Cámara térmica

Much of the neurovascular supply to the gluteal region passes through the greater sciatic foramen. The muscles of the gluteal region function generally to extend, abduct and laterally rotate the hip and thigh.

I. MUSCLES of the gluteal region A. Superficial Layer

1. Gluteus Maximus Muscle - the large muscle of the buttock - the primary extensor of the thigh

- covered by a dense layer of adipose tissue with many strong septae called the gluteal fascia, which gives this region its shape

- covers the other muscles of this region; six small muscles which together are fan-shaped

O: external iliac ala posterior to posterior gluteal line, the posterior iliac crest, the external surfaces of the sacrum and coccyx, and the sacrotuberous ligament (also gluteal fascia)

I: gluteal tuberosity of the femur and the posterosuperior iliotibial tract - passes obliquely from superomedial to inferolateral

A: extends and laterally rotates the thigh

NS: inferior gluteal nerve; dorsal divisions of ventral rami L-5, S-1 & S-2 AS: superior gluteal artery, inferior gluteal artery and the perforating branches

of the profunda femoris artery

a. Bursae (of the gluteus maximus muscle)

- there are 3 bursae associated with the gluteus maximus muscle

i. Trochanteric Bursa

- located intermediate to the gluteus maximus muscle and the lateral aspect of the greater trochanter of the femur

- inflammation of this bursa is called bursitis of the hip

- painful with extension or lateral rotation of thigh when inflamed

gluteal region, muscles, bursae of gluteus maximus muscle, con’t ii. Ischial Bursa

- located intermediate to the gluteus maximus muscle and the ischial tuberosity

- inflammation of this bursa is associated with prolonged sitting in the tailor position (Indian-style or cross-legged) or from riding horses/bicycles - inflammation of this bursa is called weaver's bottom, sometimes

called saddle sore - painful with sitting

iii. Gluteofemoral Bursa

- located intermediate to the gluteus maximus muscle and the vastus lateralis muscle, just inferior to the gluteal tuberosity of the femur

b. Intramuscular Injections

- injections into the buttock must be placed so as to miss the major neurovascular structures of this region, especially the sciatic nerve - each buttock is divided into quadrants

- the injection is given in the superolateral / upper outer quadrant B. Intermediate Layer

1. Gluteus Medius Muscle

- located deep to the gluteus maximus muscle

- extends superior to the proximal edge of gluteus maximus muscle near the center of gluteus maximus muscle

- the primary abductor of the thigh

O: external iliac ala intermediate to the anterior and posterior gluteal lines I: lateral aspect of the greater trochanter

- passes inferolaterally A: abducts the thigh;

aids with both medial and lateral rotation of the thigh

NS: superior gluteal nerve; dorsal divisions of ventral rami L-4, L-5 & S-1 AS: superior gluteal artery

a. Bursa (of the gluteus medius muscle)

- this bursa is located intermediate to the gluteus medius muscle and the superior aspect of the femoral greater trochanter

- pain from this bursa is associated with hip joint abduction and palpation C. Deep Layer - gluteal muscles

1. Gluteus Minimus Muscle

- the smallest of the 3 gluteal muscles

O: iliac ala intermediate to the anterior and inferior gluteal lines, and the superior edge of the greater sciatic notch

I: anterior aspects of the greater trochanter and the hip joint capsule - passes inferiorly

A: abduction and medial rotation of the thigh (medial rotation because the insertion of the muscle is anterior to the hip joint axis)

NS: superior gluteal nerve; dorsal divisions of ventral rami L-4, L-5 & S-1 AS: superior gluteal artery

gluteal region, muscles, con’t 2. Piriformis Muscle

- an important anatomic landmark as it aids in the identification of other structures in this region

O: pelvic surface of the sacrum (S-2, S-3, S-4) I: superior aspect of the greater trochanter

