, Norman J. Snow2 and Brian Catlin2
(1)
Anatomy and Neurology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
(2)
Anatomy, Geisel School of Medicine at Dartmouth, Hanover, NH, USA
Keywords
Common iliac vesselsExternal iliac vesselsInferior epigastric arteryDeep iliac circumflex arteryInternal iliac arteryObturator arterySuperior gluteal arteryInferior gluteal arteryInternal pudendal arteryFemoral arteryCommon femoral arterySuperficial epigastric arteryDeep femoral arteryProfunda femoris arteryProfunda-circumflex trunkPerforating branchesLateral circumflex arteryMedial circumflex arteryDescending genicular arteryPopliteal arterySuperficial sural arteryGenicular arteriesSuperomedial genicular arterySuperolateral genicular arteryMiddle genicular arteryInferomedial genicular arteryInferolateral genicular arteryAnterior tibial arteryMedial anterior malleolar arteryLateral anterior malleolar arteryPosterior tibial arteryCircumflex fibular branchNutrient arteryFibular arteryPeroneal arteryMuscular branchesLateral calcaneal branchesInterosseous branchMedial plantar arteryLateral plantar arteryDorsalis pedis arteryDeep plantar branchPlantar metatarsal arteriesPlantar digital branchesDorsal digital veinsDorsal metacarpal veinsDorsal venous archPlantar venous archPlantar digital veinsAccessory saphenous veinVessels of the Lower Limb
This chapter describes the arterial and venous circulation of the lower limbs. The arterial circulation (Fig. 8.1) begins with the external and internal iliac arteries. The internal iliac artery mostly supplies the pelvic organs, although its branches also contribute to the arterial circulation of the gluteal region and proximal thigh. The external iliac artery continues as the femoral artery after it passes the inguinal ligament. A large proximal branch, the deep femoral artery , not only supplies deeper structures of the anterior thigh but is also the main blood supply of the posterior thigh and the anastomosis around the hip joint. The continuation of the femoral artery (often referred to clinically as the superficial femoral artery) transitions to the popliteal artery as it passes through the adductor hiatus. Branches of both the femoral and popliteal arteries contribute to the anastomosis around the knee. The popliteal artery ultimately gives rise to the three main arteries that supply the leg in a region sometimes called the “trifurcation.” The posterior tibial artery is the continuation of the popliteal artery, beginning at the origin of the anterior tibial artery that branches from the anterior side of the popliteal. The anterior tibial passes between the tibia and fibula to supply the anterior leg. The fibular (peroneal) artery arises from the lateral aspect of the posterior tibial shortly after the origin of the anterior tibial. The fibular artery mostly supplies leg structures of the lateral compartment and some of the posterior compartment, and it ends by joining the anterior tibial in the distal anterior leg to contribute to the dorsalis pedis artery . Together, the fibular and anterior tibial arteries supply most of the dorsum of the foot, the lateral calcaneal region, and the deep plantar arch. The posterior tibial arteries pass posterior to the medial malleolus to reach the plantar surface of the foot where they give rise to the medial and lateral plantar arteries and the medial calcaneal artery.
Fig. 8.1
The arteries of the lower limb. Figure by permission: Basic Human Anatomy. O’Rahilly, Müller, Carpenter and Swenson (http://www.dartmouth.edu/~humananatomy)
The vascular distribution of the foot has been conceptualized as having at least five “angiosomes,” each with a relatively distinct arterial supply and restricted intercommunications through “choke vessels.” These angiosomes include the distributions of the medial and lateral plantar and the dorsalis pedis arteries, as well as the medial and lateral calcaneal artery distributions. Similarly, the leg is conceptualized as having at least three angiosomes, one for each of the major vessels (the anterior and posterior tibial and the fibular arteries).
The venous system is divisible into deep and superficial systems with more blood traveling in the deep system. The deep system consists of venae comitantes distally in the limb, with single popliteal veins and femoral veins paralleling the arteries back to the iliac system. The superficial venous system (Fig. 8.2) is complex and includes great and small saphenous veins, with communications in between and also from the superficial system to the deep system at various points along its course.
