5 Neurovascular Systems: Topographical Anatomy
5.1 Surface Anatomy and Superficial Nerves and Vessels: Anterior View
A Surface anatomy of the right lower limb
Palpable bony prominences on the lower limb are reviewed on p. 411.
B The most common variants of the forefoot and toes (after Debrunner and Lelievre)
Three types of foot shape are distinguished based on the relative lengths of the first and second toes:
a The “Greek” type, in which the second toe is longer than the first.
b The square type, in which the first and second toes are of equal length.
c The “Egyptian” type, in which the first toe is longer than the second.
In the “Greek” type, the second metatarsal is generally longer than the metatarsal of the great toe. As a result, the head of the second metatarsal is often subject to painful overloading, especially when high heels are worn.
C The dorsal surface of the right foot
The superficial venous network is visible on the dorsum of the foot (compare with D).
D Superficial cutaneous veins and nerves of the right lower limb
Anterior view. The dorsal venous network of the foot is drained by two large venous trunks (the great and small saphenous veins), which receive a variable pattern of cutaneous veins. While the small saphenous vein (see p. 553) enters the popliteal vein at the level of the popliteal fossa, the great saphenous vein extends up the medial side of the leg to a point just below the inguinal ligament, where it passes through the saphenous opening of the fascia lata to enter the femoral vein. The superficial veins of the lower limb are commonly affected by varicosity, causing them to become thickened, tortuous, and distinctly visible and palpable (see also p. 553).
E Radicular (segmental) cutaneous innervation pattern (dermatomes) in the right lower limb
As in the arm, the outgrowth of the lower limb during development causes the sensory cutaneous segments to become elongated and drawn out into narrow bands. The L4, L5, and S1 segments in particular move so far peripherally that they no longer have any connection with the corresponding segments of the trunk.
Note that the dermatomes of the lumbar trunk segments lie mostly on the front of the leg, while those of the sacral segments are mostly on the back of the leg (see p. 86). This can be of diagnostic importance in patients with a herniated disk, for example, in order to determine the level of the herniation (after Mumenthaler).
F Pattern of peripheral sensory cutaneous innervation in the right lower limb
As in the arm, the sensory distribution in the lower limb corresponds to the branching patterns of the peripheral cutaneous nerves in the subcutaneous connective tissue. The territories of the individual peripheral nerves overlap, especially at their margins. Hence the clinically determined exclusive area of a particular cutaneous nerve (the area supplied by that nerve alone) tends to be considerably smaller than the maximum area that can be demonstrated anatomically. For this reason, the traumatic disruption of a nerve causes a complete loss of sensation (anesthesia) in the exclusive area but often will cause only diminished sensation (hypoesthesia) at the perimeter of that area.
Note that the sensory loss resulting from a peripheral nerve injury presents a completely different pattern from that caused by injury to a nerve root (see p. 90) (after Mumenthaler).
5.2 Surface Anatomy and Superficial Nerves and Vessels: Posterior View
A Surface anatomy of the right lower limb
The foot is in plantar flexion. (Palpable bony prominences on the lower limb are reviewed on p. 411.)
B Footprints (podograms) of the normal right foot in an adult
A podogram provides a graphic representation of the loads borne by the foot. Besides visual inspection of the sole of the foot, analysis of the podogram supplies the most useful information on the weight-bearing dynamics of the foot.
a Footprint created with an ink pad.
b Pressure podogram showing a normal weight-bearing pattern on the foot. The concentric lines indicate that the pressure is evenly distributed over all the major points of support. These three areas are clearly defined, while the intervening plantar arches bear essentially no weight (see p. 464).
C The plantar surface of the right foot
The skin on the plantar surface of the foot serves as a sensory organ for contact with the ground, perceiving its consistency during stance and locomotion by means of receptors in the sole of the foot. Stresses acting on the heel pad and the balls of the great and little toes generate high local compressive forces at those sites, to which the subcutaneous connective tissue has adapted functionally by developing a system of pressure chambers (see p. 478).
