Popliteal Block - Hospital for Special Surgery - Anesthesiology Department - anesthesiology, anesthesia, anesthesiologists, anesthesia specialties, new york, manhattan, radiology, musculoskeletal imaging, ct scan, spiral ct scanning, ultrasound

Popliteal Block

Indications

Set-Up

Insulated 22G stimulating needle 2 inch long or 18G 2 inch Insulated Tuohy Needles for continuous nerve blocks.
For fast onset of surgical anesthesia 40-60 ml 1.5% mepivacaine with bicarbonate and epinephrine. For pain management, 30-40 ml 0.5% ropivacaine or bupivacaine.

Essential Anatomy for Posterior Approach

Technique for Posterior Approach

Place the patient prone with the leg extended in the knee joint and the long axis of the foot perpendicular to the horizontal plane.
Mark the anatomical landmarks and initial puncture site which is midpoint between the semitendinosus and biceps femoris muscle tendon 7 cm above the popliteal fossa crease.
Prepare the skin with Betadine solution.
Infiltrate the skin with local anesthetic at the injection site 7 cm above the popliteal fossa crease between tendos of biceps femoris and semitendinosus muscles using 25G needle.
Initially set the nerve stimulator current at 1.5 mA (preferably 2Hz).
Insert the stimulating needle through the initial puncture site at the midpoint between the two tendons (biceps femoris and semitendinosus), 7 cm above the popliteal fossa crease.
Advance the block needle slowly, perpendicular to the horizontal plane, while seeking a plantar or dorsiflexion of the foot or toes.
After obtaining appropriate twitches, adjust the stimulating current down to or less than 0.4 mA and after negative aspiration, inject 30-60 cc of local anesthetic of choice.
The appropriate response is dorsiflexion and eversion (common peroneal nerve) plantarflexion inversion (post tibial nerve).

Essential Anatomy for Lateral Approach

Technique for Lateral Approach

Place the patient supine with the leg extended at the knee joint and the long axis of the foot perpendicular to the horizontal plane.
Mark the crease formed by the Vastus Lateralis and the Biceps Femoris muscles and the initial puncture site which is 8-10 cm proximal to the femoral head (or the popliteal fossa crease)
Prepare the field as described for the posterior approach.
Insert the stimulating needle through the initial puncture site perpendicularly to the skin and advance it until contact is made with the femur.
Withdraw the needle to the skin, and angle it 40°posteriorly relatively to the horizontal plane.
Advance the needle slowly 1-2 cm deeper than the distance at which the femur was contacted, while seeking a plantar dorsiflexion and eversion (common peroneal nerve) or a plantarflexion inversion (post tibial nerve) of the foot or toes.
If the popliteal nerve is not stimulated, withdraw the needle to the skin and reinsert, first 5 to 10 degrees posterior relative to the initial insertion (40°) plane. If these redirections do not result in nerve localization, repeat the same insertion technique through new skin punctures in 5 mm increments posterior to the initial 40° insertion plane.
After obtaining appropriate twitches, adjust the stimulating current down to or less than 0.4 mA and after negative aspiration, inject 30-60 cc of local anesthetic of choice.

Limitations

Patients with coagulation abnormalities.
Possible masking of compartment syndrome symptoms, can limit its use to foot/ankle procedures.

Complications

As in all peripheral nerve blocks, nerve injury from needle trauma, intraneural injection, or local anesthetic toxicity.
Hematoma formation from inadvertent popliteal artery puncture.

Pearls

If the nerve is not localized on the first needle pass, withdraw the needle slowly to the skin and reinsert through the same skin puncture at an angle 5 to 10 degrees laterally to the first insertion plane.
If the popliteal nerve stimulation is not obtained on the first attempt (skin puncture) remove the stimulating needle from the skin and insert it 5 mm laterally to the initial skin puncture. This technique should be repeated using the same maneuvers through new insertion sites in 5 mm incremental lateral insertions, until the desired response is obtained.
Remember that when the surgery involves the medial aspect of the lower leg, supplementary block of the saphenous nerve is needed. This can be done at the level of the tibial tuberosity, or at the level of the medial malleolus, or around the saphenous vein, using 8 to 10 mL 0.5-1% ropivacaine or 0.5- 0.75% bupivacaine.

References

Kilpatrick AW, Coventry DM, Todd JG,: A comparison of two approaches to sciatic nerve block. Anaesthesia 47(2):155-7 (1992).

These technique descriptions are presented for educational purposes and are not intended to substitute for actual hands-on training.