Mateusz D. Kobylarz

Background/Objectives: Shear wave elastography (SWE) may provide an objective method for quantifying piriformis muscle stiffness, but its clinical and research use requires evidence that the measurement procedure is reliable. This study aimed to determine the intra- and inter-examiner reliability of a standardized SWE protocol for assessing piriformis muscle stiffness and to provide measurement error thresholds for clinical interpretation. Methods: Twenty-one healthy volunteers were assessed bilaterally by two examiners with different levels of ultrasound experience. The piriformis muscle was identified in the long axis beneath the gluteus maximus, and SWE images were acquired using a standardized protocol. Each side was measured twice by each examiner, resulting in 168 ultrasound images. Reliability was analyzed using side-specific observations (n = 42). Intraclass correlation coefficients (ICCs), standard errors of measurement (SEMs) and minimal detectable changes (MDCs) were calculated for shear modulus and shear wave speed. Results: Inter-examiner reliability was good for single measurements, with ICCs of 0.872 for shear modulus and 0.813 for shear wave speed. When the average of two measurements was used, ICCs were similar, reaching 0.876 and 0.832, respectively. Inter-examiner MDC values ranged from 6.1 to 6.2 kPa for shear modulus and from 0.37 to 0.39 m/s for shear wave speed. Intra-examiner reliability was excellent for both examiners, with ICCs ranging from 0.938 to 0.979. Test–retest MDC values ranged from 2.7 to 3.3 kPa for shear modulus and from 0.19 to 0.22 m/s for shear wave speed. Conclusions: SWE provides good inter-examiner and excellent intra-examiner reliability for assessing piriformis muscle stiffness using a standardized acquisition protocol. Longitudinal assessments should preferably be performed by the same examiner, and changes should be interpreted in relation to SEM and MDC values, particularly in multi-examiner settings where absolute measurement error is larger. These thresholds reflect measurement error and should not be interpreted as evidence of diagnostic validity or responsiveness to treatment.

Background: Latent myofascial trigger points (MTrPs) are clinically relevant because they lower local pressure pain thresholds (PPTs), can perturb motor control, and may sustain shoulder symptoms even when overt pain is absent. However, even if previous studies assessed stiffness and mechanosensitivity differences between MTrPs and asymptomatic regions, objective patient-level cut-offs and diagnostic-accuracy metrics to distinguish latent MTrPs from adjacent asymptomatic tissue are lacking. Objective: To quantify the diagnostic accuracy of pressure algometry (PPT) and shear-wave elastography (SWE) for distinguishing latent MTrPs from adjacent asymptomatic tissue. Methods: A single-center cross-sectional study was conducted including 76 volunteers with ≥1 latent infraspinatus MTrP (assessed by following the current Delphi consensus criteria). The most sensitive latent MTrP and a control site 2 cm cranial was measured on the dominant side infraspinatus muscle in each participant. PPT and SWE were acquired with a standardized protocol (long-axis imaging, anisotropy control, minimal probe pressure; three captures per site; 1 cm rectangular ROI; operator blinded to site type). ROC analyses estimated areas under the curve (AUCs), Youden-optimal cut-offs, sensitivity, specificity, and likelihood ratios (LR+/−). Results: Latent MTrPs showed lower PPTs than controls (p < 0.001) and higher stiffness (shear modulus: p = 0.009; shear-wave speed: p = 0.022). PPT yielded AUC = 0.704 with an optimal cut-off of 47.5 N (sensitivity 0.75; specificity 0.592; LR+ 1.84; LR− 0.42), outperforming SWE metrics (shear modulus AUC 0.611; cut-off 23.6 kPa; sensitivity 0.632; specificity 0.605; LR+ 1.60; LR− 0.61; shear-wave speed AUC 0.601; cut-off 2.55 m/s; sensitivity 0.592; specificity 0.632; LR+ 1.61; LR− 0.65). Conclusions: In the infraspinatus, PPT provides moderate discrimination between latent MTrPs and adjacent asymptomatic tissue, whereas resting SWE—despite small mean differences—exhibited lower accuracy. These findings support mechanosensitivity as a primary measurable signal and position SWE as an adjunct. External validation across devices and operators, and multivariable models integrating sensory, imaging, and clinical features, are warranted.

Background/Objectives: Muscle tissues are a common source of symptoms related to low back pain (LBP), with myofascial trigger points (MTrPs) being a significant contributor. Since previous meta-analyses support interventions targeting MTrPs for reducing pain and improving functional disability in patients with LBP, this review aimed to synthesize current knowledge on the prevalence of MTrPs in LBP patients. Methods: To conduct this systematic review, data were collected from PubMed, Cochrane, and Web of Science. Published articles at any time up to February 2025 that comprised descriptive, observational, or experimental studies in English/Spanish language reporting the prevalence of active or latent MTrPs in patients with LBP were eligible. After assessing the methodological quality, a structured and qualitative synthesis was conducted using a standardized form that captured participant characteristics, evaluated muscles, the number or percentage of active and latent MTrPs in each group, clinical features, summarized results, and conclusions. Results: Nine articles with acceptable methodological quality were included. The prevalence of active MTrPs in patients with LBP was quadratus lumborum (ranging from 30% to 55%), gluteus medius (from 34% to 45%), piriformis (42%), psoas (from 5% to 10%), and lumbar iliocostalis (from 33% to 38%). Latent MTrPs were most common in the gluteus medius (74%) and quadratus lumborum (14–17%), with the piriformis, psoas, and lumbar iliocostalis also affected. Conclusions: Active and latent MTrPs are common in muscles such as the quadratus lumborum, gluteus medius, and iliocostalis in individuals with LBP, with prevalence varying by pain chronicity and etiology. MTrPs in the gluteal region are more frequent in lumbosacral radiculopathy, suggesting a neurogenic-like component. Since the subjectivity of manual palpation and study heterogeneity limit generalizability of the results, future research should standardize diagnostic criteria of MTrPs to ensure the consistency of results.

