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

Introduction/Background Myofascial pain syndrome (MPS) is a prevalent pain disorder characterized by myofascial trigger points (MTrP), which are stiff contracted regions within a taut band of muscle. Clinically MTrPs can be differentiated in two groups, latent and active. Active MTrPs induce spontaneous pain whereas latent MTrPs do not. Clinicians disagree on the criteria that differentiate active and latent MTrPs, necessitating an objective method for their differentiation. Our previous work has shown that ultrasound texture features can differentiate between patients with MPS and healthy individuals in the upper trapezius muscle. The objective of this study was to determine whether ultrasound texture features can differentiate between active MTrPs, latent MTrPs, and healthy individuals in the upper trapezius muscle. Material and method We collected B-mode ultrasound images of the upper trapezius muscle from 18 latent, 19 active, and 24 healthy participants. Ninety-two Haralick, Galloway, and histogram related texture features were extracted from the images. A principal components analysis (PCA) was performed to reduce the features into components that accounted for the most variability among the images (Table 1). A MANOVA and post-hoc analyses were then performed to determine whether healthy, latent, or active group membership could be differentiated by the reduced factors (Table 2). Results The PCA identified eight components that explain 95% of the variability in the images. The features with the three highest loading factors in each component were included in the MANOVA, for a total of 23 features. All features could differentiate between at least two of the latent, active, or healthy groups. Conclusion Ultrasound texture features can differentiate between upper trapezius tissue in patients with active and latent MTrPs, and can differentiate these clinical groups from healthy tissue. Ultrasound should be further explored as a clinical diagnostic modality for differentiating MPS patients.