|ESSR 2019 / P-0138|
|US of the common peroneal nerve and ITS two terminal branches: how to do it; a detailed didattic approach|
Imaging findings OR Procedure Details
We will provide, for each of these structures, a dedicated US image compared with a detailed anatomic scheme, and a practical guide on “how we do” a US scan of common peroneal nerve, deep peroneal nerve and superficial peroneal nerve.
With the patient supine, for the study of common peroneal nerve, place the transducer in the transverse plane at the proximal popliteal fossa to visualize the distal part of the sciatic nerve, which branches into the common peroneal nerve laterally and the tibial nerve medially. (Fig2)
Follow the common peroneal nerve moving the probe along and lateral to the tendon of the biceps femoris. It passes between the biceps femoris and the lateral head of the gastrocnemius muscle and runs to the lateral aspect of the proximal third of the leg. (Fig3)
It then crosses the fibular head and passes under the proximal end of the peroneus longus. Move the probe in a transverse plane caudally until the nerve divides into the superficial and deep peroneal nerves. (Fig4)
Turn the probe by 90° to examine the nerve in a longitudinal axis to evaluate the internal echostructure.
For the study of deep peroneal nerve start the US exam placing the probe on a transverse plane on the anterolateral aspect of the proximal leg, at the level of the fibular head, where the deep peroneal nerve arises with the superficial peroneal nerve. It is very close to the fibula, under the peroneus longus muscle. Follow the nerve caudally in the leg.
The tibial artery is a very important landmark to identify the nerve course in the leg: in fact the neurovascular bundle runs superficial to the interosseous membrane and deep to the tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles. (Fig5)
In the distal third of the leg, proximal to the ankle joint, with the transducer placed in a transverse orientation at the level of the extensor retinaculum, the deep peroneal nerve crosses the anterior tibial artery from a medial to a lateral position. The nerve usually appears hyperechoic, lateral to the tibial artery, on the surface of the tibia. (Fig6)
At the level of the ankle, place the transducer at the anterior ankle joint in the transverse plane. The deep peroneal nerve is small and can be difficult to visualize: it lies, with the dorsalis pedis artery, lateral to the extensor hallucis longus tendon. (Fig7)
For the study of superficial peroneal nerve place the probe in a transverse plane on the anterolateral aspect of the proximal leg, at the level of the fibular head, where the superficial peroneal nerve merges. Follow the nerve until the proximal end of the peroneus brevis, where it passes between the fibula and the peroneus longus muscle. Distally it lies between the peroneus longus and brevis muscles. (Fig8)
At the level of the ankle, with the transducer placed on the anterior superior aspect of the lateral malleolus, the superficial peroneal nerve lies in a small groove between the extensor digitorum longus muscle anteriorly and peroneus brevis muscle posteriorly. Identify the tendon of the peroneus longus (not the muscle belly). Identify the hyperechoic structure that lies in the subcutaneous tissue immediately superficial to the fascia. (Fig9)
The nerve can then be followed more proximally, to the point where it pierces the fascia and enters the muscle. At this level the extensor hallucis longus muscle is an excellent landmark for identifying the superficial peroneal nerve, which is located in this intermuscular septum, just deep to the fascia.
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