Anatomy of Gluteal Region

Skeletal system: (340)

On lateral aspect of hip bone, have acetabulum– articulates with head of femur.
Three parts of hip bone join at acetabulum. (pubis anteriorly, ischium posteriorly, ilium superiorly)
Sacrotuberous / sacrospinous ligaments form the greater / lesser sciatic foramen.
Ilium has “gluteal lines” which mark separation of gluteal muscles.
Hip bones are part of appendicular skeleton (belong to lower limb).

Femur: Thigh bone (471)

Lower limb has gluteal region (butt), thigh (between hip / knee), leg (knee to ankle) and foot.
Femur:
- Head- fits in acetabulum to form joint. Surface is smooth, has pit called fovea that is not smooth (has small ligament that attaches here and acetabulum).
- Neck- connects head to shaft. Have an “angle of inclination” formed by the neck- is 126 degrees on average. This angle is between long axis of shaft and plane passing between head / kneck. Ranges from 115-140 for normalcy. Angle slightly less in females.

1. - Blood supply to this region is precarious.
  - A fracture to this region may not heal properly (more common in elderly). May fracture this, and it never heals due to inadequate blood supply. May require prosthesis / wheelchair.

- - Angles of stress in femur is on the neck region.

- - Fractures most common in older females.

Shaft

- Proximal end: anterior aspect has greater trochanter
- On posterior aspect, has lesser trochanter.

- Trochanters:
  - Are connected by intertrochanteric crest seen on posterior view.
  - Anterior perspective shows another attachment called intertrochanteric line.
  - Fibrous capsule of hip joint is anchored to these structures (crest and line).
- Anterior aspect of shaft normal
- Posterior aspect of shaft has linea aspera = a ridge of bone
  - At proximal end, have roughened area where ridge ends = gluteal tubercle where some gluteal muscles attach
  - Ridge is for intermuscular septae (deep fascia) attachment which separates muscle compartments. This is deep fascia.
  - Distally as approach knee: split into 2 lines
  - extend to medial / lateral aspect
  - called medial / lateral superchondyle ridges

1. - Distal end- are adjacent to each other in anatomical position.

Proximal leg:

2 bones
- Lateral fibula (more slender)

1. - Does not contribute to knee joint. At proximal end, it articulates with tibia.
  - Is present to provide an osseus attachment for muscles of leg. Does participate in ankle joint. Fractures of fibula are not as serious.

- Medial tibia

1. - Participates in the knee joint.
  - Anteriorly: roughened area beneath epichondyles = tibial tuberosity. This is subcutaneous region just below the knee joint. When are on knees, resting on tibial tuberosity.

- Have interosseus membrane between tibia / fibula in lower limb. There is no rotation as there is in upper limb.

Angles between head and shaft: (moore 5.7)

Normal angle: 135 (moore)
If the angle is less (approaching 90) = coxae varus. Refers to acute angle between head and shaft of femur. Individuals with this are knock-kneed. Knees will interfere with eachother when walking.
If the angle is greater (approaching 160) = coxae valgus. Individuals with this are bow-legged. Cannot get knees together.
Angles do vary with gender and with age.

Soft tissue anatomy of lower limb:

Lower limb begins at iliac crest
Boundary between gluteal region / posterior thigh designated by transverse crease in skin. Deep fascia at this point is fused with dermis of skin (no subcutaneous layer of fat).
Gluteal regions (R and L) are separated by gluteal cleft (separates butt cheeks).

Dermatome pattern:

Superiorly / lateral have L4 at periphery
Going further to cleft, move to S3 and S4.
Dominant for posterior thigh are S1 and S2.

Subcutaneous gluteal region (527)

Upper lateral part of dermatome is lower lumbar nerves
Closer to midline, have sacral nerve terminal branches
Lower edge of gluteus maximus have branches from Posterior cutaneous nerve of the thigh (aka posterior femoral nerve of the thigh).
- This runs with sciatic nerve
- Supplies more skin than any other sensory nerve of the body
Will find no major subcutaneous veins in the posterior thigh / gluteal region.
Deep fascia of gluteal region thigh = Fascia Lata.
- Attaches to iliac crest in upper thigh
- Specialization is iliotibial tract = lateral thickening.
Iliotibial tract (band) (476)
- Is thickening of deep fascia (specialization of fascia lata)
- Distally, it crosses the knee and attaches to bones of leg (primarily tibia, some on fibula)
- Superiorly, it attaches iliac crest.
- This deep fascia serves as attachment / insertion point for muscles.

