Rotator cuff

• ○
  

  Consists of supraspinatus, infraspinatus, teres minor, subscapularis muscles, and tendons

  
  
• ○
  

  Cuff tendons blend with shoulder joint capsule

  
  
• ○
  

  Supraspinatus and infraspinatus tendons are inseparable at insertion

  
  
• ○
  

  Anterior 2.25 cm of tendon comprises supraspinatus tendon insertional area

Supraspinatus muscle

• ○
  

  Origin: Supraspinatus fossa of scapula

  
  
• ○
  

  Insertion: Superior facet (horizontal orientation) and anterior portion of middle facet of greater tuberosity

  
  
  
  
  • –
    

    Broad insertional area

  
  
  
  
• ○
  

  Nerve supply: Suprascapular nerve

  
  
• ○
  

  Blood supply: Suprascapular artery and circumflex scapular branches of subscapular artery

  
  
• ○
  

  Action: Abduction of humerus

  
  
• ○
  

  Muscle consists of 2 distinct portions

  
  
  
  
  • –
    

    Anterior portion is larger, fusiform in shape, has dominant tendon, and is more likely to tear

    
    
  • –
    

    Posterior portion is flat and has terminal tendon

  
  
  
  
• ○
  

  Most commonly injured rotator cuff tendon

Infraspinatus muscle

• ○
  

  Origin: Infraspinatus fossa of scapula

  
  
• ○
  

  Insertion: Mid to posterior aspects of middle facet of greater tuberosity; centrally positioned within tendon

  
  
• ○
  

  Nerve supply: Suprascapular nerve, distal fibers

  
  
• ○
  

  Blood supply: Suprascapular artery and circumflex scapular branches of subscapular artery

  
  
• ○
  

  Action: External rotation of humerus and resists posterior subluxation

Teres minor muscle

• ○
  

  Origin: Lateral scapular border, middle 1/2

  
  
• ○
  

  Insertion: Inferior facet (vertical orientation) of greater tuberosity

  
  
• ○
  

  Nerve supply: Axillary nerve

  
  
• ○
  

  Blood supply: Posterior circumflex humeral artery and circumflex scapular branches of subscapular artery

  
  
• ○
  

  Action: External rotation of humerus

  
  
• ○
  

  Least commonly injured rotator cuff tendon

Subscapularis muscle

• ○
  

  Origin: Subscapular fossa of scapula

  
  
• ○
  

  Insertion: Lesser tuberosity and up to 40% may insert at surgical neck

  
  
• ○
  

  Some fibers cross over to lateral lip of bicipital groove, reinforcing and blending with transverse ligament

  
  
• ○
  

  Nerve supply: Subscapular nerve, upper and lower

  
  
• ○
  

  Blood supply: Subscapularis artery

  
  
• ○
  

  Action: Internal rotation of humerus, also adduction, extension, depression, and flexion

  
  
• ○
  

  4-6 tendon slips converge into main tendon; multipennate morphology increases strength

Rotator cuff tendon blood supply

• ○
  

  Derived from adjacent muscle, bone, and bursae

  
  
• ○
  

  Normal hypovascular regions in tendons

  
  
  
  
  • –
    

    Termed critical zone: ~ 1 cm proximal to insertion

    
    
  • –
    

    Vulnerable to degeneration and calcific deposition

    
    
  • –
    

    However, insertional area is more prone to tearing than critical zone

  
  

Biceps tendon, long head

• ○
  

  Origin: Superior glenoid labrum (biceps anchor)

  
  
  
  
  • –
    

    Portions may attach to supraglenoid tubercle, anterosuperior labrum, posterosuperior labrum, and coracoid base

  
  
  
  
• ○
  

  Runs along superior aspect of shoulder to bicipital groove

  
  
• ○
  

  Action: Stabilizes and depresses humeral head

  
  
• ○
  

  Anatomic variants: Anomalous intra- and extraarticular origins from rotator cuff and joint capsule

  
  
• ○
  

  Tendon sheath communicates with glenohumeral joint and normally contains small amount of fluid

