The vascular anatomy of the femoral head has been already described in many textbooks and studies.

First descriptions of vascular anatomy came from the 17^th century, when Hunter described circulus articuli vasculosus – the vascular ring at the base of the femoral neck (1). Many other studies from the 20^th century have assessed the vascular anatomy of the femoral head in classical anatomical studies (2-5) and in angiographic studies (6-8).

Several studies during the last 15 years have demonstrated new concepts in the vascularization of the femoral head. Recent studies have used different methods of visualization of the arteries: classical anatomical dissections preserved in formaldehyde (9), classical anatomical dissections of fresh cadavers after intra-arterial injections of colored silicone (10-13), and visualization using contrast-enhanced magnetic resonance imaging (13) or contrast-enhanced computed tomography (CT) (14).

While all authors use the same nomenclature to describe the medial femoral circumflex artery (MFCA), lateral femoral circumflex artery (LFCA), and superficial femoral and deep femoral arteries, the nomenclature of nutrient arteries is controversial. Some authors name the vessels retinacular arteries because of the neighboring retinacular fibers (6, 10-12, 15). Other authors name the vessels according to the growth period, when the epiphysis and metaphysis are supported by different arteries and the epiphyseal plate constitutes a barrier to the circulation within the epiphysis and metaphysis (8).

Crock and Chung described the arteries of the proximal end of the femur as an extracapsular and intracapsular arterial ring of the femoral neck with ascending cervical branches (anterior, posterior, lateral, and medial) and arteries of the round ligament (3, 4). Howe described the terminal branches as the posterior superior and posterior inferior capital arteries arising from the MFCA and the foveal artery (2). Judet et al. named these vessels as superior and inferior groups of arteries supplying the femoral head (5).

The anastamosis with the inferior gluteal artery (IGA) was described in the early edition of Gray’s Anatomy (16), as the anastomotic and articular branches, Jedral et al. described it as a terminal branch of the IGA (17), Gautier et al. and Grose et al. characterized it as the piriformis branch of the IGA (10, 18).

In our opinion, the most descriptive nomenclature names the vessels as nutrient arteries of the femoral head, which are delineated as posterior superior, posterior inferior, anterior, and the artery of ligamentum teres (9, 14). For the anastomosis with the IGA we used the nomenclature by Gautier et al. and Grose et al. – the piriformis branch of the IGA (10, 18).

The vascular anatomy of the femoral head is very specific because the vascular patterns established during the growth phases do not change at maturity and persist throughout life (3, 4, 8). The epiphysis and metaphysis have their own blood supply, and the arteries supporting them during the growth phase are called the epiphyseal arteries and metaphyseal arteries, respectively. Based on their sites of entry into the bone, the epiphyseal arteries are referred to as lateral and medial, and the metaphyseal arteries are indicated as superior and inferior. Lateral epiphyseal and superior metaphyseal arteries enter the bone at the superior and posterior-superior aspect of the femoral neck, near the margin of the articular cartilage. The inferior metaphyseal arteries enter the bone close to the inferior margin of the articular cartilage. The lateral epiphyseal and both groups of the metaphyseal arteries arise from the MFCA. The medial epiphyseal artery is a continuation of the artery within the ligamentum teres, arising from the acetabular branch of the obturator artery. Injections to the femoral head proved that the lateral epiphyseal arteries predominate in the epiphysis and the inferior metaphyseal arteries in the metaphysis, and any contribution to vascularization by the artery of the ligamentum teres may be negligible or absent in some cases (8).

The femoral head is supplied by many vessels arising mainly from the MFCA and IGA. Other vessels with lesser contribution arise from the LFCA, obturator artery, superior gluteal artery, and the first perforating branch of the deep femoral artery.

Most authors agree that there are 3 main groups of arteries supplying the femoral head: the posterior superior nutrient arteries of the femoral head arising from the deep branch of the MFCA; a posterior inferior nutrient artery also arising from the main trunk of the MFCA; and the piriformis branch of the IGA (2-6, 9, 10, 14).

The MFCA arises either from the profunda femoris artery (65-81%), or, less commonly, from the femoral artery (6.4-34%) (12, 19-22). It can also arise as 2 branches, as noted in a single case example in 1 study (20), or there may be no main trunk of the MFCA present, as noted in a single case example in another study (14). From this point, the MFCA travels through the space between the pectineus and iliopsoas muscles, changing course in direction to the lesser trochanter. During its course, it branches off superficially and these branches anastomose with the obturator artery in the space between the adductor longus and adductor brevis muscles (2, 9, 10). A superficial branch, usually single, is observed in 98% of cases and its diameter is 1.4 mm (0.7-3.5 mm) (19). When the main trunk of the MFCA is kinked or otherwise occluded, the superficial branch may play a crucial role in supplying blood to the deep branch of the MFCA (19). Anterior to the lesser trochanter and distal to the distal margin of the obturator externus muscle, the main trunk of the MFCA gives rise to the posterior inferior nutrient artery of the femoral head (fig. 1). At approximately 53 mm (31-87 mm) from the origin of its course, the main trunk of the MFCA bifurcates into a deep branch and a descending branch. This typical bifurcation of the main trunk of the MFCA is characteristic of 96% of the cases (9, 14, 19) (fig. 2).

The main trunk bifurcates into the descending branch, usually single with a diameter of 1.7 mm (0.8-3.6 mm) that divided into 2 branches, which supply the muscles of the posterior compartment of the thigh. The deep branch, with a diameter of 1.6 mm (1.1-2.7 mm), follows a course directed to the femoral head (7, 9, 14, 19) (fig. 3).