Choose the true statement about the ultrasound-guided popliteal sciatic block:
A) The tibial nerve is lateral to the popliteal artery
B) With the lateral approach, the resulting ultrasound image is different to the image
in the posterior approach
C) The LA should be deposited after the division of the sciatic nerve
D) The common peroneal nerve is lateral and deep to the popliteal artery
When you perform this block, the lateral and the posterior approaches show you the same ultrasound image, however there is a 180° difference in patient orientation and needle path differ between the two approaches.
The anatomy of the sciatic nerve as it approaches the popliteal fossa can be variable, and the division into the tibial nerve and common peroneal nerve occurs at a variable distance from the crease. Therefore it is important to recognise the anatomy of the popliteal fossa and the position of the nerves to the popliteal artery:
- Tibial nerve is lateral and superficial to the artery
- Common peroneal nerve is even more lateral and superficial to the tibial nerve.
The transducer should be slid proximally until the tibial and peroneal nerves are visualized coming together to form the sciatic nerve before its division. The goal is to inject the local anesthetic within the common epineurium that envelops the tibial nerve and common peroneal nerve.