Avascular necrosis is the commonest in one of the following fracture -
AVN and non-union are almost always seen with displaced fracture (Garden's III & IV) and are less common with undisplaced fractures (Garden's I & II).
Garden 1 and 2 fracture of femoral neck
Garden 3 and 4 fracture of femoral neck
Sub-trochanteric fracture of femoral neck
Baso-trochanteric fracture