Infrapiriform Foramen Space

spatium foraminis infrapiriforme

The infrapiriform foramen is the lower division of the greater sciatic foramen below the piriformis muscle, transmitting the sciatic nerve, inferior gluteal nerve and vessels, pudendal nerve, internal pudendal vessels, posterior femoral cutaneous nerve, and nerves to obturator internus and quadratus femoris.

Anatomical Data

Boundaries & Contents

Location	Lower part of the greater sciatic foramen, below piriformis
Boundaries	Lower border of piriformis (above) Sacrospinous ligament and ischial spine (below) Sacrotuberous ligament (medially)
Contents	Sciatic nerve Inferior gluteal nerve and vessels Pudendal nerve and internal pudendal vessels Posterior femoral cutaneous nerve Nerves to obturator internus and quadratus femoris

Biomechanics

Function & Actions

Carries most of the nerves leaving the pelvis for the buttock, perineum and back of the thigh. A tight piriformis or variant nerve course here is one cause of deep gluteal pain.

Clinical Relevance

Clinical Notes

The infrapiriform foramen is the exit point for the sciatic nerve from the pelvis into the gluteal region. Piriformis syndrome is characterised by sciatic nerve compression at this level. The inferior gluteal vessels may be inadvertently damaged during posterior hip arthroplasty approaches in this region. Endoscopic deep gluteal space surgery accesses the infrapiriform contents for piriformis muscle and sciatic nerve release.

Pathology

Common Injuries & Conditions

Sciatic Nerve Compression at Infrapiriform Foramen

Sciatic nerve entrapment at the infrapiriform space from piriformis hypertrophy, fibrous bands, or anatomical variants of nerve passage through the piriformis producing buttock and posterior leg pain, managed by endoscopic nerve release.

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