Chapter 78 Sciatic Nerve Block and Ankle Block

Question 1

sciatic nerve provides sensory innervation

Answer 1

to the back of the thigh and the entire leg below the knee except for its medial aspect, which is innervated by the saphenous nerve.

Question 2

sciatic nerve provides motor innervation

Answer 2

to the hamstrings

and all the muscles below the knee.

Question 3

Sciatic nerve block in conjunction with lumbar plexus block, femoral nerve block, or saphenous nerve block can be used to provide
anesthesia and analgesia for

Answer 3

surgical procedures of the lower extremity and the hip.

Question 4

Peripheral nerve blocks have the following distinct

advantages over general or central neuraxial anesthesia:

Answer 4

(1) no autonomic blockade, with no risk of hemodynamic
instability and urinary retention; (2) unilateral
block; (3) no risk of spinal hematoma in the anticoagulated patient; (4) prolonged postoperative analgesia provided either by injecting a long-acting local anesthetic or by a
continuous infusion of local anesthetic via an indwelling catheter and infusion pump; (5) decreased need for postoperative nursing due to minimal side effects such as uncontrolled pain, emesis, sedation, and respiratory depression;
(6) early ambulation and discharge.

Question 5

The sciatic nerve formed by

Answer 5

the ventral rami of L4, L5 and S1, S2, S3 nerve roots, is the largest nerve in the body,
measuring 0.8 to 1.5 cm in width.

Question 6

Sciatic Nerve course

Answer 6

The roots exit the pelvis as they unite to form the sciatic nerve through the greater sciatic foramen and travel on the anterior surface of the piriformis muscle accompanied by the superior gluteal artery, the largest and shortest branch of the internal iliac artery.

Question 7

two divisions of the

sciatic nerve

Answer 7

tibial nerve (medial position), and peroneal
nerve (lateral position)

Question 8

Proximally, the scaiatic nerve lies

Answer 8

over the posterior surface of the ischium. In this location the sciatic nerve is accompanied by the posterior cutaneous nerve of the thigh and
further down, the inferior gluteal artery

Question 9

Distal to the

piriformis muscle the sciatic nerve travels

Answer 9

posterior to the superior gemellus, tendon of obturator internus, the inferior
gemellus, quadratus femoris, and adductor magnus muscles.

Question 10

In the gluteal area the sciatic nerve is covered by

Answer 10

the gluteus maximus
muscle posteriorly. In the infragluteal location, the sciatic nerve lies in close proximity to the lesser trochanter, over the adductor magnus muscle and is crossed obliquely in a mediolateral direction by the long head of the biceps femoris muscle.

Question 11

The sciatic nerve continues distally in the thigh

Answer 11

under the biceps femoris muscle. At the cephalad portion of popliteal fossa or distal third of the thigh, the
sciatic nerve divides into its two terminal branches, the posterior tibial and common peroneal nerves.

Question 12

In the popliteal area the sciatic nerve picks up

Answer 12

more connective tissue, resulting in increased connective tissue to neuronal tissue ratio, which may explain the increased latency of onset seen with the popliteal sciatic blocks compared with more
proximal locations.

Question 13

SCIATIC NERVE BLOCK

INDICATIONS

Answer 13

used for lower extremity surgery, including hip, tibia and fibula, knee, ankle, and foot surgery, and also for above and below knee amputation. There is evidence to support its use in chronic pain
syndromes of the lower extremity, including complex regional pain syndromes, or to pre-empt phantom limb pain

Question 14

SCIATIC NERVE BLOCK

PARASACRAL APPROACH (MANSOUR)

Answer 14

The local anesthetic is deposited in the
fascial plane enclosing the L4–S3 nerve roots of sacral plexus, as they unite to form the main trunk of the sciatic nerve under the piriformis muscle.

Question 15

SCIATIC NERVE BLOCK

PARASACRAL APPROACH (MANSOUR)

This was also associated with blockade of

Answer 15

the obturator nerve in 93% of subjects

Question 16

SCIATIC NERVE BLOCK

PARASACRAL APPROACH (MANSOUR)

Surface Anatomy and Technique

Answer 16

The patient is placed in the lateral (Sim’s) position with the
operative side up. The posterior superior iliac spine (PSIS) and ischial tuberosity are marked and united by a line. The point of needle entry is approximately 6 cm from the PSIS
along this line. A 100-mm, 22-gauge insulated block needle is inserted and advanced maintaining a parasagittal
orientation, until motor responses are elicited in the foot/ankle at a current of less than 0.5 mA. The nerve roots of the sacral plexus are usually contacted at 5 to 8 cm depth. Twenty to 30 ml of local anesthetic is injected after ensuring that the twitches disappear with currents at 0.2 mA and there is no resistance to injection

