Suggested Technique

The patient is placed in supine position (flat with slight extension of the hip). Pannus retraction or reverse Trendelenburg position may be necessary in overweight patients. Place the transducer longitudinally to image the iliacus muscle lateral to the femoral nerve. Because of the inclination of the iliacus muscle, this region is slightly more superficial than the femoral nerve. The iliacus muscle forms a ridge because of the underlying bone of the superior pubic ramus. The deep circumflex artery lies superficial to the fascia iliaca 1 to 2 cm proximal to the inguinal ligament. This artery is 2 to 3 mm in diameter and lies on the central side of the iliacus ridge. Tilting the transducer laterally enhances imaging of the fascia iliaca due to its inclination.¹

In-plane approach from distal to proximal is used. For this block it is critical that the needle tip be positioned between the fascia iliaca and iliacus muscle,² just distal to the position of the deep circumflex iliac artery. The needle travels under the inguinal ligament, which lies over the ridge of the iliacus muscle. There is a handedness to this longitudinal approach (right handed for right-sided block, left handed for left-sided block).

The initial injection under the fascia iliaca forms a lens shape. As volume is administered, the injected distribution should curve along the surface of the iliacus muscle, resembling a hill shape. A long block needle can be used to hydrodissect down into the injected fluid to promote proximal distribution. Most practitioners use high volumes of local anesthetic (e.g., 20 mL for average-sized adult patients) to provide extensive distribution to the multiple nerves of the lumbar plexus.

The deep circumflex iliac artery arises as a recurrent branch from the external iliac artery and can be a valuable landmark for proximal fascia iliaca block. The lateral femoral cutaneous nerve lies between the deep circumflex iliac artery and the iliacus muscle. Therefore, the fluid injected for proximal fascia iliaca block should distribute under the deep circumflex iliac artery and around the lateral femoral cutaneous and femoral nerves.

FIGURE 39-1 Positioning for ultrasound-guided proximal fascia iliaca block. In-plane approach with longitudinal imaging is shown.

FIGURE 39-2 Longitudinal (coronal) imaging for ultrasound-guided fascia iliaca block. The deep circumflex iliac artery is shown in short-axis view (A). Verification that the deep circumflex arises from the external iliac artery is shown by rotating the transducer to obtain a long-axis view of the artery (B).

FIGURE 39-3 Longitudinal in-plane approach to ultrasound-guided fascia iliaca block. The needle tip pierces the fascia iliaca just distal to the peak of the iliacus muscle and the deep circumflex iliac artery. The injection tracks proximally and down toward nerves of the lumbar plexus.

FIGURE 39-4 Verification of distribution of the injection to the femoral nerve as assessed in short axis view. Sonograms are shown before (A) and after (B) injection. Local anesthetic has distributed over the anterior surface of the femoral nerve.

FIGURE 39-5 Longitudinal reference images for proximal fascia iliaca block. The anterior superior iliac spine is shown in coronal imaging, indicating the probe is too lateral for fascia iliaca block.