Gluteal Region

Introduction

• The gluteal region (gloutos = rump in Greek) forms the posterior aspect of the pelvis. It extends from the iliac crest superiorly to the gluteal fold inferiorly.
• Medially, the two buttocks are separated by the natal (intergluteal) cleft.
• Laterally, the region extends up to an imaginary line joining the anterior superior iliac spine (ASIS) and the tip of the greater trochanter.
• Important features:
  • Gluteus maximus is the largest and one of the most powerful muscles of the body.
  • The gluteal region is a common site for intramuscular injections because of its large muscle mass.
  • The hip forms the superolateral part of the gluteal region.

Surface Landmarks

Soft tissue landmarks

• Buttock: A rounded prominence formed by the gluteal muscles on the back of the pelvis.
• Natal (intergluteal) cleft: A vertical groove in the midline that separates the two buttocks. It extends from the level of the third sacral vertebra (S3) to the perineum.
• Gluteal fold: A horizontal skin crease that marks the junction between the buttock and the posterior thigh. It is produced by the attachment of the skin to the deep fascia and does not indicate the lower border of the gluteus maximus muscle.

Bony landmarks

• Iliac crest: A thick, curved upper border of the ilium that can be easily felt along the lower margin of the waist.
• Highest point of the iliac crest: Lies opposite the L3–L4 intervertebral level and serves as an important surface landmark for locating the L4 vertebral spine during lumbar puncture.
• Anterior superior iliac spine (ASIS): The anterior projection of the iliac crest and an important surface landmark of the pelvis.
• Posterior superior iliac spine (PSIS): The posterior end of the iliac crest. It produces a visible skin dimple on either side of the lower back at the level of the second sacral vertebra (S2), about 5 cm lateral to the midline.
• Ischial tuberosity: A large rounded bony prominence that bears body weight while sitting. It lies approximately 5 cm lateral to the midline and 5 cm above the gluteal fold. It can be palpated by pressing upward in the medial part of the gluteal fold.
• Greater trochanter: The prominent lateral projection of the femur. Its tip is palpable on the side of the hip, just anterior to the lateral hollow, about one hand’s breadth below the iliac crest.
• Second sacral spine (S2): Located midway between the two posterior superior iliac spines. It serves as a useful landmark for identifying the remaining sacral vertebrae.
• Coccyx: The terminal part of the vertebral column, palpable in the midline just posterior to the anal opening.

Nelaton’s line [Roser-Nelaton line]

• Nelaton’s line (also called the Roser-Nelaton line) is an imaginary line drawn from the anterior superior iliac spine (ASIS) to the ischial tuberosity.
• In a normal hip, the tip of the greater trochanter lies on or just below this line.

Clinical Significance

When the greater trochanter is palpated above Nelaton’s line, it suggests upward displacement of the femur and may indicate:

1. Coxa vara (neck-shaft angle of the femur less than 120°)
2. Fracture of the neck of the femur
3. Posterior dislocation of the hip joint

Clinical importance: Nelaton’s line is a simple bedside surface landmark used to assess the position of the greater trochanter and detect abnormalities of the hip joint.

Bryant’s triangle (iliofemoral triangle)

• Bryant’s triangle is a surface anatomical landmark used to assess the position of the greater trochanter and detect shortening around the hip joint.
• It is formed by drawing the following three lines:
  1. A horizontal line passing laterally from the anterior superior iliac spine (ASIS).
  2. A vertical line drawn upward from the tip of the greater trochanter to meet the horizontal line.
  3. A line joining the ASIS to the tip of the greater trochanter (forming the hypotenuse).

Clinical Significance

• The vertical side of Bryant’s triangle represents the distance between the tip of the greater trochanter and the horizontal line through the ASIS.
• Reduction in this vertical distance is known as supratrochanteric shortening, indicating upward displacement of the greater trochanter.

Supratrochanteric shortening may be seen in:

1. Dislocation of the hip joint
2. Fracture of the neck of the femur
3. Destruction of the femoral head or acetabulum
4. Coxa vara (decreased neck-shaft angle of the femur)

Superficial Fascia and Cutaneous Nerves and Vessels

Superficial fascia

The superficial fascia of the gluteal region contains a thick layer of subcutaneous fat, which is more abundant in females. This fat acts as a cushion over the ischial tuberosity, reducing pressure and helping support body weight while sitting.

