Measuring myofascial shear strain in chronic shoulder pain with ultrasound shear strain imaging: a case report.

BACKGROUND: Dysfunctional gliding of deep fascia and muscle layers forms the basis of myofascial pain and dysfunction, which can cause chronic shoulder pain. Ultrasound shear strain imaging may offer a non-invasive tool to quantitatively evaluate the extent of muscular dysfunctional gliding and its correlation with pain. This case study is the first to use ultrasound shear strain imaging to report the shear strain between the pectoralis major and minor muscles in shoulders with and without chronic pain. CASE PRESENTATION: The shear strain between the pectoralis major and minor muscles during shoulder rotation in a volunteer with chronic shoulder pain was measured with ultrasound shear strain imaging. The results show that the mean ± standard deviation shear strain was 0.40 ± 0.09 on the affected side, compared to 1.09 ± 0.18 on the unaffected side (p<0.05). The results suggest that myofascial dysfunction may cause the muscles to adhere together thereby reducing shear strain on the affected side. CONCLUSION: Our findings elucidate a potential pathophysiology of myofascial dysfunction in chronic shoulder pain and reveal the potential utility of ultrasound imaging to provide a useful biomarker for shear strain evaluation between the pectoralis major and minor muscles.

MR elastography-based slip interface imaging (SII) for functional assessment of myofascial interfaces: A feasibility study.

PURPOSE: Abnormal adherence at functional myofascial interfaces is hypothesized as an important phenomenon in myofascial pain syndrome. This study aimed to investigate the feasibility of MR elastography (MRE)-based slip interface imaging (SII) to visualize and assess myofascial mobility in healthy volunteers. METHODS: SII was used to assess local shear strain at functional myofascial interfaces in the flexor digitorum profundus (FDP) and thighs. In the FDP, MRE was performed at 90 Hz vibration to each index, middle, ring, and little finger. Two thigh MRE scans were performed at 40 Hz with knees flexed and extended. The normalized octahedral shear strain (NOSS) maps were calculated to visualize myofascial slip interfaces. The entropy of the probability distribution of the gradient NOSS was computed for the two knee positions at the intermuscular interface between vastus lateralis and vastus intermedius, around rectus femoris, and between vastus intermedius and vastus medialis. RESULTS: NOSS map depicted distinct functional slip interfaces in the FDP for each finger. Compared to knee flexion, clearer slip interfaces and larger gradient NOSS entropy at the vastus lateralis-vastus intermedius interface were observed during knee extension, where the quadriceps are not passively stretched. This suggests the optimal position for using SII to visualize myofascial slip interface in skeletal muscles is when muscles are not subjected to any additional force. CONCLUSION: The study demonstrated that MRE-based SII can visualize and assess myofascial interface mobility in extremities. The results provide a foundation for investigating the hypothesis that myofascial pain syndrome is characterized by changes in the mobility of myofascial interfaces.

Assessment of the Performance of Ultrasonography for Detecting Myofascial Trigger Points.

Needle electromyogram (EMG) research has suggested that endplate noise (EPN) is a characteristic of myofascial trigger points (MTrPs). Although several studies have observed MTrPs through ultrasonography, whether they are hyperechoic or hypoechoic in ultrasound images is still controversial. Therefore, this study determined the echogenicity of MTrP ultrasonography. In stage 1, the MTrP of rat masseter muscle was identified through palpation and marked. Needle EMG was performed to detect the presence of EPN. When EPN was detected, ultrasound scans and indwelling needles were used to identify the nodule with a different grayscale relative to that of its surrounding tissue, and the echogenicity of the identified MTrP was determined. In stage 2, these steps were reversed. An ultrasound scan was performed to detect the nodule at the marked site, and an EMG needle was inserted into the nodule to detect EPN. There were 178 recordings in each stage, obtained from 45 rats. The stage 1 results indicate that the MTrPs in ultrasound images were hypoechoic with a 100% sensitivity of assessment. In stage 2, the accuracy and precision of MTrP detection through ultrasonography were 89.9% and 89.2%, respectively. The results indicate that ultrasonography produces highly accurate and precise MTrP detection results.

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.

Viscoelasticity in trapezius myofascial pain syndrome: quantitative assessment using Real-Time Shear-Wave Elastography.

