigger points (MTrPs) that are stiff, localized spots of exquisite tenderness in a palpable taut band of skeletal muscle. Our objective was to evaluate ultrasonic methods for imaging MTrPs and surrounding soft tissue. We recruited 16 subjects with acute neck pain. Based on physical examination, four sites in each patient were labeled as active MTrP (spontaneously-painful), latent MTrP (non-painful), or palpably normal. At these sites, we performed conventional B-mode and Doppler imaging; and vibration sonoelastography (VSE) by inducing vibrations (~100Hz) with a handheld vibrator. Raw RF data were acquired for offline processing. Qualitatively, three observers scored the B-mode and VSE images on a 5-point scale based on the presence and number of nodules, and the Doppler velocity spectra on a 5-point scale based on waveform morphology. Quantitatively, we estimated the spectral parameters, midband fit, zero-frequency intercept and slope, from calibrated RF spectra, and Doppler waveform parameters from spectral envelope tracings. MTrPs appeared as focal, hypoechoic nodules, and as focal regions of reduced vibration amplitude on VSE. Sites with MTrPs on physical exam were more likely to have one or more hypoechoic and/or stiffer nodules on imaging compared to normal muscle (p<;0.05). Arteries near MTrPs had different flow waveform morphology with retrograde diastolic flow (p<;0.02). Based on quantitative measures, MTrPs were distinct from normal muscle and active MTrPs could be differentiated from latent ones (p<;0.04). With further refinement, these methods could lead to objective diagnostic criteria and clinical outcome measures for MTrPs.

Differences on lower trapezius pressure pain threshold, muscle strength and muscle thickness in individuals with chronic neck pain and active or latent myofascial triggers points.