The anterior compartment is the largest in the thigh, occupying the
region between the inguinal ligament and the knee. Lateral and anteromedial
intermuscular septa separate the contents from the posterior (hamstring) and
medial (adductor) compartments, respectively (Fig. 6.2). The anterior
compartment (Fig. 6.12) contains quadriceps femoris,
sartorius and the tendon of iliopsoas, and is innervated by the femoral nerve.
The femoral artery and vein, the principal vessels of the lower limb, traverse
the compartment and leave via the opening in adductor magnus to gain the
popliteal fossa.
The subcutaneous tissue contains the great (long) saphenous vein and its
tributaries with their accompanying arteries, superficial inguinal lymph nodes
and cutaneous nerves. The great saphenous vein ascends on the medial side of
the thigh (Fig. 6.11) and passes through the saphenous
opening in the fascia lata to empty into the femoral vein. The great saphenous
vein drains the superficial tissues of the entire limb except the lateral side
of the leg and foot. Near its termination, the vein receives tributaries, which
drain the buttock, the perineum and the abdominal wall below the umbilicus.
These tributaries are accompanied by corresponding branches of the femoral
artery. The superficial inguinal lymph nodes, often palpable in the living, lie
just distal and parallel to the inguinal ligament and adjacent to the
termination of the great saphenous vein (Fig. 6.11).
These nodes receive lymph from the same superficial tissues as those drained by
the great saphenous vein and its tributaries. Efferent lymphatics from the
superficial nodes pass through the fascia lata and drain into the deep inguinal
nodes within the femoral triangle and femoral canal, where nodes are a focal
point in lymphatic drainage of the lower limb (p. 257).
The lateral cutaneous nerve of the thigh (L2 & L3) (Fig. 6.17)
pierces the inguinal ligament close to the anterior superior iliac spine, where
it may become entrapped, causing pain in the thigh
(meralgia paraesthetica). It supplies skin as far as the knee. The intermediate
and medial cutaneous nerves of the thigh arise from the femoral nerve and
supply the anterior and medial surfaces of the thigh. Usually, the obturator
nerve gives a cutaneous supply to the medial side of the thigh. The femoral
branch of the genitofemoral nerve (L1 & L2) passes beneath the inguinal
ligament to supply skin over the femoral triangle, and the ilioinguinal nerve
emerges through the superficial inguinal ring to supply the adjacent medial
aspect of the thigh.
The fascia lata (deep fascia) completely invests the thigh, providing
attachment for muscles and associated intermuscular septa in the anterior
compartment. It attaches superiorly to the inguinal ligament and iliac crest,
and inferiorly is continuous with the deep fascia of the leg. Below and lateral
to the pubic tubercle is the saphenous opening, which transmits the terminal
part of the long saphenous vein.
Over the lateral aspect of the thigh, the fascia lata is particularly
thick, forming the iliotibial tract. Gluteus maximus and tensor fasciae latae
are attached to its upper part (Fig. 6.30).
 |
Fig. 6.13 Quadriceps femoris. Vastus intermedius is partially
revealed by removal of rectus femoris. Pectineus and adductors longus and
brevis have been excised.
The four parts of quadriceps femoris, namely rectus femoris, vastus
lateralis, vastus intermedius and vastus medialis, cover the front and sides of
the femur (Figs 6.12, 6.13 & 6.14). Rectus femoris is attached by a straight
head to the anterior inferior iliac spine and by a reflected head to the ilium
above the acetabulum.
Vastus lateralis attaches to the intertrochanteric line, the lateral lip
of the linea aspera and the lateral supracondylar ridge of the femur (Figs 6.15
& 6.16). Vastus intermedius attaches to the upper two thirds of the
anterior and lateral surfaces of the femoral shaft, while vastus medialis
anchors to the spiral line and medial lip of the linea aspera. Distally, these
four muscles form a common tendon, which attaches to the upper border (base) of
the patella. From the lower border (apex) of the patella, the tendon continues
as the patellar ligament (Fig. 6.75) to attach to the tibial tubercle.
Quadriceps femoris is a powerful antigravity muscle, extending the knee
joint during standing, walking and running. In addition, rectus femoris flexes
the hip. The lower fibres of vastus medialis stabilize the position of the
patella (p. 300). Quadriceps femoris is supplied by branches of the femoral
nerve.
Sartorius
This straplike muscle is attached proximally to the anterior superior
iliac spine and descends obliquely across the thigh (Fig. 6.12), crosses the
posteromedial side of the knee and, with gracilis and semitendinosus, attaches
to the upper end of the subcutaneous surface of the tibia (Fig. 6.79).
