As the name suggests, the local anesthetic is placed between the
posterior capsule of the knee and the popliteal artery. Here, only
the terminal sensory branches of the tibial nerve innervate the pos-
terior knee joint. It is the posterior articular nerve of the tibial
nerve that crosses the posterior capsule at the level of the oblique
popliteal ligament and supplies the capsule and meniscal synovial
junction, cruciate ligaments and the infrapatellar fat pad. This dis-
tribution makes it clear that if adequately blocked, the terminal
sensory branches of the tibial nerve should significantly decrease
posterior knee pain without potentially masking a peroneal nerve
injury.
Step by step
Here's how to administer an iPACK block:
1. Have the patient in the prone position.
2. Scan with the ultrasound probe in the popliteal fossa, just
proximal to the crease, so you find the femoral condyles.
3. From there, move proximal until you can see the shaft of
the femur and the popliteal artery. The goal is to insert the
block needle in a medial to lateral direction between the artery
and the femur.
4. In this area, place 20 to 30 cc of local anesthetic (0.2% ropiva-
caine).
F E B R U A R Y 2 0 1 6 • O U T PA T I E N TS U R G E R Y. N E T • 1 5 3
PROBLEM SPOT
What Is the 'iPACK' Block?
The "iPACK" is an ultrasound-guided infiltration of the interspace
between the popliteal artery and the capsule of the knee with a local
anesthetic solution that provides an alternative analgesic when com-
bined with a femoral nerve block. The new nerve block may provide
an effective option for controlling posterior knee pain following knee
replacement surgery. — Mike MacKinnon, CRNA
• ON TARGET The goal of an "iPACK"
block is to insert the block needle in a
medial to lateral direction between the
popliteal artery and the femur.
