the genitofemoral nerve typically pierces and passes through the psoas major muscle before bifurcating into a genital branch and a femoral branch midway along its anterior surface. in approximately 25% of cases, the genitofemoral nerve splits into these branches "before" it enters the psoas major or "within" the muscle belly of psoas major (with fibers of the psoas major separating the genital and femoral branches). usually this variation causes the split to be occur earlier in the genitofemoral nerve, at the upper rather than mid-portion of the anterior surface of the psoas major.