Greater Sciatic Foramen Space

spatium foraminis ischiadici majoris

The greater sciatic foramen is the large opening between the greater sciatic notch of the ilium and the sacrospinous ligament, through which the piriformis muscle passes and the major neurovascular structures exit the pelvis: the sciatic nerve, superior and inferior gluteal vessels and nerves, pudendal nerve, internal pudendal vessels, nerve to obturator internus, and the posterior femoral cutaneous nerve.

Anatomical Data

Boundaries & Contents

Location	Back of the pelvis, above the sacrospinous ligament
Boundaries	Greater sciatic notch of the hip bone (front and above) Sacrotuberous ligament (back) Sacrospinous ligament and ischial spine (below)
Contents	Piriformis Superior gluteal nerve and vessels (above piriformis) Inferior gluteal nerve and vessels Sciatic nerve Pudendal nerve and internal pudendal vessels Posterior femoral cutaneous nerve Nerves to obturator internus and quadratus femoris

Biomechanics

Function & Actions

The main exit from the pelvis to the buttock. Piriformis fills much of it and divides it into suprapiriform and infrapiriform openings.

Clinical Relevance

Clinical Notes

The greater sciatic foramen is divided by the piriformis into the suprapiriform and infrapiriform spaces. The sciatic nerve exits infrapiriformly in 84% of individuals. Foramen contents are compressed in piriformis syndrome, gluteal compartment syndrome, and sacral fractures with posterior displacement. CT-guided approaches to the sciatic notch are used for sciatica nerve hydrodissection and posterior hip denervation procedures.

Pathology

Common Injuries & Conditions

Piriformis Syndrome

Sciatic nerve compression in the infrapiriform space of the greater sciatic foramen by a hypertrophied or fibrotic piriformis, producing deep gluteal pain and sciatica that worsens with hip external rotation.

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