Objective: This study aimed to determine latent myofascial trigger points and asymptomatic surrounding areas differences in pain pressure thresholds and shear-wave elastography metrics differences. Design: Latent myofascial trigger points and asymptomatic control points were identified within the infraspinatus muscle. A blinded examiner assessed the pain pressure thresholds and acquired three shear-wave elastography images of each location. Pain pressure threshold and shear-wave elastography scores were compared by location (myofascial trigger point and control) and gender. Finally, correlations among demographics, pain pressure thresholds, and shear-wave elastography data were calculated. Results: Forty participants were analyzed. Pain pressure thresholds were significantly lower in latent myofascial trigger points compared with control points in males (P = 0.003) and females (P < 0.001), and lower in females compared with males (myofascial trigger point P < 0.001; control point P = 0.006). No significant shear-wave elastography differences were found between myofascial trigger points and control points (P > 0.05) nor between males and females (myofascial trigger point and control points, P > 0.05). In contrast with the accepted myofascial trigger point definition, those areas with greater pain pressure thresholds exhibited greater stiffness via shear-wave elastography (P < 0.01). Conclusions: Although pain pressure threshold scores indicated significant differences in hyperirritability between latent myofascial trigger points and control points, shear-wave elastography measurements revealed no significant differences in muscle stiffness. Furthermore, muscle stiffness was significantly associated with greater pain pressure threshold scores, challenging the hypothesis that stiffer areas can be identified as myofascial trigger points or sources of pain.

Background and Objectives: Dry needling (DN) is a technique that involves inserting a thin filament needle through the skin to target myofascial trigger points for the treatment of musculoskeletal pain and dysfunction. Despite its efficacy in a broad plethora of musculoskeletal pain conditions, its safety remains a topic of debate among clinicians and researchers. The aim of this study was to provide an overview of the current practice of DN through a national survey, focusing on the frequency of its use and the incidence of adverse events (AEs), considering factors including physiotherapist experience, clinical workload, the extent of training received by practitioners, and the use of ultrasound guidance. Materials and Methods: An online cross-sectional survey was conducted. Respondents were licensed physical therapists (PTs) working in Spain. The survey covered demographics, professional data, frequency of adverse effects, and if they use ultrasound routinary for guiding interventions. Results: A total of 422 PTs participated in the study, mostly having 21–60 h of DN training (38.6%), less than 2 years of experience (36%), and not using ultrasound during the interventions (85.5%). Post-needling soreness and bent needles were the most common AEs, with most severe events rarely reported. Adverse event frequencies varied significantly based on training hours, experience, patient percentage treated with DN, and weekly clinical dedication. Clinicians with more hours of DN training or fewer years of experience reported higher incidences of certain complications. Conclusions: DN is a common intervention among PTs, with minor AEs frequently occurring and major AEs being less common but still significant. The accidental puncture of non-desired structures highlights the necessity for improve training on anatomical landmarks, needle insertion depth, cross-sectional anatomy education, and patient monitoring. To ensure safe practice, emphasize comprehensive training, adhere to safety protocols, exercise caution, and prioritize the use of ultrasound-guide is encouraged.

The levator scapulae muscle is a key structure in the etiopathology of neck and shoulder musculoskeletal pain. Although previous studies used shear-wave elastography (SWE) for characterizing this muscle elasticity, limited evidence assessed the inter-examiner reliability of this procedure. This study aimed to analyze the inter-examiner reliability for calculating Young’s modulus and shear wave speed in a cohort of participants with and without chronic neck pain. A diagnostic accuracy study was conducted, acquiring a set of SWE images at the C5 level in participants with and without neck pain (n = 34 and 33, respectively) by two examiners (one experienced and one novel). After blinding the participants’ identity, examiner involved, and side, the stiffness indicators were calculated by an independent rater in a randomized order. Intra-class correlation coefficients (ICC), standard error of measurement, minimal detectable changes, and coefficient of variation were calculated. Both cohorts had comparable sociodemographic characteristics (p > 0.05). No significant levator scapulae elasticity differences were found between genders, sides, or cohorts (all, p > 0.05). Inter-examiner reliability for calculating Young’s modulus and shear wave speed was moderate-to-good for assessing asymptomatic individuals (ICC = 0.714 and 0.779, respectively), while poor-to-moderate in patients with neck pain (ICC = 0.461 and 0.546, respectively). The results obtained in this study support the use of this procedure for assessing asymptomatic individuals. However, reliability estimates were unacceptable to support its use for assessing elasticity in patients with chronic neck pain. Future studies might consider that the shear wave speed is more sensitive to detect real changes in comparison with Young’s modulus.