GLUTEAL REGION LOWER LIMB MBBS Anatomy Lectures

• The human lower limb is built for support and propulsion. The two hip bones articulate with one another in front at the pubic symphysis, and each is firmly fixed to the lateral part of the sacrum by the relatively immobile sacroiliac joint.
• While STANDING: The pelvis transmits the body weight through the acetabulum of the hip bone to the lower limb and likewise transmits the propulsive thrust of the lower limb to the hip bone
• While SITTING: The body weight is transmitted to the ischial tuberosities and the legs are free to rest.

• The lower limbs (extremities) are extensions from the trunk specialized to support body weight, for locomotion (the ability to move from one place to another), and to maintain balance.
• The lower limbs has these major regions:

1. Gluteal region (buttocks) is the transitional region between the trunk and free lower limbs. It is posterolateral region between the iliac crest and the gluteal fold, that defines the lower limit of buttocks 

2. Femoral region (thigh) is the region of the free lower limb that lies between the gluteal, abdominal, and perineal regions proximally and the knee region distally.

3. Leg region (L. regio cruris) is the part that lies between the knee and the narrow, distal part of the leg. It includes most of the tibia and fibula

4. Foot region (L. regio pedis) is the distal part of the lower limb containing the tarsus, metatarsus, and phalanges. The toes are the digits of the foot

Gluteal Region

• The gluteal region lies posterolateral to the bony pelvis and proximal end of the femur.
• It is bounded superiorly by the iliac crest and inferiorly by the fold of the buttock.
• The region is largely made up of the gluteal muscles and a thick layer of superficial fascia.

SKIN:

• The gluteal region is covered with hairy skin.

FASCIA:

• The superficial fascia is thick, especially in women. It is impregnated with large quantities of fat that contribute to the prominence of the buttock.
• The deep fascia is continuous below with the deep fascia, or fascia latae, of the thigh. In the gluteal region, it splits to enclose the gluteus maximus  muscle

                Above the gluteus maximus, it continues as a single layer that covers the outer surface of the gluteus medius and attaches to the iliac crest.

CUTANEOUS INNERVATION OF GLUTEAL REGION:

• Upper medial quadrant: supplied by the posterior rami of the upper three lumbar nerves and the upper three sacral nerves
• Upper lateral quadrant: supplied by the lateral branches of the anterior rami of the iliohypogastric (L1) and 12th thoracic nerves
• Lower lateral quadrant: supplied by branches from the lateral cutaneous nerve of the thigh (L2 and L3, anterior rami)
• Lower medial quadrant: supplied by branches from the posterior cutaneous nerve of the thigh (S1, S2, and S3, anterior rami)

BLOOD SUPPLY OF SKIN AND FAT:

• Derived from branches of the superior and inferior gluteal arteries

LYMPHATIC DRAINAGE:

• Into the lateral group of the superficial inguinal lymph nodes

LIGAMENTS AND FORAMINA:

                The sacrotuberous and sacrospinous ligaments are two prominent structures in the gluteal region.

• Sacrotuberous ligament connects the back of the sacrum to the ischial tuberosity
• Sacrospinous ligament connects the back of the sacrum to the spine of the ischium.
• The arrangement of these ligaments forms the greater and lesser sciatic foramina

Greater Sciatic Foramen:

• The greater sciatic foramen is formed by the greater sciatic notch of the hip bone and the Sacro tuberous and sacrospinous ligaments. It provides an exit from the pelvis into the gluteal region.

Bound by:

                1. Greater sciatic notch

                2. Lateral margin of sacrum

                3. Upper parts of Sacro tuberous and sacrospinous ligaments

Contents:

1. Piriformis muscle; which divides the greater sciatic foramen into two parts.

2. Superior gluteal nerves and vessels (above piriformis)

3. Sciatic nerve,

4. Inferior gluteal nerve and vessels,

5. Pudendal nerve and internal pudendal vessels,

6. Posterior cutaneous nerve of the thigh,

7. Nerve to the obturator internus and gemellus superior

8. Nerve to the quadratus femoris and gemellus inferior

• All structures apart from the superior gluteal nerves and vessels pass below the piriformis

Lesser Sciatic Foramen:

• The lesser sciatic foramen is formed by the lesser sciatic notch of the hip bone and the sacrotuberous and sacrospinous ligaments.
•  It provides an entrance into the perineum from the gluteal region. Its presence enables nerves and blood vessels that have left the pelvis through the greater sciatic foramen above the pelvic floor to enter the perineum below the pelvic floor.

Contents:

1. Tendon of obturator internus muscle

2. Nerve to obturator internus

3. Pudendal nerve

4. Internal pudendal artery and vein

Gluteal Muscles

Organized into two layers:

• The superficial layer of muscles of the gluteal region consists of the three large overlapping glutei (maximus, medius, and minimus) and the tensor fasciae latae. These muscles all have proximal attachments to the posterolateral (external) surface and margins of the ala of the ilium, and are mainly extensors, abductors, and medial rotators of the thigh.
• The deep layer of muscles of the gluteal region consists of smaller muscles (piriformis, obturator internus, superior and inferior gemelli, and quadratus femoris) covered by the inferior half of the gluteus maximus

SUPERFICIAL LAYER:

1. GLUTEUS MAXIMUS:

• It is the most superficial gluteal muscle. It is the largest, heaviest, and most coarsely fibered muscle of the body.

