Vasculature and Innervation of the Lower Limb and Diabetic Foot Ulcers

by Robert Tallitsch, PhD | June 2, 2022

Diabetic Foot Ulcers BodyViz Brain Builder

Video on Diabetic Foot Ulcers with a patient case example, supporting article, vocabulary terms, and questions with answer key!

Written by: Robert Tallitsch, PhD

As stated by F.N. Rosyid (2017) “Diabetic foot ulcers are an injury to all layers of skin, necrosis or gangrene that usually occur on the soles of the feet, as a result of peripheral neuropathy or peripheral arterial disease in diabetes mellitus patients.” This Brain Builder will exam the arterial vasculature and innervation of the leg and foot and see how diabetes affects these structures. Finally, we will discuss how all of this relates to the appearance of diabetic foot ulcers.

Arterial Vasculature of the Leg and Foot

The popliteal artery of the leg is a continuation of the femoral artery of the thigh. In the inferior portion of the popliteal fossa (the indentation on the posterior surface of the knee) the popliteal artery divides into two terminal branches: the anterior and posterior tibial arteries.

The anterior tibial artery is found anterior to the interosseous membrane throughout most of its course through the leg. At the ankle joint this artery passes deep to the inferior extensor retinaculum and becomes the dorsalis pedis artery. The dorsalis pedis artery passes superior to the dorsal aspects of the talus, navicular, and intermediate cuneiform bones. It then passes inferiorly as the deep plantar artery. The deep plantar artery then joins with the deep plantar arch on the sole of the foot.

The posterior tibial artery passes inferiorly through the leg, lying superficial to the tibialis posterior and flexor digitorum longus muscles. The posterior tibial artery enters the foot on the medial side of the ankle, posterior to the medial malleolus of the tibia. Here the posterior tibial artery divides into the lateral plantar artery and the much smaller medial plantar artery. The lateral plantar artery passes anterolaterally into the sole of the foot, until it reaches metatarsal V. Here it curves medially, forming the deep plantar arch, which joins with the dorsalis pedis artery.

The medial plantar artery passes anteromedially until it joins with the digital branch of the deep plantar arch.

Innervation of the Leg and Foot

Three nerves innervate muscles of the foot and supply sensory input from various segments of the skin of the foot: the tibial, sural, and medial calcaneal nerves.

The tibial nerve of the leg is a major branch of the sciatic nerve of the thigh. The tibial nerve enters the popliteal fossa and continues inferiorly in the posterior compartment of the leg, along with the arteries and veins of the posterior compartment. This nerve enters the foot by passing posteriorly to the medial malleolus of the tibia.

The sural nerve travels inferiorly from the thigh into the leg between the two heads of the gastrocnemius muscle. It continues inferiorly, superficial to the belly of the gastrocnemius, penetrating into the deep fascia of the leg slightly superior to the start of the calcaneal (Achilles) tendon. From there it continues inferiorly, around the lateral malleolus of the fibula, and into the foot.

The medial calcaneal nerve branches off of the tibial nerve low in the leg, near the ankle, terminating on the medial side of the heel.

Effects of Diabetes Mellitus Upon the Nerves and Vasculature of the Lower Limb

Peripheral Neuropathy

Diabetes mellitus is known to cause peripheral neuropathy, which is damage to the nerves of the peripheral nervous system. Peripheral neuropathy caused by diabetes mellitus typically involves both sensory and motor nerves. Symptoms may include:

Gradual onset of numbness that is often preceded by a tingling sensation in the hands and/or feet.
Extreme sensitivity to touch, often including sharp throbbing or burning pain.
Muscle weakness.
High foot plantar pressure, which is a sensation of a high degree of pressure or pain on the sole of the foot when walking or standing. This is often accompanied by reduced joint mobility and foot deformities.

