Which one of the following is correct regarding the anatomy of the fascia iliaca compartment?
a.its roof is formed by the fascia lata
b.its floor is formed by the fascia iliaca
c.the femoral artery and vein lie medial and deep to it
d.the femoral and lateral femoral cutaneous nerves lie within it
e.it is accessed by inserting a needle half way along and above the inguinal ligament
The answer is d.The femoral nerve and the lateral femoral cutaneous nerve (at least for some of its course) lie within the fascia iliaca compartment.
The fascia iliaca compartment (FIC) is a potential space in the inguinal region just above the upper thigh (fig 1). It exists between the fascia iliaca above and the iliacus and psoas major muscles below. The femoral vessels – femoral artery and vein – lie outside and above the FIC, between the fascia iliaca and the more superficial fascia lata.
The fascia iliaca compartment (FIC) contains the femoral nerve and the lateral femoral cutaneous nerve. Since local anaesthetic injected into the FIC also often blocks the obturator nerve, this is also often included in its contents but anatomically both the anterior and posterior branches of the obturator nerve are separated from the main FIC by the psoas and pectineus muscles. The femoral nerve and lateral femoral cutaneous nerve of the thigh arise from the lumbar plexus (L2, 3, 4) and supply sensation to the anteromedial surface and the lateral surfaces of the thigh respectively. Together, they also innervate the hip joint (Hilton’s law).
To access the FIC for fascia iliaca compartment block(FICB), a blunt needle is inserted 1cm below the junction of the medial two thirds and outer third of a line drawn from the anterior superior iliac spine to the pubic tubercle. The needle passes through the skin, the fascia lata and then fascia iliaca (both identified by a pop feeling as the needle pierces the fascia itself) before entering the FIC. A large volume of local anaesthetic is injected (typically 30-40ml of 0.25% bupivacaine; max dose 2mg/kg) which disperses within the compartment to reliably block the femoral and lateral femoral cutaneous nerves and often far enough to also block the obturator nerve. The resultant anaesthesia provides excellent pain relief for patients with either a neck of femur fracture or femoral fracture.
Fig 1. Anatomy of the fascia iliaca compartment.