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Lower Extremity Block. A.Ghaleb,M.D. Associate professor Medical director Acute and chronic Pain management Dept. of Anesthesiology UAMS. Lumbar plexus. The lumbar plexus is formed by the ventral rami of the first three lumbar nerves and the greater part of the fourth

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lower extremity block

Lower Extremity Block


Associate professor

Medical director

Acute and chronic Pain management

Dept. of Anesthesiology


lumbar plexus
Lumbar plexus
  • The lumbar plexus is formed by the ventral rami of the first three lumbar nerves and the greater part of the fourth
  • Two major anastomosis involving the lumbar plexus

one with a branch of the last thoracic nerve

and another between the fourth and fifth lumbar nerves

give birth respectively to the :

Infracostal nerve

Lumbosacral trunk which contributes to the sacral plexus.


plexus location
Plexus location
  • The lumbar plexus is located in a virtual space inside the Psoas major muscle. This space is limited medially by Psoas major insertions on the bodies of the vertebrae and their transverse processes and by the lumbar spine itself. The aponeurosis surrounding the plexus inside the Psoas major constitutes the anterior, posterior and lateral limits of this space.


from skin to plexus
From skin to plexus


blocked nerves
Blocked nerves
  • Upper thigh Ilio-inguinal nerve, Iliohypogastric nerve, Genitofemoral nerve.
  • Lower limb Femoral nerve, Lateral femoral cutaneous nerve, Obturator nerve.


indications of l p b
Indications Of L.P.B.
  • Alone:

It can be used for hip or knee surgery

  • Combined with a sciatic nerve block:

The lumbar plexus block can be used for most surgeries involving the lower limb

  • Vertebromeningeal infections.
  • Lumbar vertebral trauma.
  • Associated trauma or disorders making lateral positioning impossible (Femoral neck fracture is no contraindication to the lateral position).
  • Coagulation abnormalities,
  • In patients exhibiting severe lumbar scoliosis, the landmarks may be modified
The patient lays on the side opposite to the block (thigh flexion: 30°; knee flexion: 90°)

while the physician stands behind. An assistant facing the patient with hands on the

upper thorax and thigh will help maintain correct position and identify thigh

movements during neurostimulation.

  • An horizontal line joining the top of the iliac crests at the L4-L5 level.
  • A line joining the spinous processes of L3, L4 and L5.
  • A line parallel to the line joining the spinous processes and passing over the posterior superior iliac spine.
  • A line starting at the spinous process of L4 and reaching perpendicularly the line passing by the posterior superior iliac spine
puncture site
Puncture site
  • The puncture site is located at the union of the lateral 1/3 and medial 2/3 of the line joining the spinous process of L4 to the line passing through the posterior superior iliac spine (approximately 40 mm lateral the spinous process of L4).
  • This site differs from the classic one located at the junction of the line passing through the posterior superior iliac spine and the line joining the top of the iliac crests. Anatomical studies suggest that the location of the classic site is in fact too lateral. See the scanners above where we can see the puncture site and the anatomical cut .
  • A septic Technique
  • The needle is introduced perpendicularly to the skin
  • Stimulation intensity is adjusted between 1 and 2 ma for a 0.1-ms period of stimulation.
  • The needle is inserted slowly through the muscles until it reaches the transverse process of L4. This contact is expected and provides a real safeguard.
  • Anatomical studies have shown that the distance between the posterior edge of the costal process and the lumbar plexus is 15-20 mm . The insertion depth of the needle is then noted. After adding 20 mm to the depth indicator, the needle is withdrawn and reoriented with a 5° angle in cephalic or caudal direction, thus avoiding the transverse process.
  • The needle is inserted more deeply (without exceeding the additional 20 mm) until the required stimulation of the femoral nerve (ascension of the patella) can be observed. The intensity of the stimulation is then gradually reduced until the motor response disappears (0.5 ma).
  • An aspiration test is then carried out to avoid vascular or spinal injection.
suitable responses
Suitable responses
  • Stimulation of Erector spinae or Quadratus lumborum muscles: This is a usual response to initial needle insertion. Poorly defined contractions are observed around the puncture site. Progression must continue. Stimulation of the femoral nerve:Contraction of the Quadriceps femoris muscle is noted. This is the ideal and sought-after response
unsuitable responses
Unsuitable responses
  • Stimulation of the obturator nerve: Contraction of the adductors, felt by palpation of the internal portion of the thigh, reveals that the needle is located too medially. The needle is withdrawn and reoriented laterally with a 5° angle.
  • Stimulation causing thigh adduction and patella ascension. It may correspond to a stimulation of nerve near the spinal canal. This reveals that the needle is located too medially. The needle should then be withdrawn and reoriented with a 5° angle laterally.
  • Thigh flexion on the pelvis is caused by stimulation of a motor branch to the Psoas major. Needle reorientation with a 5° angle toward cephalic or caudal direction should allow for stimulation of the femoral nerve at approximately the same depth.
  • Sciatic nerve stimulation may happens if the puncture site is either too caudal or too medial (stimulation of the lumbosacral trunk). The needle must be reoriented with a 5° angle in both, cephalic and lateral direction
  • Venous puncture:The lumbar vein may be punctured. The needle is then located too medially and must be reoriented with a 5° angle laterally.
  • Ureter puncture:Needle tip is too deep.Kidney puncture :The needle is inserted too deep and too cephalic. Avoid puncture at the L3 level, particularly on the right side.
  • Peritoneal puncture:Needle tip is too deep.Spinal or epidural puncture:The puncture site or the direction of the needle are too medial. Always aspirate before injecting slowly small quantities of anesthetic solution.
  • Epidural extension of anesthesia :In this case, whether the catheter is located in the paravertebral space or in the Psoas compartment, the anesthetic solution reaches the epidural space. Analgesia is effective. The catheter can be left in place
  • Intravascular injection: Intravascular injection can be prevented with a proper test dose and divided injections.
fascia iliaca block