Atherosclerosis

Atherosclerosis is a disease of the cardiovascular system in which a substance called plaque, which is composed of fat, cholesterol, calcium, and other substances, builds up within the arterial walls. Over time this plaque hardens, narrowing the lumen of the artery, and thereby reduces blood flow to capillaries downstream of the plaque buildup. This results in reduced oxygen levels in the peripheral tissues supplied by the affected arteries and capillaries, often resulting in tissue necrosis (death).

Diabetes mellitus, and its accompanying chronic hyperglycemia (long-term increased glucose levels within the blood), results in various protein, lipid, and carbohydrate metabolic abnormalities. Long-term alterations in lipid metabolism is known to contribute to the appearance of atherosclerosis.

Diabetic Foot Ulcers

The combined effects of the reduced neural sensitivity of the skin and decreased peripheral blood flow caused by Diabetes mellitus significantly increases the risk of tissue ischemia in the lower limbs, resulting in diabetic ulcers. In addition, the reduced peripheral blood flow and accompanying tissue ischemia decreases the ability for wounds to heal properly and in a timely fashion, thereby further increasing the probability of tissue necrosis and gangrene.

Management and treatment of diabetic foot ulcers involves the following:

Debridement of non-living tissue.
Reduction of pressure on the ulcer, either through bed rest or the use of specially formed casts.
Management of any infections.
Dressing the wound area to protect the wound and to promote healing.

As the incidence of Diabetes mellitus increases within the population a better understanding of foot ulcer treatment and prevention will help to decrease the incidence of amputations secondary to the onset of diabetes.

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Key Terms:

Popliteal artery - A major artery of the leg that is a continuation of the femoral artery of the thigh.

Popliteal fossa - The indentation on the posterior surface of the knee.

Anterior tibial artery - One of the two subdivisions of the popliteal artery.

Posterior tibial artery - One of the two subdivisions of the popliteal artery.

Medial plantar artery - One of the two subdivisions of the posterior tibial artery that supplies the medial structures of the foot with blood.

Lateral plantar artery - One of the two subdivisions of the posterior tibial artery that supplies the lateral structures of the foot with blood.

Tibial nerve - One of the three nerves that innervates structures within the foot and also provides sensory perception from segments of the skin of the foot.

Sural nerve - One of the three nerves that innervates structures within the foot and also provides sensory perception from segments of the skin of the foot.

Medial calcaneal nerve - One of the three nerves that innervates structures within the foot and also provides sensory perception from segments of the skin of the foot.

Peripheral neuropathy - Damage to the nerves of the peripheral nervous system.

Atherosclerosis - A disease of the cardiovascular system in which plaque builds up within the arterial walls and overtime can cause reduced blood flow.

Questions:

True or False? Atherosclerosis is a peripheral cardiovascular disease in which plaque, composed of fat, cholesterol, calcium, and other substances, builds up within the arterial walls.
A: True
Which nerve travels inferiorly from the thigh into the leg between the two heads of the gastrocnemius muscle?
A: Sural nerve
Which nerve branches off the tibial nerve low in the leg, near the ankle, terminating on the medial side of the heel?
A: Medial calcaneal nerve
Which artery passes deep to the inferior extensor retinaculum and becomes the dorsalis pedis artery?
A: Anterior tibial artery
Which artery divides into two terminal branches: the anterior and posterior tibial arteries?
A: Popliteal artery
Which artery passes inferiorly through the leg, lying superficial to the tibialis posterior and flexor digitorum longus muscles?
A: Posterior tibial artery
Which artery passes anteromedially on the foot until it joins with the digital branch of the deep plantar arch?
A: Medial plantar artery
Which artery passes anterolaterally into the sole of the foot, until it reaches metatarsal V? This artery then curves medially, forming the deep plantar arch, which joins with the dorsalis pedis artery.
A: Lateral plantar artery
Which artery passes superior to the dorsal aspects of the talus, navicular, and intermediate cuneiform bones?
A: Dorsalis pedis artery
Which branch of the posterior artery supplies the lateral structures of the foot with blood?
A: Lateral plantar artery

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