greater sciatic foramen greater sciatic foramen the greater sciatic foramen is an opening (foramen) in the posterior human pelvis. it is formed by the sacrotuberous and sacrospinous ligaments. the piriformis muscle passes through the foramen and occupies most of its volume. the greater sciatic foramen is wider in women than in men. greater sciatic foramenthe pelvis showing the greater sciatic foramen in reddetailsidentifierslatinforamen ischiadicum majusta98a03.6.03.008ta21316fma17031anatomical terminology structure it is bounded as follows: anterolaterally by the greater sciatic notch of the ilium. posteromedially by the sacrotuberous ligament. inferiorly by the sacrospinous ligament and the ischial spine. superiorly by the anterior sacroiliac ligament. function the piriformis, which exits the pelvis through the foramen, occupies most of its volume. the following structures also exit the pelvis through the greater sciatic foramen: locationnamevesselsnerves above the piriformissuprapiriform foramensuperior gluteal vesselssuperior gluteal nerve below the piriformisinfrapiriform forameninferior gluteal vessels internal pudendal vesselsinferior gluteal nervepudendal nervesciatic nerve posterior femoral cutaneous nerve nerve to obturator internus nerve to quadratus femoris