D The epifascial cutaneous veins and nerves of the right lower limb
Posterior view.
E Radicular (segmental) cutaneous innervation pattern (dermatomes) of the right lower limb
As in the arm, the outgrowth of the lower limb during development causes the sensory cutaneous segments to become elongated into narrow bands. The L4, L5, and S1 segments in particular move so far peripherally that they no longer have any connection with the corresponding segments of the trunk.
Note that the dermatomes of the lumbar trunk segments lie mostly on the front of the leg, while those of the sacral segments are mostly on the back of the leg (see p. 88). This can be of diagnostic importance in patients with a herniated disk, for example, in order to determine the level of the herniation (after Mumenthaler).
F Pattern of peripheral sensory cutaneous innervation in the right lower limb
As in the arm, the sensory distribution in the lower limb corresponds to the branching patterns of the peripheral cutaneous nerves in the subcutaneous connective tissue. The territories of the individual peripheral nerves overlap, especially at their margins. Hence the clinically determined exclusive area of a particular cutaneous nerve (the area supplied by that nerve alone) tends to be considerably smaller than the maximum area that can be demonstrated anatomically. For this reason, the traumatic disruption of a nerve causes a complete loss of sensation (anesthesia) in the exclusive area but often will cause only diminished sensation (hypoesthesia) at the perimeter of that area.
Note that the sensory loss resulting from a peripheral nerve injury presents a completely different pattern from that caused by injury to a nerve root (see p. 90) (after Mumenthaler).
5.3 The Anterior Femoral Region Including the Femoral Triangle
A The femoral triangle
Right thigh, anterior view. The skin, subcutaneous tissue, and fascia lata have been removed to demonstrate the neurovascular structures in the femoral triangle. The femoral triangle is bounded superiorly by the inguinal ligament, laterally by the sartorius muscle, and medially by the adductor longus. It contains the neurovascular structures that emerge from the pelvis and pass below the inguinal ligament to the anterior side of the thigh through the lacuna musculorum and lacuna vasorum (see also C). The posterior muscular wall of the femoral triangle is formed from lateral to medial by the iliopsoas and pectineus.
B The branches of the external iliac artery at its junction with the femoral artery in the region of the inguinal ligament
C Inguinal region and the contents of the muscular and vascular compartments
Anterior view. The drawing shows a portion of the right hip bone and the adjacent anterior inferior abdominal wall with the superficial inguinal ring and the contents of the muscular and vascular compartments below the inguinal ligament. The site of emergence of the muscles and vessels, bounded by the inguinal ligament and the superior pelvic rim, is subdivided by the fibrous iliopectineal arch.
The vascular compartment is located medial to the iliopectineal arch and is traversed from lateral to medial by the femoral branch of the genitofemoral nerve, the femoral artery and vein, and the deep inguinal lymphatic vessels (only one lymph node is shown here). The part of the vascular compartment that lies medial to the femoral vein is called the femoral ring. The lymph vessels from the thigh pass through that ring to enter the pelvis. The femoral ring is covered by a thin sheet of connective tissue called the femoral septum (not shown here), which usually contains a lymph node (the Rosenmüller node) belonging to the group of deep inguinal lymph nodes (see also p. 534).
The muscular compartment is lateral to the iliopectineal arch and is traversed by the iliopsoas muscle, femoral nerve, and lateral femoral cutaneous nerve.
Note the iliopectineal bursa located below the iliopsoas. It is the largest bursa of the hip region and communicates in 15% of cases with the joint cavity of the hip. For this reason, an inflammatory disease of the hip joint may incite inflammation of this bursa (bursitis). When inflamed, the iliopectineal bursa is frequently painful and swollen and may occasionally be mistaken for a neoplasm on MR images.
