Avascular Necrosis

AVN frequently affects the heads of the femur and humerus.
Early AVN may present with a crescentic lucency below the cortex.
Moderate AVN usually shows sclerosis of the head.
Advanced AVN shows inhomogeneous sclerosis, fragmentation, and/or flattening of the humeral head as in this patient.
AVN is increased in patients on steroids and patients with sickle cell anemia