Question 17

It is important

to remember that the superior gluteal artery

Answer 17

curves around the upper lip of the greater sciatic notch, should not be injured, as it is a short branch of the internal iliac
artery and will retract back into the pelvis if severed

Question 18

SCIATIC NERVE BLOCK

PARASACRAL APPROACH (MANSOUR)

Ultrasound-Guided Technique

Answer 18

A
curved low-frequency (C2-5 MHz) probe is positioned across the gluteal region and slid caudad while watching the linear hyperechoic shadow of the back of the ischium. The sciatic notch looks like a discontinuity in
this line, with the piriformis muscle covering the notch.
Hip adduction and abduction help identify the piriformis.
The sciatic nerve is seen in short axis deeper to the piriformis. Rotation of the probe by 45° will bring about the long axis view of the sciatic nerve as it exits the
greater sciatic notch

Question 19

SCIATIC NERVE BLOCK
PARASACRAL APPROACH (MANSOUR)

complications of the traditional approach

Answer 19

hematoma, rectal perforation, and transient sciatic

neuralgia were not seen with the ultrasound guidance

Question 20

SCIATIC NERVE BLOCK

CLASSIC POSTERIOR APPROACH
LABAT TECHNIQUE

Answer 20

The sciatic nerve is blocked at the level of the greater

sciatic notch distal to the piriformis muscle

Question 21

SCIATIC NERVE BLOCK

CLASSIC POSTERIOR APPROACH
(LABAT TECHNIQUE)

Anatomy and Technique

Answer 21

The patient is placed in the lateral Sim’s position with the
thigh and knee flexed 90° and the dependent lower extremity
extended. A line is drawn between the tip of greater trochanter (GT) and the PSIS, line 1. A second line is drawn connecting the GT and sacral hiatus, line 2. A perpendicular line, line 3, is drawn from the midpoint of line 1 to bisect line 2. The point of intersection between lines 2 and 3 is the needle entry site. A 100- to 150-mm 22-gauge insulated block needle is inserted perpendicular to the skin and advanced and redirected as
needed until an appropriate EMR is obtained at less than
0.5 mA. The depth of the nerve from the skin usually ranges from 7 to 15 cm. Twenty to 30 ml of local
anesthetic is injected after negative aspiration and absence
of paresthesia

Question 22

SCIATIC NERVE BLOCK

CLASSIC POSTERIOR APPROACH
(LABAT TECHNIQUE)

Ultrasound-Guided Technique

Answer 22

After finding the piriformis muscle, the probe is moved further inferiorly. The ischium ends in a spiny protrusion, which is the ischial spine. With color Doppler one often will see the pudendal nerve and internal pudendal vessels close to the ischial spine. Lateral to the spine and superficial to the flat surface of the ischium, the sciatic nerve is seen in short axis with the
superior gemellus muscle underneath it. The easier
approach is to position the probe horizontally at the
level of the greater trochanter, which is a dome-shaped
hyperechoic rim with anechoic shadowing underneath.
More medially one will see the ischial tuberosity as another dome-shaped structure. Between these two shadows will be the sciatic nerve with gluteus maximus superficial and the gemellus deep to it. Moving the probe proximal to distal will bring the ischial spine into view. Inferior gluteal vessels will be seen close to the ischial tuberosity. Deep to the gemellus, one often sees
the capsule of the hip joint and the head of the femur just
outside the acetabular rim.

Question 23

SCIATIC NERVE BLOCK

SUPINE LITHOTOMY APPROACH
RAJ TECHNIQUE

Answer 23

sciatic nerve is blocked at a more distal level, between

the ischial tuberosity and the greater trochanter

Question 24

SCIATIC NERVE BLOCK

SUPINE LITHOTOMY APPROACH
(RAJ TECHNIQUE)

Surface Anatomy and Technique

Answer 24

The patient is in supine position with the extremity to be blocked supported by an assistant, in maximal hip flexion
and 90° knee flexion. Maximal flexion at the hip thins out
the gluteus maximus (GM) muscle and decreases redundant tissue on the buttock. If there is no help, alternatively, the foot can be tucked under the contralateral
thigh with some rotation at the knee level. This may reduce
the amount of stretch of the GM. The needle entry point is the midpoint of a line between the tip of the greater trochanter (GT) and ischial tuberosity (IT). A 100-mm insulated 22-gauge block needle is inserted perpendicular to the skin, advanced and redirected as needed
until an appropriate EMR is elicited at less than 0.5 mA.

