The femoral nerve block is considered one of the basic nerve block
techniques because it is relatively simple to perform, carries a low risk of
complications, and results in a high success rate. When used alone, femoral
nerve block is well suited for surgery on the anterior aspect of the thigh
and for postoperative pain management after femur and knee surgery. However,
when combined with a sciatic block, anesthesia of almost the entire lower
limb from the mid-thigh level can be achieved.
When used alone, a femoral nerve block is well suited for surgery on
the anterior aspect of the thigh and for superficial surgery on the medial
aspect of the leg below the knee. Some examples include repair of the
quadriceps tendon or quadriceps muscle biopsy, long saphenous vein
stripping, and postoperative pain management after femur and knee surgery.
Femoral nerve block significantly improves postoperative analgesia after
knee surgery during the first 8–12 hours postoperatively.1–5
However, when combined with a sciatic or popliteal block, femoral
block provides anesthesia for entire lower leg or ankle surgery.
The primary indication of continuous femoral nerve block is pain
management after major femur or knee surgery.6–22 In
addition, when compared with a single dose technique or placebo, continuous
femoral nerve block significantly reduces postoperative morphine consumption
in patients after total hip replacement.23,24 For this
application, the technique is as efficient as IV patient-controlled
analgesia (PCA) with morphine or patient-controlled epidural analgesia, and
it results in fewer technical problems and side effects.13
Continuous femoral nerve block provides excellent analgesia in patients
with femoral shaft or femoral neck fractures.14,15,21,25
Its relative simplicity makes it uniquely suitable for
analgesia in the emergency room and facilitate physical and radiologic
examinations as well as manipulations of the fractured femur or hip.
After major knee surgery, continuous femoral nerve block provides better
pain relief than parenteral administration of opioids (IV PCA,
intramuscular)7,12,16,17,20 or intraarticular
analgesia.18,26 For knee surgery, continuous femoral block
is as effective as continuous lumbar plexus block27 or
continuous epidural analgesia,12,20 with fewer risks
of complications. Because this technique results in faster postoperative
knee rehabilitation than IV PCA with morphine and fewer side effects than
epidural analgesia, continuous femoral nerve block is probably the analgesic technique of
choice in patients after total knee
Relative contraindications for femoral nerve block may include previous
ilioinguinal surgery (femoral vascular graft, kidney transplantation), large
inguinal lymph nodes or tumor, local infection, peritoneal infection, and
preexisting femoral neuropathy.
The femoral nerve is the largest nerve of the lumbar plexus. It is
formed by the dorsal divisions of the anterior rami of the L2, L3, and L4
spinal nerves. It emerges from the lateral border of the psoas muscle,
approximately at the junction of the middle and lower thirds of that muscle.
Along its course to the thigh, it remains deep to fascia iliaca. It
enters the thigh posterior to the inguinal ligament, where it is positioned
immediately lateral and slightly posterior to the femoral artery (Figure
35–1). At this level, it is situated deep to fascia lata
(Figure 35–2). As the nerve passes into the thigh, it divides into
anterior and posterior branches (Figure 35–3). Located above the fascia
iliaca, the anterior branches innervate the sartorius and pectineus muscles
(Figure 35–4) and the skin of the anterior and medial aspects of the thigh.
Located under the fascia iliaca, the posterior branches innervate the
quadriceps muscle and the knee joint and give off the saphenous nerve. The
saphenous nerve supplies the skin of the medial aspect of the leg below the
knee joint (Figure 35–5).
Anatomic relationship in the femoral triangle.
Tissue sheaths and femoral nerve. Femoral artery and vein relationships.
Composition of the femoral nerve at the level of blockade.
Motor innervation of the femoral nerve.
Sensory innervation of the femoral nerve and distribution of anesthesia with femoral nerve block.
It is useful to think of the mnemonic NAVEL (nerve, artery, vein) going
from lateral to medial when recalling the relationship of the femoral nerve
to the vessels in the inguinal crease.
The following landmarks are used to determine the site of needle
insertion: inguinal ligament, inguinal crease, femoral artery
Anatomic landmarks for femoral nerve block. IL,
Inguinal ligament; IC, inguinal crease; FA, femoral arterial pulse. The needle insertion site (X) is located just below the inguinal crease, 1–2 cm
lateral to the pulse of the femoral artery.
In obese patients, the identification of the inguinal crease can be
facilitated by asking an assistant to retract the lower abdomen laterally
(see Figure 35–7).
Maneuver to facilitate exposure of the anatomy during
femoral nerve blockade: The lower abdomen in obese patients may obstruct the
access to the femora/inguinal region. This can be remedied by simple
retraction of the lower abdomen laterally throughout the procedure.
A standard regional anesthesia tray is prepared with the following
Sterile towers and gauze packs
20-mL Syringe with local anesthetic
Sterile gloves, marking pen
One 25-gauge, 1½-in. needle for skin infiltration
A 5-cm long, short-bevel, insulated stimulating needle
A peripheral nerve stimulator and a surface electrode