Cutaneous nerves

The skin of the gluteal region is supplied by different nerves in four quadrants:

• Upper anterior quadrant:
  • Lateral cutaneous branch of the subcostal nerve (T12)
  • Lateral cutaneous branch of the iliohypogastric nerve (L1)
• Upper posterior quadrant:
  • Dorsal rami of L1, L2, and L3
  • Dorsal rami of S1, S2, and S3
• Lower anterior quadrant:
  • Posterior branch of the lateral cutaneous nerve of the thigh (L2, L3)
• Lower posterior quadrant:
  • Posterior cutaneous nerve of the thigh (S1–S3)
  • Perforating cutaneous nerve (S2, S3)

Cutaneous vessels and lymphatics

• The skin and superficial fascia of the gluteal region receive blood from the superior and inferior gluteal arteries.
• Lymph from this region drains mainly into the lateral group of superficial inguinal lymph nodes.

Deep Fascia

• The deep fascia (fascia musculorum) surrounds the gluteal muscles. It is attached superiorly to the iliac crestandposteriorly to the sacrum.
• The fascia splits to enclose the gluteus maximus and tensor fasciae latae muscles. Its thickened portion, called the gluteal aponeurosis, lies between these muscles and covers the gluteus medius.
• On the lateral side, the deep fascia continues as the iliotibial tract (IT band), a strong thickening of the fascia lata that extends along the lateral aspect of the thigh.

Gluteal ligaments

• The gluteal region contains two important ligaments: the sacrotuberous and sacrospinous ligaments.
• The sacrotuberous ligament is a strong band extending from the lateral border of the sacrum and coccyx to the ischial tuberosity. It is pierced by the coccygeal nerve.
• The sacrospinous ligament is a thin, triangular ligament extending from the lateral border of the sacrum to the ischial spine and represents a degenerated part of the coccygeus muscle. Together, these ligaments convert the greater and lesser sciatic notches into the greater and lesser sciatic foramina, respectively.

Muscles of Gluteal Region

• The gluteal region contains 10 muscles, arranged into superficial and deep layers.
• The superficial layer consists of the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae. These muscles mainly move the hip joint and assist in rotation, abduction, and extension of the thigh.
• The deep layer includes the piriformis, superior gemellus, obturator internus, inferior gemellus, quadratus femoris, and obturator externus. These muscles lie deep to the gluteus maximus. They act mainly as lateral rotators of the femur and help stabilize the hip joint during movement.

Gluteus Maximus

The gluteus maximus is the largest, thickest, and most superficial muscle of the gluteal region. It is quadrangular in shape and forms the bulk of the buttock.

Origin

The gluteus maximus arises from:

1. Posterior gluteal line and the gluteal surface of the ilium behind it.
2. Outer part of the posterior iliac crest.
3. Aponeurosis of the erector spinae.
4. Posterior surface of the lower sacrum.
5. Lateral margin of the coccyx.
6. Sacrotuberous ligament.
7. Gluteal aponeurosis covering the gluteus medius.

Insertion

The muscle has two insertions:

1. Deep lower fibres insert into the gluteal tuberosity of the femur.
2. Most superficial and upper fibres insert into the iliotibial tract. Through the iliotibial tract, the gluteus maximus and tensor fasciae latae are indirectly attached to the lateral condyle of the tibia.

Nerve supply

• Inferior gluteal nerve

Actions

1. Chief extensor of the hip joint, especially during forceful movements.
2. Extends the trunk while rising from a sitting or squatting position and helps maintain an erect posture.
3. Laterally rotates the thigh at the hip joint.
4. Upper fibres abduct the thigh.
5. Stabilizes the knee joint through the iliotibial tract in association with the tensor fasciae latae.

Gluteus Medius

• Origin: Arises from the gluteal surface of the ilium between the anterior and posterior gluteal lines.
• Insertion: Inserts into the lateral surface of the greater trochanter.
• Nerve supply: Superior gluteal nerve.
• Actions: Abducts the thigh, medially rotates the thigh (anterior fibres), and prevents pelvic drop on the unsupported side during walking.

Gluteus Minimus

• Origin: Arises from the gluteal surface of the ilium between the anterior and inferior gluteal lines.
• Insertion: Inserts into the anterolateral surface of the greater trochanter.
• Nerve supply: Superior gluteal nerve.
• Actions: Abducts and medially rotates the thigh and helps stabilize the pelvis during walking.

Piriformis

• Origin: Arises from the anterior surface of the middle three sacral segments and the upper margin of the greater sciatic notch.
• Insertion: Inserts into the apex of the greater trochanter.
• Nerve supply: Ventral rami of S1 and S2 spinal nerves.
• Actions: Laterally rotates the extended thigh and stabilizes the hip joint.

Superior Gemellus

• Origin: Arises from the ischial spine.
• Insertion: Joins the tendon of the obturator internus and inserts onto the medial surface of the greater trochanter.
• Nerve supply: Nerve to obturator internus.
• Actions: Laterally rotates the thigh and stabilizes the hip joint.

