Reliability of upper trapezius muscle thickness measurement using B-mode ultrasound Images in patients with latent trigger points

Concerning the liability of Upper trapezius as a postural muscle to permanent stressesµtraumae and therefore its high susceptibility to form trigger points, a highly reliable measurement instrument is needed to make an accurate judgment about its function& its thickness. The aim of this study was to determine the reliability of ultrasonographic measurement of upper trapezius thickness in women suffering from its latent trigger points. This methodological research was conducted by two examiners on 15 women with latent trigger points of upper trapezius. Four images of upper trapezius thickness via ultrasonography were taken on the same day with two hours interval by two examiners at separate times to assess the within- day reliability for each examiner and also the reliability between these two examiners using M-mode ultrasound images (7.5 MHz linear transducer). Muscle thickness change was measured in prone, at the end of expiration. Reliability was examined using intra-class correlation coefficients (ICC), standard error of measurement (SEM), and smallest detectable difference(SDD). The results demonstrated that intra-rater within-day reliability was good both for the first examiner (ICC=0.95,SEM=0.49,SDD=1.38) and the second examiner (ICC=0.95,SEM=0.55,SDD=1.55) and inter-rater reliability was also good between examiners (ICC=O.87,SEM=0.89,SDD=2.47). This study demonstrates ultrasonography can be used reliably with low grades of SEM&SDD to measure upper trapezius thickness following the procedure described by this paper especially in interventional & follow-up studies.