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Nerves Of Lower Limb

 

Lower limb is supplied by branches of two plexuses, i.e. lumbar plexus and sacral plexus. Ventral ramus of L4 contributes to both plexuses and is referred to as nervus forcalis.

 

Lumbar Plexus

Lumbar plexus is formed by ventral (anterior) rami 0f L1, L2, L3 and L4. Branches of lumbar plexus and their distribution are as follows:-

Branches

Distribution

Iliohypogastric nerve (LJ)

External oblique, internal oblique, transversus abdominis muscles of anterior abdominal wall; skin over lower anterior abdominal wall and buttock.

Ilioinguinal nerve (LI)

External oblique, internal oblique, transversus abdominis muscles of anterior abdominal wall; skin of upper medial aspect of thigh; root of penis and scrotum in the male; mons pubis and labia majora in the female.

Lateral cutaneous nerve of the Skin of anterior and lateral surfaces of the thigh.

thigh (L2, L3, L4)

Skin of anterior and lateral surfaces of the thigh.

Genitofemoral nerve (LI, 2)

Cremaster muscle in scrotum in male; skin over anterior surface of thigh; nervous pathway for cremasteric reflex.

Femoral nerve (L2, 3, 4)

Iliacus, pectineus, sartorius, quadriceps femoris muscles, and intermediate cutaneous branches to the skin of the anterior surface of the thigh and by saphenous branch to the skin of the medial side of the leg and foot; articular branches to hip and knee joints.

Obturator nerve (L2, 3, 4)

Iliacus, pectineus, sartorius, quadriceps femoris muscles, and intermediate cutaneous branches to the skin of the anterior surface of the thigh and by saphenous branch to the skin of the medial side of the leg and foot; articular branches to hip and knee joints.

Segmental branches

Quadratus lumborum and psoas muscles (psoas major and minor)

 

Femoral nerve  

  1. It is the largest branch of lumbar plexus. It arises from the dorsal division of ventral (anterior) rami ofL2, L3, L4 spinal nerves. It is the chief nerve of anterior compartment of thigh. It emerges from lateral border of psoas major and runs downwards. Passing deep to inguinal ligament it enters femoral triangle lateral to femoral artery. About 3-4 cm below the inguinal ligament it divides into anterior and posterior division.
  2. Branches of femoral nerve are:-
    1. From the main trunk: - Nerve supply to iliacus, nerve supply to pectineus and a few vascular branches.
    2. From anterior division: - Intermediate femoral cutaneous nerve (intermediate cutaneous nerve of thigh), medial femoral cutaneous nerve (medial cutaneous nerve of thigh) and muscular branch to sartorius.
    3. From posterior division: - Saphenous nerve, nerve supply to quadriceps femoris (rectus femoris, vastus medialis, vastus lateralis, vastus intermedius).
    4. Articular supply: - Hip joint is supplied by nerve to rectus femoris; knee joint is supplied by nerve to three vasti.
  3. Saphenous branch of femoral nerve (saphenous nerve) is the longest cutaneous nerve. It runs with the great saphenous vein in front of medial malleolus and supplies the skin of antero medial aspect of leg and medial border of foot. Saphenous nerve may be damaged in front of the medial malleolus during venesection of long saphenous vein. Therefore, femoral nerve damage can cause sensory loss over the area of great saphenous vein in leg.   

Obturator nerve

  1. The obturator nerve arises from the ventral division of ventral (anterior) rami of S2, S3, S4 spinal nerves. It is the chief nerve of the medial (adductor) compartment 0/thigh. It emerges along the medial border of the psoas major. In the obturator canal it divides into anterior and posterior division.

Distribution of obturator nerve

Anterior division

Posterior division

a) Muscular branches to: - Pectineus, adductor longus, adductor brevis, gracilis.

b) Posterior branch to :- Hip joint

c) Vascular branch to :- Femoral artery

a) Muscular branches: - Obturator externus, adductor magnus, adductor brevis (if not supplied by anterior division).

b) Articular branch: - Knee joint.

  1. Obturator nerve supplies both hip and knee joints. In case of diseases of hip joint pain may be referred to knee joint.

Accessory obturator nerve

This nerve is present in about 30% of subjects. It is a branch of lumbar plexus and arises from ventral divisions of ventral (anterior) rami ofL3 and L4 spinal nerves. It terminates by dividing into three branches: (i) one supplies deep surface of pectineus, (ii) another supplies hip joint, and (iii) the third communicates with anterior division of obturator nerve.

