Analysis of the thenar muscles with ultrasound shear wave elastography: Reliability and preliminary findings

Introduction/Aims: Ultrasound shear wave elastography (SWE) of the thenar muscles has the potential to provide a simple and noninvasive assessment of the severity of carpal tunnel syndrome (CTS), but its reliability is unknown. The purpose of this study was to assess the intra- and inter-rater reliability of SWE measurements of the elastic modulus of individual thenar muscles, to assess their suitability for clinical application. Methods: Fourteen healthy volunteers, seven male and seven female, participated in this study. The elastic modulus of the thenar muscles was measured with SWE, with two independent examiners to assess inter-rater reliability. The first examiner also performed a second measurement after an interval of least 1 day to assess intra-rater reliability. Reliability was evaluated using an intraclass correlation coefficient (ICC) and 95% confidence interval (CI). Results: For the abductor pollicis brevis (APB) and opponens pollicis (OPP), the CI of ICC in intra-rater reliability was 0.47–0.85 and 0.56–0.88, respectively. The CI of ICC in inter-rater reliability was 0.27–0.78 for the APB and 0.22–0.76 for the OPP. The ICCs of intra- and/or inter-rater reliability of other thenar muscles were less than 0.5. Discussion: In this study, SWE evaluations of thenar muscles were quite variable in terms of their reliability. A larger study will be needed to determine the source of this variability, improve reliability, and assess the value of SWE in the evaluation of the severity of CTS.