Topographical anatomy of the gluteal region

Superficial layers and fascial features

The skin of the gluteal region is thick and relatively immobile. In its medial part, it is often covered with hair, and the skin itself contains a large number of sebaceous and sweat glands (a typical localization for lipomas, atheromas, and furuncles).

The subcutaneous adipose tissue is strongly developed. In the lower medial section, directly above the ischial tuberosity (tuber ischiadicum), it has a specific cellular structure. This is due to the presence of dense connective tissue strands running from the skin to the deep fascia.

The superficial muscle layer is formed by the gluteus maximus muscle (m. gluteus maximus). It is enclosed in a strong sheath formed by the deep fascia. Multiple septa extend from the superficial layer of this fascia to the deep layer, dividing the muscle into separate bundles.

Clinical significance: The structure of the fascial sheath explains the pathogenesis of deep post-injection phlegmons. The inflammatory process does not spread along the surface, but instead directs deeper along the course of the fascial septa. As a result, the purulent exudate melts the deep layer of the fascia and ruptures into the subgluteal cellular space.

Middle and deep muscle layers

All muscles lying beneath the gluteus maximus are divided into middle and deep layers.

The middle layer is covered by the deep fascia. From top to bottom, the muscles are arranged in the following order:

1. Gluteus medius muscle (m. gluteus medius).
2. Piriformis muscle (m. piriformis).
3. Superior gemellus muscle (m. gemellus superior).
4. Obturator internus muscle (m. obturatorius internus) — its tendon emerges from the pelvic cavity, hooking around the margin of the lesser sciatic foramen and attaching to the trochanteric fossa.
5. Inferior gemellus muscle (m. gemellus inferior) — lies adjacent to the tendon of the obturator internus inferiorly, originating from the ischial tuberosity.
6. Quadratus femoris muscle (m. quadratus femoris) — runs from the ischial tuberosity to the intertrochanteric crest.

The piriformis, tendon of the obturator internus, and gemelli muscles run transversely toward the greater trochanter.

The deep layer includes muscles lying beneath the middle layer:

• Gluteus minimus muscle (m. gluteus minimus) — located superiorly, completely covered by the gluteus medius and situated together with it in a closed osteofibrous space.
• Obturator externus muscle (m. obturatorius externus) — lies inferiorly. It originates from the obturator membrane, curves inferiorly around the hip joint, and passes posteriorly into the gluteal region toward the trochanteric fossa.

Behind the deep muscles lies the osteo-ligamentous layer: the hip bone, acetabulum, hip joint with the femoral neck, and strong ligaments (including the sacrotuberous and sacrospinous ligaments).

Subgluteal cellular space

An extensive cellular space is located between the m. gluteus maximus (posteriorly) and the muscles of the middle layer (anteriorly).

Boundaries of the space:

• Anterior wall: Fascia of the middle layer muscles.
• Posterior wall: deep layer of the own fascia of the gluteus maximus muscle.
• Superiorly: Bounded by the attachment of the deep fascia to the iliac crest.
• Medially: Bounded by the attachment of the fascia to the sacrum and coccyx.

Routes of pus propagation: The space communicates extensively with neighboring regions, which is critically important in purulent surgery:

• With the pelvic cavity — through the supra- and infrapiriform foramina.
• With the ischioanal fossa — through the lesser sciatic foramen.
• With the posterior region of the thigh — inferiorly along the course of the sciatic nerve.
• With the lateral and anterior regions of the thigh — through the cleft under the proximal part of the gluteus maximus tendon.

Topography of vessels and nerves

All arteries and nerves emerge here from the pelvic cavity through the greater sciatic foramen (which is divided into the suprapiriform and infrapiriform foramina).

Sciatic nerve (n. ischiadicus) Runs vertically downward. Anterior to it lie the middle layer muscles (superior gemellus, tendon of the obturator internus, inferior gemellus, quadratus femoris). Posteriorly, it is covered by the gluteus maximus. Emerging from beneath the lower border of m. gluteus maximus, the nerve becomes superficial (covered only by the fascia lata). Conduction anesthesia of the nerve can be performed at the intersection point of the gluteal crease and the contour of the lower border of the gluteus maximus.

Inferior gluteal bundle Includes the inferior gluteal artery (2–3 times thinner than the superior one), companion veins, and the inferior gluteal nerve. In the infrapiriform foramen, this bundle lies medial to the sciatic nerve and the posterior cutaneous nerve of the thigh.

Pudendal bundle (a. et v. pudendae internae, n. pudendus) Located most medially. Emerging from the infrapiriform foramen, it lies on the sacrospinous ligament and the ischial spine. Then the bundle loops around them and passes through the lesser sciatic foramen beneath the sacrotuberous ligament into the ischioanal fossa. On the inner surface of the ischial tuberosity, it passes through Alcock's canal (canal of Alcock) — a splitting of the obturator internus fascia. Inside the canal, the pudendal nerve lies inferior and medial to the vessels.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Boundaries and contents of the supra- and infrapiriform foramina
• Syntopy of the elements of the pudendal neurovascular bundle
• Technique and landmarks for sciatic nerve block
• Intramuscular anastomoses of the arteries of the gluteal region

Other topics in the "Lower Limb" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.