 

Sacral Plexus

  1. The sacral plexus is formed from ventral (anterior) rami of L4, L5, S1, S2, S3 and S4 spinal nerves. The ventral rami of L4 and L5 unite to for lumbosacral trunk. The lumbosacral trunk (joined rami ofL4, L5) passes down into the pelvis and joins the sacral nerves.
  2. Branches of sacral plexus are :-

Branch

From ventral division of anterior rami

From dorsal division of anterior rami

1) Sciatic nerve

a) Tibial part

b) Common peroneal part

 

L4,L5,SI,S2,S3

 

L4, L5, SI, S2

2) Nerve to quadratus femoris

L4,L5,Sl

 

3) Nerve to obturator internus

L5,Sl,S2

 

4) Superior gluteal nerve

 

L4,L5,Sl,

5) Inferior gluteal nerve

 

L5,Sl,S2

6) Posterior cutaneous nerve of thigh

S2, S3

SI, S2

7) Pudendal nerve

S2, S3, S4

 

8) Pelvic splanchnic nerve

S2,S3,S4

 

9) Nerve to piriformis

 

S2

10) Branch to levator ani, coccygeus

S4

 

11) Perforating cutaneous nerve

 

S2,S3

 

Branch

Distribution

Superior gluteal nerve

Gluteus medius, gluteus minimus, and tensor fasciae lata muscles.

Inferior gluteal nerve

Gluteus maximus muscle.

Nerve to piriformis

Piriformis muscle

Nerve to obturator internus

Obturator internus and superior gemellus muscles

Nerve to quadratus femoris

Quadratus femoris and inferior gemellus muscles

Perforating cutaneous nerve

Skin over medial aspect of buttock

Posterior cutaneous nerve of thigh

Skin over posterior surface of thigh and popliteal fossa, also over lower part
of buttock, scrotum, or labium majus

Sciatic nerve (L4, 5 ; S1, 2, 3)
Tibial portion

Hamstring muscles (semitendinosus, biceps femoris [long head], adductor
magnus [hamstring part]), gastrocnemius, soleus, plantaris,
popliteus, tibialis posterior, flexor digitorum longus, flexor hallucis
longus, and via medial and lateral plantar branches to muscles of sole of
foot; sural branch supplies skin on lateral side of leg and foot.

Common peroneal portion

Biceps femoris muscle (short head) and via deep peroneal branch; tibialis
anterior, extensor hallucis longus, extensor digitorum longus, peroneus
tertius, and extensor digitorum brevis muscles; skin over cleft between first
and second toes. The superficial peroneal branch supplies the peroneus
longus and brevis muscles and skin over lower third of anterior surface of leg and dorsum of foot.

Pudendal nerve

Muscles of perineum including the external anal sphincter, mucous membrane
of lower half of anal canal, perianal skin, skin of penis, scrotum, clitoris, and
labia majors and minora.

 

Sciatic Nerve (L4. L5. S1. S2. S3)

 

  1. The sciatic nerve is the largest branch of sacral plexus and is the largest nerve in the body. It is formed at the lower margin of piriformis by union of its tibial and common peroneal parts. The main trunk has following branches:
    1. From tibial component; - Semitendinosus, semimembranosus, long head of biceps femoris, and ischeal part of adductor magnus.
    2. Common peroneal component; - Short head of biceps femoris.
  2. Thus main trunk of Sciatic nerve supplies hamstrings (semitendinosus, semimembranosus, biceps femoris) and ischeal part of adductor magnus.
  3. In the upper angle of popliteal fossa, sciatic nerve divides into tibial nerve and common peroneal nerve.