Question 25

SCIATIC NERVE BLOCK | SUPINE LITHOTOMY APPROACH RAJ TECHNIQUE

Answer 25

The block can be done supine or in Sim’s position. A C2-5 | MHz ultrasound probe positioned across the buttock will reveal the GT and IT and the sciatic nerve in between

Question 26

SCIATIC NERVE BLOCK ANTERIOR APPROACH

Answer 26

The sciatic nerve lies posterior to the muscles of the anterior compartment of the thigh, in the proximity of the lesser trochanter. The posterior cutaneous nerve of the thigh will be missed with this approach

Question 27

SCIATIC NERVE BLOCK ANTERIOR APPROACH Surface Anatomy and Technique

Answer 27

The patient is placed supine with the lower extremities in neutral position. A line is constructed between the anterior superior iliac spine and the pubic tubercle, marking the reflection of the inguinal ligament. The second line is constructed parallel to the first line, at the level of the greater trochanter. In Beck’s approach, a perpendicular line is drawn at the junction of the lateral two-thirds and medial one-third of the first line to contact the second line. The needle entry site for Beck’s approach is the junction of the perpendicular and the second line. The block is performed with a 150-mm, 22-gauge insulated block needle as the nerve lies deep under the anterior thigh muscles. Often one encounters the branches of the femoral nerve as the needle is advanced posteriorly, with potential for injury. A nerve stimulator is used during the advancement to avoid injury to the femoral nerve. The sciatic nerve may not be encountered until a depth of 12 to 15 cm. Local anesthetic is injected when an appropriate EMR is obtained at less than 0.5 mA

Question 28

SCIATIC NERVE BLOCK ANTERIOR APPROACH Limitations

Answer 28

Pain with bone contact, insertion via major muscles, and difficult landmarks in obese patients. sciatic nerve at this site lies posterior to the lesser trochanter and is not accessible to the needle using the direct anterior approach. Two strategies to overcome this limitation include the insertion of the needle at a more distal level (4 cm distal to the lesser trochanter) and internal rotation of the foot (femur) so the sciatic nerve moves medial to the lesser trochanter

Question 29

SCIATIC NERVE BLOCK ANTERIOR APPROACH Ultrasound-Guided Technique

Answer 29

positioned the patient supine, with the thigh externally rotated at ~ 45°, the hip and knee flexed, and scanned the proximal thigh approximately 8 cm distal to the inguinal crease.36 A C2-5 MHz probe is positioned at the inguinal crease and gradually moved inferiorly until the lesser trochanter is seen as a widening of the femoral circumference. One would see the femoral vessels and nerves more superficially and laterally. At the level where the adductor muscles meet the femur, the sciatic nerve is seen as a hyperechoic round or oval structure, posterior to the adductor magnus. The needle is inserted from the medial side of the thigh through the adductor muscles. Occasionally branches of the obturator nerve may be encountered.

Question 30

SCIATIC NERVE BLOCK LATERAL APPROACH

Answer 30

The sciatic nerve is blocked in the subgluteal space, dorsal to the plane of the quadratus femoris muscle, between the femur and ischial tuberosity. The other structures in the subgluteal space are the posterior cutaneous nerve of the thigh, the inferior gluteal nerve and vessels, and the ascending branch of the circumflex femoral artery.

Question 31

SCIATIC NERVE BLOCK LATERAL APPROACH Surface Anatomy and Technique

Answer 31

The block is performed with the patient supine and the hip in neutral position. The needle insertion site is 3 cm distal to the point of maximum lateral prominence of the greater trochanter. The ischial tuberosity can be palpated with the nondominant hand. The needle is inserted perpendicular to the major axis of the limb and advanced toward the femur. Once it contacts the femur it is withdrawn slightly, redirected 20° under the femur, and advanced toward the ischial tuberosity. The sciatic nerve is contacted at a depth of 8 to 12 cm. Local anesthetic solution is injected after appropriate EMR is obtained

Question 32

SCIATIC NERVE BLOCK | POSTERIOR SUBGLUTEUS APPROACH di BENEDETTO

Answer 32

approach blocks the nerve at a location the nerve overlies the adductor magnus muscle, is posterior to the lesser trochanter, and is~ 3 cm above the lower border of the gluteus maximus muscle

Question 33

SCIATIC NERVE BLOCK POSTERIOR SUBGLUTEUS APPROACH (di BENEDETTO) Surface Anatomy and Technique

