Unit 8 - Lower Extremity Blocks Flashcards
A = lateral femoral cutaneous
B = obturator
C = saphenous
D = superficial peroneal
nerves anesthetized by a 3-in-1 femoral n. block
femoral n.
lateral femoral cutaneous n.
obturator n. (commonly missed)
which nerve innervates this osteotome
superficial peroneal n.
which nerve is anesthetized by injecting LA into the plane of the line between the Achilles tendon and lateral malleolus
sural n.
LA is injected around which nerves for a popliteal block
common peroneal n.
tibial n.
assessing which movement is the best way to assess femoral n. block
knee extension
the sural n. is formed by collateral branches of what 2 nerves
tibial n
common peroneal n
largest peripheral nerve in the body
sciatic nerve
6 terminal branches of the lumbar plexus
Iliohypogastric
Ilioinguinal
Genitofemoral
Lateral femoral cutaneous
Obturator
Femoral
I
Invariably
Get
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On
Fridays
2 plexuses that innervate lower extremities
sacral plexus
lumbar plexus
where does the lumbar plexus originate
from anterior rami of L1-L4 (+T12 contribution in ~50% of the population)
what does the lumbar plexus primarily innervate
front of leg
origin of sacral plexus
originates from anterior rami of L4-S4
primary innervation of sacral plexus
back of leg
where does the lumbar plexus form
within psoas muscle and passes in front of quadratus lumborum
which nerve roots give rise to lateral femoral cutaneous n.
L2-L3 (posterior divisions)
which nerve roots give rise to femoral n.
L2-L4 (posterior divisions)
which nerve roots give rise to obturator n.
L2-L4 (anterior divisions)
where does lateral femoral cutaneous n form
midpoint of psoas muscle
where does femoral n form
near middle and lower third of psoas
branch of femoral n. that gives rise to saphenous n
posterior branch
where does obturator n form
medial border of psoas at level of SI joint
nerve often injured in pts undergoing extensive pelvic surgery
obturator
where does sacral plexus form
anterior to psoas major
5 major branches of sacral plexus
Superior gluteal
Inferior gluteal
Posterior cutaneous
Pudendal
Sciatic
SIPPS
trunks that comprise sciatic n
tibial
common peroneal/fibular
where does sciatic n divide into tibial & common peroneal nerves
proximal popliteal fossa
where does tibial n arise from
anterior branches of L4-S3
where does common peroneal n arise from
posterior branches of L4-S3
3 terminal branches of common peroneal n.
Deep peroneal n.
Superficial peroneal n.
Sural n.
terminal nerves at ankle that originate from sciatic n.
Superficial peroneal
Deep peroneal
Sural
Posterior tibial
primary nerves of coccygeal plexus
pudendal
inferior anal
perineal
sensory innervation of L2 dermatome
upper medial thigh
sensory innervation of L3 dermatome
lower medial thigh
sensory innervation of L4 dermatome
lateral thigh + anterior knee
sensory innervation of L5 dermatome
lateral lower leg + top of foot
sensory innervation of S1 dermatome
posterior leg (more lateral)
sensory innervation of S2 dermatome
posterior leg (more medial)
peripheral nerves from lumbar plexus that are sensory only
lateral femoral cutaneous, saphenous, sural
sensory & motor innervation of femoral n.
sensory = anterior thigh, medial leg
motor = hip flexion/lateral rotation, knee extension + flexion
sensory & motor innervation of obturator nerve
sensory = hip joint, medial thigh
motor = hip ADDuction, flexion, & extension
sensory innervation of lateral femoral cutaneous n
lateral thigh to knee
no motor
sensory & motor innervation of pudendal n
sensory = perineum, anal canal, external sphincter
motor = anal sphincter tone
sensory innervation of posterior femoral cutaneous n
posterior hip to midcalf
sensory & motor innervation of superficial peroneal n
sensory = dorsal surface of foot
motor = ankle eversion
sensory innervation of deep peroneal n.