D The connective-tissue and bony boundaries of the muscular and vascular compartments
Diagram of the right inguinal region, anterior view. The connective-tissue boundary between the muscular and vascular compartments is formed by the iliopectineal arch, a thickened band in the medial portion of the iliacus fascia. It extends between the inguinal ligament and the iliopubic eminence. The fibrous band that curves downward from the medial attachment of the inguinal ligament is called the lacunar ligament, which extends further medially as the pectineal ligament (Cooper’s ligament) and runs along the superior pubic ramus. This sharp-edged ligament defines the medial boundary of the vascular compartment (femoral ring) and may entrap the hernial sac in patients with a femoral hernia (see p. 216). Above the inguinal ligament is the external (superficial) inguinal ring, which is the external opening of the inguinal canal (see p. 212). The muscular compartment is bounded laterally by the anterior superior iliac spine.
5.4 Arterial Supply to the Thigh
A Course and branches of the femoral artery
The femoral artery, the distal continuation of the external iliac artery, runs along the medial side of the thigh to the adductor canal, through which it passes to the back of the leg. After emerging from the adductor hiatus, it becomes the popliteal artery. In clinical parlance the femoral artery is often called the superficial femoral artery because of its superficial course down the front of the thigh, distinguishing it from the more deeply placed deep artery of the thigh that arises from it (see D).
B Course of the profunda femoris artery and sites where the perforating arteries pierce the adductor muscles
a Right thigh, anterior view; b schematic longitudinal section through the adductor muscles at the level of the perforating arteries. The profunda femoris artery has approximately three to five terminal branches that pass from the front to the back of the thigh through the femoral insertions of the adductor muscles (= first through third perforating arteries) to supply the hamstring muscles (biceps femoris, semitendinosus, and semimembranosus). Generally, the arteries pierce the adductor muscles above and below the adductor brevis and just above the adductor hiatus. Ligation of the femoral artery proximal to the origin of the deep artery of the thigh is relatively well tolerated owing to a good collateral supply from branches of the internal iliac artery (superior gluteal artery and obturator artery).
C Variants in the femoral artery branching pattern (after Lippert and Pabst)
a Usually the deep artery of the thigh and medial and lateral circumflex femoral arteries arise from the femoral artery by a common trunk (58% of cases, also shown in the other figures on this page).
b The medial circumflex femoral artery arises directly from the femoral artery (18% of cases).
c The lateral circumflex femoral artery arises directly from the femoral artery (15% of cases).
d The circumflex arteries arise separately from the femoral artery (4% of cases).
e The descending branch of the lateral circumflex femoral artery springs directly from the femoral artery (3% of cases).
f The circumflex arteries arise by a common trunk (1% of cases).
D The blood supply to the thigh from the profunda femoris artery
Right thigh, anterior view. The sartorius, rectus femoris, adductor longus, and pectineus muscles have been partially removed, along with the central portion of the femoral artery, to demonstrate the course of the deep artery of the thigh. For clarity, the veins have also been removed to the level of the external iliac vein. This dissection does not show the anterior abdominal wall or the pelvic and abdominal organs above the level of the inguinal ligament. While the branches of the medial and lateral circumflex arteries mainly supply blood to the hip joint and extensors and adductors of the thigh, the terminal branches of the deep artery of the thigh (the first through third perforating arteries, see B) on the medial side of the femur pass to the back of the thigh through gaps in the insertions of the adductor muscles and supply the hamstrings (biceps femoris, semitendinosus, and semimembranosus).
Note: The vastoadductor membrane is pierced by the descending genicular artery and saphenous nerve (see E and F).
E The location of the adductor canal
Right thigh, anterior view. The saphenous nerve passes down the adductor canal on the anterior side of the thigh, accompanied by the femoral artery and vein. While both vessels continue toward the popliteal fossa through the adductor hiatus, the saphenous nerve pierces the vastoadductor membrane along with the descending genicular artery and passes to the medial side of the knee joint (see also F).
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