Chapter 78 Sciatic Nerve Block and Ankle Block Flashcards Preview

Essentials of Pain Medicine > Chapter 78 Sciatic Nerve Block and Ankle Block > Flashcards

Flashcards in Chapter 78 Sciatic Nerve Block and Ankle Block Deck (102):
1

sciatic nerve provides sensory innervation

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.

2

sciatic nerve provides motor innervation

to the hamstrings
and all the muscles below the knee.

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

surgical procedures of the lower extremity and the hip.

4

Peripheral nerve blocks have the following distinct
advantages over general or central neuraxial anesthesia:

(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.

5

The sciatic nerve formed by

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.

6

Sciatic Nerve course

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.

7

two divisions of the
sciatic nerve

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

8

Proximally, the scaiatic nerve lies

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

9

Distal to the
piriformis muscle the sciatic nerve travels

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

10

In the gluteal area the sciatic nerve is covered by

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.

11

The sciatic nerve continues distally in the thigh

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.

12

In the popliteal area the sciatic nerve picks up

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.

13

SCIATIC NERVE BLOCK

INDICATIONS

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

14

SCIATIC NERVE BLOCK


PARASACRAL APPROACH (MANSOUR)

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.

15

SCIATIC NERVE BLOCK


PARASACRAL APPROACH (MANSOUR)

This was also associated with blockade of

the obturator nerve in 93% of subjects

16

SCIATIC NERVE BLOCK


PARASACRAL APPROACH (MANSOUR)


Surface Anatomy and Technique

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

17

It is important
to remember that the superior gluteal artery

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

18

SCIATIC NERVE BLOCK


PARASACRAL APPROACH (MANSOUR)

Ultrasound-Guided Technique

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

19

SCIATIC NERVE BLOCK
PARASACRAL APPROACH (MANSOUR)

complications of the traditional approach

hematoma, rectal perforation, and transient sciatic
neuralgia were not seen with the ultrasound guidance

20

SCIATIC NERVE BLOCK

CLASSIC POSTERIOR APPROACH
(LABAT TECHNIQUE)

The sciatic nerve is blocked at the level of the greater
sciatic notch distal to the piriformis muscle

21

SCIATIC NERVE BLOCK

CLASSIC POSTERIOR APPROACH
(LABAT TECHNIQUE)

Anatomy and Technique

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

22

SCIATIC NERVE BLOCK

CLASSIC POSTERIOR APPROACH
(LABAT TECHNIQUE)

Ultrasound-Guided Technique

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.

23

SCIATIC NERVE BLOCK

SUPINE LITHOTOMY APPROACH
(RAJ TECHNIQUE)

sciatic nerve is blocked at a more distal level, between
the ischial tuberosity and the greater trochanter

24

SCIATIC NERVE BLOCK

SUPINE LITHOTOMY APPROACH
(RAJ TECHNIQUE)

Surface Anatomy and Technique

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.

25

SCIATIC NERVE BLOCK

SUPINE LITHOTOMY APPROACH
(RAJ TECHNIQUE)

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

26

SCIATIC NERVE BLOCK


ANTERIOR APPROACH

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

27

SCIATIC NERVE BLOCK

ANTERIOR APPROACH

Surface Anatomy and Technique

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

28

SCIATIC NERVE BLOCK
ANTERIOR APPROACH

Limitations

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

29

SCIATIC NERVE BLOCK
ANTERIOR APPROACH

Ultrasound-Guided Technique

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.

30

SCIATIC NERVE BLOCK

LATERAL APPROACH

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.

31

SCIATIC NERVE BLOCK

LATERAL APPROACH

Surface Anatomy and Technique

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

32

SCIATIC NERVE BLOCK

POSTERIOR SUBGLUTEUS APPROACH
(di BENEDETTO)

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

33

SCIATIC NERVE BLOCK

POSTERIOR SUBGLUTEUS APPROACH
(di BENEDETTO)

Surface Anatomy and Technique

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

34

SCIATIC NERVE BLOCK

POSTERIOR SUBGLUTEUS APPROACH
(di BENEDETTO)

Ultrasound-Guided Technique

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

35

SCIATIC NERVE BLOCK


INFRAGLUTEAL PARABICEPS APPROACH

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,

36

SCIATIC NERVE BLOCK


INFRAGLUTEAL PARABICEPS APPROACH

Surface Anatomy and Technique

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.

