Ana Barriga; Gerardo Méndez & Patricia Hernandez

The femoral nerve (NF) is the major branch (or ramus) of the lumbar plexus. It normally originates from the posterior divisions of the second to fourth anterior branches of the lumbar plexus (L2-L4). The psoas major muscle originates at the level of the T12 to L5 vertebrae, fuses with the iliacus muscle and then inserts into the lesser trochanter of the femur. Normally, at the level of the lesser pelvis, the NF is found between the iliacus and psoas major muscles. In this paper we present a case where the psoas major muscle is related to divisions or splitting of the NF, this is a rare variation in the division and course of the NF in relation to the psoas major muscle. The NF was observed to divide into two branches above the plane of the inguinal ligament after its origin in the lumbar plexus. The NF on the left side was formed by ventral branches from L2 to L4, at the level of L5 the nerve is perforated by fascicles of the psoas major muscle. The lower division of the NF passed deep to the fibers of the iliopsoas muscle and the upper division passed superficial to the psoas major muscle and deep to the iliac fascia. After a path of 60.21 mm both divisions joined, after trapping iliopsoas muscle fibers just immediately proximal to the inguinal ligament to form the NF trunk. While the embryological causes of peripheral nerve variations date back to the fifth and sixth week of intrauterine life, the clinical expression of neuromuscular dysfunctions will appear several decades later. Thus, physicians in the areas of traumatology and neurology should be aware of such anatomical variants to better understand pain and syndromes associated with nerve compression and during surgical maneuvers in this region.

KEY WORDS: Femoral Nerve [MeSH]; Psoas Muscle [MeSH] & Neuroanatomy [MeSH]

BARRIGA, A.; MÉNDEZ, G. & HERNANDEZ, P. Split unilateral del nervio femoral a nivel del músculo psoas mayor: reporte de caso. Int. J. Morphol., 39(6):1673-1676, 2021.