Arteries of the Leg and Foot
The lower limb is essential for our locomotion and movement. The ball and socket hip joint provides movements on all three perpendicular axes including flexion and extension, medial and lateral rotation, abduction and adduction.
The vascular supply of the leg and foot is the focus of this article, both in terms of the basic anatomy, and its clinical relevance. The origin, course and clinical points of major vessels will also be discussed below.
Origin and course
At vertebral level L4, the aorta bifurcates, into the two common iliac arteries. These then pass obliquely laterally, and give off a branch to supply the pelvic viscera (the internal iliac artery). The other branch external iliac passes under the inguinal ligament, and becomes the femoral artery. The arterial supply to the lower limb originates from the femoral artery.
The femoral artery then gives off its profunda femoris branch, which supplies the thigh (both the flexor, adductor and extensor compartments). The remaining vessel is named the superficial femoral artery. This now descends down the posterior thigh, and passes through the adductor hiatus i.e. Hunter’s canal/Subsartorial canal.
Anatomically the adductor hiatus is a space between the two insertion points of the adductor magnus muscle. As it emerges from Hunter’s canal it is known as the popliteal artery.
The artery is the deepest of the neurovascular structures within the popliteal fossa, with the vein just superficial and the sciatic nerve most superficial of the three structures. The vein and artery are closely adhered and can be difficult to separate on dissection. This popliteal artery gives the following branches:
The popliteal artery divides and gives off an anterior tibial branch that supplies the anterior compartment of the leg i.e. tibialis anterior, the extensor hallucis longus and extensor digitorum longus muscles. This artery passes through the oval aperture of interosseous membrane and travels on the anterior surface of interosseous membrane.
When this artery is found in the ankle/foot region, it is referred to as the dorsalis pedis. The artery lies lateral to the tendon of extensor hallucis longus. The dorsalis pedis gives rise to the deep plantar artery and the first dorsal metatarsal artery.
The deep plantar artery passes between the heads of the first dorsal interosseus muscle and unites with the lateral plantar artery. The first dorsal metatarsal divides into two arteries in the first web space and passes deep to the tendon of extensor hallucis longus.
The dorsalis pedis artery is an important vessel for assessing peripheral blood flow particularly in diabetics and those with existing vascular disease. The dorsalis pedis descends to supply the tarsals as well as the dorsal part of the metatarsals. Next it dives deeper into the foot and anastomoses with the lateral plantar artery to form the deep plantar arch.
The other division of the popliteal artery is the posterior tibial artery. This courses in the posterior compartment of the leg and supplies the posterior muscles and structures, such as the achilles tendon, gastrocnemius muscles, the deep posterior muscles i.e. flexor halluces longus, flexor digitorum longus and tibialis posterior muscle.
When the posterior tibial descends it eventually passes behind the medial malleolus along with a number of other structures. An acronym for remembering these structures is:
Tom Dick And a Very Nervous Harry, from closest to the medial malleolus to furthest away. The structures these words denote are the tibialis posterior tendon, flexor digitorum longus tendon, posterior tibial artery, posterior tibial vein, tibial nerve and finally flexor hallucis longus tendon.
These structures wind behind the medial malleolus and pass anteriorly to enter the foot via the tarsal tunnel. The posterior tibial artery divides to form the medial and lateral plantar arteries that broadly supply the sole of the foot. The medial and lateral plantar arteries supply the toes via the deep plantar arch. The medial plantar supplies part of the hallux (big toe), the lateral plantar supplies the vast majority of the foot.
This vessel is a branch of the posterior tibial artery. And is the artery of the lateral or fibular compartment of the leg. Although it supplies the lateral compartment, it actually runs in the posterior compartment, and from there, sends perforating branches into the lateral compartment to supply the fibularis muscles (longus and brevis).
It has three main branches which supple the lateral part of the calcaneus, the anterior part of the lateral malleolus and also a perforating branch which communicates with the anterior tibial artery.
The plantar arch is formed by the medial and lateral plantar arteries. The arch extends from the 1st to the 5th metatarsal and also unites with the deep plantar branch of the dorsalis pedis.
Peripheral vascular disease and the diabetic foot
Peripheral vascular disease usually involves peripheral vessels; the disease that involves arteries is called peripheral arterial disease. In this disease vessels get narrowed due to arteriosclerosis. This will initially manifest as angina (pain in the heart with exercise) and intermittent claudication (pain in the legs on walking).
As the extent of disease worsens, more serious complications result. These include strokes and heart attacks. Diabetes is one of the many causes of this condition and is strongly related to lower limb arterial disease. Due to loss of pain perception in the presence of peripheral neuropathy patient with diabetes are more likely to present with gangrene and diabetic foot which in some cases results in amputation.
With advances in vascular surgery, the commonest approach is now endovascular i.e. within the vessels themselves rather than making a big incision and opening the vessel. This entails a very minor amount of trauma to the patient, as well as a faster recovery time. The technique also allows for access to parts of the body that would be very traumatic to expose in open surgery.
Embolectomy is the removal of an embolus that is blocking blood flow. Angioplasty is a technique using a thin tube passed into a narrowed vessel, and a balloon inflated to squeeze the atherosclerotic plaques against the vessel walls. It is a temporary fix and the vascular disease will return and cause blockage. Hence, stents (to keep the vessel open) embedded with anti-coagulant medication are now left behind to prolong the effect of the treatment.
Bypass grafting is a technique used to bypass vascular disease by using other vessels to bridge to supply a collateral route past the blockage.