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Lumbo-Sacral Lower Extremity Nerve Blocks
needles, drugs, and nerve stimulators, OH MY!
92
Medical
Graduate
08/02/2010

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Term
The Lumbo-Sacral Plexus involves what spinal cord segments
Definition
L2 --> S3
Term
The Lumbo-Sacral Plexus is 'sandwiched' between what 3 muscles?
Definition
psoas
quadratus lumborum
iliac
Term
T/F: The lumbo-sacral anatomy is not as conducive to plexus anesthesia as in the neck, and therefor is sometimes unreliable.
Definition
TRUE
Term
These nerve roots are known as the "upper nerve roots"
Definition
L2-L4
Term
Form the lumbar portion of the Lumbar Plexus
Definition
L2 - L4, upper nerve roots
Term
The Lumbar Plexus gives off what 3 nerves?
Definition
Lateral Femoral Cutaneous
Femoral Nerve
Obturator Nerve
Term
What spinal segments form the Lateral Femoral Cutaneous (LFC) nerve?
Definition
L2 & L3
Term
What spinal segments form the Femoral nerve?
Definition
L2, L3, & L4
Term
What spinal segments form the obturator nerve?
Definition
L2, L3, & L4
Term
T/F: The femoral and obturator nerves are formed by the same spinal segments.
Definition
TRUE; L2, L3, & L4
Term
What 3 nerves supply the upper, anterior leg?
Definition
LFC, Femoral, Obturator
Term
What branch of the Femoral nerve extends medially below the knee to the foot?
Definition
saphenous nerve
Term
What nerve roots, known as the "lower Nerve roots" form the sacral plexus?
Definition
L4 --> S3
Term
The sciatic nerve is formed by what 5 spinal segments?
Definition
L4, L5, S1, S2, & S3
Term
The sciatic nerve divides to form what 2 nerves?
Definition
Tibial
Common Peroneal
Term
This nerve is often injured while a patient's leg is placed in stirrups
Definition
Common Peroneal
Term
These nerves provide the bulk of innervation below the knee
Definition
Tibial
Common Peroneal
Term
This nerve and its branches supply the posterior leg
Definition
Sciatic
Term
The Lumbo-Sacral plexus is wedged between the fascia of the quadratus lumborum and the iliacus ___________, and the psoas ____________.
Definition
posteriorly, anteriorly
Term
Arises from the posterior divisions of L2, L3, & L4
Definition
Femoral nerve
Term
Enters the thigh beneath the inguinal ligament
Definition
Femoral nerve
Term
The femoral nerve sends fibers to what 3 muscles?
Definition
sartorius
quadriceps
pectineus
Term
T/F: The femoral nerve lies anterior and slightly lateral to the femoral artery.
Definition
FALSE; posterior
Term
The main trunk of the femoral nerve
Definition
saphenous nerve
Term
Provides sensory innervation to the medial calf all the way to the medial aspect fo the foot
Definition
Saphenous nerve
Term
Formed by the posterior divisions of L2 and L3 within the substance of the psoas muscle
Definition
Lateral Femoral Cutaneous nerve
Term
Passes laterally just beneath the rim of the pelvis to enter the thigh close to the ASIS beneath and medial to the inguinal ligament
Definition
LFC
Term
Sensory branches of what nerve are distributed to the lateral buttock and thigh and occasionally as far as the knee?
Definition
LFC
Term
Arises from the anterior branches of L2, L3, & L4
Definition
Obturator nerve
Term
Forms a common trunk in the substance of the psoas
Definition
Obturator
Term
Emerges from the medial border of the psoas to enter the pelvis
Definition
Obturator
Term
Leaves the pelvis through the obturator foramen/canal to enter the thigh
Definition
Obturator
Term
Terminates by giving sensory innervation to most of the medial portion of the thigh
Definition
Obturator
Term
The obturator nerve gives branches to what 3 muscles and what joint?
Definition
external obturator
gracilis
adductor muscles

hip
Term
T/F: The posterior division of the obturator nerve supplies an articular branch to the knee joint.
Definition
TRUE
Term
T/F: The sciatic nerve is the largest nerve in the body at approximately 4 cm wide.
Definition
False, ~ 2 cm
Term
This nerve passes out of the pelvis through the greater sciatic notch
Definition
Sciatic
Term
The sciatic nerve is composed of what 2 major nerve trunks?
