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 login to view 7 more bullets may be atraumatic posttraumatic login to view 4 more bullets Anatomy Blood supply Humeral head ascending branch of anterior humeral circumflex artery and arcuate artery login to view 5 more bullets posterior humeral circumflex artery login to view 2 more bullets 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 login to view 1 more bullet 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 login to view 1 more bullet technique login to view 2 more bullets Operative core decompression + arthroscopy (confirm integrity of cartilage) indications login to view 1 more bullet humeral head resurfacing indications login to view 1 more bullet hemiarthroplasty indications login to view 1 more bullet total shoulder arthroplasty indications login to view 1 more bullet Prognosis Related to stage of disease