Obturator Internus

• Origin: Arises from the pelvic surface of the obturator membrane and the surrounding margins of the obturator foramen.
• Insertion: Inserts onto the medial surface of the greater trochanter.
• Nerve supply: Nerve to obturator internus.
• Actions: Laterally rotates the thigh and stabilizes the femoral head in the acetabulum.

Inferior Gemellus

• Origin: Arises from the upper part of the ischial tuberosity.
• Insertion: Joins the tendon of the obturator internus and inserts onto the medial surface of the greater trochanter.
• Nerve supply: Nerve to quadratus femoris.
• Actions: Laterally rotates the thigh and stabilizes the hip joint.

Quadratus Femoris

• Origin: Arises from the lateral border of the ischial tuberosity.
• Insertion: Inserts into the quadrate tubercle and the adjacent intertrochanteric crest.
• Nerve supply: Nerve to quadratus femoris.
• Actions: Laterally rotates the thigh and helps stabilize the hip joint.

Obturator Externus

• Origin: Arises from the outer surface of the obturator membrane and the margins of the obturator foramen.
• Insertion: Inserts into the trochanteric fossa of the femur.
• Nerve supply: Posterior division of the obturator nerve.
• Actions: Laterally rotates the thigh and stabilizes the hip joint.

Tensor Fasciae Latae

• Origin: Arises from the anterior part of the outer lip of the iliac crest.
• Insertion: Inserts into the iliotibial tract.
• Nerve supply: Superior gluteal nerve.
• Actions: Abducts and medially rotates the thigh, helps extend the knee through the iliotibial tract, and stabilizes the pelvis during walking.

Gluteal Bursae

• Gluteal bursae are synovial fluid-filled sacs located deep to the gluteus maximus muscle.
• They reduce friction between muscles, tendons, and bony prominences, allowing smooth movement at the hip.
• The gluteal region contains three bursae:
  1. Trochanteric bursa: Lies between the gluteus maximus and the greater trochanter of the femur. It is present at birth.
  2. Ischial bursa: Lies between the gluteus maximus and the ischial tuberosity.
  3. Gluteofemoral bursa: Lies between the iliotibial tract and the upper attachment of the vastus lateralis on the linea aspera.

Arteries of Gluteal Region

The gluteal region receives its blood supply mainly from the following arteries:

1. Superior gluteal artery
2. Inferior gluteal artery
3. Internal pudendal artery
4. Trochanteric anastomosis
5. Cruciate anastomosis

Superior gluteal artery

• The superior gluteal artery is the largest branch of the posterior division of the internal iliac artery.
• It enters the gluteal region through the greater sciatic foramen above the piriformis, accompanied by the superior gluteal nerve.
• It divides into superficial and deep branches.
• The superficial branch supplies the gluteus maximus.
• The deep branch divides into:
  • Superior division: Passes between the gluteus medius and gluteus minimus and ends by joining the spinous anastomosis near the anterior superior iliac spine.
  • Inferior division: Contributes to the trochanteric anastomosis.

Inferior gluteal artery

• The inferior gluteal artery arises from the anterior division of the internal iliac artery.
• It enters the gluteal region through the greater sciatic foramen below the piriformis.
• Its branches include:
  1. Muscular branches to the gluteal muscles.
  2. Cutaneous branches to the skin.
  3. Articular branches to the hip joint.
  4. Anastomotic branches to the trochanteric and cruciate anastomoses.
  5. Artery to the sciatic nerve (arteria nervi ischiadici), a remnant of the embryonic axial artery of the lower limb.
  6. Coccygeal branch supplying the skin over the coccyx.

Internal pudendal artery

• The internal pudendal artery is a branch of the anterior division of the internal iliac artery.
• It enters the gluteal region through the greater sciatic foramen below the piriformis, crosses the ischial spine, and leaves through the lesser sciatic foramen to enter the perineum.

Trochanteric anastomosis

• The trochanteric anastomosis is located near the trochanteric fossa.
• It is the main arterial supply to the head and neck of the femur.

Formation
It is formed by:

1. Inferior division of the deep branch of the superior gluteal artery.
2. Ascending branch of the medial circumflex femoral artery.
3. Ascending branch of the lateral circumflex femoral artery.
4. Inferior gluteal artery.

Cruciate anastomosis

• The cruciate anastomosis lies on the posterior aspect of the upper femur.
• It provides collateral circulation between the internal iliac artery and the external iliac (femoral) artery through the profunda femoris artery.