Sartorius flexes and laterally rotates the hip and flexes the knee. It is supplied
by the femoral nerve.
The femoral triangle occupies the upper medial part of the anterior
compartment of the thigh. Its upper boundary is the inguinal ligament; its
lateral limit is the medial border of sartorius and its medial boundary is the
medial border of adductor longus (some authors use the lateral border in their
definition). The roof is fascia lata and the floor comprises iliopsoas,
pectineus and adductor longus (Fig. 6.17). The triangle
contains the femoral vessels and nerve, and the deep inguinal lymph nodes.
This canal is an intermuscular space linking the femoral triangle with
the popliteal fossa. Triangular in crosssection, it lies beneath sartorius,
occupying the groove between vastus medialis and
adductor longus, and at its lower end adductor magnus (Fig. 6.14). Through the
canal run the femoral artery and vein and nerve to vastus medialis and the
saphenous nerve (Fig. 6.18).
 |
Fig. 6.17 Boundaries and floor of the femoral
triangle.
Femoral vessels
The femoral artery, a continuation of the external iliac, is the main
artery of the lower limb. It enters the anterior compartment behind the
midpoint of the inguinal ligament where it is relatively superficial, easily
palpable and accessible for catheterization to perform arteriograms. It is also
vulnerable to penetrating or stab wounds. It descends through the femoral
triangle (Fig. 6.19) and the adductor canal and continues through the opening
in adductor magnus as the popliteal artery (p. 274).
The femoral artery or its main branches supplies all three compartments
of the thigh. Subcutaneous branches of the artery traverse the saphenous
opening or pierce the fascia lata to accompany the superficial veins in the
groin (Fig. 6.11). The largest deep branch is the profunda femoris artery (Fig.
6.20), which arises from the posterolateral aspect of the femoral artery about
4 cm below the inguinal ligament and runs distally behind the femoral artery,
leaving the triangle by passing between pectineus and adductor longus. The
profunda femoris and its perforating branches pass through the adductor muscles
and contribute to the anastomosis in the posterior compartment of the thigh.
One of the perforating arteries gives a large nutrient branch to the femur.
Close to its origin, the profunda femoris artery usually gives medial and
lateral circumflex femoral branches (Fig. 6.20). The medial circumflex artery
winds round the medial aspect of the femur between iliop soas and pectineus to
join the cruciate anas tomosis (p. 271), and the lateral circumflex artery
encircles the femur, passing laterally deep to sartorius and rectus femoris.
The femoral vein is the continuation of the popliteal vein at the opening
in adduc tor magnus. In the adductor canal, it lies behind the femoral artery
and continues through the femoral triangle, lying medial to the artery (Fig.
6.19). Passing deep to the inguinal ligament the femoral vein becomes the
external iliac vein. Tributaries of the femoral vein, except the great
saphenous vein, correspond to the branches of the femoral artery.
Femoral sheath
The femoral artery and vein are invested in a thick fascial sleeve, the
femoral sheath, derived from the transversalis and iliac fasciae. The sheath
passes deep to the inguinal ligament and tapers inferiorly, blending with the
adventitia of the vessels about 2.5 cm distal to the ligament.
Two vertical septa divide the sheath into three compartments. The femoral
artery lies laterally, while the femoral vein occu pies the intermediate
compartment. The medial compartment is called the femoral canal (Fig. 6.20) and
contains fat and lymph nodes. The upper limit of the femoral canal is the
femoral ring (Fig. 4.23), an aperture bounded in front by the inguinal ligament
and behind by the superior ramus of the pubis, while laterally lies the femoral
vein and medially the lacunar ligament. A femoral hernia descends through the femoral
ring to enter the femoral canal.
Femoral nerve
The femoral nerve (L2, L3 & L4) enters the thigh beneath the inguinal
ligament, lying on iliopsoas lateral to the femoral sheath (Fig. 6.19). After a
brief course in the femoral triangle, it divides into several superficial and
deep branches. The superficial branches are the intermediate and medial
cutaneous nerves of the thigh and the nerves to sartorius and pectineus. The
deep branches include the nerves supplying rectus femoris and the vasti, and
the saphenous nerve, which enters the adductor canal.
The deep inguinal lymph nodes lie in the femoral triangle medial to the
femoral vein.
They receive lymph from the superficial inguinal nodes and from all parts
of the limb deep to the investing fascia. They also drain the glans of the
penis or clitoris. Efferent vessels pass proximally through the femoral canal
to reach the external iliac nodes.
