Greater sciatic foramen
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The greater sciatic foramen is a large osteoligamentous foramen within the pelvis that is a major conduit of neurovascular structures from the pelvis to the lower limb. The greater sciatic foramen is separated from the smaller lesser sciatic foramen below by the sacrospinous ligament.
In a clockwise fashion, its boundaries include:
- superior: anterior sacroiliac ligament
- posteromedial: sacrotuberous ligament
- inferior: sacrospinous ligament and ischial spine
- anterolateral: greater sciatic notch
Many structures enter or exit the pelvis through the greater sciatic foramen and are broadly divided based on whether they lie above or below the piriformis muscle - the suprapiriform and infrapiriform foramina respectively.