Ultrasonic Tissue Characterization of the Upper Trapezius Muscle in Patients with Myofascial Pain Syndrome

摘要

Myofascial trigger points (MTrPs) are palpable, tender nodules in skeletal muscle that produce symptomatic referred pain when palpated. MTrPs are characteristic findings in myofascial pain syndrome (MPS). The role of MTrPs in the pathophysiology of MPS is unknown. Objective characterization and quantitative measurement of the properties of MTrPs can improve their localization and diagnosis, as well as lead to clinical outcome measures. MTrPs associated with soft tissue neck pain are often found in the upper trapezius muscle. We have previously demonstrated that MTrPs can be visualized using ultrasound imaging. The goal of this study was to evaluate whether texture-based image analysis can differentiate structural heterogeneity of symptomatic MTrPs and normal muscle.Patients with chronic (>3 months) neck pain with spontaneously painful, palpable MTrPs (active MTrPs) and healthy volunteers without spontaneous pain (normal) were recruited for this study. Entropy filtering was performed on B-mode images of the upper trapezius and mean entropy values of symptomatic muscles were compared with healthy ones.Entropy analysis was also used to evaluate the size of regions with low entropy.We found that sites with active MTrPs have significantly lower entropy (p<0.05), i.e. they have more homogenous texture, than asymptomatic ones.