ANATOMY OFANATOMY OFLUMBO-SACRAL LUMBO-SACRAL

PLEXUSPLEXUS

By: Syed Irshad MurtazaTechnologist.

Neurophysiology Dept.AKUH Karachi.

12-08-2014

L.S Plexus by IM

OutlineOutline• Spinal cord.• Lumbar plexus anatomy• Sacral plexus anatomy• Components of lumbosacral plexus• Key for the L.S Plexus• Key to draw L.S Plexus.• Terminal Branches of L.S plexus.• Motor and Sensory Distribution.• Questions.• References

L.S Plexus by IM

Spinal cord Spinal cord • Lumbar and sacral

enlargement. .. The sites where the nerves serving the lower limbs, emerge.

• Conus Medullaris:• The terminal portion of the

spinal cord• Cauda equina:• The collection of nerve roots

at eh inferior end of the vertebral canal.

• Spinal cord ends at the level of L2 vertebrae (adults).

• Spinal nerves 31 pairs

L.S Plexus by IM

L.S Plexus by IM

L.S Plexus by IM

Lumbosacral plexusLumbosacral plexusLumbosacral plexus is basically combination of two plexus,Lumbar Plexus &Sacral Plexus.

1.LUMBAR PLEXUS:The lumbar plexus is formed by the ventral rami of first four lumber nerve roots (L1, L2, L3 (major) & part of L4). In 50% of cases it receives a contribution from the ventral rami of last thoracic root (T12).It lies within the substance of the posterior part of psoas major muscle, anterior to the transverse processes of the lumbar vertebrae. The branches emerge to both lateral and medial sided of psoas major muscles. L.S Plexus by IM

• "iliopsoas" are referred to as the "dorsal hip muscles“ or "inner hip muscles.

L.S Plexus by IM

Components of lumbosacral Components of lumbosacral

plexusplexus• Components of the lumbosacral plexus are as,• 1. Lumbar plexus L1, L2, L3, L4• 2. Lumbosacral Trunk L4, L5• The above roots contribute in lumbar and sacral

plexus both.• 3. Sacral Plexus S1, S2, S3, S4• Smaller branches of the lumber plexus innervate the

posterior abdominal wall and psoas muscles (psoas major, iliacus).

• Main branches innervate the anterior thigh and their relative muscles.

• Key to remember.• Root →Branches→Divisions→Terminal Branches• (RBDT)

L.S Plexus by IM

L.S Plexus by IM

L.S Plexus by IM

L.S Plexus by IM

RBDTRBDT• Root: these are constituted by the anterior primary

rami of L1, L2, L3, L4 (T12).• Branches: L1 root gives an upper and lower branch• L2 Root gives and upper and lower branch• L3 does not give any branch• L4 gives an upper and lower branch• Division: Lower branch of L2, upper branch of L4

and ventral rami of L3 nerve roots divide into small anterior and large posterior division.

• From L2 and L3 each gives two and L4 one posterior divisions, with single anterior division from all branches (L2, L3, L4).

• Lower branch of L4 and L5 unite to form lumbosacral trunk

L.S Plexus by IM

Terminal Branches of Lumbar PlexusTerminal Branches of Lumbar Plexus• L1 unites with a small branch from T12 and splits into an upper

and lower branches.

• The upper larger branch divides into two: • iliohypogastric (T12, L1) and ilioinguinal nerves (L1).

• The lower smaller branch of L1 unites with a branch from L2 to form the genitofemoral nerve.

• The remainders of L2, L3 and L4 divide into ventral and dorsal branches. Ventral (Anterior) divisions of L2, L3, L4 unite to form obturator nerve.

• The dorsal (posterior) divisions of L2 and L3 divide into small and larger parts. Smaller parts of dorsal divisions of L2 and L3 unite to form the lateral femoral cutaneous nerve.

• Larger parts of dorsal divisions of L2 and L3 unite with L4 to form femoral nerve.

L.S Plexus by IM

L.S Plexus by IM

FEMORAL NERVEFEMORAL NERVE• It is formed by the dorsal or posterior division of the

anterior rami of L2,L3, & L4 roots.

• The femoral nerve is the largest branch of the lumbar plexus. It mainly supplies the extensors muscles of the knee (quadriceps) (VL, VI, VM, RF).

• The Saphenous Nerve is a purely sensory nerve which the largest and longest cutaneous branch of the femoral nerve.

• Lateral femoral cutaneous nerve of the thigh The lateral femoral cutaneous nerve of the thigh

emerges from the lateral border of psoas major which is formed by the posterior divisions of L2 and L3.

. It gives cutaneous supply to the lateral part of the thigh. L.S Plexus by IM

L.S Plexus by IM

• KEY:• Roots • ↓• Branches • ↓• Divisions • ↓• Terminal

branches.

• R-B-D-T

• IIGOLF

L.S Plexus by IM

Sensory Distribution of the Lower Limb

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L.S Plexus by IM

Lumbosacral Trunk & sacral

plexus.• The sacral plexus is formed by the lumbosacral trunk

(L4 ,L5 ), & ventral rami of S1, S2, S3, S4 .

• Contribution of the fourth sacral ventral rami is partial & the remainder of the last (S5 ) joins the coccygeal plexus.

