Avascular necrosis of head of femur occurs commonly at :
Subcapital region
Transcervical region
Subchondral region
Trochanteric region
Avascular necrosis is common with fractures to the subcapital region. Subcapital fractures damage the ascending vessels, thereby causing avascular necrosis and nonunion. Subcapital is the most common location for a femoral fracture. Ref: Srinivasan R.C., Tolhurst S., Vanderhave K.L. (2010). Chapter 40. Ohopedic Surgery. In G.M. Dohey (Ed), CURRENT Diagnosis & Treatment: Surgery, 13e.