37

SCIATIC NERVE BLOCK


INFRAGLUTEAL PARABICEPS APPROACH

Ultrasound-Guided Technique

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

38

SCIATIC NERVE BLOCK


MID-THIGH APPROACH


ULTRASOUND-GUIDED TECHNIQUE

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

39

The popliteal fossa

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.

40

The tibial nerve

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.

41

The common peroneal nerve

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.

42

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

have motor function

43

The sensory innervation of the foot is supplied by

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

44

The posterior tibial nerve supplies

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

45

the saphenous nerve

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

46

nerve stimulator of sciatic nerve branches

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.

47

SCIATIC NERVE BLOCK AT
THE POPLITEAL FOSSA


Indications

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.

48

SCIATIC NERVE BLOCK AT
THE POPLITEAL FOSSA

Posterior Approach

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.

49

Patchy sensory blockade of the foot may result, probably secondary

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.

50

SCIATIC NERVE BLOCK AT
THE POPLITEAL FOSSA


Lateral Approach

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

51

SCIATIC NERVE BLOCK AT
THE POPLITEAL FOSSA

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.

52

With continuous sciatic blocks

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

53

CHOICE OF LOCAL ANESTHETICS

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

54

long-acting local
anesthetic favors

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

55

The use of a continuous
catheter technique is indicated primarily when

postoperative
analgesia greater than 24 hours is desired

56

intermediateacting local anesthetics

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

57

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

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

58

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

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

59

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

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

60

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

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

61

Elicitation of EMR of inversion implies

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

62

COMPLICATIONS OF SCIATIC
NERVE BLOCK

parasacral approach of Mansour

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

63

COMPLICATIONS OF SCIATIC
NERVE BLOCK

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

64

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

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

65

Ankle block

Indication

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

66

Ankle block involves anesthetizing five nerves

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.

67

The nerve supply to the foot and ankle is provided by

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

68

Except for the posterior tibial nerve, the other nerves are

all sensory nerves.

69

cutaneous innervation of Posterior tibial nerve

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

70

cutaneous innervation of Deep peroneal nerve

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

71

cutaneous innervation of Sural nerve

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.

72

cutaneous innervation of Superficial peroneal nerve

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.

73

cutaneous innervation of Saphenous nerve

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.

74

POSTERIOR TIBIAL NERVE

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

75

POSTERIOR TIBIAL NERVE

Course

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.

76

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

partial block of the
nerve

77

the medial plantar (MPN) supplies

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

78

Neurostimulation of the MPN
produces

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

79

lateral plantar (LPN) nerves supplies

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.

80

Neurostimulation of the LPN produces

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

81

POSTERIOR TIBIAL NERVE


DISTAL APPROACH (TRADITIONAL SITE)

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

82

POSTERIOR TIBIAL NERVE


DISTAL APPROACH (TRADITIONAL SITE)

limitations

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.

83

POSTERIOR TIBIAL NERVE


DISTAL APPROACH (TRADITIONAL SITE

Technique

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.

84

POSTERIOR TIBIAL NERVE

PROXIMAL APPROACH

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.

85

POSTERIOR TIBIAL NERVE

MIDTARSAL APPROACH

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

86

POSTERIOR TIBIAL NERVE

SUBCALCANEAL APPROACH

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.

87

POSTERIOR TIBIAL NERVE

ULTRASOUND-GUIDED TECHNIQUE

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

88

DEEP PERONEAL NERVE (DPN)

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.

89

DEEP PERONEAL NERVE divides into

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

90

DEEP PERONEAL NERVE BLOCK

Technique

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.

91

DEEP PERONEAL NERVE BLOCK

Ultrasound-guided technique

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

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SUPERFICIAL PERONEAL NERVE

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.

93

SUPERFICIAL PERONEAL NERVE BLOCK

Technique:

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.

94

SURAL NERVE course

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.

95

SURAL NERVE supplies

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.

96

SURAL NERVE BLOCK

Technique:

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.

97

SURAL NERVE BLOCK


Ultrasound-guided technique

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.

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SAPHENOUS NERVE

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.

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SAPHENOUS NERVE supplies

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

100

SAPHENOUS NERVE BLOCK

Technique:

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.

101

LOCAL ANESTHETIC CHOICE
AND DOSE FOR ANKLE BLOCK

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

102

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

The use of epinephrine

Decks in Essentials of Pain Medicine Class (80):