Lower Limb - Nerves

Question 1

Where is the lumbar plexus located and from what is it formed?

Answer 1

In the lumbar region within the psoas major muscle and anterior to the transverse processes of the lumbar vertebrae. Formed by the anterior rami of spinal nerves L1-L4 and contribution from T12.

Question 2

What are the 6 major branches of the lumbar plexus and their roots?

Answer 2

Iliohypogastric nerve (L1)
Ilioinguinal nerve (L1)
Genitofemoral nerve (L1-L2)
Lateral cutaneous nerve of thigh (L2-L3) - purely sensory, anterolateral thigh
Obturator nerve (L2-L4)
Femoral nerve (L2-L4)
Indecent Ian gets laid on Fridays

Question 3

Where is the sacral plexus located and from what is it formed?

Answer 3

On the surface of the posterior pelvic wall, anterior to the piriformis. Formed by the anterior rami of spinal nerves S1-4 and L4-5.

Question 4

What are the two main destinations of the peripheral nerves of the sacral plexus?

Answer 4

Leave the pelvis via the greater sciatic foramen, entering the gluteal region.
Remain in the pelvis to innervate the pelvic muscles, organs and perineum.

Question 5

What are the 5 major branches and roots of the sacral plexus?

Answer 5

Superior gluteal nerve (L4-5, S1) - only motor, innervates gluteus minimus, gluteus medius and tensor fascia lata
Inferior gluteal nerve (L5, S1-2) - only motor, innervates gluteus maximus
Sciatic nerve (L4-5, S1-3)
Posterior femoral cutaneous (S1-3) - only sensory, innervates posterior surface of thigh and leg
Pudendal nerve (S2-4) - innervates anal and external urethral sphincters (motor) and penis and clitoris (sensory). “S2,4,5 keeps poo off the floor!”

Question 6

Describe the anatomical course of the femoral nerve

Answer 6

Travels through the pelvis to the mid point of the inguinal ligament. It then splits into an anterior and posterior division and gives off articular branches to the hip and knee at the femoral triangle. It gives off its terminal cutaneous branch, the saphenous nerve, which continues down the adductor canal.

Question 7

What are the motor functions of the femoral nerve?

Answer 7

Hip flexors - pectineus, iliacus and sartorius

Knee extensors - quadriceps femoris

Question 8

What are the sensory functions of the femoral nerve?

Answer 8

The anterior cutaneous branches that arise in the femoral triangle supply the anteromedial thigh.
The saphenous nerve supplies the medial side of the leg and foot.

Question 9

What is a possible complication of stripping of the long saphenous vein?

Answer 9

Damage to the saphenous nerve

Question 10

Describe the anatomical course of the obturator nerve

Answer 10

Enters the thigh through the obturator canal and splits into anterior and posterior divisions.
The anterior division descends between adductor longus and brevis. The posterior division descends through the obturator externus before passing anteriorly to adductor Magnus.

Question 11

What are the motor functions of the obturator nerve?

Answer 11

Medial compartment of the thigh except hamstring part of adductor Magnus

Question 12

What are the sensory functions of the obturator nerve?

Answer 12

Cutaneous branch of obturator nerve supplies skin of middle part of medial thigh

Question 13

How does a patient with a damaged obturator nerve present?

Answer 13

Numbness and paraethesia on the medial aspect of the thigh and/or posture and gait problems due to weakened adduction.

Question 14

Describe the anatomical course of the sciatic nerve

Answer 14

Enters the gluteal region via the greater sciatic foramen, emerging inferiorly to the piriformis. It passes deep to the long head of biceps femoris. It terminates at the apex of the popliteal fossa into the common fibular nerve and tibial nerve.

Question 15

What are the motor functions of the sciatic nerve?

Answer 15

Posterior compartment of the thigh and hamstring part of adductor Magnus.

Question 16

Describe the anatomical course of the tibial nerve

Answer 16

Travels through the popliteal fossa, giving off branches that contribute to the Sural nerve (posterolateral part of leg). Travels down the leg posterior to the tibia to the foot where it passes posterior to the medial malleolus. Within the tarsal tunnel branches arise to supply the heel. The nerve the terminates by dividing into branches that innervate the sole of the foot.

Question 17

What are the causes, symptoms and treatments to tarsal tunnel syndrome?

Answer 17

Caused by arthritis or post trauma ankle abnormalities. There is paraethesia in the ankle and sole of the foot aggravated by activity. Treated with anti inflammatory drugs or more severely by surgically cutting the flexor retinaculum.

Question 18

What are the motor functions of the tibial nerve?

Answer 18

Posterior compartment of leg

Question 19

What is the sensory function of the tibial nerve?

Answer 19

Cutaneous branches given off in the popliteal fossa combine with branches from the common fibular nerve to form the Sural nerve - innervates posterolateral side of leg and lateral side of foot.
Medial calcaneal branches arise in the tarsal tunnel innervation the heel
Medial plantar nerve innervates plantar surface of medial 3.5 digits
Lateral plantar nerve innervates plantar surface of lateral 1.5 digits

Question 20

Describe the anatomical course of the common fibular nerve

Answer 20

Begins at the apex of the popliteal fossa and follows the medial border of the biceps femoris over the lateral head of the gastrocnemius. Here it gives rise to two cutaneous branches. The nerve wraps around the neck of the fibula passing between the attachments of the fibularis longus muscle. Here the nerve terminates by dividing into the superficial and deep fibular nerves.

Question 21

What are the motor functions of the common fibular nerve?

Answer 21

Short head of the biceps femoris

Question 22

What are the sensory functions of the common fibular nerve?

Answer 22

Two branches:
Sural communicating nerve - contributes to Sural nerve
Lateral Sural cutaneous nerve - skin of lateral leg

Question 23

Describe the anatomical course of the superficial fibular nerve

Answer 23

Descends between the fibularis muscles and lateral side of the extensor digitorum longus. Divides in the lower 1/3 of the leg into medial and intermedial dorsal cutaneous nerves.

Question 24

What are the motor functions of the superficial fibular nerve?

Answer 24

Lateral compartment of leg

Question 25

What are the sensory functions of the superficial fibular nerve?

Answer 25

Anterolateral leg and dorsum of the foot

Question 26

How can the superficial fibular nerve become damaged/compressed?

Answer 26

Compressed - ankle sprains (stretches nerve) of by compression of the nerve from where it exits the deep fascia
Damaged - fracture of the fibula or perforating wound

Question 27

Describe the anatomical course of the deep fibular nerve

Answer 27

It follows the course of the anterior tibial artery (after it has pierced the interosseous membrane) down the leg. They pass just lateral to the tibialis anterior. It travels into the foot via the extensor retinaculum and terminates into a lateral (motor) and medial (sensory) branch.

Question 28

What are the motor functions of the deep fibular nerve?

Answer 28

Anterior compartment of the leg, extensor digitorum brevis and extensor hallucis brevis.

Question 29

What are the sensory functions of the deep fibular nerve?

Answer 29

Webbed space between hallux and second toe

Question 30

How is the deep fibular nerve commonly compressed?

Answer 30

Anterior leg muscles have been excessively used

Tight fitting shoes compressing the extensor retinaculum (eg ski boots)