Week 7 Pelvis, Gluteal Region, and Hip

boundaries of gluteal region

iliac crest, intergluteal cleft, gluteal fold

bony pelvis

consists of sacrum, coxa, coccyx

Coxa

• consists of the ilium, ishium, and pubis

  • not fully fused until 20-25 yo

ilium 

• largest part, forms superior acetabulum 

• medial portions thick for weight bearing, thin ala for muscle attachment 

• iliac crest for muscle attachment and protection 

• anterior, posterior and inferior gluteal lines 

• auricular surface (medial, below PSIS)

ischium

• forms postero-inferior border of acetabulum

• ischiopubic ramus defines boundary of obturator foramen

• ischial spine on posterior between greater and less sciatic notch

• ischial tuberosity on posterior surface underneath spine, provides WB support when sitting

pubis

• forms anteromedial border of acetabulum

• attachment site for medial thigh muscles

• comprised of body and superior/inferior rami; articulates at pubic symphysis

• forms pubic crest for abdominal muscle attachment

sacrum 

• formed by 5 fused sacral vertebrae 

• sacral canal which houses cauda equina and 4 pairs of sacral foramina for spinal nerve exit 

• base formed by S1, surrounded by sacral promontory 

• articulates with L5 vertebra at lumbosacral angle (130-160 degrees)

• sacral cornua: bump on either side of sacral hiatus (bottom opening)

• lateral surface with auricular shape for articulation with ilium at sacroiliac joint, covered with hyaline cartilage 

coccyx 

• composed of 4 fused coccygeal vertebrae 

• rep remnants of embryonic tail 

• first vertebra may remain separate with cornua that articulates with sacral cornua 

• can fuse further with age, results in beak like shape 

posterior sacro-iliac ligament

spans from the posterior surface of the sacrum to the sacrotuberous ligament

sacrotuberous ligament

spans from the posterior sacroiliac ligament to the ischial tuberosity

greater sciatic foramen borders

supero-inferior: greater sciatic notch

medial: sacrum

inferior: sacrospinous ligament

structures that pass through the greater sciatic foramen 

sciatic nerve, pudendal nerve, nerve to quadratus femoris, nerve to obturator internus, posterior cutaneous nerve of the thigh, superior and inferior gluteal nerves and arteries 

lesser sciatic foramen borders

lateral: lesser sciatic notch

superior: sacrospinous ligament

inferiomedial: sacrotuberous ligament

structures that pass through the lesser sciatic foramen

pudendal nerve, obturator internus, nerve to obturator internus

sacrospinous ligament

spans from posterior sacrum to the ischial spine

pelvic girdle

• formed by sacrum, left and right hip bones, connects to axial skeleton and supports abdomen, pelvis, perineum

• functions in weight transmission by transmitting weight from vertebral column to the femurs via hip joints

hip region 

over the greater trochanter and extends to the ASIS 

Hip/Acetabulofemoral/Coxofemoral Joint

• strong, multiaxial ball and socket

• 2nd most moveable joint

• weight transmission

• femoral head in acetabulum, most of head covered by articular cartilage except for small fovea that has a ligament that houses artery to supply blood to hip joint

acetabular labrum

deepens the acetabulum by 10%

transverse acetabular ligament

bridges the notch of the acetabular articular area

optimal congruence vs mobility 

though optimal congruence of the hip is at 90 degrees flexion, 5 degrees abduction, and laterally rotated 10 degrees, and upright mobility sacrifices some stability, it is still highly stable bc of the deep socket, joint capsule, and muscular attachments 

important features of the proximal femur

• head, neck, greater trochanter, lesser trochanter, intertrochanteric line, intertrochanteric crest, gluteal tuberosity (posterior, below intertrochanteric crest)

hip joint capsule

comprised of an outer fibrous later and an inner synovial membrane, fibrous layer attaches to acetabulum and femoral neck at intertrochanteric line, contains spiraling fibers and orbicular zone around neck

iliofemoral ligament 

y shaped, prevents hyperextension, and anchors femoral head 

pubofemoral ligament

arises from the pubic bone, prevents over-abduction, tightens during extension/abduction

ishiofemoral ligament

weakest, spirals from ischium to femoral neck, tightens during flexion, internal rotation (adduction probably?)

