Download MBBS Innervation of the Lower Limb Lecture PPT

NERVES OF THE LOWER LIMB

? Derived from the ventral (anterior primary) rami of

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the lumbar and sacral nerves forming the lumbar

plexus (L1?L4) and the sacral plexus (L4?S4).

? Main nerves of the lower limb are

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1. Femoral nerve.

2. Obturator nerve.

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3. Sciatic nerve.

4. Tibial nerve.

5. Common peroneal nerve.

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6. Superficial peroneal nerve.

7. Deep peroneal nerve.
FEMORAL NERVE

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? Nerve of anterior compartment of the thigh
? It arises within the psoas major muscle from the

posterior divisions of the L2?L4 ventral rami in

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the abdomen.

? It enters the thigh posterior to the inguinal

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ligament just lateral to the femoral sheath.

? About 2 cm below the inguinal ligament it divides

into anterior and posterior divisions which are

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separated by the lateral circumflex femoral artery.

? Motor branches supply iliacus in the abdomen

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and all the muscles of anterior compartment

of the thigh.

? Cutaneous branches supply the large area on

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the anterior and medial aspect of the thigh,

medial side of leg, and foot.

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? Articular branches to the hip and knee joints.

? Injury of the femoral nerve:
? It is rare but may be injured by a stab, gunshot

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wounds, or a pelvic fracture.

? The characteristic clinical features are :
(a) Motor loss
? Weak flexion of the thigh, due to paralysis of the

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iliacus and sartorius muscles.

? Inability to extend the knee, due to paralysis of the

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quadriceps femoris.
(b) Sensory loss
? Sensory loss over the anterior and medial aspects

of the thigh, due to involvement of the

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intermediate and lateral cutaneous nerves of the

thigh.

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? Sensory loss on the medial side of the leg and foot

up to the ball of the great toe (first

metatarsophalangeal joint), due to involvement of

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the saphenous nerve.
? Femoral nerve neuropathy:
? Femoral nerve may be compressed by the

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retroperitoneal tumors.

? A localized neuropathy of the femoral nerve may

occur in diabetes mellitus.

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? The characteristic clinical features are :
(a) Wasting and weakness of quadriceps leading to

considerable difficulty in walking.

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(b) Pain and paraesthesia on the anterior and medial

aspects of the thigh extending down along the

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medial aspect of the leg and foot along the

distribution of the saphenous nerve.
OBTURATOR NERVE

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? Chief nerve of the adductor compartment of the

thigh.

? It arises from the lumbar plexus in the abdomen.

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? Formed by the ventral division of the anterior

primary rami of L2, L3, L4 spinal nerves.

? It enters the thigh by passing through the obturator

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canal.

? Near the obturator foramen it divides into anterior

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and posterior divisions.

? Motor branches supply all the muscles of the

adductor compartment of the thigh.

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? Sensory branches supply cutaneous area on the

lower-half of the medial aspect of the thigh.

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? Articular branches to the hip and knee joints.

? Injury of the obturator nerve:
? Due to anterior dislocation of the hip joint, or

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during radical retropubic prostatectomy.

? The characteristic clinical features are :
(a)Motor loss: Loss of adduction of the thigh, due to

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paralysis of adductor muscles of the thigh.

(b) Sensory loss: Sensory loss on the medial aspect of

thigh, due to involvement of the cutaneous branch

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of the anterior division of the obturator nerve.
SCIATIC NERVE

? Thickest nerve in the body.

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? Nerve of posterior compartment of the thigh.
? It arises in the pelvis from ventral rami of L4?S3

spinal nerves.

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? It leaves the pelvis through greater sciatic

foramen below piriformis to enter the gluteal

region.

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? Just above the popliteal fossa it divides into

terminal tibial and common peroneal nerves.

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? Injury of the sciatic nerve:
? Cause
? Misplaced injection in the gluteal region (mc)
? Injured by penetrating wounds

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? Posterior dislocation of the hip
? Fracture of the pelvis
? Total hip replacement surgery
? The characteristic clinical features are :
(a) Motor loss

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? Inability to extend the thigh and flex the knee,

due to paralysis of the hamstring muscles.

