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Regional Anesthesia Lower Extremity Part 1
November 2024
Final Reviewer: Justine Ko, MD, CAQ-SM
Image 1: Author's own image
Image 2: Demonstration of the ultrasound technique for this case. Author’s own image.
What is the distribution of anesthesia for a tibial nerve block?
The tibial nerve is one of the two terminal branches of the sciatic nerve (the other being the common peroneal nerve). The block is more accurately termed a ‘posterior tibial nerve block,’ as it targets the continuation of the tibial nerve—the posterior tibial nerve—which runs posterior to the medial malleolus within the tarsal tunnel. The posterior tibial nerve then divides into 3 terminal branches: lateral plantar, medial plantar, and calcaneal. These provide cutaneous sensation to the majority of the plantar surface of the foot. The calcaneal branch provides sensation to the medial portion of the calcaneus (the lateral portion comes from the sural nerve, which receives contributions more proximally from both the tibial nerve and the common peroneal nerve). Therefore, blocking the posterior tibial nerve at the medial malleolus provides comprehensive anesthesia to the entire plantar cutaneous surface and most of the plantar surface of the bones within the foot.
What is the patient positioning and positioning of the ultrasound for this procedure?
Externally rotate the hip of the patient to obtain access to the medial aspect of the lower leg. The operator should stand on the opposite leg of the affected side you want to perform the block. The ultrasound should be positioned across the bed from the operator so that the screen aligns with the operator's vision and the needle. The needle will approach from posterior to anterior.
How can you quickly identify the desired location for the tibial nerve block?
We recommend starting with the probe just above the medial malleolus in a transverse position. Identify the tibial artery, tibial nerve, and tibial veins. Then, slide the probe proximally a few centimeters, tracking the tibial nerve. Injecting 3-5 centimeters proximal to the medial malleolus is technically easier due to increased soft tissue and is more comfortable for the patient.
Image 7. Ultrasound image of the tibial nerve at the medial malleolus, author’s image
Image 8. Ultrasound image of the tibial nerve 3-5cm above the medial malleolus, author’s image
What is the target for your needle for the block?
Insert your needle from posterior to anterior, and advance the needle through the soft tissue and gastrocnemius muscle. Deposit anesthetic below, above, and around the tibial nerve. The goal is to create a “halo” around the nerve. Do not inject directly into the nerve. If you feel resistance with the syringe, this suggests the needle is in the nerve bundle or another important structure.
Image 9. Tibial nerve injection, author’s own image