Figure 1. Relationship of iliopsoas muscle, iliac muscle, femoral nerve, and external iliac artery within the pelvis. Note the probable location of a displacing and compressing retractor blade that would be used for an abdominal surgical approach to the pelvis. Note the formation of the femoral nerve from the lumbar plexus and its course in the iliopsoas muscle. Because the origin of the nerve branch to the iliopsoas muscle is proximal to the location of the retractor blade, an injury caused by this mechanism would not affect the function of the iliopsoas muscle. In contrast, any injury mechanism that would involve the lumbosacral nerve plexus likely would affect the function of this muscle. (Reprinted with permission. [2])