Arterial Supply of the Lower Limb

Question 1

Thigh and gluteal region

Answer 1

The main artery of the lower limb is the femoral artery - a continuation of the external iliac artery. It becomes the femoral artery when it crosses the inguinal ligament and enters the femoral triangle.

It gives a few branches:

1) Superficial epigastric artery - abdominal wall
2) Superficial external pudendal artery - genitalia
3) Superficial circumflex iliac artery - skin and subcutaneous tissue below inguinal ligament.
4) Descending genicular artery - supplies the knee

In the femoral triangle, the profunda femoris artery (deep femoral artery) arises from the posterolateral aspect of the femoral artery. It travels distally and posteriorly and gives off three branches:

1) Perforating branches- consists of three or four arteries that pierce the adductor magnus, contributing to muscles of the medial and posterior thigh.
2) Lateral femoral circumflex artery - wraps around the anterior, lateral side of the femur, supplying muscles of the lateral aspect of the thigh.
3) Medial femoral circumflex artery - wraps around the posterior end of the femur, supplying its neck and head. In a fracture of the neck of the femur, this artery can be damaged - avascular necrosis can occur.

After exiting the the femoral triangle, the femoral artery travels down anterior aspect of the thigh, through a tunnel, known as the adductor canal. During its descend it supplies the anterior thigh muscles.

The adductor canal ends at the opening to the adductor magnus, called the adductor hiatus. The femoral artery moves through this opening and enters the posterior compartment of the thigh, proximal to the knee. The femoral artery is now known as the popliteal artery.

Question 2

Clinical relevance: accessing the femoral artery

Answer 2

The femoral artery is located superficially in the femoral triangle and so it is easy to access. This artery is used to perform a range of procedures.

One procedure is the coronary angiograph. Here a long thin tube is passed through to the EIA, CIA, aorta, and into the coronary vessels.

A radio-opaque dye is then injected into the coronary vessels. Any thickenings or blockages can be visualised on the X-ray.

Question 3

Other arteries to the thigh

Answer 3

1) Obturator artery - arises from the internal iliac artery in the pelvic region. Descends via the obturator canal to enter the medial thigh, bifurcating into two branches:
i) Anterior branch - supplies the pectineus, obturator externus, adductor muscles, and the gracilis.
ii) Posterior branch - supplies some deep gluteal muscles.
2) Superior and inferior gluteal arteries - arises from the internal iliac artery, entering the gluteal region via the greater scieatic foramen.

The superior gluteal muscle leaves the foramen above the piriformis.

The inferior gluteal artery leaves the foramen below the piriformis. It also supplies the posterior thigh.

Question 4

In the leg

Answer 4

The popliteal artery descends down the posterior thigh, giving rise to genicular branches that supplies the knee joint. It moves through the popliteal fossal, exiting between the gastrocnemius and popliteus muscles.

The popliteal artery terminates at the lower border of the popliteus and terminates by dividing into two branches:

i) Anterior tibial artery - passes anteriorly between the tibia and fibula, through a gap in the interroseous membrane. It runs down the entire leg and then into the foot, where it becomes the dorsalis pedis artery.
ii) Tibioperoneal trunk - this divides into two branches:
- Posterior tibial artery - continues inferiorly, along the surface of the deep posterior leg muscles (such as the tibialis posterior). Enters the sole of the foot via the tarsal tunnel, accompanying the tibial nerve.
- Fibular (peroneal) artery - descends posteriorly to the fibula, within the posterior compartment of the leg. It gives rise perforating branches, which penetrate the intermuscular septum to supply muscles of the lateral compartment.

Question 5

Clinical relevance: popliteal aneurysm

Answer 5

An aneurysm is a dilation of an artery, which is greater than 50% of the diameter of a normal artery.

The popliteal fascia (the roof of the popliteal fossa) is tough and non-extensible, and so an aneurysm of the popliteal artery has consequences of other contents in the fossa.

The tibial nerve is particularly susceptible to compression. This can result in:

1) weakened or absent plantar flexion
2) paraesthesia of the foot and posterolateral leg

A popliteal aneurysm is detected by an obvious palpable pulsation in the popliteal fossa. An arterial bruit may be heard on auscultation.

Question 6

The foot

Answer 6

Arterial supply is delivered by two arteries:

1) Dorsalis pedis (a continuation of the anterior tibial artery) - passes over the dorsal aspect of the tarsal bonesm, then moves inferiorly towards the sole of the foot. It then anastomoses with the lateral plantar artery to form the deep plantar arch - it contributes supply to part of the toes.

It supplies the tarsal bones and the dorsal aspect of the metatarsals.

2) Posterior tibialis - enters the soles via the tarsal tunnel. It then splits into two arteries:
i) Lateral plantar artery
ii) Medial plantar artery

These arteries supply the plantar side of the foot, and contributes to the toes via the deep plantar arch.

Question 7

Clinical relevance: pulse points in the lower limb

Answer 7

There are four pulses of the lower limb:

1) Femoral pulse - can be palpated as it enters the femoral triangle, midway between the ASIS and the pubic symphysis.
2) Popliteal pulse - harfest pulse to find - lies deep to the popliteal fossa - requires deep palpation - ask patient to flex their leg becuase this relaxes the fascia around the popliteal fossa.
3) Dorsalis pedis pulse - found by palpating the dorsum of the foot, just lateral to the extensor hallucis longus tendon.
4) Posterior tibial pulse - can be palpated inferoposteriorly to the medial malleolus, where the artery turns to turn into the foot.