Subacromial-subdeltoid fat plane

• ○
  

  Subacromial and subdeltoid portions

  
  
  
  
  • –
    

    ± subcoracoid extension in some patients

  
  
  
  
• ○
  

  Fat plane is superficial to bursa

  
  
• ○
  

  May be interrupted or absent in normal patients

  
  
• ○
  

  Attached along free border of coracoacromial ligament, deep surface of deltoid muscle, and humeral neck

Rotator cuff interval

• ○
  

  Space between supraspinatus and subscapularis tendon through which biceps tendon passes

  
  
• ○
  

  Borders of rotatorcuffinterval

  
  
  
  
  • –
    

    Triangular-shaped space

    
    
  • –
    

    Reflections of glenohumeral ligament and coracohumeral ligament form biceps reflection pulley

    
    
  • –
    

    Biceps reflection pulley stabilizes biceps tendon within rotator cuff interval

    
    
  • –
    

    Superior border: Leading edge of supraspinatus

    
    
  • –
    

    Inferior border: Superior aspect of subscapularis tendon

    
    
  • –
    

    Lateral border: Long head of biceps tendon and bicipital groove

    
    
  • –
    

    Medial border: Base of coracoid process

  
  
  
  
• ○
  

  Contents of rotator interval

  
  
  
  
  • –
    

    Long head of biceps tendon; biceps reflection pulley

  
  

Coracoacromial ligament

• ○
  

  Forms coracoacromial arch along with acromion and coracoid process

  
  
  
  
  • –
    

    Reinforces inferior aspect of acromioclavicular joint

  
  
  
  
• ○
  

  Extends from distal coracoid to subacromial area

  
  
• ○
  

  Broad insertion to undersurface acromion

  
  
  
  
  • –
    

    Ligament is thicker at acromion (normal thickness < 2.5 mm) and may be associated with spurs

  
  

Glenoid labrum

• ○
  

  Triangular-shaped rim of fibrocartilage, which extends around periphery of glenoid

Tendons best seen when on stretch

• ○
  

  High-resolution linear transducer

  
  
• ○
  

  Long-axis (longitudinal) & transverse view of each tendon

  
  
• ○
  

  Each part of tendon needs to be examined; anisotropy prevents all parts of curved rotator cuff tendons from being seen at same time

  
  
• ○
  

  Need to realign (“toggle”) probe to see different parts of tendons

Supraspinatus tendon

• ○
  

  Arm extended and internally rotated behind lumbar region (Crass position)

  
  
  
  
  • –
    

    If too painful, hand behind hip (back pocket) with elbow close to body (modified Crass position)

  
  

Infraspinatus and teres minor tendons

• ○
  

  Arm flexed and internally rotated with hand placed on contralateral shoulder

  
  
• ○
  

  Teres minor tendon located posteroinferior to infraspinatus tendon

Subscapularis tendon: Arm neutral and externally rotated

Long head of biceps tendon

• ○
  

  Arm neutral and externally rotated

  
  
• ○
  

  Vary degree of external rotation for optimal view of biceps tendon

  
  
• ○
  

  Check for tendon subluxation

Subacromial-subdeltoid bursa

• ○
  

  Stretching tendons may squeeze fluid from area of bursa under inspection

  
  
• ○
  

  Examine in all positions and also in neutral position

  
  
• ○
  

  Fluid collects preferentially just lateral to acromion and proximal humerus and near coracoacromial ligament

Coracoid process and coracoacromial ligament

• ○
  

  Neutral position

Acromioclavicular joint

• ○
  

  Neutral position

  
  
• ○
  

  Can pull down on arm to assess joint laxity

Glenohumeral joint

• ○
  

  Neutral position

  
  
• ○
  

  Best seen from posterior aspect of joint

  
  
• ○
  

  Passive movement of arm during scanning can help in identifying posterior glenoid labrum

Spinoglenoid notch

• ○
  

  Neutral position just medial to glenohumeral joint

Supraspinatus and infraspinatus muscles

• ○
  

  Neutral position with hands resting on thigh

  
  
• ○
  

  Examine thickest part of muscles from behind (in coronal and sagittal planes)