Fig. 8.2
A simplified representation of the superficial veins of the lower limb. Details of the veins of the foot have been omitted. Figure by permission: Basic Human Anatomy. O’Rahilly, Müller, Carpenter and Swenson (http://www.dartmouth.edu/~humananatomy)
Arterial Circulation
A discussion of the arterial supply of the lower extremities must begin with the iliac (formerly hypogastric) vessels. The newer terminology will be employed here, as will English (rather than Latin) nomenclature for vessels wherever possible. The description of lower limb arterial circulation will progress from proximal to distal in the limb, first with consideration of the gluteal region and thigh followed by the leg and foot.
Iliac Vessels
Lower limb circulation (Fig. 8.1) begins with the common iliac vessels , the terminal branches of the abdominal aorta. This bifurcation occurs anterior to the fourth lumbar vertebra slightly to the left of the midline. The common iliac arteries follow a course initially anteromedial and then medial to the psoas major muscles. They are usually around 4–5 cm long and end by dividing into internal and external iliac vessels . The external iliac vessels are the major supply to the lower limbs. They travel immediately medial to the psoas major muscle and give rise to two named branches immediately prior to passing the inguinal ligament. The two consistent branches are the inferior epigastric arter y to the anterior abdominal wall and the deep iliac circumflex artery that is directed toward the anterior superior iliac spine, supplying some of the inguinal region. In as many as 20 % of cases, there is a major artery, usually called the accessory obturator artery , arising from either the distal external iliac or the inferior epigastric. This wraps around the superior pubic ramus and usually anastomoses with the obturator artery but can entirely replace it.
The internal iliac artery (Fig. 8.3) supplies most of the blood to the pelvis and gluteal region. Here we will consider its branches that supply the gluteal region. Although the classic description of the internal iliac artery is that it has anterior and posterior divisions, variations are frequent.
Fig. 8.3
Above: the branches of the internal iliac artery , medial aspect. Below: the most frequent pattern of branches of the internal iliac artery. Figure by permission: Basic Human Anatomy. O’Rahilly, Müller, Carpenter and Swenson (http://www.dartmouth.edu/~humananatomy)
The main branches extending into the gluteal and thigh regions are the obturator, the superior and inferior gluteal, and the internal pudendal arteries (Fig. 8.4). The obturator artery usually arises from the anterior division of the internal iliac. It is crossed by the ureter on its course to the obturator foramen. As mentioned previously, it may be joined by or replaced by an accessory obturator artery arising from the external iliac system. The obturator artery divides into several branches. These include an anterior and posterior branch that ramifies around the obturator foramen and an acetabular branch to the ligament of the head of the femur.
Fig. 8.4
The relationship of the superior gluteal, inferior gluteal, and the internal pudendal arteries to other structures emerging into the gluteal region from the greater sciatic foramen. Figure by permission: Basic Human Anatomy. O’Rahilly, Müller, Carpenter and Swenson (http://www.dartmouth.edu/~humananatomy)
The superior and inferior gluteal arteries (Fig. 8.4) classically arise from the anterior division of the internal iliac, but they may originate from the posterior. These arteries pass between roots of the sacral plexus, exiting the pelvis via the greater sciatic foramen immediately superior and inferior to the piriformis muscle, respectively.
The superior gluteal artery is the larger of the two gluteal arteries. Its entry to the gluteal region can be identified by a point one third of the way between the posterior superior iliac spine and the tip of the greater trochanter. It passes between the lumbosacral trunk and the first sacral nerve just prior to exiting the pelvis through the greater sciatic foramen superior to the piriformis muscle. It gives rise to muscular branches and a nutrient artery to the ilium prior to dividing into superficial and deep branches. The superficial branches enter the gluteus maximus muscle, while the deep branch passes between the gluteus maximus and medius muscles, supplying both. In its course, the deep branch is accompanied by the superior gluteal nerve.
The inferior gluteal artery is a branch of the internal iliac artery that leaves the pelvis by passing between two of the upper sacral nerves and exiting the greater sciatic foramen inferior to the piriformis muscle. Branches enter surrounding muscles, especially the gluteus maximus muscle, and it then joins the medial aspect of the sciatic nerve and then the posterior femoral cutaneous nerve. It gives branches to the deep external rotator muscles of the hip and the upper hamstrings. It provides cutaneous supply to the upper posterior thigh and, through coccygeal branches, the region around the coccyx. A branch passes laterally toward the greater trochanter of the femur, participating in the cruciate anastomosis posterior to the hip joint. There is usually a very small artery of the sciatic nerve. On occasion this artery can remain quite large (it is the remnant of a large axial artery in the embryo).
