Keywords:
Education and training, Education, Ultrasound-Colour Doppler, Neuroradiology peripheral nerve, Musculoskeletal system, Anatomy
Authors:
G. Rebella1, E. Massone1, M. De Cesari1, G. Buonomenna1, S. Perugin Bernardi2, D. Orlandi2, A. Muda2, E. Silvestri1; 1Genoa/IT, 2Genova/IT
DOI:
10.26044/essr2019/P-0043
Background
The femoral nerve,
created by the dorsal divisions of the anterior rami of L2,
L3,
and L4,
is the largest branch of the lumbar plexus.
It emerges at the inferolateral border of the psoas muscle to run caudally and laterally in the groove formed by the psoas and iliacus muscles.
Then the nerve enters the thigh passing under the inguinal ligament,
and,
within a short distance,
it divides into anterior and posterior branches.
At this level the femoral nerve is lateral and posterior to the femoral artery,
deep to the fascia iliaca,
and superficial to the iliopsoas muscle.
Note that the inguinal ligament is a convergent point of the transversalis fascia (fascial layer of the deep surface of the anterior abdominal wall) and iliac fascia (fascia covering the posterior abdominal wall) (Fig.
1).
The anterior branch provides motor innervation to the sartorius and pectineus muscles and sensory innervation to the skin of the anterior and medial thigh from the inguinal ligament to the knee.
The posterior branch provides motor innervation to the quadriceps muscle and sensory innervation to the medial aspect of the lower leg from the knee to the internal malleolus via the saphenous nerve.
Injury to the femoral nerve determines weakness of hip flexion and of knee extension and sensory loss over the territories of the anterior and medial thigh and of the medial aspect of the lower leg.
The anatomic location of the femoral nerve makes its identification simple because the landmarks are usually easy to find (except in cases of obesity) and the depth of the nerve is relatively superficial.
Ultrasonography (US) is commonly used to assess the peripheral nerves that present a characteristic “honeycomb” appearance in short axis,
and "electric cable" appearance in long axis.
We will provide a dedicated US femoral nerve image compared with a detailed anatomic scheme,
and a practical guide on “how we do” a US scan.