Formation
It is formed by:

1. Superiorly: Branch of the inferior gluteal artery.
2. Inferiorly: Ascending branch of the first perforating artery (from the profunda femoris artery).
3. Medially: Transverse branch of the medial circumflex femoral artery.
4. Laterally: Transverse branch of the lateral circumflex femoral artery.

Nerves of Gluteal Region

The gluteal region is supplied by the following nerves:

• Superior gluteal nerve
• Inferior gluteal nerve
• Sciatic nerve
• Posterior cutaneous nerve of the thigh
• Nerve to quadratus femoris
• Pudendal nerve
• Nerve to obturator internus

Superior gluteal nerve

• Root value: L4, L5, S1
• Origin: Arises from the sacral plexus (posterior divisions of the ventral rami of L4, L5, and S1).
• Course: Leaves the pelvis through the greater sciatic foramen above the piriformis and passes between the gluteus medius and gluteus minimus.
• Branches and distribution:
  • Gluteus medius
  • Gluteus minimus
  • Tensor fasciae latae
  • Hip joint

Inferior Gluteal Nerve

• Root value: L5, S1, S2
• Origin: Arises from the sacral plexus.
• Course: Leaves the pelvis through the greater sciatic foramen below the piriformis.
• Branches and distribution:
  • Supplies the gluteus maximus only.

Sciatic Nerve

• Root value: L4, L5, S1, S2, S3
• The sciatic nerve is the largest and thickest nerve in the human body.
• Course:
  • Leaves the pelvis through the greater sciatic foramen below the piriformis.
  • Passes midway between the greater trochanter and the ischial tuberosity.
  • Continues into the posterior compartment of the thigh.
• Branches in the gluteal region:
  • Does not give any branches in the gluteal region.

Posterior Cutaneous Nerve of the Thigh

• Root value: S1, S2, S3
• Origin: Arises from the sacral plexus.
• Course:
  • Leaves the pelvis through the greater sciatic foramen below the piriformis.
  • Descends medial to the sciatic nerve into the thigh.
• Branches:
  • Perineal branch: Supplies the skin of the posterior two-thirds of the scrotum in males or the labium majus in females.
  • Inferior cluneal (gluteal) branches: Supply the skin of the posteroinferior part of the buttock.

Nerve to Quadratus Femoris

• Root value: L4, L5, S1
• Origin: Arises from the sacral plexus.
• Course:
  • Leaves the pelvis through the greater sciatic foramen below the piriformis.
  • Passes deep to the sciatic nerve, obturator internus tendon, and the gemelli muscles.
• Branches and distribution:
  • Muscular branches to the quadratus femoris and inferior gemellus.
  • Articular branch to the hip joint.

Pudendal Nerve

• Root value: S2, S3, S4
• Origin: Arises from the sacral plexus.
• Course:
  • Leaves the pelvis through the greater sciatic foramen below the piriformis.
  • Winds around the ischial spine and sacrospinous ligament.
  • Enters the perineum through the lesser sciatic foramen and continues in the pudendal canal.
• Branches in the gluteal region:
  • Does not give any branches in the gluteal region.

Nerve to Obturator Internus

• Root value: L5, S1, S2
• Origin: Arises from the sacral plexus.
• Course:
  • Leaves the pelvis through the greater sciatic foramen below the piriformis.
  • Crosses the ischial spine and re-enters the pelvis through the lesser sciatic foramen.
• Branches and distribution:
  • Supplies the obturator internus.
  • Supplies the superior gemellus.

Sciatic Foramina

• The greater and lesser sciatic foramina are formed when the sacrospinous and sacrotuberous ligaments convert the greater and lesser sciatic notches into openings.
• These foramina provide important passages between the pelvis, gluteal region, and perineum.

Structures Passing Through the Greater Sciatic Foramen

Piriformis

• The piriformis muscle passes through the greater sciatic foramen and divides it into suprapiriform and infrapiriform compartments.
• It is considered the key muscle of the gluteal region.

Structures Passing Above the Piriformis (Suprapiriform Compartment)

• Superior gluteal nerve
• Superior gluteal artery and vein

Structures Passing Below the Piriformis (Infrapiriform Compartment)

• Inferior gluteal nerve
• Inferior gluteal artery and vein
• Sciatic nerve
• Posterior cutaneous nerve of the thigh
• Pudendal nerve
• Internal pudendal artery and vein
• Nerve to obturator internus
• Nerve to quadratus femoris (passes deep to the obturator internus tendon and the gemelli muscles and crosses the ischial spine)

Structures Passing Through the Lesser Sciatic Foramen

The following structures pass through the lesser sciatic foramen (Mnemonic: T-PIN):

• T – Tendon of obturator internus
• P – Pudendal nerve
• I – Internal pudendal artery and vein
• N – Nerve to obturator internus

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