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wouldn't it be great to block all or
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most of the nerves of the knee without
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getting any motor weakness if you're
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finding that your total knee patients
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just aren't quite as comfortable as they
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could be then this video on janicar
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blocks is for
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[Music]
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you the genicular nerves are often
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Zapped in the pain clinic for chronic
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osteoarthritic pain but for our purposes
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we're going to look at how to Target
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them preoperatively to reduce acute pain
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after total knee arthroplasty you may be
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wondering wait another block for total
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knees we're already doing an adductor
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Canal block and an eyac block right the
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rationale for blocking knees has to do
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with the way the knee is innervated so
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let's take a brief look at that here we
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have a view of the knee joint from the
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back the sciatic nerve descends from the
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thigh splitting into the tibial and
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common peronal nerves and from the
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sciatic nerve or its two components
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arise the genicular nerves that wind
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around from Back to Front here's the
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front view now there are four cardinal
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genic nerves that we're after the
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superomedial and the in medial both come
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off the tibial nerve to inovate the
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medial part of the knee the
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superolateral and infr lateral arise
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from the common peronal nerve to take
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care of the lateral part and then
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because of course we couldn't just have
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an even four we also have the recurrent
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peronal nerve that helps Supply the
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inferior lateral joint structures you
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can see from this figure that these
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contribute significantly to the ination
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of the anterior knee joint of course
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these nerves complement the articular
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fibers that we get from blocking the
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Emeral or a Dr Canal as well as a poal
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plexus which innervates the posterior
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capsule if you want to see how those
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nerves are blocked we have separate
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videos and there are links to those in
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the description so to get back to our
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five genicular nerves note that as is
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often the case these nerves run
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alongside arteries and we'll frequently
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see these as a surrogate Landmark the
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genicular nerve block technique involves
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using ultrasound to visualize the Bony
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anatomy of the knee joint and then
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depositing local anesthetic at each of
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these
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locations so here are the probe
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positions for the two Superior nerves
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the probe is parasagittal and angled at
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30 to 45° so that you're catching the
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interior lateral and interior medial
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femur kind of like the old 10 and two
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o00 clock of the steering wheel you're
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looking for the bright hyper aoic line
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of the femur once you get that you'll
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move the probe distal towards the joint
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until you see the femur flaring up to
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become the
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epicondilite artery that can often be
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seen right where the femur starts to
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slope up although it's not always
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visible the genicular nerves are quite
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small and for that reason we don't try
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to visualize them on ultrasound instead
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the needle is directed to contact bone
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at the bottom of the slope in the
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general vicinity of the artery I find it
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much easier and faster to advance a
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needle out of plane while you may not
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see the shaft of your needle the end
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point for advancement is bony contact so
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it's less important once we hit the bone
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we'll aspirate and then inject about 3
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to 4 MS of local anesthetic then we'll
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do the superior lateral genic block on
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the other side of the femur it's pretty
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much a mirror image of the superior
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medial
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one for the inferomedial we'll image the
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slight depression on the flare of the
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tibia if you're going to see a genicular
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artery this is often the one you'll see
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come in out of plane and land in the
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depression this is the shallowest block
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and there's not much tissue there so
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sometimes we'll only inject about 2 to 3
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MLS and now we'll get the last two
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nerves with one probe position we'll
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start by placing the probe over the head
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of the fibula from the lateral side of
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the knee the rounded fibular head is an
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easy starting Landmark then I'll slide
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the probe superiorly and slightly
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medially so I'm Imaging a bony hump the
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proper name is gery's tubercle it's a
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prominence on the tibia where the IT
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band inserts on the proximal side of the
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hump you can often see the IT band and
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the genic vessels trapped in the soft
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tissue space beneath a needle can be
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Advanced out of plane to pass just
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beneath the band and 3 to four Ms here
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fills that space and blocks the inferior
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lateral genicular nerve next we'll go
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back to the hump and move distally we
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can see the fibers of the tibialis
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anterior muscle here and the slope of
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the lateral proximal tibia we want to
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drive a needle out of plane down to that
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slope and place 3 to four Ms of local
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there once again we can frequently see
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genicular vessels to guide us but if not
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just land on the slope and lift the
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muscle up we like to use a total of 20
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Ms of local anesthetic here preferably
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something long acting we'll use about 3
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to four MLS for each of the five blocks
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these blocks BLS are easy to do anytime
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the endpoint is hit a bone it's pretty
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simple to teach and learn and they can
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be done in about 90 seconds from start
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to finish the next question is do they
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work well they sure do this randomized
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controlled double blind study compared
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patients who received genic blocks with
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qu% bivan to those who received sham
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saline blocks every patient got a
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standard general anesthetic and inductor
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Canal catheter and an iack block the
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group who got the real genicular blocks
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used 60% Less open oids in the first 24
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hours and 50% Less in the second 24
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hours for an intervention that takes
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less than 2 minutes to do that's a lot
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of bang for your
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buck here are some things we learned
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along the way despite it being the
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biggest long bone it's surprisingly easy
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to miss the femur toggle the probe back
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and forth until you see the bright white
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line that represents the beam hitting
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the cortex directly the hazy structures
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either side represent the beam catching
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the femur tangentially second remember
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that without out of plane you want to
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keep your needle angle as close to the
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beam as possible otherwise you may miss
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the femur entirely there has been a
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concern raised about targeting the
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inferior lateral and recurrent peronal
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nerves when using neuroablative
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techniques because of the proximity to
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the common peronal nerve nobody will
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thank you for causing a long-term foot
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drop but using the technique we
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described with a small dose of local
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anesthetic and ultrasound guidance we
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just don't see this and for that reason
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we do perform the inferior lateral
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blocks like a lot of bony contact blocks
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the muscle can be adherent to the Bone B
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we like to use saline to test if our
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needle tip is truly on the periostium
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that way we're not wasting local
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anesthetic if we do see intramuscular
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spread it's useful to do a little
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twizzle with the needle to break through
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those last few layers of soft
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tissue because we're doing these close
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to the Joint we are super attentive to
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sterile technique use a probe cover
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sterile gloves and lots of skin prep to
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avoid the risk of joint infection
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finally while we're in the vicinity we
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also block the nerve to vastest
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intermediates just above the knee it
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lies in a reliable location running
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along the anterior surface of the
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femoral shaft and it's easy to Target
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while you're doing the genics bring the
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needle down out of plane and place the
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usual 3 to four Ms there if you've been
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counting that's a total of six
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injections of 3 to 4 MLS so one 20 mil
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stick of local anesthetic is absolutely
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sufficient genic blocks are safe easy
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and have contributed significantly to
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our patients Comfort after total knee
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replacement if you're doing an inductor
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Canal block ey pack and genitors you've
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almost completely blocked the knee in a
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way that allows for maximum Comfort
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afterwards I say almost because there's
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one more set of simple blocks that we
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use to get even more pain relief with
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knee patients the anterior femoral
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cutaneous nerves to learn about those
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check out this
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video
