Objectives:
- to understand the complex anatomy of the rotator cuff as it pertains to US and MRI images
- to recognize common pathologies of the rotator cuff on US and MRI
- to appreciate potential pitfalls of diagnostic shoulder US

Tendon pathology
Tendonopathy results in focal or diffuse tendon thickening and on- US appears as inhomogeneous, predominantly hypoechoic echotexture

Partial thickness tears -
US appear as 1. Defined hypoechoic or mixed hypoechoic and hyperechoic defects seen in both longitudinal and transverse planes incompletely traversing the tendon
2. A contour deformity NOT extending as far medial as the head/neck junction of the humerus.

Full thickness tears -
US 1. Absent tendon
2. Hypoechoic defect or non-fibrillar tissue extending from the articular to bursal surface.
3. Contour defect extending medial to the head/tuberosity junction.

There are a number of secondary signs of rotator cuff tears. Whilst not specific, the presence of any of these findings should prompt careful review for rotator cuff tear. This includes:

1. Contour deformity
2. Cartilage Interface Sign
3. Cortical Irregularity
4. Combined effusions within both the subacromial subdeltoid bursa and the glenohumeral joint


Potential pitfalls in the diagnosis of rotator cuff tendon pathology include:

A. Anisotropy

B. Rotator cuff interval - small hypoechoic area on transverse images between the supraspinatus and LHB.

C. Large rotator cuff tears

D. Subscapularis tendon tears.

E. Attritional Rotator Cuff Tears - instead of the rotator cuff tear occurring in a swollen tendonopathic tendon, the tear occurs as extensive longitudinal tearing of the tendon along its long axis at the deep surface, resulting is extensive tendon thinning. This occurs most frequently within subscapularis.

F. Thickened Subacromial Subdeltoid Bursa - the thickened bursa conforms to the shape of the defect within the tendon and is of similar echogenicity to tendon. This can be a real problem! Helping confirm the soft tissue is bursa includes:

i. Lack of fibrillar pattern
ii. Compressibility
iii. Extension peripheral to the greater tuberosity