Gluteal region

cutaneous nerves

· buttock supplied by

1. posterior rami

· L1-3 and S1-5

2. anterior rami

· T12-L2 and S2-3

· L3-S1 supplies lower limb

Upper central

· posterior rami

· L1-3 - upper

· S1-5 - natal cleft and skin over coccyx

Lateral skin

· anterior rami

· subcostal n (T12)

· iliohypogastric n (L1)

· lateral FCN (L2)

Lower central skin

· anterior rami

· posterior FCN (S2,3)

gluteal muscles

Gluteus maximus

Origin

· gluteal surface of ilium

· behind posterior gluteal line

· lumbar fascia

· lateral mass of sacrum

· below auricular surface

· sacrotuberous ligament

Path

· enclosed by splitting of fascia lata

· except deep half of lower half

· fibres run at 45^o

Insertion

· deep half of lower half

· gluteal ridge behind greater trochanter

· remainder

· upper end of iliotibial tract

Nerve supply

· inferior gluteal nerve (L5,S1,2)

Gluteus medius

Origin

· gluteal surface of ilium

· between middle and posterior gluteal lines

Path

· lies under gluteus maximus

· free borders lie edge to edge

· bursa between tendon and greater trochanter

Insertion

· lateral surface of greater trochanter

· oblique line

· starts at apex

· slopes downwards and fowards

Nerve supply

· superior gluteal nerve (L4,5,S1)

Gluteus minimus

Origin

· gluteal surface of ilium

· between middle and inferior lines

Path

· under gluteus medius

· anterior borders lie edge-to-edge

Insertion

· anterior surface of greater trochanter

· J-shaped area

Nerve supply

· superior gluteal nerve (L4,5,S1)

deep muscles

Foramina

· greater sciatic notch between

· auricular surface

· ischial spine

· lesser sciatic notch between

· ischial spine

· ischial tuberosity

· 2 ligaments convert notches to foramina

· sacrotuberous ligament

· sacrospinous ligament

Piriformis

Origin

· S2,3,4

Path

· passes laterally behind sacral plexus

· emerges through greater sciatic foramen

· upper border lies alongside GMed

· lower border lies along InfG

Insertion

· inner surface of apex of greater trochanter

Nerve supply

· S1,S2 (segmental)

Obturator internus

Origin

· internal surface of obturator membrane and bony margins

Path

· bursa beneath muscle on wall of pelvis

· makes right-angled bend

· exits lesser sciatic foramen

· gamelli converge with its tendon

· forms tricipital tendon

· upper surface edge-to-edge with piriformis

· lower surface edge-to-edge with quadratus femoris

Insertion

· medial surface of greater trochanter

Nerve supply

· nerve to obturator internus (L5,S1,2)

Gamelli

Origin

· either side of obturator internus

· superior

· ischial spine

· inferior

· ischial tuberosity

Path

· converge with tendon of obturator internus

Insertion

· medial surface of greater trochanter

Nerve supply

· superior

· nerve to obturator internus

· inferior

· nerve to quadratus femoris

Quadratus femoris

Origin

· ischial tuberosity

· below inferior gamellus

Insertion

· posterior femur

· from quadrate tubercle of femur

· to level bisecting lesser trochanter

Nerve supply

· nerve to quadratus femoris (L4,5,S1)

deep neurovascular

Above piriformis

Superior gluteal nerve

· L4,5,S1

· disappears under posterior border of GMed

· runs between and supplies GMed and GMin

· ends in and supplies TFL

Superior gluteal artery

· gives off

1. superficial branch

· to GMax

2. deep branch

· runs between and supplies GMed and GMin

· divides into upper and lower branch

· upper branch to anastomosis at ASIS

· lower branch to trochanteric anastomosis

Below piriformis

· from medial to lateral

Inferior gluteal nerve

· L5,S1,2

· enters and supplies GMax

Inferior gluteal artery

· sends branches to

· trochanteric anastomosis

· cruciate anastomosis

· artery of sciatic nerve

Pudendal nerve

· S2,3,4

· turns forward around sacrospinous ligament

· lies on ischial spine

· re-enters pelvis

· via lesser sciatic foramen

Internal pudendal artery

· follows path of pudendal nerve

· lies on tip of ischial spine

Nerve to obturator internus

· L5,S1,2

· supplies

· obturator internus

· superior gamellus

Sciatic nerve

· L4,5,S1,2,3

· lies on ischium

· 1/3 of way up from ischial tuberosity to PSIS

· passes over

· obturator internus

· quadratus femoris

· lies under GMax

· halfway between greater trochanter and ischial tuberosity

· disappears under biceps femoris

Posterior femoral cutaneous nerve

· S2,3

· lies on sciatic nerve

· passes down midline of back of thigh

· beneath fascia lata

· superficial to hamstrings

· hamstrings separate it from sciatic nerve

· branches

· perforating branches to overlying skin

· recurrent branch to buttock

· perineal branch to perineum

Nerve to quadratus femoris

· L4,5,S1

· lies beneath sciatic nerve

· lies deep to obturator internus and gamelli

· separate it from sciatic nerve

· supplies

· quadratus femoris

· inferior gamellus

Anastomoses

ASIS

· formed by

· ascending branch of LFCA

· ascending branch of superficial gluteal a

· deep circumflex iliac a

· superficial circumflex iliac a

· lumbar branch of iliolumbar artery

Trochanteric

· lies near trochanteric fossa

· formed by

· descending branch of superior gluteal a

· ascendng branch of inferior gluteal a

· ascending branch of MCFA

· ascending branch of LCFA

Cruciate

· lies at middle of lesser trochanter

· formed by

· transverse branch of MCFA

· transverse branch of LCFA

· ascending branch of 1st perforator

· descending branch of inferior gluteal a