Ultrasound Signs of Rotator Cuff Tear: Differentiation of Full-Thickness, Partial-Thickness Tear, and Tendinosis

Method for Assessing the Supraspinatus Tendon

The initial assessment of the supraspinatus tendon should be conducted in the long axis, as this visualizes the three surfaces of the cuff (articular, bursal, greater tuberosity) and characteristic bony contours, which are necessary for accurate tear classification. All detected changes should be confirmed in two planes.

Full-Thickness Tear

Tears that encompass the entire thickness and width of the rotator cuff tendon are considered full-thickness. Tendon tears appear as anechoic or hypoechoic defects, with acute tears often being anechoic due to fluid. As the tear enlarges, tendon retraction and loss of volume occur, with flattening of the normal convex shape of the upper surface. Anteriorly located full-thickness tears are associated with tendon retraction, muscle atrophy, and progression over time. Retraction of multiple tendons occurs when the ends diverge by 2–4 cm. The frequency of tears in descending order: supraspinatus, infraspinatus, subscapularis, and very rarely teres minor.

A large amount of fluid in the subacromial-subdeltoid bursa reduces the ability to visualize a full-thickness tear.

Partial-Thickness Tear

A partial-thickness tear affects one surface of the tendon. Hypoechoic concave tears of the bursal surface are the second most common type of partial cuff tears. An indirect sign is the irregularity of the anterior part of the greater tuberosity (found in approximately 75% of partial tears): cortical defects, fragmentation, and/or osteophytes. There is also a noted reduction in tendon thickness. Fluid around the biceps tendon indicates a possible articular surface tear.

Tendinosis

Tendinosis is manifested by a thickened hypoechoic tendon with mottled and linear areas of more pronounced hypoechogenicity. It is graded as mild, moderate, or severe based on the degree of thickening, hypoechogenicity, and loss of the normal fibrillar pattern. Measuring tendon thickness is generally not useful due to the lack of clear landmarks and the dependence of thickness on patient size. Cortical irregularity at the attachment site occurs in more severe degrees of tendinosis.

Differentiation of Tear and Tendinosis

Unlike focal hypoechoic zones of proteoglycan deposition, which can mimic intrasubstance tears, true tears are more linear, more hypoechoic/anechoic, with a clearer outline and are accompanied by tendon volume loss. Non-intrasubstance tears are recognized by changes in tendon contour, retraction, fluid gap, and volume loss.

Imaging Pitfalls

Anisotropy is the main artifact: cuff tendons have a curved course and are prone to anisotropy; when the probe is not perpendicular, the tendon appears iso- or hypoechoic relative to the muscle, mimicking tendinosis or partial tear. Other mimickers: tendon interfaces with adjacent structures; tendon interspace in the cuff interval (between the anterior edge of the supraspinatus and the long head of the biceps — overcome by recognizing the ovoid shape of the biceps tendon); supraspinatus-infraspinatus transition zone (relatively hypoechoic due to fiber interweaving); fibrocartilaginous attachment (enthesis — may mimic avulsive tear); musculotendinous junction. All pathology should be confirmed in two planes.

Ultrasound and MRI have comparable accuracy in detecting and measuring rotator cuff tears; a meta-analysis of 65 articles also showed comparable sensitivity and specificity.