Speckle Track Analysis of Ultrasound Images Produce Reliable Measures of Supraspinatus Tendon Strain During a Maximal Isometric Contraction

Abstract

Introduction: Ultrasound speckle tracking is an emergent method in studying musculoskeletal physiology and disease. The precision and reliability of supraspinatus tendon strain measurements have not been explored. The purpose of this study was to examine the reliability of speckle tracking to measure supraspinatus tendon strain. Methods: Forty-two (42) participants participated in this study. Five (5) ultrasound images of the participant’s right shoulder supraspinatus tendon were collected during a maximal voluntary isometric abduction contraction. Cine loop video files of the 5 imaging trials were imported into Ncorr software for speckle track analysis. Axial and longitudinal strain measurements were made for the bursal side, midsubstance, and joint side of the thickest portion of the supraspinatus tendon. Reliability of the strain measures was determined using interclass correlation coefficients (ICC). Bland-Altman plots were created in order to explore systematic error. Results: Mean strain of the supraspinatus tendon ranged from 1.791 to -2.120 %. ICC values for the longitudinal and axial strains of both within and between images were high (>0.9) for all locations of the tendon, demonstrating very good reliability. The 95% for the MDC was large for all measurements of strain, except the axial strain at the mid-substance demonstrating poor precision. Conclusion: The results of the investigation show evidence of very good reliability, poor precision, and some evidence of systematic error. The very good ICC values support the hypothesis that speckle tracking does produce reliable strain measurements. The large MDC values do not support the hypothesis that speckle tracking produces precise strain measurements. Improvements in ultrasound image quality and the shoulder stabilization process need to be made before ultrasound speckle tracking will be a viable research method for the supraspinatus tendon.