Sonographic appearance of rotator cuff tendon pathology on an Ultrasound
The spectrum of tendon pathology on US includes tendinosis, partial tear, full-thickness tear, and tenosynovitis, not just in the rotator cuff of the shoulder joint but in other sites as well. In the following examples, pathology of the supraspinatus tendon will be discussed.
Tendinosis indicates a degenerative process that may be focal or diffuse. Tendinosis is characterized by a swollen, hypoechoic tendon, with loss of the normal fibrillar architecture. There may be hyperemia on color Doppler imaging. It is important to distinguish tendinosis from anisotropy by making sure the portion of the tendon that is being evaluated is perpendicular to the ultrasound beam.
Partial-thickness tears may demonstrate a variety of appearances on US and often occur on a background of tendinosis. The most common appearance is a well-defined hypoechoic or anechoic cleft that partially disrupts the tendon fibers.
Types of partial-thickness tears include intrasubstance or delaminating tears, intrasubstance tearing at the tendon footprint, partial bursal sided tears, and partial articular sided tears. Full-thickness tears demonstrate full-thickness disruption of fibers with a fluid-filled gap. There may be retraction of the tendon fibers if the tear is large. There may also be hemorrhage or synovial hypertrophy filling the tendon gap.
Tenosynovitis is often mechanical or traumatic in nature and may be associated with underlying tendon pathology. Inflammatory/infectious etiologies may also result in tenosynovitis. On US, synovial tissue and/or fluid surrounds the tendon within the tendon sheath. The synovial tissue may appear isoechoic to hyperechoic to the adjacent tendon. A peripheral rim of hyperemia may be observed on Doppler imaging