Expansion
Structures above and below piriformis as they leave the pelvis
Mnemonic
Everything is named for piriformis, which divides the foramen:
Above piriformis: superior gluteal nerve and vessels.
Below piriformis, remembered as “Insufficient Practice Perhaps Never Increases Skill” running lateral to medial:
- I - Inferior gluteal nerve and vessels
- P - Pudendal nerve
- P - internal Pudendal vessels
- N - Nerve to obturator internus
- I - Sciatic nerve
- S - posterior femoral cutaneous nerve, nerve to quadratus femoris
The pudendal nerve is the one that leaves the pelvis through the greater foramen and immediately re-enters through the lesser foramen, hooking around the sacrospinous ligament, which is the point at which a pudendal nerve block is given.
Expansion
Above piriformis:
- Superior gluteal nerve and vessels
Below piriformis:
- Sciatic nerve
- Inferior gluteal nerve and vessels
- Posterior femoral cutaneous nerve
- Nerve to quadratus femoris
- Pudendal nerve and internal pudendal vessels
- Nerve to obturator internus
The pudendal nerve and internal pudendal vessels then re-enter the pelvis through the lesser sciatic foramen.