Lat fem cut n: Ext landmarks

Basic, Basic Sciences, Statistics

The lateral femoral cutaneous nerve (LFCN) divides into several branches that innervate the lateral and superior aspects of the thigh.  The LFCN may be blocked for meralgia paresthetica as well as post-op analgesia for hip surgery and muscle biopsy of the proximal lateral thigh.  Due to the variable anatomy of the LFCN, it is difficult to perform an effective block without the use of ultrasound to identify the appropriate fascial plane through which the LFCN passes.  The LFCN is usually located about 0.5 to 1 cm deep between the tensor fascia latae and sartorius muscles, and it is typically 1-2 cm medial and inferior to the ASIS.

To perform a LFCN block, the ultrasound transducer should be placed 2 cm inferior to the ASIS and parallel to the inguinal ligament.  The LFCN will appear as a round, hypoechoic structure between the tensor fascia latae and sartorius muscles (in short axis view).  The needle is typically inserted in a lateral to medial direction (in-plane); a “pop” is typically felt as the needle tip enters the fascial plane between the tensor fascia latae and sartorius muscles.  Spread of local anesthetic should be visualized in this fascial plane. A total of 5-10 mL of local anesthetic is generally sufficient to provide analgesia.


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Kevin Greer, MD