Download MBBS Innervation of the Lower Limb Lecture PPT

Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Innervation of the Lower Limb Lecture PPT


NERVES OF THE LOWER LIMB

? Derived from the ventral (anterior primary) rami of

the lumbar and sacral nerves forming the lumbar

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

? Main nerves of the lower limb are

1. Femoral nerve.

2. Obturator nerve.

3. Sciatic nerve.

4. Tibial nerve.

5. Common peroneal nerve.

6. Superficial peroneal nerve.

7. Deep peroneal nerve.
FEMORAL NERVE

? 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

the abdomen.

? It enters the thigh posterior to the inguinal

ligament just lateral to the femoral sheath.

? About 2 cm below the inguinal ligament it divides

into anterior and posterior divisions which are

separated by the lateral circumflex femoral artery.

? Motor branches supply iliacus in the abdomen

and all the muscles of anterior compartment

of the thigh.

? Cutaneous branches supply the large area on

the anterior and medial aspect of the thigh,

medial side of leg, and foot.

? Articular branches to the hip and knee joints.

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

wounds, or a pelvic fracture.

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

iliacus and sartorius muscles.

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

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

of the thigh, due to involvement of the

intermediate and lateral cutaneous nerves of the

thigh.

? 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

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

retroperitoneal tumors.

? A localized neuropathy of the femoral nerve may

occur in diabetes mellitus.

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

considerable difficulty in walking.

(b) Pain and paraesthesia on the anterior and medial

aspects of the thigh extending down along the

medial aspect of the leg and foot along the

distribution of the saphenous nerve.
OBTURATOR NERVE

? Chief nerve of the adductor compartment of the

thigh.

? It arises from the lumbar plexus in the abdomen.
? 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

canal.

? Near the obturator foramen it divides into anterior

and posterior divisions.

? Motor branches supply all the muscles of the

adductor compartment of the thigh.

? Sensory branches supply cutaneous area on the

lower-half of the medial aspect of the thigh.

? Articular branches to the hip and knee joints.

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

during radical retropubic prostatectomy.

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

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

of the anterior division of the obturator nerve.
SCIATIC NERVE

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

spinal nerves.

? It leaves the pelvis through greater sciatic

foramen below piriformis to enter the gluteal

region.

? Just above the popliteal fossa it divides into

terminal tibial and common peroneal nerves.


? Injury of the sciatic nerve:
? Cause
? Misplaced injection in the gluteal region (mc)
? Injured by penetrating wounds
? Posterior dislocation of the hip
? Fracture of the pelvis
? Total hip replacement surgery
? The characteristic clinical features are :
(a) Motor loss
? 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

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

and foot.

? The motor loss leads to flail foot which leads to

great difficulty in walking.

? The patient walks with high stepping gait.
(b) Sensory loss:
? The sensory loss on the back of the thigh and whole

of the leg and foot (except the area innervated by

the saphenous nerve)

? Due to involvement of the cutaneous nerves

derived from the tibial and common peroneal

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

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

posterior aspect of thigh, lateral aspect of leg, and

dorsum of the foot).

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

spinal nerve roots by herniated intervertebral disc

of the lumbar vertebrae.
TIBIAL NERVE

? Larger terminal branch of the sciatic nerve.
? It arises above the popliteal fossa
? Passes downward successively through the middle

of popliteal fossa and posterior compartment of

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

nerves.

? Effects of injury of the tibial nerve:
? Injured by a lacerated wound in the popliteal fossa
? posterior dislocation of the knee joint.
? The characteristic clinical features are :
(a) Motor loss:
? Foot is held dorsiflexed and everted, due to paralysis of

the muscles of posterior compartment of the leg.

? Loss of prominence of calf and tendocalcaneus, due to

paralysis of the triceps surae muscle (gastrocnemius

and soleus).

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

flexors of ankle.

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

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

of the toes including the dorsal aspects of their

distal phalanges, due to involvement of the

cutaneous branches.

? Tarsal tunnel syndrome:
? It occurs due to compression of the tibial nerve in

the osseofibrous tunnel under the flexor

retinaculum of the ankle.

? It clinically presents as pain and paresthesia in the

sole of the foot, which often becomes worse at

night.


Morton's metatarsalgia (plantar digital neuroma)

? It occurs due to the formation of a

neuroma following pressure on

one of the plantar digital nerves

just prior to its bifurcation at one

of the toe clefts.

? It most commonly affects the

plantar digital nerve running

between the 3rd and 4th

metatarsal heads to the third web

-space

? it presents as intermittent pain on

the plantar aspect of the forefoot

usually between the 3rd and 4th

metatarsals.
COMMON PERONEAL NERVE

? Smaller terminal branch of the sciatic nerve.
? It arises just above the popliteal fossa.
? it divides into two terminal branches --deep and

superficial peroneal nerves.

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

vulnerable to injury as it winds around the

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.


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

muscles of the anterior compartment

of the leg.

? Loss of extension of toes, due to the

paralysis of extensor digitorum longus

and extensor hallucis longus.

? Loss of eversion of foot, due to the

paralysis of peroneus longus and

peroneus brevis.

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

branches, on the anterolateral aspect

of the leg, and whole of dorsum foot

(except the areas supplied by the

saphenous and sural nerves).


CUTANEOUS INNERVATION OF THE LOWER LIMB


SEGMENTAL INNERVATION OF THE SKIN (DERMATOMES)

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

This post was last modified on 30 November 2021