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Ultrasound for fascia iliaca and inguinal region blocks
Key Points
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A high-frequency linear transducer is preferred for this block.
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The fascia iliaca compartmental block (FICB) can be used as an alternative anterior approach to the lumbar plexus block, targeting the femoral, obturator, and lateral femoral cutaneous nerves.
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The suprainguinal approach to the FICB is associated with better cranial spread of local anesthetic and more complete sensory blockade of the anterior, medial, and lateral thigh compared with the traditional infrainguinal approach.
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The traditional infrainguinal approach required great volumes of local anesthetic to achieve adequate cephalad spread. The suprainguinal approach requires less volume to achieve adequate sensory blockade.
Perspective
The fascia iliaca compartmental block (FICB) can be used to provide complete sensory blockade of the medial, anterior, and lateral thigh. This block has been used effectively for postoperative analgesia following hip and knee surgery. It can be used as an alternative to a traditional lumbar plexus block by targeting the femoral nerve, obturator, and lateral femoral cutaneous nerves, which lie deep to the fascia iliaca. It can also provide adequate analgesia for hip and proximal femur fractures as well as for total hip arthroplasty. As with any fascial plane block within the fascia iliacus plane, blockade of the femoral, obturator, and lateral femoral cutaneous nerves is achievable with a large enough volume of local anesthetic. Traditionally, the fascia iliaca block was performed using a ‘double pop’ technique as the needle traversed the fascia lata and fascia iliaca. This was associated with a significant block failure rate, as high as 10%–37%. However, with advancements in ultrasound and the use of direct needle visualization under continuous ultrasound guidance, the success rate and consequently the popularity of this block is beginning to regain favor.
Anatomy
The iliacus muscle lies over the ilium. It is a large flat triangular shaped muscle that joins with the psoas major muscle forming the anisotropic hypoechoic iliopsoas muscle. The iliopsoas is covered by the hyperechoic broad ligament and fascia iliaca. The iliopsoas muscle then travels beneath the inguinal ligament, exiting the pelvis, winding around the proximal neck of the femur, and inserts into the lesser trochanter of the hip, functioning as a powerful hip flexor.
The fascia iliaca is located anterior to the iliacus muscle, bound superiorly and laterally by the iliac crest and merges with the overlying psoas muscle fascia medially. The femoral nerve descends through the psoas major muscle passing through its lateral border coursing between psoas and the iliacus muscle deep to the fascia iliaca.
The obturator nerve crosses the iliacus muscle deep to the fascia, innervating the distal medial thigh. The lateral femoral cutaneous nerve emerges from the lumbar plexus and courses inferiorly just lateral to the psoas muscle before crossing the iliacus just deep to the fascia iliaca ( Fig. 16.1 ).
Sonoanatomy
Technique
The FICB has been traditionally performed below the level of the inguinal ligament. However, substantial clinical evidence and radiological studies suggest that the infrainguinal approach does not reliably block the femoral, obturator, and lateral femoral cutaneous nerves. Indeed block failure rate has been described as high as 10%–37%.
An alternative technique, the suprainguinal approach has been gaining favor because of improved outcomes in terms of median pain scores in hip fracture patients, and has a more consistent spread of local anesthetic to the lumbar plexus. A recent study identified improved cranial spread of local anesthetic with the suprainguinal approach, compared with a more caudal spread with the traditional infrainguinal injection. The suprainguinal approach has been shown to provide comparable analgesic efficacy to periarticular infiltration for total hip arthroplasty.
Typical injectate volumes include 20 mL of local anesthetic solution such as 0.5% ropivacaine for hip fractures and lower concentrations for postoperative analgesia following hip or knee surgery to minimize motor block.
The patient is positioned supine and a high frequency linear probe is placed in the inguinal crease to identify the femoral artery. Typical depths are 3-4cm from the skin. The probe is moved laterally to identify the sartorius muscle, which is then traced cephalad to its insertion point over the anterior superior iliac spine (ASIS). The ASIS can be easily identified by its hump-like hypoechoic shadow. Moving the probe 2-3 cm medial to the shadow identifies the iliacus muscle, which covers the ilium. The bright hyperechoic band covering the iliacus is the fascia iliaca.
The probe is then rotated in a slight parasagittal plane such that the medial end is pointing towards the umbilicus. At this position the anterior abdominal muscles may be identified from superficial to deep, as the internal oblique muscle, transversus abdominis, and the fascia iliaca overlying the iliacus muscle. The curve of the ilium will be identified on the inferior caudal side of the ultrasound image with the iliacus muscle overlying it. With this view, the classical “bow-tie” appearance may be appreciated ( Fig. 16.2 ).
The block needle is inserted and advanced caudad to cephalad such that it traverses the sartorius muscle above the inguinal ligament. It is then advanced in-plane just deep to the fascia iliaca. After piercing the fascia, 1-2 mL of local anesthetic is injected to confirm adequate spread cranially, and peeling of the fascial layers lifting the fascia off the superficial layer of the iliacus muscle. Then 20-30mL of the block solution is deposited superficial to the iliacus muscle and deep to the fascia iliaca. Adequate spread of local anesthetic will expand the space between the iliacus muscle and fascia iliaca in a cephalad direction towards the superior edge of the iliacus muscle. In order to improve the spread of local anesthetic superiorly, the needle tip may be advanced superiorly into the space created by the injectate.
Although the FICB has enjoyed renewed interest and is deemed a safe and effective block, complications that have been described include bladder perforation, and inadvertent puncture of the deep circumflex iliac artery, inferior epigastric artery, external iliac artery, spermatic cord, and hernia contents. Careful use of real-time ultrasound and maintaining an in-plane needle approach should help mitigate these potential complications.
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