Detection of muscle atrophy on routine sonography of the shoulder

Objective. To describe the utility of sonography in visualizing muscle atrophy during routine sonographic examination of the shoulder for evaluation of the rotator cuff tendons. Methods. A retrospective review of 199 shoulder sonographic examinations performed by 2 musculoskeletal radiologists trained in musculoskeletal sonography with knowledge of the typical sonographic findings of muscle atrophy was performed. Reports were reviewed for the presence of muscle atrophy. If atrophy was present, the reports from those examinations were rereviewed for concomitant rotator cuff abnormalities. Results. Forty-five examinations (23%) showed atrophy in at least 1 muscle on the basis of the criteria of increased echogenicity and decreased bulk. There were a total of 81 individual muscles that showed atrophy, with the following distribution: 16% supraspinatus (n = 13), 31% infraspinatus (n = 25), 36% teres minor (n = 29), 2% subscapularis (n = 2), and 6% biceps brachii (n = 5). n 34 of the 45 examinations with muscle atrophy, there were 57 concomitant full-thickness tendon tears: 64% supraspinatus (n = 29), 38% infraspinatus (n = 17), 7% subscapularis (n = 3), 0% teres minor (n = 0), 16% long head of biceps (n = 7), and 2% deltoid (n = 1). Conclusions. Although primary sonographic evaluation of the painful shoulder concentrates on the tendons of the rotator cuff, we suggest that examination of the muscles should become a standard component of the comprehensive shoulder sonographic examination, particularly given the potential clinical implications of muscle atrophy on the outcome of rotator cuff surgery.