Fascia Iliaca Block



*Pubic tubercle

Connect & divide into thirds Junction of lateral 1/3rd & medial 2/3rd

1 cm inferior to mark

  • Insert the needle at right angles to the skin until two clearly identifiable losses of resistance are felt, respectively at the crossing of the fascia lata then the fascia iliacaSingle shot technique: inject the local anaesthetic through the lumen of the needle according the usual safety rules, then massage the swelling produced in order to favour the upward spread of the local anaestheticContinuous infusion or iterative injection technique: when the tip of the needle is below the fascia iliaca, remove the obturator and introduce the catheter through the lumen in order to insert 2-3 cm of catheter at the inner aspect of the fascia iliaca. Set the connecting device and interpose an antibacterial filter before carefully dressing and fixing the catheter on the skin.
ilio inguinal block
Ilio inguinal block
  • ASIS
  • 2 cm inferior, 2 cm medial
  • perpendicular
  • advance needle through skin
  • discern a 'pop' or click as external oblique aponeurosis penetrated
  • inject 5 - 7 ml LA to block iliohypogastric nerve
  • advance needle a further 1 - 2 cm to penetrate softer resistance of internal oblique muscle
  • inject 5 - 7 ml LA to block ilioinguinal nerve
femoral nerve block

Femoral Nerve Block

provides sensory anesthesia of :

the anterior thigh


medial aspect of the calf, ankle and foot

  • foot and ankle surgery
  • femoral neck fractures
  • total hip arthroplasty
  • foot and ankle surgery
  • femoral shaft fractures
  • saphenous vein stripping
  • outpatient knee arthroscopy etc..
  • prosthetic femoral artery graft
  • dense sensory block could mask the onset of lower extremity compartment syndrome (e.g., fresh fractures of the tibia and fibula)
The point of needle insertion is marked 1.5 cm

