18. Nerves, arteries and veins of the leg

Question 1

What is the nerve root value of the tibial nerve?

Answer 1

L4-S3

Question 2

Where does the tibial nerve come from?

Answer 2

• larger terminal branch of the sciatic nerve

- arises from the sciatic nerve at the apex of the popliteal fossa

Question 3

What does the tibial nerve innervate?

Answer 3

• skin of the posterolateral side of the leg
• skin of lateral side of the foot and sole of the foot
• motor innervation to deep and superficial muscles in the leg

Question 4

How does the tibial nerve innervate the deep/ superficial muscles of the posterior leg?

Answer 4

• crosses the popliteal fossa, giving off branches to the muscles of the superficial posterior compartment of the leg
• then passes deep to the soleus muscle to enter the deep posterior compartment of the leg
• here, it lies between the flexor digitorum longus and the flexor hallucis longus muscles

Question 5

How does the tibial nerve contribute to the formation of the sural nerve?

Answer 5

As it crosses the popliteal fossa, as well as giving off branches to the superficial posterior compartment of the leg, it also gives off a branch that, together with a branch from the common peroneal nerve, contributes to the formation of the sural nerve

Question 6

What does the sural nerve do?

Answer 6

Innervates the posterolateral aspect of the leg and the lateral border of the foot

Question 7

How does the tibial nerve innervate the ankle/ foot?

Answer 7

• at the ankle, it passes beneath the flexor retinaculum behind the medial malleolus and gives off a medial calcaneal branch to the heel
• then divides into medial and lateral plantar nerves to supply sole of foot

Question 8

In summary, what muscles does the tibial nerve supply?

Answer 8

Posterior thigh:
 Long head of biceps femoris
 Semimembranosus
 Semitendinosus
 Hamstring component of adductor magnus

Superficial posterior compartment of the leg:
 Plantaris
 Soleus
 Gastrocnemius

Deep posterior compartment of the leg:
 Popliteus
 Flexor hallucis longus
 Flexor digitorum longus
 Tibialis posterior

Question 9

What are the sensory branches of the tibial nerve?

Answer 9

 Medial sural cutaneous nerve (which unites with a branch of the common
peroneal nerve called the lateral sural cutaneous nerve to form the sural nerve)
 Medial calcaneal branches
 Medial plantar nerve (also motor to intrinsic muscles of foot)
 Lateral plantar nerve (also motor to intrinsic muscles of foot)

Question 10

What is the common peroneal (fibular) nerve?

Answer 10

Smaller terminal branch of the sciatic nerve

Question 11

What are the root values of the peroneal nerve?

Answer 11

L4-S2 (not s3)

Question 12

What does the peroneal (fibular) nerve do?

Answer 12

• provides motor innervation to the short head of the biceps femoris in the thigh
• supplies muscles of the anterior and lateral compartments of the leg
• provides cutaneous innervation to the skin of the anterolateral leg, and the dorsum of the foot

Question 13

Where does the common peroneal nerve arise from?

Answer 13

From the bifurcation of the sciatic nerve at the apex of the popliteal fossa

Question 14

How does the peroneal nerve supply its areas?

Answer 14

• travels along the superolateral border of the popliteal fossa on the medial border of the biceps femoris
• then winds around the neck of the fibula to pierce the peroneus longus muscle
• then, divides into the superficial and deep peroneal nerves
• before dividing, it gives off a cutaneous branch which supplies the skin of the upper lateral leg

Question 15

What muscles are supplied by the common peroneal nerve?

Answer 15

Short head of biceps femoris

Question 16

What is the cutaneous supply of the common peroneal nerve?

Answer 16

• skin of upper lateral leg

- lateral sural cutaneous nerve (unites with medial sural cutaneous nerve from the tibial nerve to form the sural nerve)

Question 17

Where does the superficial peroneal (fibular) nerve arise from?

Answer 17

L4-S1

• arises from the bifurcation of the common peroneal nerve into the superficial and deep peroneal nerves

Question 18

Describe the route of innervation of the superficial peroneal nerve

Answer 18

• Lateral compartment of the leg
• Commences at the neck of the fibula and descends between the peroneus longus and brevis and the lateral aspect of extensor digitorum longus
• supplies peroneus longus and brevis
• continues as a purely cutaneous nerve supplying anterolateral leg
• when it reaches the distal third of the leg it pierces the deep fascia to run subcutaneously and supply dorsum of the foot (excluding the first web space which is supplied by the deep peroneal nerve, the medial border of the foot which is supplied by the saphenous nerve and the lateral border of the foot which is supplied by the sural nerve)

Question 19

Which muscles are supplied by the superficial peroneal nerve?

