The blood supply to the proximal femur

1.6.1 Anatomy of the arterial supply

For hundred years the idea prevailed that fractures of the femoral neck and their complications were foremost due to already inadequate vascularization of femoral head and neck that worsened with age (Cordasco, 1938). Nowadays, we are of the opinion that the vulnerability of the supplying vessels is the deciding factor; it is due to the intraarticu-lar position of the 7 cm long portion of head and neck. During childhood this vulnerability is already present and is increased by the absence of anastomoses and the fact that vessels do not cross the growth plate (Trueta, 1957).

The most important vessel supplying the head is the medial femoral circumflex artery that is a branch of the deep femoral artery or, less frequently, the common femoral artery (Fig. 37, see also Fig. 7).

The extraarticular network of vessels plays an important role thanks to its richness of anastomoses. This network includes the lateral femoral circumflex artery, superior and inferior gluteal arteries and also the obturator artery via the Weathersby anastomosis (see Fig. 41b) (Weathers-by, 1959). Thanks to the anastomoses a blockage of the main artery has no catastrophic consequences in respect to femoral head necrosis. On the other hand, the rich extracapsular network of vessels confirms the clinical experience that per- inter- and sub-trochanteric fractures are usually accompanied by considerable local blood loss.

The blood supply of the femoral head has been summarized by Trueta and Harrison (1953), Sevitt and Thompson (1965) and Judet and collaborators (1981) after decades of research (Fig. 38).

The lateral epiphyseal vessels (branches of the medial femoral circumflex artery and vein), that normally play an important part in the vasculariza-tion of the head, are particularly prone to injury (Fig. 39, see also Fig. 8).

The cranial retinaculum is attached tightly to bone and ruptures therefore easily torn during fracture, particularly in the presence of displacement. If the fracture is impacted, the vessels can become incarcerated (see Fig. 49). It can happen that the fracture line reaches the cranial part of the femoral neck at a point where the vessels already lie inside the bone (medial to Claffey's point). This leads to a rupture of the vessels (Claffey, 1960). It has been assumed that this fact plays an important role in the

Medial Circumflex Femoral Artery

Fig. 37. Course of the principle arteries in relation to the proximal femur (as seen from the medial aspect of the left lower limb drawn after an angiography with the hip in slight external rotation).

Common femoral artery (1.), deep femoral artery (2.), medial femoral circumflex artery (3.)

Fig. 37. Course of the principle arteries in relation to the proximal femur (as seen from the medial aspect of the left lower limb drawn after an angiography with the hip in slight external rotation).

Common femoral artery (1.), deep femoral artery (2.), medial femoral circumflex artery (3.)

etiology of head necrosis. However, clinical results failed to confirm this assumption.

The incidence of necrosis in Pauwels-III fractures, that start subcapital, is not much different from that in Pauwels-II fractures. Some authors even attribute the more favorable results to Pauwels-III fractures (Banks, 1962; Bohler, 1996). These authors explain this observation by the fact that the caudal fracture line does not disrupt the

Vascular Supply Femoral Head

Fig. 38. Arterial supply to the femoral head.

a, b. Horizontal cut through a femoral head specimen of a 70-year-old man using Trueta and Harrison's technique (1953). One can recognize: lateral epiphyseal arteries (1.), medial epiphyseal artery (2.), superior metaphyseal arteries (3.), inferior metaphyseal arteries (4.) and Claffey's point (5). c, d. Horizontal cut through a femoral head specimen using Sevitt and Thompson's technique (1966). The cut (d) shows very well the variation first described by Judet et al (1981) whereby the superior metaphyseal arteries separate from the lateral epiphyseal arteries (6.) only at Claffey's point. In such an instance a neck fracture can affect the supplying branch and also damage the blood supply to the neck (risk of necrosis) (Manninger et al, 1979)

Metaphyseal Epiphyseal Junction Fracture

Fig. 39. Importance of the lateral epiphyseal arteries.

In this specimen of a 40-year-old man the distribution of the supplying vessels is well demonstrated: a. At the cranial aspect multiple opening for vessel entrance averaging four to eight in number can be seen at the cartilage/bone junction; b. On the caudal aspect only a few small vessel entries are seen at the border of the head a b loose network of vessels (inferior metaphyseal arteries). Consequently the major part of the head receives adequate blood supply through anastomoses (see Figs. 6 and 8).

