Background: Myofascial pain syndrome (MPS) is a common non-articular musculoskeletal disorder. It is characterized by local and referred pain due to the presence of myofascial trigger points (MTrPs). MTrPs most commonly involve the upper trapezius muscle and can be visualized using ultrasound imaging. This study was designed to determine the inter-rater reliability of some new ultrasonographic indices of the upper trapezius muscle and the sensitivity and specificity of 2D ultrasound imaging in the diagnosis of MPS.
Materials and methods: This semi-experimental study enrolled 15 participants of both genders (mean age: 40.60 ± 5.74 years) with suspected symptoms of MPS. In the first step of the study, the sensitivity and specificity of ultrasonography for diagnosis of MPS was determined in a double blind manner. In the second step, some ultrasonographic measurements, such as muscle thickness, area of MTrPs in longitudinal view, echogenicity of MTrPs in longitudinal view, echogenicity of muscle with MTrPs in longitudinal and transverse views, and the pennation angle of the upper trapezius muscle were measured twice and their reliability was determined using the value of the mean of the two measurements.
Results: The sensitivity and specificity of ultrasonographic diagnosis were 91% and 75%, respectively. The inter-rater reliability of upper trapezius muscle thickness, pennation angle, area of MTrPs, echogenicity of active MTrPs in longitudinal view, echogenicity of muscle with MTrPs in transverse view and echogenicity of muscle with MTrPs in longitudinal view were 0.91, 0.96, 0.93, 0.83, 0.93, and 0.91, respectively.
Conclusions: 1. Our findings indicated that ultrasonography is a useful method for the diagnosis of MPS owing to its high sensitivity. 2. Appropriate reliability of the quantitative ultrasonographic indices of interest, especially the area of MTrPs and their echogenicity, could be useful for long-term monitoring and designing interventional studies for better management of the syndrome.