Anatomical Target
The popliteal nerve block or popliteal fossa block describes the block of the distal sciatic nerve in the popliteal fossa. The sciatic nerve at this location is actually two nerves in close apposition, the tibial and common peroneal (fibular) nerves.
- These two nerves usually do not separate until the mid-thigh, although separation as proximal as the pelvis occurs in about 12% of patients.
- 10 cm above the level of the popliteal crease is generally believed to be adequately above the usual branch point for most patients.
- Ultrasound guidance can confirm adequate LA placement around the conjoined sciatic nerve or the tibial and peroneal branches, individually.
Coverage
The sciatic nerve supplies motor innervation to the entire lower leg via the posterior tibial nerve, superficial and deep peroneal nerves. These, along with the sural nerve, also supply sensory innervation to the lower leg, except for the medial inner strip, which is supplied by the saphenous nerve (a branch of the femoral nerve).
In the popliteal fossa, the nerve lies in its most superficial location and can be used to block the entire lower leg, if the nerve is targeted before it splits into its tibial and common peroneal halves. Unlike more proximal approaches to the sciatic nerve, the popliteal nerve block preserves hamstring function, allowing safer post-block ambulation.
Since medial lower leg sensation is supplied by the saphenous nerve, a terminal branch of the femoral nerve, complete anesthesia of the lower leg also requires the blockade of the saphenous (or femoral) nerve.
Indications
- Blockade of the sciatic nerve in the popliteal fossa is well-suited for pathology or surgeries of the lower leg below the knee. Ideal for surgeries or pain conditions of the ankle, achilles tendon and foot.
- Surgery or pain including the medial lower leg will require additional saphenous nerve blockade for complete coverage.
- Pathologies of the knee will need additional femoral nerve coverage as well.
Block Technique
- Patient positioned supine or in the lateral decubitus position, with hip and knee flexed.
- Popliteal artery and vein are easily identified at the level of the popliteal crease allowing the tibial and peroneal nerves to be traced proximally to facilitate blockade prior to branching of the tibial and peroneal nerves.
- Local Anesthetic is being deposited around the distal sciatic nerve as it divides into two distinct fibular and tibial nerves. This split is most commonly seen 5-10 cm above the popliteal crease.
Block Duration
- Sciatic nerve blocks require adequate set-up because this large nerve resists local anesthetic penetration, leading to longer block onset times.
- Duration of the block will depend on the properties of the local anesthetic chosen. With a long lasting local anesthetic such as ropivacaine 0.5%, block duration can last 12 to 24 hours.
- Catheters can be placed and secured for continuous infusion.
Special Considerations
Contraindications
- Coagulopathy
- Pre-existing motor or sensory deficits
- Infection at site of block
- Consider avoidance where sensory blockade might mask compartment syndrome
Side effects
- Side effects are similar for any regional anesthetic technique including:
- Block Failure
- Hemorrhage, bruising, hematoma
- Infection
- Nerve damage
- Local anesthetic (LA) toxicity
- Allergy to LAs
- Caution against bearing weight on the blocked lower extremity for 24 hours due to possible hamstring weakness and risk of falls, recognizing lower risks with more distal sciatic nerve blocks.
Who do I contact if I feel my patient could benefit from a regional anesthesia technique?
Please see the link for the pain team consult service:
https://anesthesia.ucsf.edu/divisions/pain-medicine#for-providers--request-consult-or-refer-a-patient
Defense and Veterans Center for Integrative Pain Management, Chapter 20: Popliteal Nerve Block
NYSORA Textbook of Regional Anesthesia and Acute Pain Management Hadzic A et al. McGraw-Hill, 2017, 2nd Edition, Chapter 33G.
Atlas of Ultrasound-Guided Regional Anesthesia, Gray A et al. Elsevier, 2019, 3rd Edition, Chapter 46: Popliteal Nerve Block.