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to the quadriceps weakness and
atrophy that can result from a
femoral nerve injury.
A recent study
(osmag.net/nJU5nT) by Stanford's
Christopher Webb, MD, and
Edward R. Mariano, MD, concludes that "when not contraindicated,
intraoperative neuraxial anesthesia combined with a continuous
adductor canal block and a multimodal medication regimen for post-
operative pain control is the best analgesic protocol for knee arthro-
plasty."
The block is performed with an injection of local anesthetic at the
mid-thigh. The anatomical boundaries of the adductor canal are the
sartorius muscle medially, the vastus medialis anterolaterally and the
adductor magnus (and femoral artery and vein) posteriorly. The tech-
nique would be very challenging to perform solely with landmarks,
but with high-frequency ultrasound and a little practice, you can easi-
ly visualize the muscles, vessel landmarks, needle and injected local
anesthetic.
The canal contains several nerve branches that provide sensory
innervation to the knee, including the saphenous nerve, the nerve to
vastus medialis and the posterior branch of the obturator nerve. The
saphenous nerve is probably the most important, but the total analge-
sia is likely due to the cumulative effect of blocking all 3 branches.
That's why it's not simply called a "saphenous nerve block" when it's
used for knee analgesia.
How it's done
Here are the steps I use to place non-stimulating adductor canal
catheters pre-operatively, using a catheter-through-needle approach
See How It's Done
See Dr. Winchester's step-by-step video on
how to place an adductor canal block at
bit.ly/blockjocksadductorcanal.