Radiological manifestation of avascular necrosis (AVN) in sickle cell disease (SCD): a review of diagnostic imaging.

Symptomatic avascular necrosis (AVN) imposes a higher risk for acute care consumption in adults living with SCD. Symptomatic AVN, have higher rates of visits to the emergency department, higher rates of admissions, and longer lengths of stay in hospitals. Properly timed diagnosis and early interventions can reduce morbidity and enhance the quality of life in these patients. Vaso-occlusion secondary to sickling leads to osteonecrosis of the joint/bone (AVN, dactylitis) and invites infection (osteomyelitis and septic arthritis). Understanding and awareness of the imaging features related to this major morbidity complication are essential for early diagnosis and prompt management. In about half of the patients with SCD, AVN can lead to chronic pain, particularly in the head of the femur and humerus. Humeral and femoral head AVN tend to be linked with each other.  Vertebral bone compression and collapse secondary to AVN have also been reported.  The diagnosis of AVN must be accurate, as the condition is complex requiring specific treatment according to the grade of bone and joint involvement. There are several classifications or staging systems used for grading bone and joint involvement. Knowledge of the image patterns and grade of affection in different joints and bones and the degree of progression of AVN lesions can markedly improve management decisions on AVN-specific surgical versus non-surgical interventions and improve patient outcomes. The aim of this report is to summarize the different imaging techniques and their role in the proper/early diagnosis and follow up of patients with AVN with detailed examples of the common sites involved.