Avascular necrosis (Osteonecrosis)

• Avascular necrosis (AVN) is death of a bony structure secondary to insufficient blood supply.
• Primary pathology is of unknown aetiology, but secondary AVN is linked with a variety of pathologies.
• Idiopathic avascular necrosis occurs in childhood in the proximal femoral epiphysis and it is known as Perthes’ disease.
• Associated with steroid use, alcohol abuse, metabolic disease (e.g.Gaucher’s disease), vasculitis (SLE), sickle cell disease, malaria, occupational causes (e.g. deep-sea divers – caisson disease), venous thromboembolism and bone-marrow transplants.
• Certain bones in adulthood are particularly associated with AVN; e.g. femoral head, distal femur, proximal humerus – idiopathic and post-traumatic, talus, lunate – Kienbock’s disease, metatarsal head – Freiburg’s disease for second metatarsal head, navicular – Kohler’s disease, scaphoid – Preiser’s disease and capitellum – Panner’s disease – associated with osteochondritis.
• Clinically present with pain of insidious onset and the pain often worse at night. Pain is usually severe and often becomes more bearable after several weeks. Joint locking with loose bodies – separated osteochondral fragments. Reduced function of adjacent joints.
• The initial radiograph if taken early may be normal. The affected bone becomes sclerotic with later collapse and remodelling. Degenerative changes within adjacent joints. MRI is 90–100% sensitivity for symptomatic disease.

Freiberg’s osteonecrosis of the second metatarsal head.