UGRAbas

35 – The endpoint of injection

The endpoint of injection is complete perineural spread of local anaesthetic

Click on the VIDEO CLIP button to view the video

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This video clip demonstrates complete perineural spread of local anaesthetic around the common peroneal nerve (P) and the tibial nerve (T) distal to the branching of the sciatic nerve in the popliteal fossa

27 – Use the popliteal artery as a proxy marker

– Locate the pulsating popliteal artery at the level of the popliteal crease

– Look for the tibial nerve between the artery and the skin

– Look for the common peroneal nerve lateral to the tibial nerve

– Track the tibial nerve and the common peroneal nerve proximally until they unite and become the sciatic nerve

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The image displays the peroneal nerve (P) and the tibial nerve (T) just distal to the bifurcation of the sciatic nerve in the popliteal fossa

22 – Non-sciatic innervation of the leg, ankle and foot

The sciatic nerve branches (the tibial nerve and the common peroneal nerve) innervate the entire leg, ankle and foot

The only exception is the saphenous nerve territory and a strip of skin distal to the popliteal fossa which is innervated by the posterior femoral cutaneous nerve

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The green area is the cutaneous innervation area of the saphenous nerve. The saphenous nerve innervates the skin on the medial side of the leg and foot. The saphenous nerve is the major branch from the femoral nerve (see the femoral nerve).

23 – Non-sciatic innervation of the leg

The posterior cutaneous nerve of thigh (also known as the posterior femoral cutaneous nerve) is a branch of the sacral nerve plexus and leaves the pelvic cavity through the greater sciatic foramen

It supplies a vertical strip of skin extending from the distal gluteal region down to mid-calf level

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The green colour depicts the posterior femoral nerve territory below the popliteal crease

26 – How to perform a sciatic popliteal nerve block

– Place the patient in the lateral position and the probe in the popliteal crease

– Visualise the tibial nerve between the popliteal artery and the probe

– Track the tibial nerve proximally until it unites with the peroneal nerve and the two become the sciatic nerve

– Insert the needle from the lateral end of the probe and advance the needle in-plane until the tip of the needle touches the peroneal nerve tangentially

– Inject the local anesthetic

– Relocate the tip of the needle until you obtain complete perineural spread of local anaesthetic around both the peroneal and the tibial nerve

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Top image: In-plane approach to block the two branches of the sciatic nerve.
Bottom image: Sonoanatomy of the tibial and the peroneal nerve distal to the bifurcation of the sciatic nerve. (A) = popliteal artery; P = common peroneal nerve; T = tibial nerve; ant = anterior; post = posterior; lat = lateral; med = medial

29 – Appearance of the peroneal nerve at the bifurcation

The common peroneal nerve (P) typically presents as one single round anehoic (black) profile just before it branches off from the sciatic nerve (S)

Click on the VIDEO CLIP button to view the video

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PN common peroneal nerve; TN tibial nerve

28 – The benefit of blocking the branches after the bifurcation

It is easy and requires only a small volume of local anaesthetic to anaesthetise the two branches of the sciatic nerve – the tibial nerve and the common peroneal nerve – individually

The two sciatic branches are easy to access as they are more superficially located than the sciatic nerve before the bifurcation

Click on the VIDEO CLIP button to view the video

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Complete perineural spread around the two sciatic nerve branches separately with only a few milliliters of local anaesthetic
Peroneal nerve (PN), tibial nerve (TN)

19 – Cutaneous distribution of the superficial peroneal nerve

The superficial fibular nerve emerges through the fibular musculature about halfway down the leg

It innervates the dorsum of the foot and the toes – except the interspace between the first and the second toe

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The green colour depicts the cutaneous distribution of the superficial peroneal nerve

18 – The superficial peroneal nerve – a terminal branch of the common peroneal nerve

The superficial fibular nerve is the smallest of the two terminal branches of the common fibular nerve

It innervates the muscles of the lateral compartment of the leg

It supplies cutaneous branches to the lateral aspect of the distal half of leg

The branches of the superficial peroneal nerve supply the dorsum of the foot and the toes

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The green colour depicts the superficial peroneal nerve

17 – Lateral cutaneous nerve of the calf

The lateral cutaneous nerve of calf (also known as the lateral sural nerve) is a cutaneous branch of the common fibular nerve

It arises near the neck of the fibula and supplies skin over the lateral aspect of the leg just distal to the knee

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The green colour depicts the cutaneous distribution of the lateral cutaneous nerve of the calf