OBJECTIVE: To investigate the differences in the viscoelastic properties between normal trapezius muscles and those in patients with trapezius myofascial pain syndrome (MPS) using real-time shear-wave elastography (SWE). MATERIALS AND METHODS: This study included 31 patients with trapezius MPS and 31 volunteers. Sixty-one trapezius muscles (41 and 20 on the affected and non-affected side, respectively) of patients with MPS and 62 normal trapezius muscles in volunteers were assessed. Conventional ultrasonic parameters, including skeletal muscle thickness, resistance index (RI), and mean shear wave velocity (SWVmean) of trapezius muscles, were obtained in the seated position with the shoulders and neck relaxed. The daily neck leaning time (unit:hours) of all participants was obtained using a questionnaire. RESULTS: Ultrasound showed no statistically significant differences in thickness or RI of the trapezius muscles of the affected and non-affected sides in MPS patients versus normal trapezius muscles (p = 0.976 and 0.106, respectively). In contrast, the SWVmean of trapezius muscles in patients with MPS was significantly higher than that of normal trapezius muscles in both the affected and non-affected sides (4.41 ± 1.02 m/s vs. 3.35 ± 0.79 m/s, p < 0.001; 4.05 ± 0.63 m/s vs. 3.35 ± 0.79 m/s, p = 0.002). There was no significant difference between the SWVmean of the trapezius muscles on the affected and non-affected sides in patients with MPS (4.41 ± 1.02 m/s vs. 4.05 ± 0.63 m/s, p = 0.225). Correlation analysis showed that daily neck forward time was positively correlated with the SWVmean of the trapezius muscles on the affected and non-affected sides in patients with MPS (r = 0.635, p < 0.001; r = 0.576, p = 0.008). CONCLUSION: SWE can quantitatively evaluate stiffness of trapezius muscles in patients with trapezius MPS. The stiffness of both affected and non-affected trapezius muscles increased in patients with trapezius MPS, and the degree of increase positively correlated with the time of cervical forward leaning.

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

OBJECTIVE: Myofascial pain syndrome (MPS) is one of the most common causes of chronic pain and affects a large portion of patients seen in specialty pain centers as well as primary care clinics. Diagnosis of MPS relies heavily on a clinician's ability to identify the presence of a myofascial trigger point (MTrP). Ultrasound can help, but requires the user to be experienced in ultrasound. Thus, this study investigates the use of texture features and deep learning strategies for the automatic identification of muscle with MTrPs (i.e., active and latent MTrPs) from normal (i.e., no MTrP) muscle. METHODS: Participants (n = 201) were recruited from Toronto Rehabilitation Institute, and ultrasound videos of their trapezius muscles were acquired. This new data set consists of 1344 images (248 active, 120 latent, 976 normal) collected from these videos. For texture analysis, several features were investigated with varying parameters (i.e., region of interest size, feature type and pixel pair relationships). Convolutional neural networks (CNN) were also applied to observe the performance of deep learning approaches. Performance was evaluated based on the classification accuracy, micro F1-score, sensitivity, specificity, positive predictive value and negative predictive value. RESULTS: The best CNN approach was able to differentiate between muscles with and without MTrPs better than the best texture feature approach, with F1-scores of 0.7299 and 0.7135, respectively. CONCLUSION: The results of this study reveal the challenges associated with MTrP identification and the potential and shortcomings of CNN and radiomics approaches in detail.

Concurrent validity of palpation and musculoskeletal ultrasound in evaluating the fascia of individuals with and without myofascial pain syndrome.

BACKGROUND AND PURPOSE: Palpation evaluates the fascia, a three-dimensional web of connective tissues. We propose altered fascia system displacement in patients with myofascial pain syndrome. This study determined the concurrent validity of palpation and musculoskeletal ultrasound (MSUS) videos played on Windows Media Player 10 (WMP) when evaluating the direction of the fascia system's displacement at the end of the cervical active range of motion (AROM). METHODS: This cross-sectional study used palpation as index test and MSUS videos on WMP as reference test. First, three physical therapists palpated right and left shoulders for each cervical AROM. Second, during cervical AROM, PT-Sonographer recorded the fascia system displacement. Third, using the WMP, the physical therapists evaluated the direction of skin, superficial and deep fascia displacements at the end of cervical AROM. MedCalc Version 19.5.3 determined the "exact" Clopper-Pearson Interval (CPI). RESULTS: We found strong accuracy between palpation and MSUS videos on WMP when determining the direction of skin displacement during cervical flexion and extension (CPI= 78.56 to 96.89). There was moderate agreement between palpation and MSUS videos on WMP when determining the direction of the skin, superficial fascia, and deep fascia displacements during cervical lateral flexion and rotation (CPI= 42.25 to 64.13). CONCLUSION: Skin palpation during cervical flexion and extension may be useful in evaluating patients with myofascial pain syndrome (MPS). It is unclear what fascia system was evaluated when shoulders were palpated at the end of cervical lateral flexion and rotation. Palpation as diagnostic tool for MPS was not investigated.

