LUMBOSACRAL PLEXUS

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Lumbar plexus (T12- L4):

Lumbar Plexus

• Femoral nerve:

L2—L4.Largest branch of lumbar plexus.Emerges from lateral side of psoas major.

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Lumbar Plexus

• Femoral nerve:

Enters thigh behind inguinal ligament.Supplies:

In iliac fossa:Iliacus (GSE); pectineus (GSE);

femoral artery (GVE).

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Lumbar Plexus

• Femoral nerve:

Supplies:Distally:

Sartorius; quadriceps femoris; anterior thigh (GSA).

Terminates as:Saphenous nerve (GSA) to medial thigh and foot.

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Lumbar Plexus

• Obturator nerve:

L2..L4.Emerges from medial side of psoas major.Descends along lateral wall of pelvis.

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Lumbar Plexus

• Obturator nerve:

Enters thigh through obturator foramen:In obturator groove it divides into:

Anterior branch (anterior to adductor brevis).Posterior branch (posterior to

adductor brevis).

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Lumbar Plexus

• Obturator nerve:

Supplies:Medial thigh muscles (GSE).Skin on medial thigh (GSA).

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Sacral Plexus

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Sacral Plexus

• Superior gluteal nerve:

L4..S1.Passes through greater sciatic notch above piriformis.Supplies lateral gluteal compartment.

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Sacral Plexus

• Inferior gluteal nerve:

L5..S2.Passes through greater sciatic notch below piriformis.Supplies posterior gluteal compartment.

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Sacral Plexus

• Posterior femoral cutaneous:

Runs with gluteal nerves deep to gluteus maximus.

Then runs with sciatic nerve and gluteal artery.

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Sacral Plexus

• Posterior femoral cutaneous:

Supplies:Skin on buttock (GSA) via inferior cluneal

nerve.Skin of external genitalia (GSA) via perineal branches.Skin on back of thigh.

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Sacral Plexus

• Nerves to lateral thigh compartment:

To inferior gemellus (GSE):L4..S1.

To quadratus femoris (GSE):L4..S1.

To piriformis (GSE):S1..S2.

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Sacral Plexus

• Sciatic nerve:

Fusion of:Common peroneal (fibular).Tibial.

Largest physical nerve in the body.

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Sacral Plexus

• Sciatic nerve:

Exits pelvis through greater sciatic foramen:Inferior to piriformis (usually).

Descends between gluteus maximus.Between greater trochanter and ischial

tuberosity.Lies on:

Ischium, gemelli, obturator internus, quadratus femoris.

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Nerve Injuries

• Peripheral:

All motor function and sensation supplied by nerve distal to injury is lost.Total muscle function is lost.Sensation over more than one dermatome is lost.

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Nerve Injuries

• Nerve root:

Usually affected by disc herniation immediately cranial (superior) to it.

Sensory impairment over one dermatome.Muscle weakening.May only affect one root or the other.

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Lumbar Plexus

• Femoral nerve• Cutaneous branches

• Thigh, leg, foot (e.g. saphenous nerve)• Motor branches

• Anterior thigh muscles (e.g. quadriceps, sartorius, iliopsoas)

• Obturator nerve• Sensory

• Skin medial thigh; hip, knee joints• Motor

• Adductor muscles• Lateral femoral cutaneous

• Sensory• Skin lateral thigh

• Genitofemoral • Sensory

• Skin scrotum, labia major, anterior thigh• Motor

• Cremaster muscle

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Sacral plexus (L4-S4)

Sciatic nerve (L4-S3)

Tibial nerve

Common peroneal (fibular) nerve

Motor to muscles of pelvis and lower extremity (gluteal, posterior femoral, lower leg & foot)Sensory from posterior pelvis, posterior thigh, anterior, posterior & lateral leg

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femurmedial

lateral

Anterior compartment-

Extensors of the knee

Femoral Nerve

Medial compartment-

Adductors of the knee

Obturator Nerve

Posterior compartment-

Flexors of the knee

Sciatic Nerve

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L2

L3

L4

iliopsoas

Rectus femoris

pectineus

Vastus medialis

Vastus intermedius

sartorius

Vastus lateralis

Motor Branches of the

Femoral Nerve

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Adductus magnus

gracilis

Adductor longus

Adductor brevis

Motor Branches of the

Obturator Nerve

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L4

L5

S1

S2

S3

Semitendinosis

Biceps femoris

semimembranosus

Ham

stri

ng

s

Gastrocnemius and posterior compartment of the leg and foot

Tibial nerve

Common peroneal nerve Deep

peroneal nerve Anterior

compartment of leg

Lateral compartment of leg

Superficial peroneal nerve

Motor Branches of the

Sciatic Nerve

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Dermatomes (innervation of skin)

Dermatomes

(area of skin innervated by the cutaneous branches from a

single spinal nerve is called a dermatome)

Reveal sites of damage to spinal

nerves or spinal cord

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