Origin: Ilium posterior to posterior gluteal line; dorsal surface of sacrum and coccyx; sacrotuberous ligament

Insertion: Most fibers end in iliotibial tract, which inserts into lateral condyle of tibia; some fibers insert on gluteal tuberosity

• The fibers of gluteus maximus slope inferolaterally at a 45° angle from the pelvis to the buttocks

Action:

                Extension and lateral rotation of the thigh

• Although a strong extensor, it acts mostly when force is necessary (rapid movement or movement against resistance)
• It functions primarily between the flexed and standing (straight) positions of the thigh, as when rising from the sitting position, straightening from the bending position, walking uphill and up stairs, and running.
• It is used only briefly during casual walking and usually not at all when standing motionless

• Because the iliotibial tract crosses the knee and attaches to the anterolateral tubercle of the tibia, the gluteus maximus and tensor fasciae latae together are also able to assist in making the extended knee stable.
• It also assists the lateral rotators of thigh.

Nerve supply:

                Inferior gluteal nerve.

• Gluteal Bursae.

                Gluteal bursae separate the gluteus maximus from adjacent structures.

1. Trochanteric bursa separates superior fibers of the gluteus maximus from the greater trochanter. It is the largest and is present at birth.

2. Ischial bursa separates the inferior part of the gluteus maximus from the ischial tuberosity; it is often absent.

3. Gluteofemoral bursa separates the iliotibial tract from the superior part of the proximal attachment of the vastus lateralis.

2. GLUTEUS MEDIUS:

Origin:

                External surface of ilium between anterior and posterior gluteal lines

Insertion:

                Lateral surface of greater trochanter of femur

Action:

                Abduct and medially rotate thigh;

• keep pelvis level when ipsilateral limb is weight-bearing and advance opposite (un supported) side during its swing phase

Nerve supply:

                Superior gluteal nerve

3. GLUTEUS MINIMUS:

Origin:

                External surface of ilium between anterior and inferior gluteal lines

Insertion:

                Anterior surface of greater trochanter of femur

Action:

                Abduct and medially rotate thigh;

• keep pelvis level when ipsilateral limb is weight-bearing and advance opposite (un supported) side during its swing phase

Nerve supply:

                Superior gluteal nerve

• The two muscles together are constantly called into play as the foot on one side is raised during walking and running, when the muscles on the opposite (supporting) side contract to prevent the pelvis from sagging on the unsupported side
• If they are paralyzed the gait is markedly affected, the trunk swaying from side to side towards the weightbearing limb to prevent downward tilting of the pelvis on the unsupported side.

4. TENSOR FASCIAE LATAE:

Origin:

  Anterior superior iliac spine; anterior part of iliac crest

Insertion:

  Iliotibial tract, which attaches to lateral condyle of tibia

Action:

  Assits gluteus maximus

Nerve supply:

  Superior gluteal nerve

DEEP LAYER

1. PIRIFORMIS: muscle of pelvic wall and gluteal region

Origin:

                Anterior surface of sacrum; sacrotuberous ligament

Insertion:

                Superior border of greater trochanter of femur

• The piriformis leaves the pelvis through the greater sciatic foramen, almost filling it, to reach its attachment to the superior border of the greater trochanter

Action:

                Laterally rotate extended thigh and abduct flexed thigh

Nerve supply:

                Branches of anterior rami of S1, S2

• These muscles form a triciptal muscle which occupies the gap between the piriformis and the quadratus femoris. The common tendon of these muscles lies horizontally in the buttocks as it passes to the greater trochanter of the femur.
• The obturator internus is located partly in the pelvis, where it covers most of the lateral wall of the lesser pelvis. It leaves the pelvis through the lesser sciatic foramen, makes a right-angle turn becomes tendinous, and receives the distal attachments of the gemelli before attaching to the trochanteric fossa of the femur.

4. QUADRATUS FEMORIS:

Origin:

                Lateral border of ischial tuberosity

Insertion:

                Quadrate tubercle on intertrochanteric crest of femur and area inferior to it

Action:

                Laterally rotates thigh; steadies femoral head in acetabulum

Nerve supply:

                Nerve to quadratus femoris (L5, S1)

Clinical Correlates

Gluteus Maximus and Intramuscular Injections

                The gluteus maximus is a large, thick muscle with coarse fasciculi that can be easily separated without damage. The great thickness of this muscle makes it ideal for intramuscular injections. The injection should be given well forward on the upper outer quadrant of the buttock to avoid injury to the underlying sciatic nerve.

• IM injections can also be given safely into the anterolateral part of the thigh, where the needle enters the tensor fasciae latae as it extends distally from the iliac crest and ASIS.

Gluteus Maximus and Bursitis

• Bursitis, or inflammation of a bursa, can be caused by acute or chronic trauma. An inflamed bursa becomes distended with excessive amounts of fluid and can be extremely painful. The bursae associated with the gluteus maximus are prone to inflammation.
• Ischial bursitis is a friction bursitis resulting from excessive friction between the ischial bursae and the ischial tuberosities. Localized pain occurs over the bursa, and the pain increases with movement of the gluteus maximus. Calcification may occur in the bursa with chronic bursitis.

Injury to Superior Gluteal Nerve

• Injury to this nerve results in a characteristic motor loss, resulting in a disabling gluteus medius limp, to compensate for weakened abduction of the thigh by the gluteus medius and minimus, and/or a gluteal gait, a compensatory list of the body to the weakened gluteal side.
• Abduction and Medial rotation of thigh are also impaired

• Normally: When a standing person is asked to lift one foot off the ground and stand on one foot, the gluteus medius and minimus normally contract as soon as the contralateral foot leaves the floor, preventing tipping of the pelvis to the unsupported side
• When a person who has suffered a lesion of the superior gluteal nerve is asked to stand on one leg, the pelvis on the unsupported side descends, indicating that the gluteus medius and minimus on the supported side are weak or non-functional.