The internal pudendal artery (Fig. 8.3) also usually arises from the anterior division and exits the pelvis through the greater sciatic foramen inferior to the piriformis muscle. It subsequently crosses the posterior aspect of the ischial spine and sacrospinous ligament and enters the lesser sciatic foramen to reach the perineum. It is accompanied by the pudendal nerve and is the source of the inferior rectal artery and vessels supplying the scrotum (or labia), perineum, bulb of the penis (or vestibule), and urethra.
The remainder of the visceral and parietal branches of the internal iliac system will not be described here.
Femoral Vessels
The main blood supply to the anterior thigh is the femoral artery (often referred to clinically as the common femoral artery ). This is the continuation of the external iliac as it passes the inguinal ligament (Fig. 8.5). It is quite superficial in the upper thigh, but it becomes deep by passing posterior to the sartorius muscle in the adductor canal about a third of the way down the thigh. About 2/3–3/4 of the way down the thigh it passes through the adductor hiatus to leave the anterior thigh and assume a posterior position as the popliteal artery .
Fig. 8.5
Structures entering the thigh deep to the inguinal ligament. Figure by permission: Basic Human Anatomy. O’Rahilly, Müller, Carpenter and Swenson (http://www.dartmouth.edu/~humananatomy)
The initial (superior) parts of the femoral artery and vein are enclosed in a fascial investment called the femoral sheath. This is located medial to the iliopsoas muscle and anterior to the pectineus muscle (Fig. 8.5) and consists of fascial continuations from the transversalis fascia of the abdomen and the iliac fascia over the iliacus muscle. The sheath is a few centimeters long, tapering to fuse with the adventitia of the blood vessels. It is divided by connective tissue septae into three compartments with a lateral one for the artery, a middle one for the vein, and a medial, one called the femoral canal, containing fat and a few lymph vessels. Its superior end is termed the femoral ring and is normally closed by a condensation of connective tissue known as the femoral septum. There is a thickening of connective tissue, Henle’s ligament, which borders the medial aspect of the femoral ring. Clinically, the femoral canal is the location of femoral hernias. The anterior aspect of the femoral sheath is pierced by small arteries and by the great saphenous vein.
The most proximal named branches of the femoral artery (Fig. 8.1) arise immediately after the femoral artery enters the femoral sheath by passing deep to the inguinal ligament. These arteries pierce the femoral sheath, entering the superficial fascia. They include the superficial epigastric artery , the superficial iliac circumflex artery, the superficial external pudendal artery, and the deep external pudendal artery. There are also several muscular and musculocutaneous branches. The superficial epigastric artery runs superiorly to enter the superficial fascia of the abdomen anterior to the inguinal ligament. It follows a course roughly toward the umbilicus, anastomosing with branches of the inferior epigastric artery . The superficial iliac circumflex artery passes superolaterally toward the anterior superior iliac spine, where it anastomoses with the deep iliac circumflex artery . The external pudendal arteries pass medial to the tissues over the medial part of the inguinal ligament and anterior structures of the pudendum (anterior scrotal/labial branches).
The superior 1/3 of the femoral artery is in the femoral triangle. This triangle is inferior to the inguinal ligament and is bounded on the lateral side by the medial border of the sartorius muscle and medially by the medial border of the adductor longus muscle. The floor of the triangle is formed by the iliopsoas, pectineus, and adductor longus muscles from lateral to medial. Anteriorly, the triangle is covered by the fascia lata (the investing fascial layer of the thigh). Just inferior to the inguinal ligament, the fascia lata is perforated by the small anterior branches of the femoral artery and by the great saphenous vein. This perforated fascia has been termed the cribriform fascia, and the fascial gap has been called the saphenous hiatus. Within the more inferior portions of the femoral triangle, the femoral artery assumes a position anterior to the femoral vein, while the majority of the branches of the femoral nerve remain lateral to the artery in the triangle.
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