An elderly woman was admitted with a fracture of the neck of right femur which failed to unite. On examination an avascular necrosis of the head of femur was noted. The condition would have resulted most probably from the damage to:

Ans. is 'd' i.e. Retinacular branches of circumflex femoral arteriesRef: Apley's 8th/e p 684; Adams 10th/e p 195; Maheshwari 3rd/e p 118Normally blood is supplied to the head of the femur by three routes-Intramedullary vessels in the femoral neckVessels in the ligament of head of the femur (ligamentum teres)Ascending cervical branches of the medial and lateral circumflex anastomosis which run within the capsular retinaculum before entering the bone at the edge of the femoral head.Out of these vessels the main supply to the femoral head is by intramedullary vessels and vessels which run within capsular retinaculum.Damage of the vessel in Fracture neck femur occurs in following manner.The intramedullary vessel is almost always damaged.The other vessel which can also be damaged is the retinacular vessels.So, the only vessel left to supply the femoral head during fracture neck femur is the vessel of the ligamentum teres. The supply from this vessel is not enough. It supplies only 20% of the blood to the fractured neck of femur.