LUMBOSACRAL PLEXUS
Lumbosacral Plexus

Components:
Lumbar plexus:
L1--L4.
Lumbosacral trunk:
L4—L5.
Sacral plexus:
S1—S4.
Lumbar Plexus

Formed in psoas major:
From ventral rami of L1..L4.
Branches emerge from both lateral and
medial sides of psoas major:
Connect to sympathetic trunk.
Lumbar Plexus

L1:
Variably connected to T12 (subcostal) and
L2.
Two branches emerge from lateral side of
psoas major:
Iliohypogastric (GSA):
to side of buttock and pubis.
Ilioinguinal (GSA):
to anterior thigh, scrotum,
labia majora.
Lumbar Plexus

Genitofemoral nerve:
Emerges on anterior surface of psoas major.
Genital branch:
Enters inguinal canal.
Supplies scrotum and labia majora
(GSA).
Supplies cremaster muscle (GSE).
Femoral branch:
Enters femoral sheath.
Supplies skin over femoral triangle.
Lumbar Plexus

Femoral nerve:
L2—L4.
Largest branch of lumbar plexus.
Emerges from lateral side of psoas major.
Lumbar Plexus

Femoral nerve:
Enters thigh behind inguinal ligament.
Supplies:
In iliac fossa:
Iliacus (GSE); pectineus (GSE);
femoral artery (GVE).
Lumbar Plexus

Femoral nerve:
Supplies:
Distally:
Sartorius; quadriceps femoris;
anterior thigh (GSA).
Terminates as:
Saphenous nerve (GSA) to medial thigh
and foot.
Lumbar Plexus

Obturator nerve:
L2..L4.
Emerges from medial side of psoas major.
Descends along lateral wall of pelvis.
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).
Lumbar Plexus

Obturator nerve:
Supplies:
Medial thigh muscles (GSE).
Skin on medial thigh (GSA).
Sacral Plexus

Superior gluteal nerve:
L4..S1.
Passes through greater sciatic notch above
piriformis.
Supplies lateral gluteal compartment.
Sacral Plexus

Inferior gluteal nerve:
L5..S2.
Passes through greater sciatic notch below
piriformis.
Supplies posterior gluteal compartment.
Sacral Plexus

Posterior femoral cutaneous:
Runs with gluteal nerves deep to gluteus
maximus.
Then runs with sciatic nerve and gluteal
artery.
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.
Sacral Plexus

Nerves to lateral thigh compartment:
To inferior gemellus (GSE):
L4..S1.
To quadratus femoris (GSE):
L4..S1.
To piriformis (GSE):
S1..S2.
Sacral Plexus

Sciatic nerve:
Fusion of:
Common peroneal (fibular).
Tibial.
Largest physical nerve in the body.
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.
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.
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.