  
  
• ○
  

  ↓ muscle bulk, ↑ echogenicity, and ↓ visibility of central tendon are signs of atrophy with fatty replacement

  
  
  
  
  • –
    

    Compare muscle echogenicity to that of trapezius or deltoid muscle

  
  

Look for tears particularly at anterior leading edge of supraspinatus tendon

• ○
  

  Unexplained bursal fluid is good secondary sign of rotator cuff tear

Bursal fluid is often best seen with arm in neutral position or ↓ internal rotation (hand in back pocket)

Anisotropy

• ○
  

  Echoes are optimally reflected when transducer is parallel to tendon fibers

  
  
• ○
  

  Rotator cuff tendons are prone to anisotropy due to curved course

  
  
• ○
  

  If transducer is not at right angles to tendon, it will appear either isoechoic or hypoechoic to muscle

  
  
  
  
  • –
    

    May simulate tendinosis or partial tear

  
  

Tendon edges

• ○
  

  Interfaces of tendons with adjacent structures may simulate tears

  
  
• ○
  

  All pathology should be confirmed in 2 planes

Rotator cuff cable

• ○
  

  Thick band of fibers running perpendicular to supraspinatus tendon

  
  
• ○
  

  Located on deeper aspect of tendon just proximal to insertional area

  
  
• ○
  

  May reinforce critical zone supraspinatus fibers

  
  
• ○
  

  Cable thicker in young subjects but more easily seen in elderly subjects due to supraspinatus tendinosis

  
  
• ○
  

  Can simulate tendinosis or partial-thickness tear

Tendinous interspace at rotator cuff interval

• ○
  

  Interspace between leading (anterior) edge of supraspinatus and long head of biceps tendon may simulate tear

  
  
• ○
  

  Overcome by recognizing ovoid or rounded shape of biceps tendon

  
  
• ○
  

  Rotator cuff interval best seen with external rotation

Focal thinning at supraspinatus-infraspinatus junction

• ○
  

  Mild diffuse thinning of supraspinatus and infraspinatus tendon junction is normal finding

  
  
• ○
  

  Should not be mistaken for tendon attenuation or partial-thickness tear

Musculotendinous junction

• ○
  

  Supraspinatus tendon

  
  
  
  
  • –
    

    Hypoechoic muscle extending along superficial aspect of tendon may simulate subacromial-subdeltoid bursal distension

    
    
  • –
    

    Interdigitating tendons of anterior and posterior portions may simulate tendinosis or tear

  
  
  
  
• ○
  

  Infraspinatus tendon

  
  
  
  
  • –
    

    Muscle fibers surrounding centrally positioned tendon may be confused with tear

  
  
  
  
• ○
  

  Subscapularis tendon

  
  
  
  
  • –
    

    4-6 tendon slips converging into main tendon may simulate tendinosis

  
  

Fibrocartilaginous insertion

• ○
  

  Thin layer of fibrocartilage exists between tendon and bone at insertional area

  
  
• ○
  

  Steeper tendon insertion = thicker fibrocartilaginous layer

  
  
• ○
  

  This thin hypoechoic layer of fibrocartilage may simulate avulsive tear

Subacromial-subdeltoid fat plane

• ○
  

  Fat plane lies mainly superficial to bursa and deep to deltoid muscle

  
  
• ○
  

  Normal bursa is very thin

  
  
• ○
  

  Thickness of echogenic fat plane is variable among patients though usually similar from side to side

  
  
• ○
  

  May be wrongly interpreted as bursal fluid

  
  
  
  
  • –
    

    Look for intrabursal fluid ± hyperemia (latter is feature of inflammatory arthropathy)

  
  

Fluid in biceps tendon sheath

• ○
  

  Communicates with glenohumeral joint

  
  
• ○
  

  Small amount of fluid is normal

  
  
  
  
  • –
    

    Do not misinterpret as long head of biceps tenosynovitis

  
  
  
  
• ○
  

  ↑ fluid in biceps tendon sheath usually reflects ↑ fluid in glenohumeral joint