lower limb nerve supply

Question 1

Name the nerves of the lower limb and state their origins and root values

Answer 1

LUMBAR PLEXUS:
1. Femoral nerve(L2,3,4)- to anterior compartment (posterior division)
2. Obturator nerve(L2,3,4)- to medial compartment (anterior division)

SACRAL PLEXUS:
1. Gluteal nerves
-superior(L4,5,S1): Gmed, Gmin & TFL
- inferior(L5,S1,2): gluteus Maximus
2. Sciatic nerve(L4,5,S1,2,3)
- common peroneal
- tibial nerve

Question 2

Discuss the femoral nerve, stating it’s origin,course and branches

Answer 2

Origin: L2,3,4
Course:
-between psoas and iliacus
- outside the femoral sheath
-lateral to femoral artery

Branches:
1. Cutaneous branches- medial and intermediate cutaneous nerves of thigh, saphenous nerve
2. Muscular branches- quadriceps, Sartorius, pectineus and iliacus
3. Articular branches- to the knee and hip joints

Question 3

Discuss obturator nerve

Answer 3

Origin: L2,3,4
Course: divided by adductor brevis into anterior and posterior division
Branches:
1. Cutaneous- anterior division only, to middle third of medial side
2. Muscular branches- anterior division; adductor longus and brevis, gracilis. Posterior; adductor magnus(pubic part) and obturator externus
3. Articular - anterior division; hip joint. Posterior; knee joint

Question 4

Discuss sciatic nerve

Answer 4

Origin: L4,5,S1,2,3
Landmarks/course:
-Passes in GSF below piriformis
- covered by gluteus Maximus & hamstring
- may be injured by wrong IM injection
Termination: in the middle of back of thigh
1. Tibial nerve
2. Common peroneal(lateral)

Branches:
1. Muscular- hamstrings & ischial part of adductor magnus
2. Articular- knee and hip joints
3. Two terminal branches
Lesion:
-Due to compression by piriformis or wrong IM injection.
-It causes:
1. Paralysis of hamstring muscles and muscles of leg and foot
2. Loss of sensation below the knee except medial side of leg & foot

Question 5

Discuss Tibial and common peroneal nerves

Answer 5

Origin: terminal branches of sciatic nerve in middle of back of thigh
Termination:
-tibial- terminates deep to flexor retinaculum by dividing into medial and lateral plantar nerves
- common peroneal-terminates on lateral side of neck of fibia by dividing into deep and superficial peroneal nerves

Landmarks:
- tibial nerve is the most superficial structure in the popliteal fossa
- in the leg it is covered by gastrocnemius and popliteal fossa
- common peroneal- lateral side of neck of fibular

Branches:
1. Cutaneous-tibial nerve; sural. Common peroneal; sural communicating and lateral cutaneous nerve of calf
2. Muscular- Tibial nerve ; gastrocnemius, plantaris,soleus, popliteus, TP, FHL, FDL. CP has no muscular branches
3. Articular- tibial; knee and ankle. CP; 3 articular branches to knee joint.

Lesion:
Injury to CP( mostly at lateral side of neck of fibula) causes paralysis of anterior and lateral compartment leading to foot drop. Foot will be inverted due to paralysis of lateral compartment.

Question 6

Discuss deep peroneal nerve

Answer 6

Origin: terminal branch of common peroneal
Termination: in front of ankle by dividing into medial and lateral branches
Branches:
1. Muscular- anterior compartment (TA, EDL, EHL & PT)
2. Articular- ankle joint and joints of foot
3. Cutaneous- adjacent sides of big toe and 2nd toe
Lesion: paralysis of dorsiflexors leading to foot drop

Question 7

Discuss superficial peroneal nerve

Answer 7

Origin: terminal branch of common peroneal at lateral side of fibula
Branches:
1. Muscular- lateral compartment; PL & PB
2. Cutaneous- middle of dorsum of foot
Lesion:
Loss of eversion

Question 8

Dermatomes of the lower limb

Answer 8

Thigh:
1. Front and medial side- L1,2,3
2. Back S2

Leg:
1. Medial side- L4
2. Lateral side- L5
3. Upper and lower back- S2 and S1

Foot:
1. Big toe-L5
2. Little toe- S1