? Loss of all movements below the knee with foot

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drop, due to paralysis of all the muscles of the leg

and foot.

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? The motor loss leads to flail foot which leads to

great difficulty in walking.

? The patient walks with high stepping gait.

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(b) Sensory loss:
? The sensory loss on the back of the thigh and whole

of the leg and foot (except the area innervated by

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the saphenous nerve)

? Due to involvement of the cutaneous nerves

derived from the tibial and common peroneal

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nerves.
? SCIATICA
? It is a term applied to a clinical condition
? characterized by shooting pain felt along the course

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of distribution of the sciatic nerve (e.g., buttock,

posterior aspect of thigh, lateral aspect of leg, and

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dorsum of the foot).

? It occurs due to compression and irritation of L4?S3

spinal nerve roots by herniated intervertebral disc

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of the lumbar vertebrae.
TIBIAL NERVE

? Larger terminal branch of the sciatic nerve.

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? It arises above the popliteal fossa
? Passes downward successively through the middle

of popliteal fossa and posterior compartment of

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the leg, and then enters the sole of the foot by

passing deep to the flexor retinaculum.

? It divides into the medial and lateral plantar

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nerves.

? Effects of injury of the tibial nerve:
? Injured by a lacerated wound in the popliteal fossa

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? posterior dislocation of the knee joint.
? The characteristic clinical features are :
(a) Motor loss:
? Foot is held dorsiflexed and everted, due to paralysis of

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the muscles of posterior compartment of the leg.

? Loss of prominence of calf and tendocalcaneus, due to

paralysis of the triceps surae muscle (gastrocnemius

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and soleus).

? Loss of plantar flexion of foot, due to paralysis of the

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flexors of ankle.

? Inability to stand on the toes, due to loss of plantar

flexion of foot

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(b) Sensory loss:
? The loss of sensation in the sole and plantar aspects

of the toes including the dorsal aspects of their

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distal phalanges, due to involvement of the

cutaneous branches.

? Tarsal tunnel syndrome:

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? It occurs due to compression of the tibial nerve in

the osseofibrous tunnel under the flexor

retinaculum of the ankle.

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? It clinically presents as pain and paresthesia in the

sole of the foot, which often becomes worse at

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night.


Morton's metatarsalgia (plantar digital neuroma)

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? It occurs due to the formation of a

neuroma following pressure on

one of the plantar digital nerves

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just prior to its bifurcation at one

of the toe clefts.

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? It most commonly affects the

plantar digital nerve running

between the 3rd and 4th

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metatarsal heads to the third web

-space

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? it presents as intermittent pain on

the plantar aspect of the forefoot

usually between the 3rd and 4th

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metatarsals.
COMMON PERONEAL NERVE

? Smaller terminal branch of the sciatic nerve.

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? It arises just above the popliteal fossa.
? it divides into two terminal branches --deep and

superficial peroneal nerves.

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? Effects of injury to the common peroneal nerve:
? The common peroneal nerve is extremely

vulnerable to injury as it winds around the

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posterolateral aspect of the neck of the fibula.

? At this site it may be injured by the direct trauma,

fracture neck of fibula, or tightly applied plaster cast.

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? The characteristic clinical features:
(a) Motor loss:
? Foot drop, due to the paralysis of

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muscles of the anterior compartment

of the leg.

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? Loss of extension of toes, due to the

paralysis of extensor digitorum longus

and extensor hallucis longus.

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? Loss of eversion of foot, due to the

paralysis of peroneus longus and

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peroneus brevis.

(b) Sensory loss:
-Due to involvement of the cutaneous

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branches, on the anterolateral aspect

of the leg, and whole of dorsum foot

(except the areas supplied by the

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saphenous and sural nerves).


CUTANEOUS INNERVATION OF THE LOWER LIMB

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SEGMENTAL INNERVATION OF THE SKIN (DERMATOMES)

Area of the skin supplied by a spinal nerve is termed dermatome

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