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.

Ultrasound-Guided Trigger Point Injections for the Treatment of Neck and Back Pain in the Emergency Department: A Randomized Trial.

OBJECTIVES: Patients frequently present to the emergency department (ED) with neck or back pain, which can be difficult to treat. We sought to compare ultrasound-guided trigger point injection (TPI) to standard medications for patients with neck or back pain. METHODS: We performed a single-center, open label, randomized controlled trial on ED patients with neck or back pain from myofascial pain syndrome comparing ultrasound-guided TPIs to those who received the combination of a nonsteroidal anti-inflammatory drug (NSAID) and a muscle relaxant (MR). The primary outcome of this study was the reduction in mean pain score at the time of ED disposition. RESULTS: In total, we analyzed 196 patients. At the time of ED disposition, patients in the TPI group had a mean reduction in their pain scores of 45.0 mm as compared to 49.9 mm in the NSAID plus MR group (difference: 4.9 [95% confidence interval (CI) -3.0 to 12.7], P = .22). At the first reassessment, patients in the TPI group had greater pain reduction by 10.7 mm (95% CI 3.1 to 18.4). The rate of rescue therapy use was higher in the NSAID plus MR group (difference: 17.5% [95% CI 4.4 to 36.2]). CONCLUSIONS: We found no difference in pain reduction at the time of ED disposition between patients randomized to the ultrasound-guided TPI group as compared to those who received an NSAID plus a MR. However, patients in the TPI group had greater pain reduction at the time of first reassessment and lower rates of rescue therapy use.

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.

Ultrasound-Guided Erector Spinae Plane Block and Trapezius Muscle Injection for Myofascial Pain Syndrome.

OBJECTIVE: There were two goals to this study: the first goal was to research the analgesic effectiveness of erector spinae plane block (ESPB) added to the treatment after trapezius muscle injection (TMI) and the second was to investigate whether repeated TMI increases the analgesic effect in myofascial pain syndrome (MPS). METHODS: Sixty patients with a diagnosis of MPS were randomized into two groups. The TMI group (n = 30) received ultrasound-guided (USG) TMI with 5 mL of 0.25% bupivacaine two times, with a 1-week interval in between. The ESPB group (n = 30) received USG TMI with 5 mL of 0.25% bupivacaine in the first week and USG ESPB with 20 mL of 0.125% bupivacaine in the second week. The pain severity of the patients was evaluated using the visual analog scale (VAS). The data obtained before (week 0) and after (weeks 1, 2, 3, and 4) the injections were statistically compared between the groups. RESULTS: In both groups, the mean VAS score decreased in the first week compared to the mean pretreatment score (p < .001). When the VAS scores were compared between the first and second weeks, a decrease was observed in both groups (p < .001), but it was more evident in the ESPB group. Compared to previous weeks, there was no significant difference in VAS scores at the third and fourth weeks. CONCLUSIONS: The analgesic effect of repeated TMI for MPS was superior to a single injection, but ESPB combined with TMI provided more effective analgesia than repeated TMI.

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.

Comparing muscle thickness and function in healthy people and subjects with upper trapezius myofascial pain syndrome using ultrasonography.

BACKGROUND: The reliability of the muscle function using ultrasonography is not reported in patients with myofascial pain syndrome and healthy individuals. The main aim of this study was to compare muscle thickness and function of two matched healthy and patients groups with neck pain due to upper trapezius myofascial pain syndrome. METHODS: 40 subjects (20 healthy and 20 patients) participated in this study. Two examiners measured the upper trapezius thickness and function 3 times by ultrasonography independently in the test and retest sessions. RESULTS: There were not significant differences between two groups with respect to demographic characteristics. The ICC values were good to excellent for both measurements. There were no significant differences between the two groups, in terms of upper trapezius muscle thickness in rest (p = 0.63), fair (p = 0.75) and normal (p = 0.73) contractions. On the other hand, % rest-thickness fair (p = 0.006), % rest-thickness normal (p = 0.006), % MVC-thickness (p = 0.02) showed significant differences between two healthy and myofascial pain syndrome groups. CONCLUSIONS: Ultrasonography is a reliable technique used to measure muscle thickness and function. Muscle thickness in rest, fair and normal contractions is not different between the matched groups of healthy people and myofascial pain syndrome subjects. Additionally, muscle function is less in myofascial pain syndrome subjects than healthy people specially % MVC thickness.

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.