In adults the intraosseous metaphyseal vessels supply also the femoral head. They originate

Blood Supply Femoral Head
a

mostly from the inferior metaphyseal arteries

(and to a smaller part from superior metaphyseal arteries) situated in the caudal retinaculum. The importance of the intraosseous blood supply increases particularly during the revascularization after injury.

Vessels in the femoral head ligament supply normally the femoral head to different degrees. Their contribution is rather small. Their importance may play a considerable compensatory role in vascular disturbances after injury (Hulth, 1956; Manninger, 1963; Sevitt, 1964; Forgon and Miltényi, 1970; Manninger et al, 1979).

1.6.2 Anatomy of the venous network

(Pernkopf, 1989; Hulth, 1956; Manninger et al, 1979)

The venous blood drains from the double circumflex femoral vein system via the deep femoral vein into the common femoral vein and from the medial epiphyseal vessels via the obturator vein into the internal iliac vein. The posterior inferior and superior gluteal veins play also an important role; they likewise drain into the internal iliac vein (Figs. 40-43).

Hulth found that the venous network (with paired veins) runs closely to the arteries at the

Epiphyseal Arteries

Fig. 39. Importance of the lateral epiphyseal arteries.

In this specimen of a 40-year-old man the distribution of the supplying vessels is well demonstrated: a. At the cranial aspect multiple opening for vessel entrance averaging four to eight in number can be seen at the cartilage/bone junction; b. On the caudal aspect only a few small vessel entries are seen at the border of the head

Fig. 40. Intraoperative intraosseous venography.

a. Lateral radiograph; b. Schema as seen from the medial side of the left lower limb drawn after an intraosseous venography with the hip in slight external rotation.

Recognizable are: medial femoral circumflex vein (1.), deep femoral vein (2.), common femoral vein (3.), the latter is paler due to the thinning. The double gluteal vein (4) is seen posteriorly. On the a.-p. film this vein is usually obscured by the cranial part of the head. On the point of the needle entry the contrast material leached into the capsule (5.)

Intraosseous Femoral Head Blood Supply

Fig. 41. Intraoperative intraosseous venography.

In both cases femoral heads are well filled but congested (1.). The double medial circumflex vein (2.) and the intraosseous drainage into the metaphysis (3.) are better seen in picture b. The deep femoral vein (4.) and the common femoral vein (5.) are better seen in picture a., whereas the Weathersby anastomosis (6.) and the obturator vein (7.) are better recognized in picture b. The good filling is a positive sign

Fig. 41. Intraoperative intraosseous venography.

In both cases femoral heads are well filled but congested (1.). The double medial circumflex vein (2.) and the intraosseous drainage into the metaphysis (3.) are better seen in picture b. The deep femoral vein (4.) and the common femoral vein (5.) are better seen in picture a., whereas the Weathersby anastomosis (6.) and the obturator vein (7.) are better recognized in picture b. The good filling is a positive sign

Blood Supply Caput Femoris

Fig. 42. Most frequent appearance of the entire venous network of the proximal femur. Schema. Result of many positive intraosseous venographies (Manninger, 1979).

The medial femoral vein (vena capitis femoris) (1.) flows into the obturator vein (3.) at a site (2.) where it meets the Wheathersby anastomosis (5.) originating from the medial femoral circumflex vein (4.). The lateral femoral circumflex vein (6.) empties in general into the deep femoral vein (7.). At this site one or several venous valves are found (8.). The superior gluteal vein (9.) is often doubled and communicates cranially via an anastomosis with vessels of the proximal femoral region. Caudally the inferior metaphyseal veins (10.) drain the venous blood from the head and neck into the medial femoral circumflex vein. The superior gluteal vein (11.) and the inferior gluteal vein (12.) run in a posterior direction whereby the inferior gluteal vein also flows into the obturator vein (13.). Often the intraosseous drainage (14.) is well visible with a flow of the contrast material through the fracture site into the trochanter. The principle collector vessel is the superficial femoral vein (15.). It empties into the common femoral vein (16.). The flow continues into the external iliac vein (17.) as well as into the internal iliac vein (18.)

Internal Iliac Vein

Fig. 43. The venous drainage in relation to the proximal femur.

a. As seen on lateral radiographs of the intraosseous venography; b. Schema (slightly external rotation of the left lower limb as seen from the medial side).

