A multiply split femoral nerve and psoas quartus muscle.

Anat Cell Biol. 2019 Jun;52(2):208-210. doi: 10.5115/acb.2019.52.2.208. Epub 2019 Jun 30.

Wong TL, Kikuta S, Iwanaga J, Tubbs RS.

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Abstract

The femoral nerve is the largest branch of the lumbar plexus. It is normally composed of the ventral rami of spinal nerves L2 to L4. The psoas major has proximal attachments onto the T12 to L5 vertebrae and related intervertebral discs, fuses with the iliacus deep to the inguinal ligament and then attaches onto the lesser trochanter of the femur. Normally, the anatomical relationship is that the femoral nerve is located between the iliacus and psoas major. Herein, we report a case of the psoas quartus muscle related to several splits of the femoral nerve within the pelvis. Although the embryology for this is unclear, surgeons and physicians should be aware of such anatomical variants in order to better understand pain and entrapment syndromes and during surgical maneuvers in this region such as lateral transpsoas approaches to the lumbar spine.

KEYWORDS:

Anatomical variation; Cadaver; Femoral nerve; Posterior abdominal wall; Psoas muscles

Fig. 1

(A) Photograph of the left anterior view of the case presented herein. The psoas quartus (asterisk) and split femoral nerve is shown. (B) The psoas quartus is outlined by the white dotted line. (C) After cutting and reflecting the psoas quartus (asterisks and white solid lines) and the psoas major (red solid lines) the following structures are shown. CIA, common iliac artery; I, iliacus; PM, psoas major; QL, quadratus lumborum; 1, the most medial branch of the FN; 2, the second branch of the FN; 3, the third branch of the FN; 4, the most lateral branch.