Muscle volume of supraspinatus and infraspinatus in dogs: a computed tomography reliability study

Computed tomography (CT) is an established imaging technique for diagnosing shoulder pathology in dogs. CT images can be used to measure muscle volume, however the reliability of measuring supraspinatus and infraspinatus muscle volume on CT images in dogs is unknown. The aims of this study were to assess the intra- and inter-rater reliability of muscle volume measurements of supraspinatus and infraspinatus in clinically asymptomatic dogs, evaluated on CT images. The CT images of 10 asymptomatic American Staffordshire Bull Terriers were evaluated by two blinded observers. With manual segmentation of muscle boundaries, the muscle volumes were computed using third-party DICOM viewers (OsiriX and Horos). Two-way mixed model intraclass correlation coefficient (ICC) for absolute agreement was used to analyse the reliability of the shoulder muscle volume. The results showed 'excellent' intra-rater (ICC 0.972-0.996) and inter-rater reliability (ICC 0.958-0.988) for all measurements, although wide 95% CIs were observed for some measurements. The muscle volume of supraspinatus and infraspinatus with teres minor can be reliably measured using CT images in asymptomatic American Staffordshire Bull Terriers. Further research focusing on the development of more time-efficient techniques designed specifically for clinical practice is recommended.