**4. Dynamics of development of hip blood supply**

Final branches of the a. circumflexae femoris medialis and lateralis form anastomoses that together with a. obturatoria and a. glutealis make circulus arteriosus—arterial ring around the femoral neck (**Figure 4**). This ring can be found pericapsullary as well as intracapsullary. From extracapsular arterial ring, retinacular arteries are formed that diverge in regular interval and pass through capsule forming ascendant cervical arteries. These arteries, by their position, can be divided into anterior, posterior, medial, and lateral, and their function is to supply femoral head and neck. Extracapsular ring forms medial metaphyseal and lateral epiphyseal arteries that supply blood to epiphyseal gap. These nutritional arteries pass through the capsule in the lower lateral part of the femoral neck parallel with intertrochanteric line where arterial circulation can be jeopardized leading to avascular necrosis (AVN) of

**Figure 3.** Scheme of arterial blood supply of the femoral head and neck (anterior view).

**Figure 4.** Scheme of extracapsular and intracapsular arterial ring.

The intracapsular arterial ring is positioned subsynovially around the distal part of the femoral neck. This ring forms vascular borderline of the joint (circulus articuli vasculorum

the femoral head.

12 Osteonecrosis

Dynamics of hip development blood supply are intensified by movements in the joint through stages of development of a person. The entire dynamic process can be divided into five phases:

