Lesson 42, Topic 6
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42.6 Technique

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Scanning technique

  • Place the transducer transversely over the medial aspect of the knee, approximately 2-3 cm above the patella.

  • Slide the transducer proximally/distally to identify the distal femoral shaft and popliteal artery.

SmM, semimembranosus muscle; PA, popliteal artery; PV, popliteal vein; TN, tibial nerve; CPN, common peroneal nerve.
Tips
If the femoral condyles are initially visualized, slide the transducer proximally until the condyles disappear, and the femoral shaft is identified.
While scanning, routine identification of the saphenous nerve is recommended to avoid its injury during needle insertion.
Use color Doppler to facilitate the identification of the popliteal vessels.

Needle insertion

  • Insert the needle in-plane, from the anteromedial aspect of the knee, toward the space between the popliteal artery and femur. 

  • When the posterior aspect of the popliteal artery is reached, inject 2 mL of the local anesthetic to confirm proper needle position.

SmM, semimembranosus muscle; StM, semitendinosus muscle; PA, popliteal artery; PV, popliteal vein; TN, tibial nerve; CPN, common peroneal nerve.
Tips
Use a steep angle of needle insertion to always stay close to the femoral shaft. This decreases the risk of popliteal nerves and vessel injury.
An adequate spread should layer the local anesthetic in the space between the popliteal artery and femur shaft.

Let’s review the block:

IPACK block; transducer position and sonoanatomy. SmM, semimembranosus muscle; PA, popliteal artery; PV, popliteal vein; TN, tibial nerve; CPN, common peroneal nerve.
IPACK block; Reverse Ultrasound Anatomy. SmM, semimembranosus muscle; StM, semitendinosus muscle; PA, popliteal artery; PV, popliteal vein; TN, tibial nerve; CPN, common peroneal nerve.

Alternative approach

  • Place the transducer over the popliteal fossa crease in order to visualize the tibial nerve, common peroneal nerve, popliteal artery, and femoral condyles.
  • From this location, slide the transducer proximally until the flat posterior aspect of the shaft of the femur becomes visible.
  • Insert the needle in-plane from the medial (or lateral) side, toward the space between the popliteal artery and femur.
  • Inject 1-2 mL of local anesthetic to confirm correct needle position.
  • Complete the block with 15-20 mL.
  • This approach can be performed with the patient either in prone or supine position.

Alternative transducer positions for an IPACK block.