Answer 33

The patient is placed in the lateral (Sim’s) position with the operated side up. A line is drawn from the greater trochanter to the ischial tuberosity and a second line is drawn from the midpoint of this line, extending caudally for 4 cm. The needle insertion site is the distal point of the second line. A stimulating 100-mm, 22-gauge insulated block needle is inserted perpendicular to the skin and advanced to elicit an appropriate EMR at less than 0.5 mA. In the midgluteal approach, the patient is placed in lateral decubitus with the operating site up and the entry point of the needle is 10 cm from midline, from the midpoint of the intergluteal sulcus. In the subgluteal approach, the entry point of the needle is in the subgluteal fold. at 10 cm from midline

Question 34

SCIATIC NERVE BLOCK POSTERIOR SUBGLUTEUS APPROACH (di BENEDETTO) Ultrasound-Guided Technique

Answer 34

the greater trochanter, ischial tuberosity, and the sciatic nerve in between, is gradually moved caudad on the posterior thigh. The shadows of the hip joint will disappear and the nerve will move into an intermuscular cleft just medial to the femur. In this location it is covered by the lower end of the gluteus maximus, which is thin

Question 35

SCIATIC NERVE BLOCK INFRAGLUTEAL PARABICEPS APPROACH

Answer 35

The sciatic nerve is blocked at a site more distal to the classic Labat approach. Distal to the gluteus maximus, the sciatic nerve lies over the adductor magnus and is crossed obliquely in a mediolateral direction by the long head of the biceps femoris muscle. The sciatic nerve therefore lies further lateral and subsequently deep to the long head of the biceps femoris. For a short distance of 3 to 4 cm, where the nerve is lateral to the long head of the biceps femoris,

Question 36

SCIATIC NERVE BLOCK INFRAGLUTEAL PARABICEPS APPROACH Surface Anatomy and Technique

Answer 36

The surface landmarks for this approach are the lateral border of the biceps femoris and the gluteal crease. The lateral border of the biceps femoris muscle is identified by asking the patient to flex the knee while resistance is applied to the calf muscles. The site of needle insertion is along the lateral border of the biceps femoris 1 cm caudal to the gluteal crease. A 100-mm, 22-gauge insulated block needle is inserted at an angle of 70° to 80° to the skin with a cephalad and anterior orientation within the parasagittal plane. The femur lies lateral to the nerve and the biceps femoris is medial to the nerve. The needle is moved only in one plane from the lateral to medial, and redirected to elicit the appropriate EMR.

Question 37

SCIATIC NERVE BLOCK INFRAGLUTEAL PARABICEPS APPROACH Ultrasound-Guided Technique

Answer 37

The patient is positioned prone and the biceps tendon is identified by asking the patient to flex the knee. A high frequency ultrasound probe is placed at the level of the gluteal crease or slightly below, and the sciatic nerve is identified at the lateral border of the biceps femoris, posterior to the muscle . An appropriate EMR at less than 0.5 mA may be used if needed

Question 38

SCIATIC NERVE BLOCK MID-THIGH APPROACH ULTRASOUND-GUIDED TECHNIQUE

Answer 38

evaluated the mid-thigh approach under ultrasound guidance in a clinical and anatomic study. Biceps femoris, vastus lateralis, adductor magnus muscles, the lateral intermuscular septum between biceps femoris and vastus lateralis, and linea aspera were among the landmarks on the mid-thigh sonograms

Question 39

The popliteal fossa

Answer 39

diamond-shaped area bound by the semitendinosus and semimembranosus muscles medially, the biceps femoris muscle laterally, and by the two heads of the gastrocnemius muscle inferiorly. The popliteal vessels, with the artery located deeper and anterior to the vein, are medial to the sciatic nerve.

Question 40

The tibial nerve

Answer 40

immediately gives off the sural nerve and, at the level just above the sole of the foot, gives off the medial calcaneal. The tibial nerve then continues as the posterior tibial nerve that terminates into the medial plantar and lateral plantar nerves. nerve.

Question 41

The common peroneal nerve

Answer 41

gives off a sural communicating branch and, once it is below the head of the fibula, divides into the deep peroneal and superficial peroneal nerves.

Question 42

Except for the sural nerve, the | major branches of the sciatic nerve

Answer 42

have motor function

Question 43

The sensory innervation of the foot is supplied by

Answer 43

branches of the tibial nerve, the common peroneal nerve, and the saphenous nerve.

