Accessory Iliacus Muscle with Split Femoral Nerve: A Case Report

Background: The femoral nerve originates from the anterior rami of nerve roots L2, L3, and L4 of the lumbar plexus. In its usual course, the femoral nerve descends down between the psoas major and iliacus muscles of the posterior abdominal wall where it supplies branches to the iliacus and pectineus muscles prior to entering the thigh through the femoral triangle. Subsequently, it splits into multiple branches to supply the muscles and skin of the anterior thigh. Case Information: Herein, we report a variant of this course where during routine dissection of the posterior abdominal wall, an accessory iliacus muscle and split femoral nerve was observed on the right side of a 75-year-old female cadaver. The femoral nerve had divided into two branches that passed anterior and posterior to the accessory iliacus muscle prior to leaving the pelvis. After the two branches descended below the inguinal canal, the posterior branch split again into medial and lateral branches. The original anterior branch combined with the medial branch before splitting again. In addition, the accessory iliacus muscle had its own tendon that inserted a few millimeters below the lesser trochanter of the femur. Conclusions: Knowledge of the existence of muscle and nerve variants is useful in determining the pathology and proper treatment for tendinopathies, compressive neuropathies, and other pathological states. In this study, a rare nerve variant and accessory muscle has been described along with potential clinical implications.