stabilizing forces on the hip joint

ligaments and medial rotators

synovial membrane of hip joint 

lines inner surfaces, contains retinacula with blood vessels 

ligament of the head of the femur

conducts a small artery, minor role in joint strength

fat pad

located in acetabular fossa, accommodates joint movement, cushions

abduction vs adduction

abduction more extensive, with approx 60 degrees possible

superficial layer of gluteal region 

gluteus maximus, medius, minimis, tensor fascia latae 

attachment of superficial gluteal muscles 

external surface of ilium 

deep layer of gluteal region 

piriformis, obturator internus, superior gemelus, inferior gemelus, quadratus femors 

action and attachment of deep layer

lateral rotation of thigh and stabilization of hip, near the intertrochanteric crest of the femur

gluteus maximus

O: ilium posterior to posterior gluteal line; dorsal surface of sacrum and coccyx, sacrotuberous ligament

I: iliotibial tract, which inserts into lateral condyle of tibia, some fibers on gluteal tuberosity

Inn: inferior gluteal n (L5, S1, S2)

A: extends hip joint, and assists in lateral rotation, fixes hip and assists in rising from sitting position

gluteus medius 

O: external surface of ilium between anterior and posterior gluteal lines 

I: lateral surface of greater trochanteric line 

Inn: superior gluteal. n (L5, S1)

A: abducts and medially rotate hip; keep pelvis level when ipsilateral limb is WB and advance opposite side during its swing phase 

gluteus minimus

O: external surface of ilium between anterior and inferior gluteal lines

I: anterior surface of greater trochanter of femur

Inn: superior gluteal n (L5, S1)

A: abduct and medially rotate hip, keep pelvis level when ipsilateral limb is WB and advance opposite side during its swing phase 

tensor fascia latae

O: anterior superior iliac spine, anterior part of iliac crest

I: iliotibial tract, which attaches to lateral condyle of tibia

Inn: superior gluteal n (L5, S1)

A:  abducts and medially rotates hip joint, keeps pelvis level when ispilateral limb is WB and advance opposite side during swing phase

piriformis

O: anterior surface of sacrum, sacrotuberous ligmment

I: superior border of greater trochanter of femur

Inn: branches to anterior rami of S1 and S2 (nerve to piriformis)

A: laterally rotates the extended hip and abduct hip when flexed, stabilize hip joint

obturator internus

O: pelvic surface of obturator membrane and surrounding bones

I: medial surface of greater trochanter of femur

Inn: nerve to obturator internus (L5, S1)

A:  laterally rotate the extended hip and abduct hip joint when flexed, stabilize hip joint

superior and inferior gemeli

O: superior: ischial spine, inferior: ischial tuberosity

I: trochanteric fossa

Inn: superior: nerve to obturator internus, inferior: nerve to quadratus femoris

A: laterally rotate the extended hip and abduct the flexed hip, stabilize hip joint

quadratus femoris

O: lateral border of ischial tuberosity

I: quadrate tubercle of intertrochanteric crest of femur and area inferior to it

Inn: nerve to quadratus femoris (L5, S1)