web space between big toe and 2nd toe
motor innervation of tibial n
Toe: ABduction + ADDuction + extension + flexion
Ankle: plantar flexion
motor innervatin of sciatic n
hip extension
knee flexion
peripheral nerve responsible for sensory innervation of dorsal surface of foot
superficial peroneal n
peripheral nerve responsible for hip flexion and knee extension
femoral n
peripheral n responsible for hip extension and knee flexion
sciatic n
peripheral n responsible for plantar flexion
tibial n
peripheral nerve responsible for dorsiflexion
peroneal n
peripheral nerve responsible for ankle eversion
superficial peroneal n
peripheral nerve responsible for ankle inversion
deep peroneal n
nerves that innervate the hip joint
femoral
obturator
sciatic
nerve that innervates the biceps femoris, semitendinosus, and semimembranosus
sciatic n
spinal nerve roots posterior femoral cutaneous n arises from
S1-S3
spinal nerve roots lateral femoral cutaneous n arises from
L2-L3
provides sensory and motor innervation to lower abd wall, anteromedial thigh, and knee
lumbar plexus
provides sensory and motor innervation to gluteal region, posterior thigh, lower leg, and foot
sacral plexus
A = lateral femoral cutaneous n
B = femoral n
C = posterior femoral cutaneous n
D = obturator n
E = saphenous n
F = common peroneal n
G = superficial peroneal n
H = deep peroneal n
I = sural n
J = medial calcaneal n
K = lateral plantar n
L = medial plantar n
how to assess motor function of femoral n
hip: flexion & rotation
knee: extension & flexion
how to assess function of obturator n
hip adduction, flexion, & extension
how to assess function of pudendal n
anal sphincter tone
how to assess function of sciatic n
hip extension
knee flexion
how to assess function of tibial n
toe abduction, flexion, & extension
ankle plantar flexion
how to assess function of superficial peroneal n
ankle eversion
how to assess function of deep peroneal n
ankle dorsiflesion + inversion
objective of PENG block
inject LA deep into psoas tendon at level of iliopubic prominence
PENG block indications
hip fracture, hip arthroplasty
why are high conncentrations of LA not required for PENG block
LA volume for PENG block
30-40 mL
what is the iliopublic eminence
junction of ilium and pubis
what does PENG block target
articulating branches from lumbar plexus that supply only sensory innervation to hip capsule
*Femoral nerve is spared
why are high concentrations of LA not required for PENG block
analgesic block (not anesthetic)
PENG block complications
few
direct injection in psoas = quad weakness
ureter injury
3 nerves targeted by fascia iliaca block
femoral, obturator, lateral cutaneous
advantages of fascia iliaca block over lumbar plexus block
faster and more consistent blockade of femoral & lateral cutaneous nerves
increases risk of ureter injury with PENG block
Inserting needle above level of inguinal ligament & advancing too
fascia iliaca block indications
- Surgical procedures of femur, quadriceps, knee
- Acute pain management for hip fractures
lower extremity block only performed with US
PENG
objective of fascia iliaca block
deposit LA below fascia iliaca that travels towards lumbar plexus
transducer used for fascia iliaca block
high-frequency linear array transducer in a sagittal orientation
total LA volume for fascia iliaca block
40 mL
landmarks for fascia iliaca block
ASIS
pubic tubercle
sartorius
internal oblique
sartorius & IO form “bowtie”
when is LOR felt with fascia iliaca block (landmark technique)
as needle passes through fascia lata
2nd loss of resistance as it pierces fascia iliaca
what happens if you if needle inserted too superficially and medial to femoral nerve for fascia ilacia block
stimulation of sartorius mucle (inner thigh twitching)
If it happens, withdraw needle and advance slightly laterally until you obtain a ‘patellar snap’
what happens if you if needle inserted too superficially and medial to femoral nerve for fascia ilacia block
stimulation of sartorius mucle (inner thigh twitching)
If it happens, withdraw needle and advance slightly laterally until you obtain a ‘patellar snap’
fascia iliaca block complications
failed/incomplete block if LA injected above fascia
LAST
quad weakness
where do L2-L4 roots merge to form femoral n
in psoas major
borders of femoral triangle
- Sartorius muscle
- Adductor longus muscle
- Inguinal Ligament
“SAIL”
borders of femoral triangle
- Sartorius muscle
- Adductor longus muscle
- Inguinal Ligament
“SAIL”
anatomic structures inside the femoral triangle
femoral vein
femoral artery
femoral nerve
where does femoral n divide into anterior and posterior branches
once under the inguinal ligament
best assessment of femoral n block
assess knee extension
what does the anterior branch of femoral n innervate
ventral surface of the thigh and sartorius muscle
what does the posterior branch of femoral n innervate
quadriceps muscle, knee joint, and its medial ligament
combination of what 2 blocks provides almost complete surgical coverage to lower extremity
femoral + sciatic blocks
can femoral n block be used for surgical anesthesia?