- passes laterally, exiting the pelvis via the greater sciatic foramen A: lateral rotation of the thigh;

assists in abduction and extension of the thigh

NS: dorsal division of S-2 ventral ramus, (nerve to piriformis muscle) AS: superior and inferior gluteal arteries

3. Superior Gemellus Muscle

- a small muscle situated inferior to piriformis muscle and deep to some neurovascular structures

- its muscle belly lies adjacent to the inferior gemellus muscle belly

O: ischial spine and superior edge of lesser sciatic notch

I: anterior fossa (unnamed) at the medial aspect of the greater trochanter, with the tendons of obturator internus and inferior gemellus muscles - passes laterally

A: lateral rotation of the thigh

NS: nerve to obturator internus and superior gemellus muscles, from the sacral plexus; ventral divisions of ventral rami L-5, S-1 and S-2

AS: inferior gluteal artery

4. Inferior Gemellus Muscle

- its muscle belly lies adjacent to the superior gemellus muscle belly

O: inferior margin of lesser sciatic notch and superior border of ischial tuberosity

I: anterior fossa (unnamed) at the medial edge of the greater trochanter, with the tendons of superior gemellus and obturator internus muscles

- passes laterally

A: lateral rotation of the thigh

NS: nerve to inferior gemellus muscle and quadratus femoris muscle, from the from the sacral plexus; ventral divisions of ventral rami L-4, L-5 & S-1 AS: medial femoral circumflex artery

5. Obturator Internus Muscle

- the tendon is generally deep and intermediate to the gemelli muscles

O: pelvic surfaces of the obturator foramen and obturator membrane I: anterior fossa (unnamed) on the medial edge of the greater trochanter,

with the gemelli muscles

- passes posterolaterally to exit the pelvis via the lesser sciatic foramen, then angles anteriorly around the lesser sciatic notch

A: external rotation of the thigh;

extension and abduction of the thigh when the hip is flexed

NS: nerve to obturator internus and superior gemellus muscles, from the sacral plexus; ventral divisions of ventral rami L-5, S-1 and S-2

gluteal region, muscles, con’t

6. Quadratus Femoris Muscle

- rectangular shaped muscle, the most inferior of the gluteal muscles

O: external border (of the posterior squared part) of the ischial tuberosity I: quadrate tubercle of the femur

- passes directly lateral A: lateral rotation of the thigh

NS: nerve to inferior gemellus muscle and quadratus femoris muscle, from the sacral plexus; ventral divisions of ventral rami L-4, L-5 and S-1 AS: medial femoral circumflex artery

7. Obturator Externus Muscle

- its tendon can be found deep to the quadratus femoris muscle in the gluteal region; its origin may be seen deep to the pectineus muscle at the antero- superior thigh region

O: external surfaces of the obturator foramen and the obturator membrane I: trochanteric fossa of the femur

- passes posterolaterally around the inferior surface of the femoral neck (a spiral course)

A: lateral rotation of the thigh (due to insertion posterior to the hip joint axis);

aids in flexion and adduction of the thigh (due to its course around the femoral neck)

NS: obturator nerve; ventral divisions of ventral rami L-2, L-3 and L-4

- the only gluteal region muscle to receive innervation from the lumbar plexus AS: obturator artery

II. NERVES of the gluteal region

A. Pudendal Nerve

- from the ventral divisions of ventral rami S-2, S-3 and S-4

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle - passes posterior to the sacrospinous ligament

- reenters the pelvis via the lesser sciatic foramen

B. Nerve to Obturator Internus and Superior Gemellus Muscles - from the ventral divisions of ventral rami L-5, S-1 and S-2

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle - it lies lateral to the pudendal nerve as it passes posterior to the sacrospinous ligament and sends a branch laterally to supply the superior gemellus m.