lateral and 1.5 cm distal to the intersection of

the inguinal ligament and the femoral artery

  • LOSS OF RESISTANCE lies below two facial planes: the fascia lata and the fascia iliacus
three in one block
"Three-in-One" Block
  • A single injection of large volume within the neural "sheath" with the needle directed cephalad + pressure applied distal to the femoral nerve sheath
  • Block obturator and lateral femoral cutaneous nerves as well as the femoral nerve
sciatic nerve block
Sciatic Nerve Block
  • Anatomy The largest single nerve trunk of the body (a diameter about as large as the thumb (16-20 mm).
  • It arises from the L4, L5, S1, S2, S3 spinal roots and exits the pelvis posteriorly through the greater sciatic foramen and runs laterally along the posterior surface of the ischium anterior to the piriformis muscle.
  • The posterior cutaneous nerve of the thigh accompanies the sciatic nerve as it exits the greater sciatic foramen. The sciatic nerve has medial and lateral components which separate into the tibial and the common peroneal nerves in the superior aspect of the popliteal fossa.
classic posterior approach
Classic Posterior Approach
  • lateral (Sim's) position, with the operative side nondependent. The operative extremity is flexed 45 degrees at the hip and 90 degrees at the knee and rests against the dependent lower extremity
  • The posterior superior iliac spine (PSIS), greater trochanter, and sacral hiatus are identified and marked
  • A line is drawn between the greater trochanter and PSIS . This line is bisected. A perpendicular is dropped 3-5 cm from the midpoint of this line to the point of needle insertion.
classic posterior approach1
Classic Posterior Approach
  • The point of needle insertion should lie along a third line drawn between the greater trochanter and the sacral hiatus .
  • 6 inch nerve stimulator needle is advanced perpendicular to the skin. The nerve lies about 6-8 cm deep
  • motor response . Plantar flexion (downgoing toes) at less than 0.5 mA is the desired motor response and indicates placement of the needle near the medial part (tibial component) of the nerve
parasacral approch
Parasacral approch
  • lateral recumbent position
  • thigh slightly folded forming an angle of 135 -140° with the trunk.
  • The knee flexed at 90°.
  • A line is drawn between the postero-superior iliac spine and the ischial tuberosity
  • puncture point is situated at 6 cm from the postero-superior iliac spine following this line
  • The needle is inserted perpendicularly and progressed slowly,
  • at approximately 6 cm-8 cm a motor response is obtained rarely more than 8 cm
  • A bone contact may be the sacral ala or the iliac bone, superior and near the greater sciatic foramen. In this case needle should be withdrawn and reinserted inferior to the first point.
  • Moreover this bone contact can be used as a depth test. Needle depth should be noted and it is recommended not to go more than 2 cm beyond this depth
popliteal block
Popliteal Block
  • Prone position
  • Tendons of biceps femoris (lateral) and semitendinosus (medial)
  • Popliteal crease
  • Midpoint between tendons at a point 7 -10 cm superior to popliteal crease .
lateral popliteal
Lateral popliteal


  • In the mid thigh, the sciatic nerve more superficial lies medial to the biceps femoris
  • It is also distant from the femoral vessels
  • The sciatic nerve is reached at a depth averaging 6 cm
Position :
  • The patient lies in supine. The ankle is posed on a pillow to raise the lower limb from the table.
  • places one hand on the knee to move the leg to zero rotation for better exposure. With other hand insert the needle at the puncture site
  • Landmarks : A line is drawn from the posterior aspect of the great trochanter towards the knee, parallel to the femur. The puncture site is situated along this line, at mid thigh, from the knee to the great trochanter
  • Anaesthetic injection after stimulation of the common peroneal nerve provides blockade of the latter within 10-20 min followed by the blockade of the tibial nerve being effective within 40-60 min. Anaesthetic injection after stimulation of the tibial nerve provides blockade of the two nerves in much less time.
  • If no stimulation is obtained, it is recommended to re-insert a centimetre above or below the initial puncture site, instead of probing in vain.
  • Hamstring Contractions indicate that the needle is beneath the sciatic nerve. Try and insert the needle one centimetre above
Motor response

Stimulation of

tibial (plantar flexion +Inversion )

common peroneal (dorsiflexion + eversion)

saphenous block
Saphenous block
  • Sartorious muscle on medial aspect of thigh
  • Grip muscle between index finger & thumb at distal end of thigh. Midpoint of muscle belly between fingers
lateral popliteal block
Lateral Popliteal Block
  • Lateral femoral condyle
  • Groove between biceps femoris (posterior) and vastus lateralis (anterior)
  • Horizontal plane to contact femur (approx 5 cm)
  • Re-direct needle posteriorly at 30° angle
ankle block
Ankle Block
  • medial malleolus Saphenousnerve1cm anterior to malleolus, 1cm proximal to inter-malleolus line (skin crease) 5ml LA

Tibial nerve Posterior to posterior tibial artery Contact bone and withdraw needle by 1mm 5ml LA