Indications

Contraindications

Clinical anatomy

The iliacus fascia covers the iliacus and psoas muscles in the pelvis and descends into the thigh with these muscles (Fig. 28.1). The femoral nerve lies anterior to the psoas muscle initially, with the lateral cutaneous nerve of the thigh lateral to the psoas muscle and obturator nerve medial. At the inguinal ligament, the femoral nerve lies in a gutter between the psoas and iliacus muscles. These nerves thus lie beneath the iliacus fascia (Fig. 28.1). Spread of local anesthetic (Figs 28.2 and 28.3) beneath the iliacus fascia produces a higher success rate of anesthesia of the femoral nerve, lateral cutaneous nerve of the thigh, and obturator nerves than the femoral nerve block technique.

Figure 28.1 Cadaver structures illustrating anatomy relevant to the iliacus block technique. 1: anterior superior iliac spine; 2: pubic tubercle; 3: inguinal ligament with abdominal muscles sectioned and removed; 4: iliacus muscle; 5: iliacus fascia; 6: femoral nerve; 7: lateral cutaneous nerve of thigh; 8: genitofemoral nerve. The obturator nerve is not visible on the medial aspect of the psoas muscle.

Figure 28.2 Axial T1-weighted MR image after injection of 40 mL of contrast, showing spread of injectate. Compare with Figure 21.5. Note contrast surrounding femoral and obturator nerves. Spread is via the plane between the iliacus and psoas muscles. 1: psoas muscle; 2: iliacus muscle; 3: femoral nerve; 4: obturator nerve.

Figure 28.3 (Right) Sagittal T1-weighted MR image demonstrating spread of contrast toward the anterior superior iliac spine, where the lateral cutaneous nerve of the thigh lies. Compare with Figure 21.6. 1: psoas muscle; 2: contrast spread; 3: anterior superior iliac spine; 4: iliacus muscle.

Surface anatomy

The main landmarks for iliacus block are the anterior superior iliac spine, pubic tubercle, and inguinal ligament. The pubic tubercle can be palpated three fingers’ breadth from the midline, along the upper border of the pubis.

The inguinal ligament is outlined by a line connecting the anterior superior iliac spine and the pubic tubercle. The inguinal ligament is divided into equal thirds. At the junction between the outer one-third and inner two-thirds, a perpendicular line is drawn; 1 cm along this line is the needle insertion point (Fig. 28.4). The femoral artery can be palpated 2–3 cm more medially in the groin.

Figure 28.4 Landmarks for the iliacus block. The anterior superior iliac spine, pubic tubercle, and inguinal ligament are outlined. The inguinal ligament is divided into equal thirds. At the junction between the outer one-third and inner two-thirds, a perpendicular line is drawn extending into the thigh; 1 cm down this line is the needle insertion point.