The posterior inferior nutrient artery of the femoral head is not present in all cases. Incidence of appearance depends on the method of visualization used by different authors; it is observed in 11 % of cases by angiographic CT examination [14] compared to 100 % of cases in a classical anatomical study with colored silicone injection [6, 11–13, 15]. Its diameter has been estimated in a microangiographic study to be approximately 0.4 mm (0.1–0.6 mm) [6]. In its intra-articular course, it runs proximally on the medial aspect of the neck toward the femoral head on top of the mobile fold of tissue commonly referred to as the Weitbrecht ligament [12] (Figs. 2.2, 2.3, and 2.5). During the growth phase, the posterior inferior nutrient artery—under the name “inferior metaphyseal artery”—was found to supply approximately two-thirds of the metaphyseal tissue of the femoral head [8]. Almost 18 % of the vascular foramina around the head are located in the posterior inferior aspect of the femoral head in comparison to approximately 80 % located in the posterior superior and anterior superior quadrants of the femoral head [23].

After bifurcation, the deep branch arises proximally, posterior to the obturator externus muscle and anterior to the quadratus femoris muscle. It is easily identifiable in the adipose tissue between these two muscles and is usually closely associated with two veins [9]. In this area, the deep branch of the MFCA can rupture during traumatic hip dislocation when the obturator externus tendon ruptures. The obturator externus muscle and its tendon protects the vessel [10, 24] (Fig. 2.6). In that area, the deep branch is also at risk of iatrogenic damage during posterior exposure of the hip. During the Kocher-Langenbeck approach, division of the tendon of the obturator externus should be avoided. It is also unsafe to divide the distal part of the conjoined tendon comprised of the gemellus inferior and fibers of the obturator internus muscle [10]. After bypassing the obturator externus, the deep branch goes into the trochanteric fossa where it gives off trochanteric branches toward the greater trochanter [2, 10]. In this region, the deep branch of the MFCA anastomoses with the piriformis branch of the IGA. Moving in a cranial direction toward the femoral head, it lies anterior to the conjoined tendon of gemelli and obturator internus and enters the hip joint through a femoral attachment of the posterior capsule, superior to the insertion of gemellus superior and distal to the insertion of the piriformis [2, 9–11, 23]. On this course, it becomes intracapsular, obliquely through the capsule. To protect the deep branch of the vessel, approximately 1.5 cm of the conjoined tendon and capsule should be left undivided from the trochanteric crest during posterior exposure of the hip [10]. During its intracapsular and intra-articular courses, the deep branch is at risk of stretching and increased vessel resistance because of intra-articular pressure [25].

Intra-articularly, it travels subsynovially along the femoral neck within the retinacular fibers.

In its intra-articular course, it divides into 1–5 posterior superior nutrient arteries of the femoral head, continuing within the retinaculum toward the femoral head [9, 10, 12] (Fig. 2.7a, b). Many authors agree that the deep branch divides into the terminal nutrient arteries in all cases [2–15]. Posterior superior nutrient arteries are the most important source of blood supply; they can completely perfuse the femoral head without any other vascular input [15]. The estimated size, via microangiographic studies, of a nutrient artery from the group of posterior superior nutrient arteries of the femoral head in adults is 0.8 mm (0.3–1.6 mm) [6]. Zlotorowicz found that the deep branch was absent in 1/55 cases—the femoral head then being supplied by a well-defined piriformis branch of the IGA—using angiographic CT [14].