Question 44

The posterior tibial nerve supplies

Answer 44

the sole of the foot, the deep peroneal nerve supplies the web between the great toe and the second toe, the superficial peroneal nerve supplies the dorsum of the foot, and the sural nerve supplies the lateral aspect of the heel and foot and the fifth toe

Question 45

the saphenous nerve

Answer 45

the terminal branch of the femoral nerve, supplies the medial aspect of the foot

Question 46

nerve stimulator of sciatic nerve branches

Answer 46

Eliciting foot inversion is the best EMR since it signifies stimulation of both branches of the sciatic nerve. Elicitation of foot dorsiflexion signifies stimulation of the deep peroneal nerve, while plantar flexion signifies stimulation of the tibial nerve. The needle would have to be redirected medially or laterally to elicit the other response to block both branches of the sciatic nerve.

Question 47

SCIATIC NERVE BLOCK AT THE POPLITEAL FOSSA Indications

Answer 47

Popliteal sciatic block is indicated for anesthesia/analgesia for foot and ankle surgery or for diagnostic/therapeutic blockade for pain management. The block is especially useful when ankle blocks are contraindicated because of the presence of swelling or infection in the ankle, and can be accomplished with a single needle insertion.

Question 48

SCIATIC NERVE BLOCK AT THE POPLITEAL FOSSA Posterior Approach

Answer 48

The patient is positioned prone with a pillow or rolled blanket under the ankle. A 22-Ga insulated block needle is inserted 5 to 7 cm above the popliteal crease and 1 cm lateral to a line that bisects the superior part of the fossa. The needle is advanced at a 45° angle to the skin and inserted to a depth of 2 to 5 cm until the desired EMR of inversion or combined inversion and plantar flexion is elicited with the stimulating current of less than 0.5 mA. A volume of 30 ml of local anesthetic is adequate to block the sciatic nerve.

Question 49

Patchy sensory blockade of the foot may result, probably secondary

Answer 49

to the considerable size of the sciatic nerve, the thickness of its epineurium, increased fibrofatty perineural tissue, as well as the variable level at which the sciatic nerve divides into the tibial and common peroneal nerves.

Question 50

SCIATIC NERVE BLOCK AT THE POPLITEAL FOSSA Lateral Approach

Answer 50

The patient is supine and the upper edge of the patella and the groove between the tendon of the biceps femoris and the iliotibial tract are palpated. Identification of the groove is made easier by flexion followed by extension of the patient’s knee. The site of needle insertion is at the intersection of a line drawn from the upper edge of the patella and the intermuscular groove. The insulated needle is inserted 20° to 30° posteriorly to the horizontal plane and directed slightly caudad. The common peroneal nerve, located laterally, is stimulated first followed by the tibial nerve. After obtaining an appropriate EMR at less than 0.5 mA, 10 to 15 ml of local anesthetic is injected for each nerve

Question 51

SCIATIC NERVE BLOCK AT | THE POPLITEAL FOSSA

Answer 51

The patient is positioned prone. Depending on the size of the patient, a curved 2-5 MHz or a high frequency linear probe is positioned at the popliteal crease horizontally. Release of pressure on the probe reveals the popliteal vein as it fills up, with the tibial nerve located posterolateral to the vein. The tibial nerve is traced proximally in the thigh and the nerve looks broader as the peroneal nerve joins the tibial nerve. At this location, caudad angling of the probe will reveal the two components as two distinct bundles and the common peroneal is often more hypoechoic. The needle may be inserted where the sciatic is a single bundle to surround the entire nerve with local anesthetic.

Question 52

With continuous sciatic blocks

Answer 52

the opioid analgesic requirements are reduced, patient satisfaction is increased, and earlier discharge is feasible.

Question 53

CHOICE OF LOCAL ANESTHETICS

Answer 53

single injection of 20 to 30 ml of a long-acting local | anesthetic such as bupivacaine provides 12 to 24 hours of postoperative analgesia

Question 54

long-acting local | anesthetic favors

Answer 54

the use of a single-injection technique for postoperative analgesia for the vast majority of orthopedic surgical procedures below the knee.

Question 55

The use of a continuous | catheter technique is indicated primarily when

Answer 55

postoperative | analgesia greater than 24 hours is desired

Question 56

intermediateacting local anesthetics

Answer 56

mepivacaine and lidocaine have a faster onset time to surgical anesthesia compared with bupivacaine, the duration of the postoperative analgesia is limited to 4 to 6 hours

Question 57

For a continuous infusion technique for lower extremity | nerve blocks, a dilute solution of a

Answer 57

long-acting local anesthetic such as bupivacaine 0.1% to 0.25% or ropivacaine 0.2% is adequate.

