Intra-and inter-rater reliability of ultrasound imaging of the lower trapezius muscle thickness

Abstract

Lower trapezius muscle has an important role in scapula stabilization and normal scapulohumeral rhythm.  Ultrasound imaging (USI) for measurement of the lower trapezius muscle thickness is safe and simple to be used in a clinical setting.  However, there has been little research conducted on the reliability of USI measurement.  The aim of the study was to examine intra-inter reliability of USI measurement of the lower trapezius muscle thickness by two physiotherapists who received 16 hours of USI training.  Fifteen healthy volunteers (5 men and 10 women) aged between 18 and 59 years participated in the study.  The lower trapezius muscle was measured twice using ultrasound at the right side of the spinous process of T8.  The thickness of the lower trapezius muscle for each image was measured twice by Image J program 3 cm lateral to the lateral edge of the spinous process.  The results demonstrated that the intraclass correlation for intra-rater reliability (ICC_{3, 1}) ranged from 0.86 to 0.89 and the intraclass correlation for inter-rater reliability (ICC_{2, 1}) ranged from 0.90 to 0.91.  Standard error of measurement (SEM) and minimal detectable change (MDC) ranged from 0.11 to 0.18 and 0.30 to 0.50, respectively.  From the Bland Altman plots, the mean differences between days were -0.13 to 0.02 and between investigators were 0.05 to 0.21.  The results of this study suggest that the ultrasound imaging of the lower trapezius thickness by the physiotherapists who had 16 hours of USI training is reliable.