Answer 19

Peroneus (fibularis) longus and brevis

Question 20

What is the cutaneous supply of the superficial peroneal nerve?

Answer 20

The dorsum of the foot, except the first web space and the medial and lateral borders of the foot

Question 21

Where does the deep peroneal (fibular) nerve arise from?

Answer 21

(L4,5)

arises from the bifurcation of the common peroneal nerve into the superficial and deep peroneal nerves

Question 22

Describe the route of innervation of the deep peroneal nerve

Answer 22

• innervates the anterior compartment of the leg.
• It commences at the neck of the fibula and passes between the peroneus longus muscle and the neck of the fibula.
• It enters the anterior compartment of the leg by piercing the intermuscular septum.
  It then pierces extensor digitorum longus and lies adjacent to the anterior tibial artery in the anterior compartment of the leg, following the course of the
  artery.
• Together, the two structures pass between the tibialis anterior and the extensor digitorum longus in the proximal portion of the leg, then between the tibialis anterior and the extensor hallucis longus in the distal leg.

Question 23

Which muscles are supplied by the deep peroneal nerve?

Answer 23

 Tibialis anterior
 Extensor hallucis longus
 Extensor digitorum longus
 Fibularis tertius

Question 24

What is the cutaneous supply of the deep peroneal nerve?

Answer 24

cutaneous innervation is to the dorsum of the first webspace; this is the webbed skin between the great and second toe

Question 25

What is the sural nerve formed from?

Answer 25

The sural nerve is formed from the union of the medial and lateral sural cutaneous branches of the common peroneal and tibial nerve in the posterior leg

Question 26

What does the sural nerve supply?

Answer 26

passes behind the lateral malleolus to enter the foot. It supplies the skin over the lateral border of the foot.

Question 27

what is the popliteal artery

Answer 27

popliteal artery is the continuation of the superficial femoral artery as it passes through the adductor hiatus

Question 28

What does the popliteal atery do as it enters and exits the popliteal fossa?

Answer 28

In the popliteal fossa, it gives off genicular branches that supply the knee joint. It then exits the popliteal fossa, passing between the gastrocnemius and popliteus muscles

Question 29

What does the popliteal artery divide into and where?

Answer 29

At the inferior border of the popliteus muscle, the popliteal artery terminates by dividing into the anterior tibial artery and the tibioperoneal trunk

Question 30

What does the tibioperoneal trunk bifrucate into?

Answer 30

tibioperoneal trunk bifurcates into the posterior tibial and the peroneal (fibular) arteries

Question 31

Why can sural nerves be harvested for use in reconstructive surgery?

Answer 31

- relatively small cutaneous distribution - no motor branches - removal leaves only a tiny area of loss of sensation

Question 32

Briefly describe what areas the common peroneal nerve supplies?

Answer 32

Back of thigh, lower leg, foot

Question 33

Where does the anterior tibial artery pass?

Answer 33

- passes anteriorly between the tibia and fibula through a gap in the interosseous membrane to enter anterior compartment of leg - along with the deep peroneal nerve, it passes between the tibialis anterior and the extensor digitorum longus in the proximal leg, then between the tibialis anterior and extensor hallucis longus in distal leg - passes under the extensor retinaculum into dorsum of foot to become the dorsalis pedis artery

Question 34

Where does the posterior tibial artery pass?

Answer 34

- descends in the deep posterior compartment of leg, lying on the tibialis posterior muscle, flexor digitorum longus and the tibia and posterior ankle joint - covered superficially by the deep transverse fascia of leg which separates it from the soleus muscle - accompanied by the tibial nerve and its two venae comitantes (small veins that accompany an artery) (collectively referred to as the tibial vein) - passes behind the medial malleolus to enter the sole via the tarsal tunnel, together with the tibial nerve

Question 35

Where does the peroneal (fibular) artery pass?

Answer 35

- descends of the medial side of the fibula in a fibrous canal between the tibialis posterior and flexor hallucis longus - perforating branches penetrate the inter muscular septum to supply muscles in the lateral compartment of the leg

Question 36

What is a good way to remember the arrangement of the structures behind the medial malleolus?

Answer 36

``` “Tom, Dick, And Very Nervous Harry”:  Tibialis posterior  flexor Digitorum longus tendon  posterior tibial Artery  posterior tibial Vein (as venae comitantes of artery)  tibial Nerve  flexor Hallucis longus ```