nope, not alone
combine with sciatic block
can femoral n block be used for surgical anesthesia?
nope, not alone
combine with sciatic block
femoral n block indications
- Surgical anesthesia & analgesia for procedures involving hip, femur, quadriceps, and knee
- acute pain management for hip fractures
position for femoral n block
supine position with slight external extremity rotation
transducer used for femoral n block
high-frequency linear array transducer (10-12 MHz) in transverse orientation
major anatomical landmarks for US-guided femoral n block
femoral artery
femoral vein
femoral n
LA volume for femoral n block
20-30 mL
regardless of technique, needle must penetrate ____ to ensure efficacious block
fascia lata & fascia iliaca
indicates proper needle placement for nerve stim. guided femoral n block
quadriceps contraction
3-in-1 block approach to femoral n is designed to block what 3 nerves
femoral n
lateral femoral cutaneous n
obturator n (often missed)
why is femoral block assoc with falls
quadriceps weaness
boundaries of femoral triangle
- Base of triangle = inguinal ligament
- Medial side of triangle = Medial aspect of sartorius
- Lateral side of triangle = medial aspect of adductor longus
nerves in adductor canal
- saphenous n. (terminal branch of femoral n.)
- the nerve that innervates the vastus medialis (branch of posterior femoral n.)
lateral wall of adductor canal
vastus medialis
where does the femoral artery become popliteal artery
popliteal fossa
indications for adductor canal block
ACL repair, MCL repair, patella fracture, vein stripping & harvesting, supplementation to sciatic nerve block for foot/ankle surgery
transducer used for adductor canal block
high-frequency linear array transducer (10 - 12 MHz) in transverse orientation
May need a lower frequency for patients with increased body habitus
transducer used for adductor canal block
high-frequency linear array transducer (10 - 12 MHz) in transverse orientation
May need a lower frequency for patients with increased body habitus
how does saphenous n appear on US in adductor canal approach
hyperechoic - anterolateral to artery
LA volume for adductor canal lbock
15-20 mL
increases likelihood of quadriceps weakness with adductor canal block
proximal injections and local anesthetic volumes that exceed 20 mL
where is the popliteal fossa formed
between muscles in posterior compartment of the lower extremity
key anatomic landmarks for popliteal block
- Popliteal artery & vein
- Biceps femoris, semitendinosus, semimembranosus muscles
- Bifurcation of sciatic n. into common tibial n. and common peroneal n.
where does the sciatic n become superficial and divide into tibial & common peroneal n
approx 7-10 cm proximal to popliteal fossa
how to identify the approximate location of the sciatic nerve
by finding the ‘triangle’ in the posterior knee created by the popliteal crease (the base) and the convergence of the biceps femoris and semitendinosus muscles (the apex)
target of popliteal block
sciatic nerve branches in proximal popliteal fossa
indications of popliteal n block
- Provides pain control for below-the-knee surgical procedures (ankle surgery, Achilles repair, foot surgeries)
- Helps manage acute pain
- Combined with saphenous n. block, provides complete coverage of lower extremity and knee
how does tibial n appear on US for popliteal block
hyperechoic structure dorsal and lateral to anechoic artery and vein in popliteal fossa
what positions can patient be in for an US-guided popliteal block
prone, lateral, or supine
total LA volume for popliteal block
25 mL
optimal location for LA placement for popliteal block
point where sciatic n. divides into TN & CPN
Some use PNS with US
main drawback of popliteal block
foot drop
numbness of sole
may contribute to patient falls
main drawback of popliteal block
foot drop
numbness of sole
may contribute to patient falls
5 nerves blocked for a total ankle block
- saphenous
- sural
- superficial peroneal
- deep peroneal
- posterior tibial
nerves of ankle block that are sensory only in the ankle and foot
saphenous
sural
superficial peroneal
mnemonic for nerves and actions at ankle/foot
TIPPED
Tibial: Inversion, Plantarflexion
Peroneal: Eversion, Dorsiflexion
landmarks for ankle block -posterior tibial n
posterior tibial artery
achilles tendon
medial malleolus
landmarks for ankle block - sural n
lesser saphenous vein
Achilles tendon
lateral malleolus
landmarks for ankle block - deep peroneal n
medial malleolus
tendons of anterior tibial & long mucles of great toe
landmarks for ankle block - superficial peroneal n
lateral malleolus
landmarks for ankle block - saphenous n
greater saphenous vein, medial malleolus
nerves of ankle block in close proximity to arteries
posterior tibial n. (posterior tibial a.)