Question 58

Three methods of peripheral nerve localization have been | used in clinical practice:

Answer 58

(1) elicitation of paresthesia; (2) neurostimulation technique with a low-intensity electrical current (PNS); (3) ultrasound guidance.

Question 59

Two strategies have been proposed to improve the latency of onset, and the success of a complete block of the sciatic nerve.

Answer 59

The proximity of the stimulating needle tip to both components of the sciatic nerve is ensured prior to local anesthetic injection. The EMR to neurostimulation determines the sciatic nerve component being stimulated

Question 60

There are four possible foot movements in response | to sciatic nerve stimulation:

Answer 60

(1) plantar flexion; (2) dorsiflexion; (3) inversion; and (4) eversion.

Question 61

Elicitation of EMR of inversion implies

Answer 61

that the nerve needle is | stimulating both the tibial and deep peroneal nerve

Question 62

COMPLICATIONS OF SCIATIC NERVE BLOCK parasacral approach of Mansour

Answer 62

the local anesthetic is deposited on the sacral plexus within the pelvis, in close vicinity of pelvic vasculature and viscera.

Question 63

COMPLICATIONS OF SCIATIC | NERVE BLOCK

Answer 63

The complications of sciatic nerve block, common to | peripheral nerve blockade, can be categorized into systemic toxicity, infectious, and neurologic complications.

Question 64

A few strategies could be considered to minimize the | risk of neurologic injury following peripheral nerve blocks:

Answer 64

l Moderate sedation should be used, so that the patient is able to report paresthesia if it occurs. l If neurostimulation is used to localize the nerve, EMR elicited at currents of less than 0.5 mA ensures that the needle is close enough to the nerve to obtain a successful block. The EMR at currents lower than 0.2 mA, however, may suggest that the needle is too close to nerve with a risk of nerve damage from intraneural injection of local anesthetic

Question 65

Ankle block Indication

Answer 65

means of providing surgical anesthesia and postoperative analgesia for midfoot and forefoot surgery. Ankle block is not suitable for ankle surgery.

Question 66

Ankle block involves anesthetizing five nerves

Answer 66

the posterior tibial, superficial peroneal, deep peroneal, saphenous, and sural. All are branches of the sciatic nerve except for the saphenous, which is the terminal branch of the femoral nerve.

