The saphenous nerve block is most commonly used in combination with a
sciatic nerve block or popliteal block to complement anesthesia of the lower
leg for various vascular, orthopedic, and podiatry procedures. The saphenous
nerve is a terminal cutaneous branch of the femoral nerve. Its course is in
the subcutaneous tissue of the skin on the medial aspect of the ankle and
foot. All cutaneous nerves of the foot should be thought of as a neuronal
network rather than single strings of nerves with a well-defined and
consistent anatomic position.
Distribution of Anesthesia
The saphenous nerve innervates the skin over the medial, anteromedial,
and posteromedial aspect of the lower leg from above the knee (part of the patellar
plexus) to as low as the first metatarsophalangeal joint in some instances
(Figures 40–1 and 40–6).
Saphenous nerve anatomy. Saphenous nerve pierces
through the sartorius muscle (1), subpatellar branch (2), saphenous nerve in
its descent on the medial aspect of the thigh (3).
The patient is placed supine with the leg to be blocked supported by a
The main landmark for this block is the tibial tuberosity, an easily
recognizable and easily felt bony prominence on the anterior aspect of the
tibia a few centimeters distal from the patella (Figure 40–7). The
saphenous nerve is the largest cutaneous branch of the femoral nerve. It
descends laterally to the femoral artery into the adductor canal, where it
crosses anteriorly to become medial to the artery. It proceeds vertically
along the medial side of the knee behind the sartorius, pierces the fascia
lata between the tendons of the sartorius and gracilis, and then becomes
subcutaneous. From here, it descends on the medial side of the leg with the
long saphenous vein along the medial tibial border. Note that the saphenous
nerve branches into numerous small branches as it enters the subcutaneous
space, and, as such, it is often difficult to achieve blockade of the entire
extensive saphenous nerve network. For this reason, it is always preferable
to block the saphenous nerve as distally as possible. For instance, to
achieve anesthesia of the foot, the saphenous nerve is best approached at
the level of the ankle, which is identical with the technique for performing
an ankle block.
Tibial tuberosity. Palpation of the landmark for the
saphenous nerve block.
The below-knee field block is performed with the patient in supine
position. Five to 10 mL of local anesthetic are injected as a ring deeply
subcutaneously, starting at the medial surface of the tibial condyle and
ending at the dorsomedial aspect of the upper calf (Figure 40–8).
Saphenous nerve block. Shown is a subcutaneous
injection of 10 mL of local anesthetic in a circumferential fashion on the
medial aspect of the leg at the level of the tibial tuberosity.
The paravenous technique has also been described, which is based on the
close relation of the saphenous vein and nerve, to achieve a higher success
rate. First, the saphenous vein is identified using a tourniquet around the
leg in dependent position. The technique involves injection of 5 mL of local
anesthetic in a fan-like fashion around the vein on the medial side of the
leg just distal from the patella.12 This technique,
however, carries a small risk of creating a hematoma when the saphenous vein
In the transsartorial approach, with the patient in the supine position, a
skin wheal is raised over the sartorius muscle belly. The sartorius muscle
can be palpated just above the knee with the leg extended and actively
elevated. The needle is inserted at one finger-width above the patella
slightly posterior to the coronal plane and slightly caudad through the
muscle belly of the sartorius until a loss of resistance identifies the
subsartorial adipose tissue. The depth of insertion is typically between 1.5
and 3 cm. After negative aspiration for blood, 10 mL of local anesthetic are
For surgery on the foot, the saphenous nerve is best blocked just above the
medial malleolus, similar to the technique in ankle block (Figure
40–9). Using a 1½-in. needle, 6–8 mL of local anesthetic are
injected subcutaneously immediately above the medial malleolus in a
ring-like fashion. The most commonly reported complication of this block is
a painless hematoma of the saphenous vein at the injection site.
Saphenous nerve block, distal approach above the
The saphenous nerve can also be blocked by using a nerve stimulator
technique and performing a low-volume femoral nerve block. Injection of 10
mL of local anesthetic after obtaining either a medial muscle response,
signified by contraction of the vastus medialis muscle, or an anterior
muscle response, signified by contraction of the rectus femoris muscle and
elevation of the patella, results in a high rate of block
success.13,14 Neurostimulation of the medial
compartment of the femoral nerve requires even less volume of local
anesthetic, compared with that of a standard femoral
The most effective method of blocking the saphenous nerve is a
low-volume femoral nerve block.
Injection of a mere 10 mL of local anesthetic upon obtaining twitches of the
patella or vastus medialis muscle results in a high success rate.
In a recent comparison of the different approaches to saphenous nerve
block, the transsartorial, perifemoral, below-knee field block, and block at
the medial femoral condyle were evaluated for efficacy. The transsartorial
approach resulted in 100% sensory blockade of the medial aspect of the
leg, whereas the perifemoral and the below-knee field block resulted in
70%. The medial femoral condyle block resulted in 40% of the patients
having sensory blockade of the medial aspect of the leg with only 25%
having complete anesthesia at the medial malleolus.16 This
supported the findings of a previous study in which 94% of patients had
complete anesthesia of the medial malleolus after a transsartorial saphenous
nerve block.17 However, both of these studies have limited
numbers of patients, and more research needs to be conducted.