Avascular necrosis is death of a segment of bone. AVN may affect the proximal humerus due to interruption of the blood supply. The ascending branch of the anterior humeral circumflex artery runs in the lateral bicipital groove and then becomes the arcuate artery. The other artery that is important to the blood supply is the posterior humeral circumflex artery.
There are several risk factors for AVN including: Alcohol, Systemic Lupus Erythematosus, infection, trauma, and steroid use. 5-25% of AVN cases are due to steroid usage. Steroids increase the serum lipids in the blood which may precipitate fat embolism into the humeral head blood vessels.
Progressive collapse of the humeral head occurs due to bone death, reabsorption, remodeling, micro fractures and final collapse with joint changes and arthritis. Symptoms include: shoulder pain, weakness, crepitus, and a decreased range of motion. Symptoms are gradual and insidious with delay in the diagnosis and treatment. The patient usually has a history of risk factors.
In regards to imagining, x-rays will show the best in the neutral rotation AP view. AVN located on the superior middle part of the humeral head just deep to the articular cartilage. If the crescent sign is seen, this is an indicator of collapse. An MRI is going to be the best imaging study. A patient with AVN of the humerus should have a hip radiograph. If the x-ray is negative and the patient has hip pain, you should obtain an MRI of the hip. It is recommended that a patient with osteonecrosis at the site of the shoulder should undergo an MRI of the hip to rule out asymptomatic osteonecrosis of the hip. You may also need to do an x-ray of the knee. AVN may involve three or more anatomic sites (multifocal osteonecrosis).
Treatment typically consists of:
- Physical Therapy
- Core decompression for Stage I and Stage II
- Resurfacing for Stage III
- Hemiarthroplasty for Stage III and Stage IV
- Total shoulder surgery for Stage V
- Advanced disease
- The results of total shoulder are inferior to patients with osteoarthritis