Common peroneal (fibular) nerve (L4, L5, S1, S2)

  1. The common peroneal nerve supplies the extensor and peroneal compartments of the leg and dorsum of the foot. It winds around the neck of fibula is closely related to lateral surface of neck of fibula. Thus, injuries around neck of fibula cause common peroneal nerve palsy. After curving around the neck of fibula it pierces the peroneus longs and divides into superficial and deep peroneal nerves.
  2. Branches of common peroneal nerve are:
    1. Cutaneous branches
      1. Lateral cutaneous nerve of calf:- Supply the skin of the upper two-thirds of the lateral side of the leg.
      2. Peroneal communicating nerve; - Joins the sural nerve.
    2. Articular branches
      1. Superior lateral genicular.
      2. Inferior lateral genicular.
      3. Recurrent genicular.
    3. Terminal branches
      1. Deep peroneal nerve (anterior tibial nerve); - It is the nerve of anterior compartment of leg and dorsum of the foot. It supplies:
        1. Muscles of anterior compartment of leg: - EDL, EHL, tibialis anterior, peroneus tertius.
        2. Extensor digitorum brevis.
        3. Cutaneous supply to adjacent sides of first and second toe (i.e. first interdigital).
        4. Articular supply to ankle joint, tarsal joints, tarsometatarsal and metatarsophalangeal joints of big toe.
      2. Superficial peroneal nerve; - It is the main nerve of lateral compartment of leg. It supplies: 
        1. Muscles oflateral compartment of leg: - Peroneus longus and peroneus brevis.
        2. Cutaneous supply to lower one third of the lateral side of leg and most of the dorsum of foot except for the territories supplied by the saphenous, sural, deep peroneal and plantar nerves.
        3. Medial branch breaks to supply the medial side of big toe and the 2nd interdigital cleft (adjoining side of 2nd and 3rd toes).
        4. Lateral branch breaks to supply 3rd & 4th interdigital clefts (adjoining sides of 3rd & 4th, and 4th & 5th toes).

Injury to common peroneal nerve

Common peroneal nerve is the most commonly injured nerve in lower limb. It is closely related to lateral surface of neck of fibula and hence injured in injuries around fibular neck. Clinical features of common peroneal nerve injuries are;-

  1. Motor
    1. Foot drop and weakness of ankle dorsiflexion-, extension of toes. Due to paralysis of muscles of anterior compartment of leg.
    2. Loss of eversion: - Due to paralysis of evertors of foot (peroneus longus & peroneus brevis).
    3. Plantar flexion and inversion are unaffected which results in 'equinovarus deformity' due to unopposed action of these muscles. For the same reason, ankle reflex is unaffected.
  2. Sensory
    Sensory loss along anterior and lateral side of leg, dorsum of foot and toes, including medial side of big toe. The lateral border of foot and lateral side of little toe are unaffected (supplied by sural nerve); and medial border of foot up to ball of big toe is unaffected (supplied by saphenous nerve).

Tibial nerve (L4. L5. S1. S2. S3)

It is the larger terminal branch of sciatic nerve. It is the nerve of posterior compartment of leg and the sole of the foot. Tibial nerve has following distribution -

  1. Branches in popliteal fossa
    1. Three articular (genicular) nerves: - Superior medial genicular, middle genicular, inferior medial genicular.
    2. Five muscular branches: - Plantaris, medial head of gastrocnemius, lateral head of gastrocnemius,
    3. Single cutaneous: - Sural nerve supplies the skin of lower half of back of leg and whole oflateral border of the foot till the tip of great toe. Sural nerve runs along with short saphenous vein behind lateral malleolus. (Note; Saphenous nerve runs along with long saphenous vein in front of medial malleolus)
  2. Branches in calf
    1. Four muscular branches; - Soleus (deep foot), tibialis posterior, flexor hallucis longus, and flexor digitorum longus.
    2. Medial calcaneal branches; - Supply the skin of back and lower surface of heel.
    3. Articular- Ankle joint.
    4. Terminal branches; - Medial plantar and lateral plantar nerves.

 

  1. Behind the medial malleolus, beneath the flexor retinaculum the tibial nerve divides into its two terminal branches;
    1. Medial plantar nerve: - It corresponds approximately to the median nerve in the hand as far as skin and muscle supplies are concerned. It supplies medial part of sole, plantar surface of medial 3 1/2 digits, and innervates
    2. Lateral plantar nerve: - It corresponds approximately to the ulnar nerve. It supplies the lateral part of sole, plantar surface oflateral 1 1/2 digits and innervates flexor digitorum accesorius, abductor digiti minimi, flexor digiti minimi brevis, adductor hallucis, all interossei and 2nd, 3rd, 4th lumbricals.

Clinical features of tibial nerve injury

  1. Loss of plantar flexion and inversion.
  2. Sensory loss on sole of foot, lateral border of foot and little toe and posterolateral calf.
  3. Unopposed action of dorsiflexors and evertors results in calcaneovalgus deformity. 




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