Common femoral vein (1.); deep femoral vein (2.); medial femoral circumflex vein (3.); pair of superior gluteal veins (4.)

Fig. 43. The venous drainage in relation to the proximal femur.

a. As seen on lateral radiographs of the intraosseous venography; b. Schema (slightly external rotation of the left lower limb as seen from the medial side).

Common femoral vein (1.); deep femoral vein (2.); medial femoral circumflex vein (3.); pair of superior gluteal veins (4.)

Double Circumflex

Fig. 44. Parallel course of the retinacular vessels on a proximal femur specimen. Original photograph by Hulth (1956)

a. Artery and vein of the caudal retinaculum side by side;

b. Vessels of the cranial retinaculum side by side a b

Fig. 44. Parallel course of the retinacular vessels on a proximal femur specimen. Original photograph by Hulth (1956)

a. Artery and vein of the caudal retinaculum side by side;

b. Vessels of the cranial retinaculum side by side femoral neck. Therefore, indirect information about arteries can be gained, when we follow the veins (intraosseous venography) (Fig. 44) (Hulth, 1956). If the intraosseous venography shows intact veins, one can assume that the arteries are not damaged.

1.6.3 The capillary circulation

As in other organs arteries branch into arterioles that continue as capillaries; the latter consist of arterial and venous portions. Special to the intra-osseous circulation is the fact that cancellous bone has a honeycomb structure with rigid walls preventing dilation of draining vessels. The walls of the cancellous bone are lined with osteoblasts, the spaces are filled with red marrow in children and with yellow marrow in adults. On the other hand, similar to liver and spleen sinusoids, vessel enlargements without adventitia are found here that are responsible for the nutrition of bone tissue (Fig. 45).

The significance of intraosseous drainage, interrupted by the fracture, has been highlighted in the last years (Kazar et al, 1992; Kazar and Manninger, 1993). The development of avascular necrosis often depends on the increased pressure in the femoral head. Its etiology includes: (1) compression of sinusoids due to an altered fat metabolism

Fig. 45. Capillary network in the proximal femur.

a. Schematic representation of sinusoids according to Solomon (1990). Structure of a sinusoid: artery (1.), arteriole (2.), network of capillaries without adventitia (3.), venule (4.), vein (5.), bone (6.), marrow (7.); b, c. Sinusoids in the cancellous bone of the head. Histologic sections with different magnifications.

Sinusoids are found between the trabeculae. Greater magnification (c) allows to recognize better sinusoids, five thin-walled venules and a small arteriole in an intertrabecular space. At the wall of this space osteoblasts can be seen as small dots; osteocytes are seen in the bone (Lang and Nagy, 1951).

In the presence of a fracture, a congestion develops in the inelastic sinusoids; it leads to an increase in pressure similar to a compartment syndrome

Fig. 45. Capillary network in the proximal femur.

a. Schematic representation of sinusoids according to Solomon (1990). Structure of a sinusoid: artery (1.), arteriole (2.), network of capillaries without adventitia (3.), venule (4.), vein (5.), bone (6.), marrow (7.); b, c. Sinusoids in the cancellous bone of the head. Histologic sections with different magnifications.

Sinusoids are found between the trabeculae. Greater magnification (c) allows to recognize better sinusoids, five thin-walled venules and a small arteriole in an intertrabecular space. At the wall of this space osteoblasts can be seen as small dots; osteocytes are seen in the bone (Lang and Nagy, 1951).

In the presence of a fracture, a congestion develops in the inelastic sinusoids; it leads to an increase in pressure similar to a compartment syndrome

(alcohol consumption, Gaucher's disease, steroid medication), (2) venous congestion due to post-capillary blockage and increased pressure secondary to displaced neck fractures with damage to the intraosseous circulation in the femoral metaphysis (Arnoldi and Linderholm, 1969; Arnoldi et al, 1970; Arnoldi and Linderholm, 1972). The immediate reduction and internal fixation is not only important for the restoration of circulation but also for the prevention of closure of fractured cancellous bone surfaces. On the condition of early and good reduction and adaptation of fragments the congested blood can drain through the fracture gap. As in adults the circulation of epiphysis and metaphysis is not anymore separated by the physis, a drainage of the femoral head through the metaphysis is possible (see Figs. 55 and 56).

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    Which femoral circumflex artery is the most important?
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