Continuum of disease: Subacromial or subcoracoid impingement, calcific tendonitis, partial- or full-thickness rotator cuff (RTC) tears, massive tears, and cuff tear arthropathy.

Prevalence: 7–40% in cadaveric studies

Age >60: 28% have full-thickness tear

Age >70: 65% have full-thickness tear

In those with unilateral painful full-thickness tears, there is 56% chance of having an asymptomatic contralateral full- or partial-thickness tear

Of all asymptomatic tears, 50% will get symptoms in 3 years. Of these, 40% will have progression of tear.

Chronic degenerative tear:

1. 
   

   Seen in older patients

   
   
2. 
   

   Most commonly involves the supraspinatus and infraspinatus

   
   
3. 
   

   Can extend to subscapularis and teres minor

   
   
4. 
   

   Attributed to age-related intrinsic degeneration of the tendon

   
   
5. 
   

   Disoriented collagen fibers, myxoid, and hyaline degeneration.

Chronic impingement:

1. 
   

   Typically starts at bursal surface of supraspinatus and infraspinatus

   
   
2. 
   

   Os acromiale or bony acromial spur causes direct pressure and attritional injury to the bursal tendon

   
   
3. 
   

   Deteriorated scapular motion most common cause of extrinsic RTC tearing

   
   
4. 
   

   Also seen in internal impingement in overhead throwing athletes:

   
   
   
   
   1. 
      

      Partial articular supraspinatus tendon avulsion (PASTA) tears seen from impingement of posterosuperior glenoid and articular RTC.

Acute traumatic avulsions:

1. 
   

   Seen with shoulder dislocations in age >40 years

   
   
2. 
   

   Subscapularis avulsions seen in younger patients from hyperabduction/external rotation injuries

   
   
3. 
   

   Acute avulsion may have better prognosis than chronic degenerative tear, if repaired in the acute phase.

Iatrogenic:

1. 
   

   Subscapularis failure seen after open anterior shoulder surgery from failure of repair.

Five layers:

1. 
   

   Layer I: Most superficial thin layer, composed of fibers from coracohumeral ligament

   
   
2. 
   

   Layer II: Dense collage fibers parallel to long axis of tendon (3–5 mm thick)

   
   
3. 
   

   Layer III: Smaller loose bundles of collagen at 45 degrees angle to Layer II (3 mm thick)

   
   
4. 
   

   Layer IV: Loose connective tissue continuous with coracohumeral ligament

   
   
5. 
   

   Layer V: Shoulder capsule (2 mm thick).

Articular-side fibers have only half the strength of bursal side

Rotator interval:

1. 
   

   Located in between supraspinatus and subscapularis

   
   
2. 
   

   Comprises superior glenohumeral ligament (SGHL), coracohumeral ligament, long head of biceps tendon, and capsule.

Rotator cable:

1. 
   

   Runs perpendicularly along the insertions of supraspinatus and infraspinatus

   
   
2. 
   

   Thick fibers at the avascular zone of the coracohumeral ligament.

Cuff tear size (DeOrio and Cofield):

1. 
   

   Small: Less than 1 cm

   
   
2. 
   

   Medium: 1–3 cm

   
   
3. 
   

   Large: 3–5 cm

   
   
4. 
   

   Massive: lLrger than 5 cm (multiple tendons).

Partial-thickness RTC tears (Ellman):

1. 
   

   Grade I (<3 mm, <25% thickness), Grade II (3–6 mm, 25–50%), Grade III (>6 mm, >50%)

   
   
2. 
   

   A – Articular sided, B – Bursal sided, C – Intratendinous.

Cuff atrophy (Goutallier grade)

1. 
   

   0–Normal

   
   
2. 
   

   1–Some fatty streaks

   
   
3. 
   

   2–More muscle than fat

   
   
4. 
   

   3–Equal amounts of fat and muscle

   
   
5. 
   

   4–More fat than muscle.

Cuff tear shape (▶ Fig. 8.1 )—Site Burkhart: Crescent, U-shape, L-shape, massive and immobile.