Evaluacióndelospuntosgatillomiofascialesconecografía:unametodologíaquecombinavibraciónexternacon"PowerDopplerImaging"ymodoB

Myofascial pain syndrome affects millions of people worldwide, yet diagnosing myofascial trigger points (MTPs) remains challenging. Currently, clinicians rely mainly on manual palpation—pressing on muscles to find tender, taut bands that reproduce a patient's pain. However, this method depends heavily on the examiner's experience and cannot reliably detect deep trigger points. More advanced techniques like MRI, electron microscopy, muscle biopsies, and elastography exist, but they are expensive, complex, and not practical for everyday clinical use.

Musculoskeletal ultrasound has become increasingly popular in rehabilitation because it is portable, relatively inexpensive, and provides real-time imaging. Unfortunately, using ultrasound to diagnose MTPs has been inconclusive due to the lack of standardized protocols and validated diagnostic criteria. The central problem this study addresses is whether conventional ultrasound modes—specifically Power Doppler Imaging (PDI) and B-mode—could be combined with external vibration to create an accessible, objective method for identifying MTPs. The researchers hypothesized that healthy muscle tissue would transmit mechanical vibrations detectable by Doppler ultrasound, while stiffer regions like trigger points would block or attenuate this transmission, creating a recognizable pattern.

This proof-of-concept case series included five participants: four healthy individuals (three men aged 61, 27, and 25; one woman aged 25) and one 75-year-old man who had experienced a stroke. The researchers developed a custom portable vibration device after finding that tuning forks produced uneven, short-duration vibrations unsuitable for scanning. The final device used a mechanical motor with 10 adjustable intensity levels, transferring vibration through ECG electrode patches attached to the skin. An accelerometer confirmed stable, reproducible vibration patterns ranging from 303 Hz at 10% intensity to 899.91 Hz at maximum intensity.

The study focused on the medial gastrocnemius muscle. Participants lay on their side with the leg in a neutral, relaxed position. To minimize operator-dependent variability, the ultrasound probe was secured in a fixed position using a camera tripod, avoiding manual compression artifacts. The researchers tested different electrode placements (longitudinal, transverse, and oblique) and compared color Doppler versus PDI modes.

After manual palpation identified suspected trigger points using 2018 international consensus criteria, the ultrasound evaluation followed. Control areas within the same muscle without trigger points were also examined. For reproducibility testing, the probe was removed and repositioned between measurements.

The PDI mode proved more sensitive than conventional color Doppler for detecting vibration-induced muscle responses. Transverse electrode placement produced more effective and homogeneous vibration propagation, particularly with PDI. An oblique electrode configuration allowed smooth transitions between transverse and longitudinal imaging planes without repositioning.

Across all healthy participants, a consistent pattern emerged in suspected trigger point regions: well-defined non-vibrating areas surrounded by vibrating tissue. These non-vibrating zones corresponded to hypoechoic (darker) regions on B-mode ultrasound. This pattern differed from other stiff anatomical structures like fascia, tendons, or fibrotic tissue, which appeared hyperechoic (brighter) on B-mode. Control areas without trigger points showed homogeneous vibration distribution without the characteristic non-vibrating zone.

In the stroke patient, pathological muscle adaptations created challenges. Vibration transmission was unstable and inhomogeneous, with larger non-vibrating regions than would be expected for isolated trigger points, likely due to increased muscle stiffness and fibro-adipose tissue. Nevertheless, some areas compatible with trigger points were identified using the same pattern of a non-vibrating zone surrounded by Doppler activity. Notably, dry needling in one of these regions altered the Doppler signal—the previously non-vibrating area showed increased Doppler activity after needle insertion and removal, with less clear demarcation.

The vibration device caused no adverse events or side effects in any participant, even at maximum intensity.

This proof-of-concept study demonstrates that combining external vibration with PDI and B-mode ultrasound is feasible and reproducible for identifying myofascial trigger points. The key practical implication is that clinicians may eventually have an objective, low-cost diagnostic tool using ultrasound modes already available on most basic to mid-range devices—no expensive elastography equipment required. The method leverages PDI's sensitivity to detect vibration transmission changes, while B-mode helps distinguish trigger points (hypoechoic) from other stiff structures like fascia (hyperechoic).

For patients, this could mean more reliable diagnosis of trigger points, including deeper ones that are difficult to find by touch alone. For clinicians, especially in settings without advanced imaging, this approach could standardize evaluation and reduce dependence on subjective palpation skills. The finding that dry needling changed the Doppler pattern in the stroke patient also hints at potential for using this method to monitor treatment response, though this was only exploratory.

However, significant work remains before clinical implementation. The study included only five people, and the stroke patient served merely as an exploratory example without direct comparison to healthy controls. The ultrasound device used limited the Doppler box size, preventing full muscle visualization in one view. Future research needs larger controlled studies to establish diagnostic accuracy, reliability, and whether manual probe handling (rather than tripod fixation) yields equally clear results.

If validated and refined—perhaps with flexible Doppler settings and image processing algorithms—this methodology could eventually integrate into routine musculoskeletal practice, making objective trigger point assessment widely accessible.