Reliability of Upper Trapezius Muscle Thickness Measurement Using B-Mode Ultrasound Images in Patients with Latent Trigger Points

The myofascial trigger points are very sensitive points in tight bundles of the skeletal muscle and contribute to pain and motor limitation and ultimately cause functional impairment. The myofascial trigger points are divided into two active and latent groups clinically. Latent trigger points are more common compared with active trigger points. Among the muscles of the body, the upper trapezius muscle, has the lowest pressure pain threshold against the allgometer, is the most common site of the trigger points in which the trigger points develop, and can cause the myofascial pain syndrome in the neck and shoulders. Methods and Materials: The current study was performed on 10 women with an upper trapezius latent trigger points. Upper trapezius muscle thickness and pennation angle at rest and then thickness and angle pennation of muscle in contraction were measured using a Honda ultrasound machine (2100) Japan – 7.5 MHz linear transducer) in a sitting position on an armchair. Measurements were repeated twice on the same day for half an hour. Intra-class correlation coefficients (ICC), Standard Error of Measurement (SEM), and Minimal Detectable Change (MDC) tests were used to measure the intrarater reliability and to estimate measurement errors.

The results for ICC, SEM, and MDC were used to examine the interrater reliability measuring the thickness of the upper trapezius muscle at rest (ICC = 0.962, SEM = 1.43, MDC = 3.97) and the  pennation angle of the upper trapezius at rest (ICC = 0.913 , SEM = 1.46, MDC = 4.06), the thickness of the upper trapezius muscle in contraction (ICC = 0.979, SEM = 1.95 MDC = 5.43), and pennation angle of the upper trapezius in contraction (ICC = 0.870, SEM = 1.46, MDC = 4.06).

It can be cloncluded that ultrasound, according to the method used in the present study, is a reliable method with small SEM and MDC values in the thickness and pennation angle measurements of upper trapezius muscle at rest and the thickness and pennation angle of the upper trapezius muscle in the contraction.