Quantitative Ultrasonographic Assessment of Supraspinatus Insertion Tendon in Non-Lame Dogs (Thickness and Relative Echogenicity).

The canine supraspinatus insertion tendon (SIT) is frequently involved in shoulder disorders; however, objective ultrasonographic reference data remain limited. This study aimed to describe the ultrasonographic appearance of the SIT in clinically non-lame dogs and to develop a reproducible protocol for the quantitative analysis of tendon thickness and relative echogenicity. Thirty-five clinically non-lame dogs (70 shoulders) underwent prospective B-mode ultrasonography. On ultrasonographic examination, the SIT appeared as a structure composed of two clearly differentiated regions: a proximal region, which was thinner and more hyperechoic, and a distal region, which was thicker, relatively more hypoechoic, and attached to the bone surface. These findings were consistent with previous descriptions of the SIT ultrasonographic appearance reported in the literature. Tendon thickness and mean echogenicity were evaluated in both regions. Mean echogenicity was quantified using region-of-interest analysis and pixel intensity histograms, with trapezius muscle echogenicity used for background normalisation. Paired statistical tests and Pearson correlation analyses were performed. No significant differences were identified between the left and right SIT measurements for either thickness or relative echogenicity (