Question 67

The nerve supply to the foot and ankle is provided by

Answer 67

``` the four terminal branches of the sciatic nerve and the saphenous nerve (terminal branch of the femoral nerve). ```

Question 68

Except for the posterior tibial nerve, the other nerves are

Answer 68

all sensory nerves.

Question 69

cutaneous innervation of Posterior tibial nerve

Answer 69

plantar surface of the foot and toes by its three divisions: medial plantar nerve, lateral plantar nerve, and medial calcaneal nerve. the PTN being the major component as it innervates all five toes

Question 70

cutaneous innervation of Deep peroneal nerve

Answer 70

the dorsal surface of the foot | between the great and second toe

Question 71

cutaneous innervation of Sural nerve

Answer 71

the lateral surface of the foot (dorsolateral cutaneous nerve) and the heel (lateral calcaneal nerve). A medial branch unites with the intermediate cutaneous nerve of the superficial peroneal nerve innervating the web spaces of the third and fourth toes.

Question 72

cutaneous innervation of Superficial peroneal nerve

Answer 72

the dorsal surface of the foot and toes, except the web space between the first and second toes and the lateral aspect of the foot, including the fifth toe and lateral half of the fourth toe.

Question 73

cutaneous innervation of Saphenous nerve

Answer 73

the skin over the medial malleolus, medial surface of the foot up to the medial arch, and to the medial side of the great toe.

Question 74

POSTERIOR TIBIAL NERVE

Answer 74

one of the two terminal divisions of the sciatic nerve and consists of muscular, cutaneous, and articular branches.

Question 75

POSTERIOR TIBIAL NERVE Course

Answer 75

In the upper two-thirds of the leg the nerve is located deep in the posterior compartment, while in the lower one-third of the leg it assumes a superficial location along the medial border of the Achilles tendon. The PTN lies lateral and posterior to the posterior tibial artery and vein. In the talocalcaneal canal the PTN divides into its terminal branches: the medial plantar (MPN) and lateral plantar (LPN) nerves.

Question 76

Blocking the PTN at a distal | site in these patients may result in

Answer 76

partial block of the | nerve

Question 77

the medial plantar (MPN) supplies

Answer 77

the muscular branches to the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis, and lumbricals.

Question 78

Neurostimulation of the MPN | produces

Answer 78

flexion of all toes, except the great toe, and | abduction of the great toe.

Question 79

lateral plantar (LPN) nerves supplies

Answer 79

muscular branches to the abductor digiti minimi, adductor hallucis, quadratus plantae, short flexors, and opponens of the fifth and fourth toes (sometimes the third toe), lumbricals, and interossei.

Question 80

Neurostimulation of the LPN produces

Answer 80

adduction of the great toe, abduction of the fifth toe, and contraction of the musculotendinous arch of the foot. The PTN also gives off a medial calcaneal branch, with variable origin, supplying the medial side of the heel

Question 81

POSTERIOR TIBIAL NERVE DISTAL APPROACH (TRADITIONAL SITE)

Answer 81

The PTN can be blocked at the level of the medial malleolus within 2 to 3 cm of its tip, within the tibiocalcaneal canal. The nerve in this location lies under the flexor reticulum, posterior to the tibial artery and vein

Question 82

POSTERIOR TIBIAL NERVE DISTAL APPROACH (TRADITIONAL SITE) limitations

Answer 82

l The diffusion barrier imposed by the flexor reticulum. l A partial and incomplete block because the calcaneal branch may have taken off at a higher level (40%) and the two terminal divisions of the nerve may have separated (7%–13% of cases). l In patients with an altered and/or distorted ankle anatomy (inflammation, edema, poor vascular anatomy) the block may be technically difficult.

Question 83

POSTERIOR TIBIAL NERVE DISTAL APPROACH (TRADITIONAL SITE Technique

Answer 83

The patient is positioned prone or supine with the foot elevated. The needle entry site is 2 to 3 cm proximal to the tip of the medial malleolus and 1 cm from the medial border of the Achilles tendon. A 22-gauge insulated needle is directed toward the posterior aspect of the tibia, posterior to the tibial artery pulsation (if palpable), seeking to obtain toes flexion at less than 0.5 mA. Five to 7 ml of local anesthetic is injected incrementally after negative aspiration of blood.

Question 84

POSTERIOR TIBIAL NERVE PROXIMAL APPROACH

Answer 84

The PTN is blocked before it has given off its medial calcaneal branch and before its division. The needle entry site is 7 to 8 cm proximal to the superior border of the medial malleolus and approximately 1 cm anterior to the medial border of the Achilles tendon, in the groove between the flexor digitorum and flexor hallucis longus. A 50-mm, 22-gauge insulated needle is directed anterior and slightly caudad 60° to the sagittal plane until the appropriate EMR is obtained at less than 0.5 mA. Seven to 10 ml of local anesthetic is injected incrementally after negative aspiration of blood.

Question 85

POSTERIOR TIBIAL NERVE MIDTARSAL APPROACH

Answer 85

The PTN can be blocked distal to the flexor reticulum where it is relatively superficial. The needle is inserted on either side of the posterior tibial artery and advanced toward the calcaneus. After bone contact is made, the needle is slightly withdrawn and 5 to 7 ml of local anesthetic is injected. This a more distal PTN block for mid- or forefoot surgery and the calcaneal branch may be missed

Question 86

POSTERIOR TIBIAL NERVE SUBCALCANEAL APPROACH

Answer 86

The PTN is in close and consistent relation to the bony ridge of the calcaneus. The needle is inserted posteroinferiorly to the bony ridge until bone is contacted. The needle is slightly withdrawn and 5 to 7 ml of local anesthetic is injected. The calcaneal branch may be missed.

