OBJECTIVE: To provide a video tutorial on the diagnostic ultrasound approach to the medial compartment of the canine shoulder and provide comparisons of normal and pathological images with corresponding MRI. ANIMALS: Dogs undergoing diagnostic ultrasound of the medial shoulder. METHODS: The medial shoulder was positioned in flexion with external rotation to allow transducer access, clipped, and scrubbed with dilute chlorhexidine. A 2- to 14-MHz linear array probe with a footprint of 50 mm (V8 ultrasound system
Samsung) was used to visualize the medial glenohumeral ligament (MGL), subscapularis, and coracobrachialis with coupling gel, confirmed by cadaveric ultrasound-guided dye injection and dissection. Ultrasound and corresponding MRI were then used to contrast normal anatomy to a live sedated dog with clinical subscapularis tendinopathy and MGL desmopathy. Proton density-weighted MRI sequences (1.5T Vantage Orian
Canon) using a flex coil were able to identify all 3 structures and corresponded to ultrasound findings for normal and pathological anatomy. RESULTS: Diagnostic ultrasound identified normal and abnormal structures of the medial shoulder (coracobrachialis, subscapularis, and MGL). All imaging correlated well to MRI. CLINICAL RELEVANCE: Medial compartment disease of the shoulder is a well-described cause of canine lameness, but diagnosis has traditionally relied on MRI or arthroscopy. Prior ultrasound approaches did not distinguish MGL components, failed to consistently identify normal or surgically transected ligaments, and have not been studied in vivo. Our approach is different and can play an important role in diagnosing medial compartment lesions, as it possesses greater anatomical visualization than arthroscopy and is noninvasive, accomplished with sedation, and relatively accessible and affordable.