• Key to remember sacral plexus:• Root Divisions Terminal Branches (R.D.T/B)• Roots: These are constituted by the anterior primary

rami of L4 , L5, S1, S2, S3, & S4

• Divisions: The lower branch of L4 ventral rami & ventral rami of L5 , S1 & S2 give anterior and posterior divisions. While S3 forms & shares only anterior division .

• Terminal Branches: These anterior and posterior divisions unite to form the terminal nerve branches.L.S Plexus by IM

Terminal BranchesTerminal Branches• The posterior division of L4 ,L5 & S1 joins to form Superior Gluteal

Nerve .

• The posterior divisions of L5,S1 & S2 unites to form the Inferior Gluteal Nerve.

• The posterior divisions of L4 ,L5 ,S1 & S2 joins to form Common fibular or Peroneal Nerve. It’s the about one-half the size of the tibial nerve.

• The anterior divisions of L4 ,L5 ,S1,S2 & S3 unites to form Poterior Tibial Nerve.

• The anterior divisions of S2,S3& S4 unites to form Pudendal Nerve.

• So both these nerves i.e. Tibial and peroneal run in a single covering of sheath and called as Sciatic Nerve (L4 ,L5,S1,S2 &S3) . Which is the largest nerve of the body.

• L.S Plexus by IM

Sciatic Sciatic NerveNerve

• Sciatic Nerve descends along the back of the thigh and through the middle of the popliteal fossa, to the lower part of the Popliteus muscle. It divides just 5cm above the politial fossa into Common Peroneal & Tibial nerves to supply their relative muscles.

L.S Plexus by IM

Key to Draw sacral Key to Draw sacral PlexusPlexus

111221 Anterior 2332 Posterior

• SIPPP

• S. Superior Glutal Nerve (L4, L4, S1) Posterior• I. Inferior Glutal Nerve (L5, S1, S2) Posterior• P. Peroneal (common fibular) Nerve (L4,L5,S1,S2)

Posterior

• P. Posterior Tibial Nerve (L4,L5,S1,S2,S3 )Anterior• P. Pudendal Nerve. (S2, S3, S4) Anterior

L.S Plexus by IM

L.S Plexus by IM

Sensory Distribution to the Sensory Distribution to the

Legs:Legs:• Superficial Peroneal: it’s the cutaneous branch

from the common peroneal nerve which supplies to the anterio-lateral aspect of leg upto dorsum of the foot.

• Sural nerve formed by the junction of the medial sural cutaneous (it is the sensory branch of tibial nerve) with the peroneal anastomotic branch (its branch of lateral sural cutaneous nerve), passes downward near the lateral margin of the tendo-calcaneous, lying close to the small saphenous vein, to the interval between the lateral malleolus and the calcaneous.

• It supplies to the posterio-lateral aspect of the leg upto lateral malleolus.

L.S Plexus by IM

Nerve Name Origin SuppliesIliohypogastric T12,L1 Motor supply to internal oblique, transverses

muscles, sensation over lower anterior abdominal wall

Ilioinguinal L1 Sensation over anterior pubis (mons) and anterior scrotum or labia

Genitofemoral L1, L2 Genital branch: motor supply to cremastor muscle, sensation to anterior scrotum; femoral branch: sensation to anterior thigh

Femoral L2, L3, L4 Motor supply to extensors of the knee, sensation to anterior thigh

Obturator L2, L3, L4 Motor supply to adductors of the thigh, sensation to medial thigh

Lumbosacral trunk L4, L5 Joins the sacral nerves to form the lumbosacral plexus that supplies motor and sensory innervations to the lower extremities

Posterior femoral cutaneous

S2, S3 Sensation to perineum, posterior scrotum, and posterior thigh

Pudendal S2, S3, S4 Motor to levator ani, muscles of the urogenital diaphragm, anal and striated urethral sphincter, sensation to the perineum, scrotum, and penis

L.S Plexus by IM

12/08/2014

Nerve Name Origin SuppliesNerve to quadratus femoris

L4,L5,S1 quadratus femoris, inferior gemellus

Superior gluteal L4,L5,S1 gluteus medius & minimus, tensor fasciae latae

Inferior gluatel L5,S1,S2 Gluteus maximus

Nerve to obturator

internus L5,S1,S2 obturator internus, superior gemellus

sciatic sacral plexus (ventral primary rami of L4-L5, S1-S3)

(via its tibial & common peroneal branches) semitendinosus, semimembranosus, biceps femoris, part of adductor magnus, muscles of leg & foot skin of leg & foot (excluding medial side of leg & foot)

L.S Plexus by IM

L.S Plexus by IM

L.S Plexus by IM

L.S Plexus by IM

ReferencesReferences• Electromyography and neuromuscular

disorders• By David C. Preston• Snell's Clinical Anatomy 9th Edi• By Richard S. Snell• Electrodiagnosis in Diseases of Nerve and

Muscle: Principles and Practice• By Jun Kimura• http://en.wikipedia.org/wiki/Sural_nerve• http://en.wikipedia.org/wiki/Quadriceps_femoris_m

uscle

Thanks for the patienceThanks for the patienceL.S Plexus by IM