A:  lateral rotation of extended hip, abduction of flexed hip, stabilization of joint

trochanteric bursa

largest bursa, located between the greater trochanter and gluteus maximus, present at birth

ischial bursa

separates the inferior gluteus maximus and ischial tuberosity, often absent

gluteofemoral bursa

located between IT tract and vastus lateralis attachment, helps facilitate movement

arterial supply of the gluteal region 

abdominal aorta branches into the R and L common iliac arteries, which branches at the the start of gluteal supply to the R and L internal iliac artery and external iliac arteries. The internal iliac branches into the superior and inferior gluteal arteries, and lower the pudendal artery, the external iliac continues as the femoral artery 

superior gluteal artery

branch from the internal iliac artery, enters through the greater sciatic foramen, superficial branch passes onto deep surface of gluteus maximus, deep branch travels between medius and minimus

inferior gluteal artery

branches from internal iliac artery, enters through greater sciatic foramen, supplies (inferior) gluteus maximus, piriformis, and quadratus femoris, anastomoses with SGA

medial and lateral circumflex femoral arteries 

supply the hip joint, as branches of the profunda femoris or the femoral artery itself 

artery to the head of the femur

variable sized branch from the obturator artery, supplies the head of the femur (aka acetabular branch)

retinacular arteries

along with the circumflex femoral arteries are the primary blood supply of the hip joint, though medial CFA provides more blood and these are fewer and smaller and penetrate the iliofemoral ligament

superior and inferior gluteal veins 

accompany the corresponding SGA and IGA, connect with femoral vein for alternative blood return routes from the lower limb 

internal pudendal vein

drain blood from external genitalia, forms a single vein that enters internal iliac vein

perforating veins

drain blood from posterior thigh into profunda femoris vein, communicate with popliteal vein and inferior gluteal vein

deep buttock lymph

follows vessels to superior/inferior gluteal lymph nodes , then to iliac and lateral lumbar nodes

superficial lymph 

from gluteal region/thigh enters superifical inguinal lymph nodes, sending efferent vessels to external iliac nodes 

anteriomedial aspect of lower limb

most arterial blood and venous drainange occurs on this aspect because well protected (flexor muscles are more protected)

sacral plexus

general innervation of the gluteal region, gives rise to key nerves in the region: superior and inferior gluteal nerves, pudendal nerve, sciatic nerve

only superfical nerve from the sacral plexus

pudendal nerve

superior gluteal nerve 

located between the gluteal medius and gluteus minimus, travels alongside the deep branch of the superior gluteal artery, divides into two branches: superior branch to gluteus medius, inferior to gluteus medius, minimus, and tensor fascia latae 

inferior gluteal nerve

innervates gluteus maximus, exits the pelvis underneath piriformis

sciatic nerve

largest nerve in the body, supplies posterior thigh, leg, and foot muscles, branching into tibial and common fibular nerves

nerve to quadratus femoris

• exits the pelvis in front of the sciatic nerve and obturator internus

• passes over the posterior surface of the hip joint

• provides an articular branch to the hip joint

• innervates the inferior gemellus muscles and quadratus femoris

posterior cutaneous nerve of the thigh

• supplies sensation to the perineum, inferior buttocks, posterior thigh, and proximal leg, lies deep to fascia lata

pudendal nerve

• exits the pelvis through the greater sciatic foramen

• enters the perineum via the lesser sciatic foramen

• supplies perineal structres

• does not supply gluteal region or posterior thigh

nerve to obturator internus 

• arises from L5- S2, innervates superior gemellus and obterator internus, enters perineum 

clunial nerves

superior, middle, and inferior clunial nerves innervate the gluteal skin

femoral nerve

hip flexors innervation

nerve to obturator internus, nerve to quadratus femoris, nerve to piriformis, IGN

hip lateral rotators innervation, SGN just to gluteus maximus  

superior gluteal nerve

hip abductors innervation

iliac tubercle

can be palpated 5-6 cm posterior to ASIS, marks the widest point of the crest at the L5 vertebral level

surface anatomy of pubic bones and symphysis 

located one hand’s width below the umbilicus, pubic tubercle is 2 cm from the symphysis

femoral head surface anatomy 

a thumb’s breadth below the midpoint of the inguinal ligament 

greater trochanter surface anatomy

palpable 10 cm below the iliac crest on the lateral thigh, indicates pelvis width

highest points of iliac crest

L4-L5

PSIS surface anatomy

located at posterior ends of iliac crest, about 3.75 cm from midline, indicated by skin dimples