1. - Tensor fascia lata muscle = puts tension on fascia lata.
  - Gluteus maximus: upper ¾ of fibers insert into iliotibial tract. Lower ¼ fibers attach gluteal tuberosity (upper end of linea aspira)

- - Muscles acting here do not produce movement at knee joint.

- - When knee is in locked position, these muscles create traction to maintain joint in full extension (standing at attention).

Muscles: (477)

Gluteus maximus: forms contour of butt

- Origin is extensive
  - Sacrum
  - Ilium
  - Sacrotuberous ligament
- Superior to gluteus maximus, have fascia lata that extends to iliac crest.
  - Deep to this portion of fascia, have Gluteus medius
  - Thus, gluteus maximus covers the other two gluteal muscles, except for a small portion of gluteus medius at the superior edge of maximus.
  - Intermuscular injection given to gluteal region common. It is not injected into gluteus maximus (called careful area), it is put into G.medius (called care-free area).

1. 1. 1. Many important structures deep to G. maximus
    2. Injection may go through muscle and into many nerves / vessels beneath it.

- Deep to G. maximus (477)
  - G. medius (has G. minimus on its deep surface)
  - G. medius / minimus have similar origin = ala of ilium (external surface).

1. 1. 1. Both attach at greater trochanter
    2. Fiber direction is the same, thus have similar action.

- Actions of gluteal muscles:
  - G. maximus: extension of the hip (back kick).

1. 1. 1. Is not important in walking, only minimally involved in early stages.
    2. Is essential when powerful extension needed- running, stairs, standing from seated position.

- G. Medius / minimus:

1. - Primarily for Abduction of hip joint
  - Raising limb to side (side kick)

- - These are essential to normal gait, but do not abduct hip in walking. On weight bearing side during gait- they stabilize / slightly tip pelvis by contraction to allow free limb to move forward.

- - Paralysis of these muscles: walking still possible, except they have a duck waddle type walk. Their swing phase of walking involves swinging foot outward. Affected side will show “positive Trendelanburg sign” when asked to raise opposite limb (they can’t stand on affected sided limb).

Lateral rotators of the hip joint

- Are muscles inferior to G. medius / minimus
- They turn foot so toes points laterally, rotation is in the hip, not knee or foot
- 6 muscles total (moore 5.24)
  - Piriformis muscle: forms inside the pelvis

1. 1. 1. Origin is pelvic surface of the sacrum (is related to sacral nerve plexus)
    2. Muscle emerges from greater sciatic foramen and attaches to greater trochanter

1. 1. 1. Described as key stone for understanding the region. Superior gluteal nerve / vessels are superior to it. Inferior gluteal nerve / vessels are below (inferior) to it.

1. - Obturator internis:

1. 1. 1. Tendon exits pelvis through lesser sciatic foramen and goes into gluteal region to attach greater trochanter. Tendon makes a 90 degree turn to do this.
    2. Has muscles on either side (superior / inferior) to tendon in gluteal region:

1. - Gemellis (superior / inferior)

1. 1. 1. Superior takes origin from ischial spine and radiates laterally: tendon will join with the tendon of obterator internis. Insertion on greater trochanter.
    2. Inferior takes origin fron ischial tuberosity and radiates laterally where its tendon joints that of obterator internis. Also inserts on greater trochanter.

1. - Quadratus Femoris

1. 1. 1. Thick fleshy muscle extending laterally
    2. Origin from ischial tuberosity

1. 1. 1. Attaches to intertrochantery crest

1. 1. 1. Is the most powerful lateral rotator and most inferior

1. - Obterator Externis

1. 1. 1. Bony origin is from external side of the pubic bone
    2. Tendon extends to attach greater trochanter

1. 1. 1. Is buried beneath the Quadratus Femoris (deep to it)

1. 1. 1. Supplied by obterator nerve

Innervated by “nerve to the muscle” nerves. All branches of the sacral plexus. One exception is obterator externis (gets it form obterator nerve).

Nerves / vessels (484)

Nerves
- All go through greater sciatic foramen from the sacral plexus
- Superior gluteal nerve:

1. - Superior to piriformis
  - Courses laterally and lies between G. medius and G. minimus.

- - Supplies G. medius / minimus, and tensor fascia lata.

- - Has companion Artery / Vein (superior gluteal A/V) with same distribution pattern. Small branch of artery may go to G. maximus.

- Inferior gluteal nerve:

1. - Inferior to piriformis
  - Supplies Gluteus Maximus

- - Also with companion A/V (inferior gluteal A/V)

- Internal pudendal nerve / vessels
- Sciatic nerve:

- - Is really common connective tissue containing two independent nerves
  - They come out of the sacral plexus as two entities (sometimes they aren’t fused-12%)
    1. Tibial nerve
    2. Common fibular nerve