deep peroneal n. (anterior tibial a.)
sensory and motor functions of deep peroneal n.
- Sensory innervation = Lateral side of the great toe (hallux),medial side of the 2nd digit
- Motor innervation = eversion + dorsiflexion
sensory and motor innervation of posterior tibial n.
- Sensory innervation = Sole of the foot
- Motor innervation = Inversion + plantar flexion
transducer used for ankle blocks
- high-frequency (10-12 MHzO) linear array
- Use a small footprint transducer, such as a “hockey stick,” to reduce the incidence of air artifact due to the limited surface area of the ankle.
equipment needed for ankle block with landmark technique
10 mL syringe with 1.5” 25g needle
nerve stimulation not necessary
nerves of ankle block that can be blocked without removing the needle (one skin puncture)
deep peroneal, superficial peroneal, and saphenous nerves
LA volume of ankle block
3-5 mL per nerve
where must LA reach to anesthetize sural n
superior border of lateral malleolus (landmark technique)
goal of LA distribution in US-guided sural n block
circumferential spread around lesser saphenous vein
complication of nerve blocks
vascular injury (except superficial peroneal n)
nerve compression/ischemia
avoid excessive LA volumes, vasoconstrictors
complication of nerve blocks
vascular injury (except superficial peroneal n)
nerve compression/ischemia
avoid excessive LA volumes, vasoconstrictors
where is the lumbar plexus contained
within a sheath inside psoas compartment
location of lumbar plexus within the psoas compartment
- Lateral to the vertebral column
- Anterior to the quadratus lumborum muscle
- Posterior to the psoas muscle
3 major nerves targeted by psoas compartment (lumbar plexus) block
- lateral femoral cutaneous n
- femoral n
- obturator n
patient position for lumbar plexus block
lateral decubitus - block side up
landmarks for lumbar plexus block
intercristal line/L4-L5 interspace
PSIS
point of needle entry for lumbar plexus block
3 cm caudad from L4 and 5 cm lateral from the midline.
mean skin to lumbar plexus depth
8 cm
total LA volume for lumbar plexus block
20-30 mL
complications of lumbar plexus block
- sympathectomy of ipsilateral extremity
- retroperitoneal hematoma
- renal capsular injection
what increases risk of bilateral extremity spread in lumbar plexus block
LA volumes > 20 mL
contraindication to lumbar plexus block
coagulopathies
nerve roots that contribute to sciatic nerve
L4-L5 and S1-S3
where does the sciatic nerve divides into tibial and common peroneal nerves
As it passes between the major trochanter and the tuberosity of the ischium into the lower third of the thigh
uses of sciatic n block by itself
useful for procedures on the back of the thigh, lower leg, ankle, and foot
sciatic n. block approach often combined with femoral n block to provide complete coverage for TKA
posterior landmark approach (Labat approach)
landmarks for sciatic n block
greater trochanter
PSIS
sacral hiatus
what motor response is desired when using nerve stimulation for a sciatic n block
dorsiflesion or plantarflexion
For surgical anesthesia, plantar flexion (foot inversion) is preferred
what motor response is desired when using nerve stimulation for a sciatic n block
dorsiflexion or plantarflexion
For surgical anesthesia, plantar flexion (foot inversion) is preferred
at the level of the ankle, which nerve is not immediately adjacent to a vascular structure
superficial peroneal n.
