Lumbosacral Plexus

Question 1

6 major terminal branches

Answer 1

Femoral nerve (L2,3,4)

Obturator nerve (L2,3,4)

Superior gluteal nerve (L4,5,S1)

Inferior gluteal nerve (L5,S1,S2)

Common peroneal nerve (L4,5,S1,2)
- divides into superficial & deep peroneal nerves

Tibial nerve (L4,5,S1,2,3)
- combines with common peroneal nerve to make up the sciatic nerve

Question 2

Most common injury affecting the lumbosacral plexus

Answer 2

Herniation of intervertebral disk

Question 3

Anterior compartment of thigh:

• quadriceps
• femoris
• sartoris
• pectineus

Action: extend knee

Answer 3

Femoral nerve (L2,3,4 posterior divisions)

Question 4

Medial compartment of thigh:

• gracious
• adductor longus & brevis
• anterior portion of adductor magnus

Action: adduct thigh, medially rotate thigh

Answer 4

Obturator nerve (L2,3,4 anterior divisions)

Question 5

Posterior compartment of thigh: (flex knee, extend knee)

• semimembranous
• semitendinosus
• long head of biceps femoris
• posterior portion of adductor magnus

Posterior compartment of leg: (plantar flex foot, flex digits, inversion)

• gastrocnemius
• soleus
• flexor digitorum longus
• flexor hallucis longus
• tibialis posterior

Answer 5

Tibial nerve (L4,5,S1,2,3, anterior divisions)

Question 6

Short head of biceps femoris

Action: flex knee

Answer 6

Common peroneal (fibular) nerve (L4,5,S1,2, posterior divisions)

Question 7

Lateral compartment of leg:
- peroneus longus & brevis

Action: eversion

Answer 7

Superficial peroneal (fibular) nerve

Question 8

Anterior compartment of leg:

• tibialis anterior
• extensor hallucis
• extensor digitorum
• peroneus tertius

Action: dorsiflex foot, extend digits, inversion

Answer 8

Deep peroneal (fibular) nerve

Question 9

Components: L1-5 and S1-4 ventral primary rami of the spinal nerves

Answer 9

Lumbosacral plexus