Sciatic Foramina

These are two foramina of the gluteal region, which provide a path for entrance and exit of structures to and from pelvis.

Greater Sciatic Foramen:

It is formed by the greater sciatic notch of the hip bone. The foramen is partly filled by the emerging piriformis muscle. Above this muscle, the superior gluteal vessels and nerves leave the pelvis and below it, the inferior gluteal vessels and nerves leave the pelvis.

Boundaries of greater sciatic foramen:

  • Anteriosuperior = Greater sciatic notch
  • Posterior = Sacrotuberous ligament
  • Inferior = Sacrospinous ligament and ischial spine

Lesser Sciatic Foramen:

It is smaller than the greater sciatic foramen and is formed by the lesser sciatic notch of the hip bone. It transmits the tendon of obturator internus muscle, nerve to obturator internus, internal pudendal vessels and pudendal nerve. Actually the lesser sciatic foramen provides a pathway for structures that exit the pelvis through the greater sciatic foramen to re-enter the pelvis.

Boundaries of lesser sciatic foramen:

  • Anterior = Body of ischium
  • Superior = Ischial spine and sacrospinous ligament
  • Posterior = Sacrotuberous ligament