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Introduction
  • A condition caused by interruption of blood supply to humeral head
  • Pathophysiology
    • pathoanatomy 
      • decreased blood supply to humeral head leading to death of cells in bony matrix.
      • bone is resorbed and remodeled, causing subchondral bone collapse and may lead to joint incongruity and arthritic changes
    • etiology similar to hip
      • Remember ASEPTIC mneumonic 
        • Alcohol, AIDS
        • Steroids (most common), SickleSLE
        • Erlenmeyer flask (Gaucher’s)
        • Pancreatitis
        • Trauma
        • Idiopathic/ Infection
        • Caisson’s (the bends)
      • may be atraumatic
      • posttraumatic
        • four-part fracture-dislocations approach 100% AVN
        • displaced four-part fractures ~45% AVN
        • valgus impacted four-part ~11% AVN
        • three-part ~14% AVN
  • Prognosis
    • related to stage of disease
Anatomy
  • Blood supply
    • Humeral head
      • ascending branch of anterior humeral circumflex artery and arcuate artery
        • provides blood supply to humeral head
        • vessel runs parallel to lateral aspect of tendon of long head of biceps in the bicipital groove
          • beware not to injure when plating proximal humerus fractures
        • arcuate artery is the interosseous continuation of ascending branch of anterior humeral circumflex artery and penetrates the bone of the humeral head
        • provides 35% of blood supply to humeral head
      • posterior humeral circumflex artery
        • most current literature supports this as providing the main blood supply to humeral head 
        • provides 65% of blood supply 
Classification
 
Cruess Classification (stages)
Stage I Normal x-ray. Changes on MRI. Core decompression.

Stage II Sclerosis (wedged, mottled), osteopenia. Core decompression.
Stage III Crescent sign indicating a subchondral fracture. Resurfacing or hemiarthroplasty.
Stage IV Flattening and collapse. Resurfacing or hemiarthroplasty.
Stage V Degenerative changes extend to glenoid. TSA.  
 
Presentation
  • Symptoms
    • insidious onset of shoulder pain
      • often without a clear inciting event
    • pain, loss of motion, crepitus, and weakness
  • Physical exam
    • limited range of motion
    • crepitus
    • weakness of the rotator cuff and deltoid muscles
Imaging
  • Radiographs
    • recommended views
      • five views of shoulder (shown best in neutral rotation AP)
    • findings
      • no findings on radiograph at onset of disease process
      • osteolytic lesion develops on radiograph demonstrating resorption of subchondral necrosis
        • most common initial site is superior middle portion of humeral head
      • crescent sign demonstrates subchondral collapse
      • may progress to depression of articular surface and consequent arthritic changes.
  • MRI
    • preferred imaging modality
      • ~100% sensitivity in detection
    • will demonstrate edema at the site of subchondral sclerosis 
Treatment
  • Nonoperative
    • pain medications, activity modification, physical therapy
      • indications
        • first line of treatment
      • technique
        • physical therapy
          • restrict overhead activity and manual labor
  • Operative
    • core decompression + arthroscopy (confirm integrity of cartilage)  
      • indications
        • early disease (precollapse Cruess Stage I and II)
    • humeral head resurfacing
      • indications
        • Stage III disease with focal chondral defects, and sufficient remaining epiphyseal bone stock for fixation.
    • hemiarthroplasty  
      • indications
        • moderate disease (Cruess Stage III and IV)
    • total shoulder arthroplasty 
      • indications
        • advance stage (Cruess V)
 

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