Anatomy

The aim of the FI block is to introduce a high volume of local anaesthetic to spread into the potential space under the fascia iliaca. It targets the 3 nerves which run in this area. These are the femoral nerve, the lateral femoral cutaneous nerve and the obturator nerve. In the FI compartment block the obturator nerve is usually only partially blocked.

The needle is inserted laterally and the structures pierced during passage are skin, subcutaneous tissue, fascia lata and then fascia iliaca. The landmark technique has been called the “two pop” technique as loss of resistance is felt as the needle passes through the 2 fascial layers.

The ultrasound approach is safer and more accurate as it allows visual confirmation that local anaesthetic is delivered to the correct fascial plane.

The sonographic anatomy is shown in the later section on performing the block.