Definition
Lateral
Medial
Term
Formed from the nerve roots of L4-S2, and eventually becomes the common peroneal nerve
Definition
Lateral trunk (of sciatic nerve)
Term
Formed from the nerve roots of L3 - S3, and eventually becomes the tibial nerve
Definition
Medial Trunk (of the Sciatic nerve)
Term
These combined nerves exit through the sciatic notch and pass anteriorly to the piriformis muscle between the ischial tuberosity and the greater trochanter of the femor
Definition
Common peroneal/tibial
Term
Divide into their respective nerves at about the lower-third of the thigh
Definition
tibial/common peroneal
Term
Curve caudad and descend to the posterior thigh immediately behind the femor
Definition
common peroneal, tibial
Term
What are the landmarks for a lumbar plexus block and where is the needle insertion point?
Definition
spinous process in the midline
iliac crest

needle insertion point --> 4 cm lateral to the intersection of the the above landmarks
Term
This perivascular approach to blocking the lumbar plexus involved a single injection below the inguinal ligament
Definition
Three-in-One
Term
The 3-in-1 block entails blocking what nerves?
Definition
Femoral
LFC
Obturator
Term
In combination with _____________________, the 3-in-1 technique will anesthetize the entire lower extremity.
Definition
sciatic nerve block
Term
How is the patient positioned for a 3-in-1 block?
Definition
Supine, with thigh abducted ~ 15 degrees
Term
How is the patient positioned for a lumbar plexus block?
Definition
Lateral decubitus
Term
List 4 common drugs and their dosages for the 3-in-1 technique per Winnie
Definition
1.5% Lidocaine 25-30 mL
1.5% Mepivacaine 25-30 mL
0.5% Bupivicaine 25-30 mL
1.0% Etidocaine 25-30 mL (no longer used)
Term
Catheter is inserted cephalad effectively anesthetizes the iliohypogastic and genitofemoral nerves (branches of T12 & L1 respectively)
Definition
Psoas compartment block
Term
Two disadvantages of 3-in-1 block
Definition
in combo with sciatic nerve block may lead to systemic reactions --> large volumes of local anesthestics
nerve damage if intraneural injection
Term
Why may the 3-in-1 block be more appropriately called the 2.5-in-1 block?
Definition
Because the posterior branch of the obturator nerve is seldom blocked.
Term
The 3-in-1 block is the simplest to perform use a/an ________________ technique.
Definition
Ultrasound
Term
What block, when used alone, is well suited for procedures of the anterior aspect of the thigh and for postop pain relief after femur and knee surgery?
Definition
Femoral nerve block
Term
Where is the needle inserted when performing a femoral nerve block
Definition
The needle is inserted below the inguinal crease and immediately lateral (~ 1 cm) to the pulse of the femoral artery.
Term
Where is the needle inserted when performing a block of the LFC?
Definition
Inserted perpendicular to the skin at a point ~0.5 - 1 inch medial to the ASIS and just inferior to the inguinal
ligament

(medial and deep to ASIS)
Term
Anesthesia of this nerve is necessary for surgery of the knee, but is more challenging because of its deeper location and early branching pattern.
Definition
Obturator nerve
Term
A valuable technique in diagnosing painful conditions of the hip and in relief of adductor spasm of the hip.
Definition
Obturator nerve block
Term
Provides motor function to the adductor muscles and cutaneous sensation to a small area behind the knee.
Definition
Obturator nerve
Term
Describe the patient positioning for obtuator nerve block.
Definition
Supine with legs slightly spread
Term
What landmark is first identified when performing an obturator nerve block?
Definition
Lateral pubic turbercle on side to be blocked
Term
Describe the steps of blocking the obturator nerve.
Definition
1) 22g, 3-in needle is introduced at a point ~1.5 cm below and 1.5 lateral to the pubic tubercle.
2) The needle is slowly advanced until it contacts bone (inferior ramus of the pubis)
3)Redirecting the needle slightly lateral and caudad will move it off the bone and into the obturator foramen
4)The needle is advanced further 2-3 cm and after careful aspiration, 10-15 mL of local anesthetic is injected as the needle is withdrawn and again as it is reinserted with a slight lateral direction.
