60-year-old patient with a history of shoulder trauma several years ago, resulting in axillary nerve injury. The patient presents with chronic shoulder dysfunction, weakness, and pain. Longstanding symptoms suggest significant structural and neuromuscular impairment.
Ultrasound examination of the shoulder demonstrates a full-thickness tear of the supraspinatus tendon, involving part of the tendon width (partial-width). The tendon shows discontinuity with loss of normal fibrillar architecture.
The long head of the biceps tendon demonstrates moderate tendinopathy, with associated moderate to marked fluid distension of the biceps tendon sheath, consistent with tenosynovitis or communication with intra-articular pathology.
There is a known history of axillary nerve injury. Correspondingly, the deltoid muscle demonstrates severe atrophy and fatty infiltration, consistent with chronic denervation.
Due to the pronounced fatty infiltration of the deltoid muscle, the ultrasound image quality of deeper structures is significantly reduced. The imaging appearance is described as “milky” or “foggy,” with decreased resolution and poorly defined margins of deeper tissues. As a result, diagnostic confidence is high for larger structural abnormalities, such as the supraspinatus tear, but limited for subtle findings including small partial tears or mild tendinopathy in deeper structures.
1. Final diagnosis
Partial-width full-thickness tear of the supraspinatus tendon, with associated biceps tendinopathy and sheath effusion, in the context of chronic axillary nerve injury causing severe deltoid atrophy and fatty infiltration.
2. Differential diagnosis
Consider additional rotator cuff pathology (e.g., infraspinatus or subscapularis involvement), though evaluation is limited by poor acoustic window. Biceps sheath fluid may reflect intra-articular effusion rather than primary tenosynovitis.
3. Teaching points
Severe muscle atrophy and fatty infiltration can significantly degrade ultrasound image quality and limit diagnostic accuracy. Larger pathologies remain detectable, but subtle lesions may be missed. Knowledge of prior nerve injury is essential when interpreting muscle changes and imaging limitations.
4. Injury/disease information
Axillary nerve injury leads to denervation of the deltoid muscle, resulting in progressive atrophy and fatty infiltration over time. This not only impairs shoulder function but also affects imaging quality. Rotator cuff tears frequently coexist in chronically dysfunctional shoulders and may contribute to ongoing pain and disability.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at the Laurentius Hospital in Roermond, the Netherlands.
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