**3. Specificity of hip vascular supply**

a great importance for compensatory mechanisms. The disturbance of local arterial blood vessels, at a time when they dominate the blood supply and affect the quality of hip development and maturation, leads to reduced perfusion, and consequently, to the lack of development,

The problem of the circulation and vascular network supplying bones is exposed as a main problem in the etiology and pathogenesis of hip disorders in children which can affect later stages of life. The authentication of the problem is quite hard since bone biology is inappropriate for the assessment of vascular status. Results and first signs of diseases are visible after a couple

Acute or chronic ischemia in other tissues has a specific clinical presentation and symptomatology, which is not the case with the hip joint. Also, techniques that are applicable for vascular status assessment in other tissues are almost useless for the estimation of the vascular

As in other tissues, vascular system of the bones can be divided into three levels: afferent and efferent blood vessel and a microvascular network that fills in the space between them (**Figure 1**). Afferent blood vessel is composed of epiphyseal, metaphyseal, nutrient, and periosteal arteries. Microvascular network consists of medullar sinusoid, cortical, and periosteal capillaries, while the efferent blood vessel is formed of epiphyseal, metaphyseal, nutrient and periosteal veins, and collective sinusoids. None of the mentioned vascular elements can be considered independent. There are numerous anastomoses between them and opinions about

ossification, and possible osteonecrosis.

of months or even longer.

10 Osteonecrosis

status on bone tissue.

**2. Bone vascular system**

**Figure 1.** Bone vascularization.

one's participation in bone nutrition are still divided.

Blood supply of the hip is specific. It is formed of rich vascular network, that is, in great deal, responsible for the development of the joint. Blood vessels that participate in the hip vascularization can be divided into nutritive, retinacular, and foveolar. Retinacular blood vessels are the main source of hip supply and are extremely vulnerable (**Figures 2** and **3**). They can be damaged by infection, joint fluid, trauma, or forced position of the joint. Blood supply of the hip changes and adjusts during joint stages of development, from embryonal to the adolescent stage, when it adopts definite appearance and functional characteristics. Stages of vascular supply of the hip consist of fetal, infantile, intermediary, prepuberty, adolescent, and adult stage [2]. Each stage is different by the role of main nutritive artery of the diaphysis, metaphysis, periosteal, and anastomoses. The only constant factor in all of the mentioned stages is that the supplying blood vessels come from the a. femoralis communis, a. profundae femoris, and branched of the a. iliacae internae—a. gluteae and a. obturatoriae. The most important artery for hip supply is a. profunda femoris with its branches—a. circumflexa femoris medialis and lateralis.

**Figure 2.** Scheme of arteries of the coxofemoral region.

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

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 the femoral head.

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

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

Hunteri). Out of this ring, short arteries depart to the bone metaphysis or articular cartilage of the femoral head in which ossification nuclei end. Every artery supplies only one ossification nucleus. In the case where there are multiple secondary ossification nuclei, every one of them is supplied by separate artery that anastomoses in between which can explain partial necrosis of the femoral head [3].