Term
Provides innervation to the posterior aspect of the lower extremity
Definition
Sciatic nerve
Term
The classical posterior approach to blocking the sciatic nerve requires that the patient....
Definition
be able to lie in the lateral position and flex the hip & knee.
Term
Name the 3 landmarks when blocking the Sciatic nerve using the classical posterior approach?
Definition
The greater trochanter of the femur
Posterior Superior Iliac Spine (PSIS)
Tip of the Coccyx (or sacral hiatus)
Term
Name the 3 landmarks when blocking the Sciatic nerve using the classical posterior approach?
Definition
The greater trochanter of the femur
Posterior Superior Iliac Spine (PSIS)
Tip of the Coccyx (or sacral hiatus)
Term
In the popliteal fossa, the sciatic nerve is positioned between the _______ and __________________ muscles.
Definition
biceps and semitendinosus muscles
Term
What size stimulating needle is used when using a lateral mid-femoral approach to block the sciatic nerve?
Definition
10 cm
Term
What the 3 landmarks for a lateral mid-femoral approach/popliteal block?
Definition
popliteal fossa crease
vastus lateralis muscle
bicpes femoris muscle
Term
Where is the needle inserted when performing a lateral mid-femoral approach/popliteal block?
Definition
In the groove between the vastus lateralis and biceps femoris muscles.
Term
Twitches of the ____ or _____ denote correct needle placement when performing a lateral mid-femoral approach/popliteal block.
Definition
foot or toes
Term
T/F: The tibial nerve is larger than the common peroneal nerve.
Definition
TRUE
Term
Posteriorly in the popliteal fossa, the sciatic nerve components are ________ and ______________ to the popliteal artery and vein.
Definition
Lateral and superficial
Term
Where is the needle insertion site when performing a posterior approach/popliteal fossa block?
Definition
7 cm above the popliteal fossa crease at the midpoint between the biceps femoris tendon and semitendinosus muscle tendon
Term
What are the 4 P's of assessing blockade of the lower extremity?
Definition
Push, pull, pinch, punt
Term
'Push'
Definition
to evaulate sciatic nerve anesthesia
Term
'Pull'
Definition
to evaluate obturator nerve anesthesia
Term
'Pinch'
Definition
to evaulate LFC nerve anesthesia
Term
'PUNT'
Definition
to evaluate femoral nerve anesthesia
Term
"step on the gas"
Definition
Push
Term
Evaluates plantar flexion which is controlled by the sciatic nerve
Definition
'Push'
Term
To assess ____________ nerve function, the clinician abducts the patient's leg and then asks them to PULL the leg back toward the midline against resistance.
Definition
Obturator
Term
Sensory innervation to the lateral buttcocks and lateral thigh
Definition
LFC
Term
The inability of the patient to detect a PINCH on the proximal thigh signals successful conduction block of the _______.
Definition
LFC
Term
Provides motor innervation to the quadriceps and sartorius muscles.
Definition
Femoral nerve
Term
Provides sensory innervation to the anterior thigh, branches of the hip joint and the majority of the knee joint.
Definition
Femoral nerve
Term
"Punt an imaginary football" against resistance
Definition
Assesses femoral nerve function
Term
T/F: The 4-P's take advantage of the principle that outer 'mantle' fibers (i.e., "motor) are anesthetized first, before the 'core' fibers which are sensory and located more distally.
Definition
TRUE
Term
The sciatic nerve is formed by all of the following nerve roots EXCEPT
A) L3
B) L4
C) L5
D) S1
E) S2
Definition
A) L3
Term
The obturator nerve
A) is unimportant in arthoscopic surgery of the knee
B) supplies motor innervation to the adductor muscles of the hip
C) supplies sensory innervation to the skin overlying the patella
D) is derived from the first and second sacral roots
E) supplies sensory innervation to the lateral aspect of the knee
Definition
B) The obturator nerve supplies motor innervation to the adductor muscles of the hip and sensory innervation to the medial aspect of the knee.
Term
The relationship of the femoral nerve in the inguinal area is that it lies
1) superficial to the inguinal ligament
2) lateral to the femoral artery
3) medial to the femoral vein
4) lateral to the obturator nerve
Definition
C) The femoral nerve lies lateral to the femoral artery and lateral to the obturator nerve. The femoral vein lies medial to the femoral nerve, and the inguinal ligament is superficial to the femoral nerve.
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