LOWER EXTREMITY
NEUROANATOMY
Wyndam M. Strodtbeck, MD
Section Head, Acute Pain
Dept of Anesthesiology and Pain Medicine
Virginia Mason Medical Center
wyndam.strodtbeck@vmmc.org
Disclosures
 No financial disclosures
 No off-label use of medications or devices will
be discussed
 Patient permission was explicitly granted for
any pictures used
Objectives for our talk
 Describe the clinical anatomy of the
innervation of the lower extremity
 Identify surrounding structures and their
implications for sonoanatomy and potential
variation
Lumbosacral
plexus
L1-L4 form the lumbar plexus
Branches from L4 –S2 from the
lateral trunk
Other branches from L3-S3 make
up the medial trunk
S1-S5 make up the sacral plexus
Early branching of the lumbar plexus
and thick musculature makes
identifying a single compartment for
lumbosacral blockade difficult
Early Branches of the Lumbar Plexus
 Ilioinguinal and iliohypogastric nerves
 From L1
 Iliohypogastric supplies anterior and lateral cutaneous
innervation in hypogastric and gluteal region
 Ilioinguinal supplies cutaneous innervation of genital
region
 Genitofemoral nerve
 From L1 and L2
 Genital division supplies cremasteric muscle and
sensory over genital region
 Femoral branch supplies cutaneous innervation over
femoral triangle
Early Branches of the Lumbar Plexus
Gray, H. Anatomy of the human body, 1918.
Femoral Nerve
Origin is dorsal divisions
of L2-L4
Divides into anterior
and posterior division
typically at level of
profunda femoris artery
Nader, Relationship Between Ultrasound Imaging and Eliciting Motor Response, J
Ultrasound Med, 28(3):345-350, 2009
Femoral Nerve
Origin L2-L4
Anterior division
-Medial and intermediate cutaneous nerves
-Muscular branches to sartorious
-Articular branch to hip joint
Posterior Division
-Muscular branches to quads
-Articular branches to knee joint
-Saphenous nerve is terminal cutaneous branch and provides
lower leg anteromedial sensation
Nader, Relationship Between Ultrasound Imaging and Eliciting Motor Response, J
Ultrasound Med, 28(3):345-350, 2009
Femoral Nerve
Nader, Relationship Between Ultrasound Imaging and Eliciting Motor Response, J
Ultrasound Med, 28(3):345-350, 2009
Femoral Nerve
Ultrasound image shows
anterior and posterior
divisions
Keep in mind the variations
in location and appearance
of the nerve
Groups of authors have
reported variable splits in
the femoral nerve in 2.2-35%
of subjects.
Nader, Relationship Between Ultrasound Imaging and Eliciting Motor Response, J
Ultrasound Med, 28(3):345-350, 2009
Lateral femoral cutaneous nerve
Originates from dorsal
divisions of L2 and L3
May have a variable course as
it emerges from psoas
Passes under inguinal
ligament and superficial to the
sartorious muscle
Located between fascia lata
and fascia iliaca
Responsible for pain
transmission in meralgia
paresthetica
Hurdle, MF et al. Ultrasound-guided blockade of the lateral femoral
cutaneous nerve. Arch Phys Med Rehab 88:1362-1364, 2007.
Saphenous Nerve
Terminal branch of posterior division of femoral nerve
Provides cutaneous sensation around patella,
anteromedial lower leg, and medial ankle
Travels in adductor canal with femoral artery and vein
In distal thigh, the saphenous nerve can be identified
deep to the sartorious and between the vastus medialis
and the adductor magnus
Saphenous Nerve
Image courtesy of FV Salinas, MD
Saphenous Nerve
Obturator nerve
Originates from ventral
branches of L2-L4
Supplies articular
branches to hip and knee
Adductors are supplied
Similar to femoral nerve
in having anterior and
posterior divisions
Obturator nerve
Anterior division
Motor innervation to pectineus (may be an accessory
obturator nerve) , adductor longus and brevis, gracilis
Articular branch of the hip
Posterior division
Motor inneravtion to adductor magnus and brevis as
well as obturator externus
Articular branches to hip and knee
Nerves of the
Sacral Plexus
Gray, H. Anatomy of the human body, 1918.
Posterior femoral
cutaneous nerve
Provides sensation for
posterior thigh and leg,
gluteal region, and
perineum
Originates from S1-S3
Posterior femoral
cutaneous nerve
Gray, H. Anatomy of the human body,
1918.
Sciatic Nerve
Largest nerve in the body
Joining of L4-S3
Two parts:
-Tibial (medial)
(L4-S2)
- Common Peroneal
(L4-S3)
Provides sensation for posterior
leg and foot (except for saphenous
distribution) as well as motor for
posterior thigh, and all of leg and
foot, and articular branches for hip
and knee
Wikipedia, Feb 10, 2012
Sciatic Nerve
At gluteal level, Sciatic is deep to gluteus maximus and passes out below
piriformis muscle, located lateral to ischial spine
This level is useful due to the close proximity of the posterior femoral
cutaneous nerve to the sciatic nerve
Sciatic Nerve
At subgluteal level, the
sciatic nerve is
positioned between
the gluteus maximus
and the quadratus
femoris
Sciatic Nerve
Subgluteal ultrasound
Image courtesy of FV Salinas, MD
Sciatic Nerve
-Shared epineural
sheath for tibial and
common peroneal
nerves separates
above popliteal crease
-Schwemmer et al
(2005) demonstrated
high variability for
division of sciatic
nerve above popliteal
crease (1-15 cm with
mean of 8 cm)
Schwemmer et al. Sonographic imaging of the sciatic
nerve division in the popliteal fossa. Ultraschall in Der
Medizin, 2005.
Wikipedia, Feb 10, 2012
Nerves of the ankle and foot
Primarily consists of terminal
branches from the sciatic
Exception is the saphenous
branch of the femoral nerve
NYSORA.com, accessed 2-10-2012
Gray, H. Anatomy of the human body, 1918.
Special Thanks
 Francis V. Salinas, MD