- it then, reenters the pelvis via the lesser sciatic foramen to innervate the obturator internus muscle

gluteal region, nerves, con't

C. Posterior Femoral Cutaneous Nerve

- from the dorsal divisions of ventral rami S-1 and S-2, and ventral divisions of ventral rami S-2 and S-3

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle and usually posterior to the sciatic nerve; the main branch lies within the fascia on the deep surface of gluteus maximus muscle, then passes inferiorly through the posterior thigh, deep to or within the fascia lata to the inferior knee region - the cutaneous branches penetrate the fascia lata along this course

1. Inferior Cluneal Nerves (not pictured)

- cutaneous branches of the posterior femoral cutaneous nerve that supply a portion of the gluteal region skin

- arise near the proximal end and pass along the deep surface of the gluteus maximus muscle, then pass around its inferior edge to the skin

D. Nerve to Quadratus Femoris and Inferior Gemellus Muscles - from the ventral divisions of ventral rami L-4, L-5 and S-1

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle (usually located anterior to the sciatic nerve)

- passes anterior to the obturator internus tendon and the gemelli muscles where it sends a branch to the inferior gemellus muscle; it continues inferiorly and sends branches to the hip joint and the deep side of the quadratus femoris muscle

E. Sciatic Nerve

- the largest nerve in the body, the primary formation of the sacral plexus - from dorsal divisions of ventral rami L-4, L-5, S-1 and S-2, and ventral divisions of ventral rami L-4, L-5, S-1, S-2 & S-3

- exits the pelvis via the greater sciatic foramen, deep to the gluteus maximus muscle and usually inferior to the piriformis muscle

- passes inferiorly into the thigh usually midway between the ischial tuberosity and the greater trochanter, and continues inferiorly along the posteromedial aspect of the thigh, deep to the muscles to the level of the knee region where it normally divides

variation:

- the common fibular part may exit the pelvis either superior to or through the piriformis muscle belly and then course with the tibial part

- when this occurs, the sciatic nerve has split into its component parts already F. Inferior Gluteal Nerve

- from dorsal divisions of ventral rami L-5, S-1 and S-2

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle - passes directly posterior and into the gluteus maximus muscle to innervate it

G. Superior Gluteal Nerve

- from dorsal divisions of ventral rami L-4, L-5 and S-1

- exits the pelvis via the greater sciatic foramen, superior to the piriformis muscle - passes laterally, intermediate to the gluteus medius and gluteus minimus

muscles; it supplies both of them and continues anterolaterally to supply the tensor fascia lata muscle (a thigh muscle in this course)

gluteal region, nerves, con't

H. Perforating Cutaneous Nerve (not pictured) - from dorsal divisions of ventral rami S-2 and S-3

- exits the pelvis by piercing the sacrotuberous ligament, usually near the sacrum - may be a direct course or pass within the ligament for a short distance

- passes inferiorly around the distomedial edge of the gluteus maximus muscle to innervate a small area of skin at the inferomedial gluteal region

III. ARTERIES

A. Internal Pudendal Artery

- from the anterior trunk of internal iliac artery

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle, usually lies intermediate to the pudendal nerve and the nerve to obturator internus and superior gemellus muscles

- passes posterior to the sacrospinous ligament

- reenters the pelvis via the lesser sciatic foramen, then supplies obturator internus m.

B. Inferior Gluteal Artery

- from the anterior trunk of internal iliac artery

- before exiting the pelvis it supplies the piriformis, levator ani and coccygeus mm.

- exits the pelvis via the greater sciatic foramen, inferior to the piriformis muscle - passes posterior, lateral and inferior to supply gluteal region structures

- after exiting, it supplies gluteus maximus and superior gemellus muscles, the sciatic nerve and the hip joint

C. Superior Gluteal Artery

- from the posterior trunk of internal iliac artery

- before exiting the pelvis it supplies piriformis and obturator internus muscles - exits the pelvis via the greater sciatic foramen, superior to the piriformis muscle - a superficial branch passes posterior to supply the gluteus maximus muscle - a deep branch passes lateral to supply the gluteus medius, gluteus minimus and tensor fascia lata muscles and the hip joint; travels with the superior gluteal n.