Ultrasound-guided supra-inguinal fascia iliaca block: a cadaveric evaluation of a novel approach

Abstract

Existing descriptions of ultrasound-guided fascia iliaca block focus on injection of local anaesthetic inferior to the inguinal ligament, relying on supra-inguinal spread to block the lateral femoral cutaneous nerve in the iliac fossa. In this study, we explored injectate spread and nerve involvement in a cadaveric dye-injection model, using a supra-inguinal ultrasound-guided technique that places local anaesthetic directly into the iliac fossa. Bilateral injections of 20 ml 0.25% aniline blue dye were made in six unembalmed cadavers. The femoral nerve was stained by the dye in all twelve injections. The lateral femoral cutaneous nerve was stained bilaterally in five cadavers, but the nerve was absent on both sides in the sixth cadaver. The ilio-inguinal nerve passed into the iliac fossa over the iliacus muscle in eight of the hemi-pelvi and was stained in seven of these occasions. We have performed more than 150 blocks in patients using this approach without complications. Injection using this technique in cadavers leads to extensive fluid spread throughout the iliac fossa. In patients this approach may allow a lower volume block of the femoral nerve and lateral femoral cutaneous nerve while still injecting at a distance from the femoral nerve.