<prompt> The most common site of fracture neck of femur that cause Avascular necrosis is-Sub- capital zone of head of femurInterochanteric zoneTrans-cervical areaBasal pa of head of femur  <response>: The more proximal the location of a femoral neck fracture, the more likely there is to be nonunion andor AVN. Thus non-union and AVN will be most common in subcapital fracture and least in basicervical fracture. Mc affects Femoral Head Mc site Anterolateral aspect Being principal Wt. bearing poion Incidence;dt t Steroid usage Trauma AVN only occurs in FATTY MARROW, which contains a Sparse vascular supply. In contrast to Hematopoietic marrow which has a rich blood supply CAUSES Trauma Alcohol consumption Coicosteroid intake Gout and hyperuricemia Hypercholesterolemia Hypercoagulable states Hypercoisolism Hyperlipidemia Cushing disease Hyperparathyroidism Hemoglobinopathies Intravascular coagulation SCD;Hb SC;Polycythemia Organ transplantation Caisson disease Pregnancy Dysbaric osteonecrosis Congenital dislocation Hip Pancreatitis Ehlers-Danlos synd Neoplasms Heredity dysostosis CRF Legg-Calve-Pehes dis Hemodialysis Fabry disease Cigarette smoking Gaucher disease Collagen Vascular dis Giant cell aeritis SLE Thrombophlebitis Idiopathic Ref: maheswari 9thed p.311 