Keywords:
Education and training, Technical aspects, Education, Ultrasound-Colour Doppler, Ultrasound, Neuroradiology peripheral nerve, Musculoskeletal system, Musculoskeletal soft tissue
Authors:
S. Perugin Bernardi1, E. Massone2, D. Orlandi1, A. Muda1, E. Silvestri2; 1Genova/IT, 2Genoa/IT
DOI:
10.1594/essr2018/P-0004
Background
The Sciatic nerve is the longest and thickest peripheral nerve of the human body,
with a diameter of about 2 cm.
It supplies motor and sensory innervation to the posterior aspect of the thigh and of the whole lower leg,
except for the medial aspect of the leg,
which is supplied by the Saphenous nerve (the terminal branch of the femoral nerve).
It originates from the ventral rami of spinal nerves L4-L5,
S1-S3.
It leaves the lesser pelvis,
where it is anterior to the piriformis muscle and posterior to the iliac vessels,
through the greater sciatic foramen,
emerging from beneath the Piriformis muscle (in 85% of cases).
(Fig.1)
In the upper part of its course,
ithe nerve runs under the Gluteus Maximus muscle and it is accompanied on its medial side by the Posterior Femoral Cutaneous nerve and the inferior gluteal artery.
In the thigh it lies between the greater trochanter of the femur and the ischial tuberosity,
always under the gluteal muscles.
The nerve runs distally in the thigh posteriorly to the Adductor Magnus muscle,
and it is obliquely crossed by the long head of the Biceps Femoris muscle.
It then runs in the groove between the semimembranosus and Biceps Femoris muscles.
(Fig.2)
Usually at lower third of the thigh,
where the Semimembranosus splits medially and the Biceps Femoris laterally (forming the superior angle of the popliteal fossa),
it divides into two large branches,
the Tibial and Common Peroneal nerves.
The Tibial nerve continues in the same direction of the main trunk,
at the center of the popliteal fossa,
while the Common Peroneal nerve turns laterally,
medial to the biceps tendon.