summary Avascular necrosis of the shoulder is a condition characterized by interruption of blood supply to the humeral head which may lead to humeral head sclerosis and subchondral collapse. Diagnosis is made radiographically with orthogonal radiographs of the shoulder in moderate/late disease. MRI may be needed for detection of early or subclinical avascular necrosis. Treatment may be observation for very early and minimally symptomatic disease. Surgical management is indicated for progressive symptoms in the setting of moderate to advanced disease. Etiology 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), Sickle, SLE 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 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) Radiographic findings Treatment StageI Normal x-ray, changes on MRI only 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 Total shoulder arthroplasty 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) Prognosis Related to stage of disease