Trans-axillary sonography in the ABER (ABduction and External Rotation) position: a window to the subscapularis, teres major and latissimus dorsi.

Shoulder ultrasound is a key tool used by musculoskeletal practitioners to diagnose and treat a variety of upper girdle diseases. While magnetic resonance imaging is the cornerstone of shoulder imaging, sonography is readily available, practical and superior in its ability for dynamic assessment of musculoskeletal pathologies. The subscapularis, teres major and latissimus dorsi muscles are commonly involved in a myriad of pathology including myofascial pain and spasticity. There is scarce literature on the assessment of these muscles for diagnostic and therapeutic purposes. Conventional approaches to shoulder ultrasound have not included a dedicated assessment of the subscapularis muscle due to its inherent anatomical location deep to the scapular blade which blocks sound wave penetration. We describe an approach to visualizing the subscapularis muscle as a short addition to the established shoulder sonography format, which also permits assessment of both the latissimus dorsi and teres major muscles, which are important muscles for shoulder spasticity. The patient is imaged in a semi-recumbent position with the arms elevated above and behind the head in the ABduction and External Rotation (ABER) position. The relative ease of positioning and sonographic access to the musculature coupled with the potential for assessment and intervention makes this approach extremely desirable to the musculoskeletal practitioner looking to diagnose or treat muscle belly pathologies of the subscapularis, teres major or latissimus dorsi.