LOWER EXTREMITY NEUROANATOMY

Wyndam M. Strodtbeck, MDSection Head, Acute PainDept of Anesthesiology and Pain MedicineVirginia Mason Medical Centerwyndam.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 NerveOrigin 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 NerveOrigin 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 NerveUltrasound 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 nerveOriginates 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 nerveOriginates 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 nerveAnterior division

Motor innervation to pectineus (may be an accessory obturator nerve) , adductor longus and brevis, gracilis

Articular branch of the hip

Posterior divisionMotor inneravtion to adductor magnus and

brevis as well as obturator externusArticular branches to hip and knee

Nerves of theSacral Plexus

Gray, H. Anatomy of the human body, 1918.

Posterior femoralcutaneous nerveProvides sensation for posterior thigh and leg, gluteal region, and perineum

Originates from S1-S3

Posterior femoralcutaneous nerve

Gray, H. Anatomy of the human body, 1918.

Sciatic NerveLargest 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 NerveAt 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 NerveAt subgluteal level, the sciatic nerve is positioned between the gluteus maximus and the quadratus femoris

Sciatic NerveSubgluteal 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) Wikipedia, Feb 10, 2012

Schwemmer et al. Sonographic imaging of the sciatic nerve division in the popliteal fossa. Ultraschall in Der

Medizin, 2005.

Nerves of the ankle and footPrimarily consists of terminal branches from the sciatic

Exception is the saphenous branch of the femoral nerve

Gray, H. Anatomy of the human body, 1918.NYSORA.com, accessed 2-10-2012

Special Thanks

Francis V. Salinas, MD