Suprapiriform foramen
The suprapiriform foramen (foramen suprapiriforme) is a narrow space located in the upper part of the gluteal region.
Topographic boundaries:
- Superiorly: lower margin of the gluteus medius muscle.
- Inferiorly: upper margin of the piriformis muscle.
Passing through this foramen is the superior gluteal neurovascular bundle, the elements of which have a strict spatial organization.
The main arterial vessel here is the superior gluteal artery (a. glutea superior). It originates in the pelvic cavity as a branch of the posterior trunk of the internal iliac artery. The supply zone of this artery is quite extensive: it nourishes the piriformis, gluteus maximus, gluteus medius, and gluteus minimus muscles. The artery is covered by a dense plexus formed by the corresponding veins.
Motor innervation of these muscles is provided by the superior gluteal nerve (n. gluteus superior). Topographically, it is located inferiorly and laterally relative to the blood vessels of the bundle.
Infrapiriform foramen
The infrapiriform foramen (foramen infrapiriforme) is localized inferior to the previous one and serves as a gateway for the exit of several important structures into the subgluteal space.
Topographic boundaries:
- Superiorly: lower margin of the piriformis muscle.
- Inferiorly: superior gemellus muscle.
Several anatomical complexes exit the pelvic cavity through this foramen simultaneously:
- Sciatic nerve.
- Inferior gluteal neurovascular bundle.
- Pudendal neurovascular bundle.
Topography of structures in the infrapiriform foramen
The mutual arrangement of elements in the infrapiriform foramen is of critical importance for operative surgery.
The most lateral position is occupied by the sciatic nerve (n. ischiadicus). This is the largest nerve in the human body. In surgical practice, the sciatic nerve serves as the main internal landmark for identifying the foramen itself and locating the other neurovascular bundles.
Strictly medial to the sciatic nerve are the following structures:
- Posterior cutaneous nerve of the thigh (n. cutaneus femoris posterior).
- Comitant artery of the sciatic nerve (a. comitans n. ischiadici). It is important to note that this vessel is a branch of the inferior gluteal artery.
| Structure | Foramen | Localization relative to vessels/nerves |
|---|---|---|
| Superior gluteal nerve | Suprapiriform | Inferior and lateral to vessels |
| Sciatic nerve | Infrapiriform | Most lateral |
| Posterior cutaneous nerve of the thigh | Infrapiriform | Medial to the sciatic nerve |
Briefly: answers to topical questions
What are the exact anatomical boundaries of the suprapiriform foramen?
The exact anatomical boundaries of the suprapiriform foramen (foramen suprapiriforme) are the margins of two muscles of the gluteal region between which this canal is formed.
- Superiorly — the boundary is formed by the lower margin of the gluteus medius muscle (m. gluteus medius).
- Inferiorly — the boundary is formed by the upper margin of the piriformis muscle (m. piriformis).
The superior gluteal neurovascular bundle exits the pelvic cavity through this space.
What are the exact anatomical boundaries of the infrapiriform foramen?
The exact anatomical boundaries of the infrapiriform foramen (foramen infrapiriforme) are formed by two muscles of the gluteal region between which the cleft is formed.
- Superiorly — the foramen is bounded by the lower margin of the piriformis muscle (m. piriformis).
- Inferiorly — the boundary is formed by the superior gemellus muscle (m. gemellus superior).
Large vessels and nerves exit the pelvic cavity into the subgluteal space through this foramen.
Which nerves and vessels exit through the infrapiriform foramen?
The following nerves and blood vessels exit into the subgluteal space through the infrapiriform foramen:
- Sciatic nerve (n. ischiadicus).
- Posterior cutaneous nerve of the thigh (n. cutaneus femoris posterior).
- Inferior gluteal neurovascular bundle — includes the inferior gluteal artery (a. glutea inferior), corresponding veins, and the inferior gluteal nerve (n. gluteus inferior).
- Pudendal neurovascular bundle — includes the internal pudendal artery and veins (a. et vv. pudendae internae) and the pudendal nerve (n. pudendus).
- Comitant artery of the sciatic nerve (a. comitans n. ischiadici).
Which structures are located medial to the sciatic nerve in the infrapiriform foramen?
The following anatomical structures are located medial to the sciatic nerve in the infrapiriform foramen:
- Posterior cutaneous nerve of the thigh (n. cutaneus femoris posterior).
- Comitant artery of the sciatic nerve (a. comitans n. ischiadici).
- Inferior gluteal neurovascular bundle — inferior gluteal artery (a. glutea inferior), veins, and branches of the inferior gluteal nerve (lying medial to the sciatic nerve).
- Pudendal neurovascular bundle (a. et vv. pudendae internae, n. pudendus) — located most medially.
Where does the pudendal neurovascular bundle go after exiting the infrapiriform foramen?
After exiting the infrapiriform foramen, the pudendal neurovascular bundle heads into the ischioanal (ischiorectal) fossa.
Its topography and course:
- The bundle lies on the sacrospinous ligament (lig. sacrospinale) and the ischial spine, winding around it.
- Then it passes through the lesser sciatic foramen (foramen ischiadicum minus) beneath the sacrotuberous ligament (lig. sacrotuberale).
- It returns to the pelvic cavity, reaching the inner surface of the ischial tuberosity within the pudendal canal (Alcock's canal).
Which muscle divides the greater sciatic foramen into the supra- and infrapiriform foramina?
The greater sciatic foramen (foramen ischiadicum majus) is divided into two separate passages by the piriformis muscle (m. piriformis).
This muscle originates from the anterior surface of the sacrum and emerges into the gluteal region, yet it does not fill the foramen completely. As a result, two gaps are formed:
- Suprapiriform foramen (foramen suprapiriforme).
- Infrapiriform foramen (foramen infrapiriforme).
Only the SUPERIOR gluteal bundle passes above the piriformis muscle. Everything else — the sciatic nerve, inferior gluteal, and pudendal bundles — descends BENEATH it.
Class and exam questions
Where is the superior gluteal artery located and what is its origin?
The superior gluteal artery passes through the suprapiriform foramen. It originates within the lesser pelvis as a branch of the posterior trunk of the internal iliac artery.
Which structure serves as a landmark for locating elements in the infrapiriform foramen?
The internal landmark for locating the foramen and the neurovascular bundles contained within it is the sciatic nerve, the largest nerve in the body, occupying the most lateral position.
What is the origin of the artery accompanying the sciatic nerve?
The artery accompanying the sciatic nerve (a. comitans n. ischiadici) branches off from the inferior gluteal artery and lies medial to the nerve itself.
What else to study on this topic
- Formation of the venous plexus around the superior gluteal artery
- Course and distribution of the branches of the inferior gluteal artery
- Topography of the pudendal neurovascular bundle after emerging from the infrapiriform foramen
- Innervation zone of the posterior femoral cutaneous nerve
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