Question 87

POSTERIOR TIBIAL NERVE ULTRASOUND-GUIDED TECHNIQUE

Answer 87

The patient is positioned supine with the foot elevated, or prone, and using a high-frequency transducer, the area proximal to the medial malleolus is scanned to visualize the PTN, located posteromedial to the posterior tibial artery. It is important to remember that blockade in this area will not cover the area of tourniquet

Question 88

DEEP PERONEAL NERVE (DPN)

Answer 88

The DPN is located ~ 2.5 to 5 cm above the ankle, between the extensor digitorum longus (EDL) and extensor hallucis longus (EHL) tendons, mostly lateral to the anterior tibial artery. At the level of the malleoli, the nerve becomes more medial.

Question 89

DEEP PERONEAL NERVE divides into

Answer 89

lateral and medial terminal branches 1 cm above the ankle joint. The lateral branch supplies the extensor digitorum brevis. The medial branch supplies dorsal cutaneous branches to the great toe and the second toe

Question 90

DEEP PERONEAL NERVE BLOCK Technique

Answer 90

The most consistent location of the DPN is 2.5 cm above the level of the ankle joint at the upper border of EHL laterally and EDL medially. Dorsiflexion of the great toe (EHL) and small toes (EDL) allows identification of these two tendons. The needle is advanced perpendicular to the ankle joint until bone is contacted, withdrawn slightly, and 5 ml of local anesthetic is injected. If a nerve stimulator is used, the appropriate EMR is extension of the lateral four toes.

Question 91

DEEP PERONEAL NERVE BLOCK Ultrasound-guided technique

Answer 91

A high-frequency ultrasound probe is placed on the ankle proximal to the malleoli line to identify the pulsating posterior tibial artery between EDL and EHL tendons. The DPN is usually visualized lateral to the artery. If the nerve is not visualized, perivascular spread of the local anesthetic may suffice

Question 92

SUPERFICIAL PERONEAL NERVE

Answer 92

The SPN is a sensory branch of the common peroneal nerve. After coursing in the anterolateral compartment of the leg, the nerve pierces the deep fascia 10 to 15 cm from the tip of lateral malleolus. Afterward the SPN lies subcutaneously and divides into branches that supply the dorsum of the foot and toes.

Question 93

SUPERFICIAL PERONEAL NERVE BLOCK Technique:

Answer 93

The SPN can be blocked by subcutaneous infiltration of 5 to 7 ml of local anesthetic between the lateral border of the tibia and the superior aspect of the lateral malleolus.

Question 94

SURAL NERVE course

Answer 94

The sural nerve is formed by the union of the medial sural nerve (branch of the tibial nerve) and the lateral sural nerve (branch of the common peroneal nerve). It courses along the lateral border of the Achilles tendon, posteromedial to the lesser saphenous vein, and then around the posterior border of the lateral malleolus. At the level of the base of the fifth metatarsal, the nerve divides into its two terminal branches.

Question 95

SURAL NERVE supplies

Answer 95

sensory innervation to the lateral border of the foot, the fourth and fifth toes, and the web spaces of the third and fourth toes. It also gives off two lateral calcaneal branches above the tip of the lateral malleolus.

Question 96

SURAL NERVE BLOCK Technique:

Answer 96

The patient is positioned supine and the foot is internally rotated. Up to 5 ml of local anesthetic is infiltrated subcutaneously anterolateral to the lateral border of the Achilles tendon at the level of lateral malleolus. The nerve may also be blocked 7 to 10 cm above the superior border of the lateral malleolus, at the lateral border of Achilles tendon, posteromedially to the lesser saphenous vein. For surgery on the midfoot or third and fourth toes, a full sural nerve block may not be needed if the lateral aspect of the foot is not involved. The medial branch of the sural nerve can be blocked with 3 to 5 ml of local anesthetic superficially infiltrated at the anterior border of the lateral malleolus.

Question 97

SURAL NERVE BLOCK Ultrasound-guided technique

Answer 97

The patient is positioned prone with a tourniquet on the proximal calf to distend the lesser saphenous vein. A high-frequency ultrasound probe is placed above the lateral malleolus and the vein is visualized. Using an in- or out-of-plane approach, the block needle is directed as needed with the goal of circumferential spread of local anesthetic around the vein.

Question 98

SAPHENOUS NERVE

Answer 98

terminal branch of the femoral nerve. After travelling in the subsartorial canal along with the femoral artery and nerve to vastus medialis, the nerve becomes superficial at the medial border of the knee joint as it pierces the fascia between the gracilis and sartorius muscles. It runs distally behind the medial border of the tibia, posterior to the greater saphenous vein. It divides into two branches, one ending at the ankle and the second one passing in front of the medial malleolus, close to the greater saphenous vein.

Question 99

SAPHENOUS NERVE supplies

Answer 99

It provides cutaneous innervation to the medial site of the foot up to the medial side of the big toe.

Question 100

SAPHENOUS NERVE BLOCK Technique:

Answer 100

The saphenous nerve is blocked by subcutaneous infiltration of 3 to 5 ml of local anesthetic along the upper border of the medial malleolus near the greater saphenous vein.

Question 101

LOCAL ANESTHETIC CHOICE | AND DOSE FOR ANKLE BLOCK

Answer 101

If an appropriate EMR at less than 0.5 mA is obtained, 5 to 7 ml of local anesthetic may suffice, otherwise a higher volume of local anesthetic may be preferable to ensure adequate diffusion

Question 102

an absolute contraindication in an ankle block, as it can have a major impact on the blood supply in the foot.

Answer 102

The use of epinephrine