Gluteal region
Topographic Anatomy of the Gluteal Region
The *gluteal region* is located posteriorly, between the iliac crests superiorly and the gluteal fold inferiorly. It forms the bulk of the buttocks and plays a key role in locomotion and posture, involving powerful muscles, neurovascular structures, and bony landmarks.
*1. Skeletal Framework*
The skeletal foundation of the gluteal region includes parts of the pelvis, sacrum, and femur:
1. *Ilium*:
- *Iliac crest*: Forms the upper boundary of the gluteal region.
- *Anterior superior iliac spine (ASIS)*: Found anteriorly, an important landmark for muscle attachment.
- *Posterior superior iliac spine (PSIS)*: Found posteriorly and marked by skin dimples in the lower back.
2. *Ischium*:
- *Ischial tuberosity*: The bony prominence that serves as a weight-bearing structure when sitting and an attachment site for muscles.
3. *Sacrum*:
- *Sacral hiatus*: An important landmark for the sacroiliac joint and attachment of ligaments.
4. *Femur*:
- *Greater trochanter*: Located laterally, an important bony landmark for muscle attachments in the hip joint.
2. Muscles of the Gluteal Region*
The gluteal region contains several powerful muscles, divided into *superficial* and *deep* layers, responsible for the movement of the hip joint, including extension, abduction, and external rotation.
Superficial Muscles*:
1. *Gluteus Maximus*:
- *Origin*: Ilium, sacrum, coccyx, and sacrotuberous ligament.
- *Insertion*: Iliotibial tract and gluteal tuberosity of the femur.
- *Function*: Extends and externally rotates the thigh, assists in rising from a seated position and climbing stairs.
- *Innervation*: Inferior gluteal nerve.
2. *Gluteus Medius*:
- *Origin*: Outer surface of the ilium.
- *Insertion*: Greater trochanter of the femur.
- *Function*: Abducts and medially rotates the thigh, stabilizes the pelvis during walking.
- *Innervation*: Superior gluteal nerve.
3. *Gluteus Minimus*:
- *Origin*: Outer surface of the ilium, below the origin of the gluteus medius.
- *Insertion*: Greater trochanter of the femur.
- *Function*: Abducts and medially rotates the thigh, stabilizes the pelvis during walking.
- *Innervation*: Superior gluteal nerve.
4. *Tensor Fasciae Latae*:
- *Origin*: ASIS and anterior part of the iliac crest.
- *Insertion*: Iliotibial tract.
- *Function*: Stabilizes the pelvis, assists in flexion, abduction, and medial rotation of the thigh.
- *Innervation*: Superior gluteal nerve.
#### *Deep Muscles*:
1. *Piriformis*:
- *Origin*: Anterior surface of the sacrum.
- *Insertion*: Greater trochanter of the femur.
- *Function*: Externally rotates and abducts the thigh.
- *Innervation*: Nerve to piriformis (S1-S2).
2. *Obturator Internus*:
- *Origin*: Obturator membrane and surrounding bone.
- *Insertion*: Greater trochanter of the femur.
- *Function*: Externally rotates the thigh.
- *Innervation*: Nerve to obturator internus.
3. *Superior and Inferior Gemelli*:
- *Origin*: Superior (ischial spine), Inferior (ischial tuberosity).
- *Insertion*: Greater trochanter of the femur.
- *Function*: Externally rotate the thigh.
- *Innervation*: Nerve to obturator internus (superior) and nerve to quadratus femoris (inferior).
4. *Quadratus Femoris*:
- *Origin*: Lateral aspect of the ischial tuberosity.
- *Insertion*: Intertrochanteric crest of the femur.
- *Function*: Externally rotates the thigh.
- *Innervation*: Nerve to quadratus femoris.
3. Neurovascular Structures of the Gluteal Region*
The *gluteal region* is richly supplied by nerves and vessels that pass through the greater sciatic foramen.
Nerves*:
1. *Sciatic Nerve*:
- Largest nerve in the body, exiting the pelvis through the greater sciatic foramen, passing beneath the piriformis, and continuing down the posterior thigh.
- *Function*: Supplies sensation and motor function to the lower extremity.
2. *Superior Gluteal Nerve*:
- Exits through the greater sciatic foramen above the piriformis.
- *Innervation*: Gluteus medius, gluteus minimus, and tensor fasciae latae muscles.
3. *Inferior Gluteal Nerve*:
- Exits through the greater sciatic foramen below the piriformis.
- *Innervation*: Gluteus maximus.
4. *Pudendal Nerve*:
- Passes through the greater sciatic foramen, then re-enters the pelvis through the lesser sciatic foramen.
- *Function*: Innervates structures in the perineum.
Vascular Supply*:
1. *Superior Gluteal Artery*:
- Exits the pelvis through the greater sciatic foramen above the piriformis and supplies the gluteus medius, minimus, and tensor fasciae latae.
2. *Inferior Gluteal Artery*:
- Exits the greater sciatic foramen below the piriformis, supplying the gluteus maximus and some of the deep gluteal muscles.
3. *Venous Drainage*:
- Parallels the arterial supply, with veins draining into the superior and inferior gluteal veins.
4. Borders of the Gluteal Region*
- *Superior*: Iliac crest.
- *Inferior*: Gluteal fold.
- *Medial*: Sacrum and coccyx.
- *Lateral*: Greater trochanter of the femur.
*5. Important Structures and Pathways*
*Greater Sciatic Foramen*:
This foramen allows for the passage of key neurovascular structures from the pelvis to the gluteal region, including the *sciatic nerve, **superior and inferior gluteal arteries*, and associated veins and nerves.
*Lesser Sciatic Foramen*:
The pudendal nerve and internal pudendal artery re-enter the pelvis through this foramen to supply the perineum.
*Piriformis Syndrome*:
Compression or irritation of the sciatic nerve as it passes beneath the piriformis muscle can cause pain radiating down the leg, often mimicking symptoms of sciatica.
*6. Clinical Considerations*
1. *Intramuscular Injections*:
- The *gluteus medius* is a common site for intramuscular injections, as it avoids major nerves and vessels.
2. *Sciatica*:
- Compression of the sciatic nerve, leading to radiating pain along the course of the nerve.
3. *Piriformis Syndrome*:
- Pain and discomfort caused by the compression of the sciatic nerve by the piriformis muscle.
Clinical correlation[edit | edit source]
Intramuscular injections are applied to the upper, outer quadrant of the gluteal landscape.