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Gluteal region

  • Muscles
    • Gluteus maximus, medius, minimus
    • Piriformis
    • Superior gemellus
    • Obturator internus
    • Inferior gemellus
    • Quadratus femoris
  • Subcutenous tissue
    • Blood supply – superior & inferior gluteal arteries
    • Lymph – lateral group of superficial inguinal lymph nodes
    • Nerves – posterior & anterior rami
  • Posterior Rami
    • 3 lumbar nerves – upper skin of buttock
    • upper 3 sacral – natal cleft
    • lower 2 with coccygeal nerve – skin over coccyx
  • Anterior rami
    • Upper part of lateral skin
    • Lateral cutaneous branches of subcostal & iliohypogastric nerves (T12, L1)
    • Lower part of branch of lateral femoral cutaneous nerve (L2)
    • Lower central part of buttock
    • Perforating cutaneous nerve (S2,3)
    • Branches of posterior femoral cutaneous nerve

Gluteus maximus

Pelvis

  • Largest & most superficial of gluteal muscles
  • Large fibre bundles
  • 3 bursae beneath it – ischial tuberosity, greater trochanter, vastus lateralis
  • Origin
    • Gluteal surface of ilium behind the posterior gluteal line, from lumbar fascia, lateral mass of sacrum below the auricular surface, sacrotuberous ligament
  • Insertion
    • Deep segment (1/4) – gluteal tuberosity
    • ¾ - upper end of iliotibial tract
  • Nerve Supply
    • Inferior gluteal nerve (L5, S12)
    • Only muscle supplied by this nerve
  • Blood supply
    • Superior & inferior gluteal arteries
    • Veins form a plexus beneath the muscle
  • Action
    • Lateral rotation & extension of hip joint
    • Throught the iliotibial tract it supports the extended knee
    • Antigravity muscle
    • Extension of hip joint only in extremes of hip movement

Gluteus medius

  • Posterior 1/3 is covered by maximus
  • Anterior 2/3 is covered by thick deep fascia
  • Brusa – upper part of lateral surface of greater trochanter
  • Origin
    • Gluteal surface of the ilium between the middle & posterior gluteal lines
  • Insertion
    • Lateral surface of greater trochanter
  • Nerve Supply
    • Superior gluteal nerve (L45S1)
  • Action
    • Abduct hip & anterior fibres rotate the thigh medially
  • Test
    • Trendelenburg test

Gluteus minimus

  • Anterior border lies edge to edge with medius from origin to insertion
  • Bursa – medial part of anterior surface of greater trochanter
  • Origin
    • Between middle & inferior lines
  • Insertion
    • Anterior surface of greater trochanter
  • Nerve Supply
    • Superior gluteal nerve (L45S1)
  • Action
    • As for medius

Piriformis

  • Key to arrangement of gluteal region
  • Upper border lies alongside gluteus medius
  • Lower border alongside superior gemellus
  • Origin
    • Front of the middle 3 pieces of sacrum
    • Upper margin of greater sciatic notch
  • Insertion
    • Passes laterally behind sacral plexus to emerge throught greater sciatic foramen
    • Medial surface of upper border of greater trochanter
  • Nerve Supply
    • Anterior rami of S1 & 2
  • Action
    • Adjusting & stabilizing the hip, especially in abduction
  • Surface Markings
    • Lower border – midpoint of line from PSIS (dimple) & tip of coccyx to the tip of greater trochanter

Obturator internus

  • Sciatic nerve passes on its posterior surface
  • Bursa
    • Lesser sciatic notch (hyaline cartilage)
  • Origin
    • Internal surface of lateral wall of pelvis
    • Margins of lesser sciatic notch (superior & inferior gemelli)
  • Insertion
    • Right angle bend around the lesser sciatic notch to enter gluteal region
    • Medial surface of the greater trochanter above the trochanteric fossa
  • Nerve Supply
    • Nerve to obturator internus (L5, S12)
  • Action

Superior gemelli

  • Origin
    • Spine of the ischium
  • Nerve supply
    • Nerve to obturator internus (L5, S12)

Inferior gemelli

  • Origin
    • Ischial tuberosity at the margin of the lesser sciatic notch
  • Nerve Supply
    • Nerve to Quadratus femoris

Quadratus femoris

  • Separated by neck of femur by tendon of obturator externus
  • Above – inferior gemellus
  • Below – adductor magnus
  • Origin
    • Ischial tuberosity
  • Insertion
    • Quadrate tubercle of femur
  • Nerve Supply
    • Nerve to Ouadratus femoris

Greater Sciatic Foramen

  • Above Piriformis
    • Superior Gluteal nerve & vessels
  • Below Piriformis
    • Inferior gluteal nerve & vessels
    • Pudendal nerve & vessels
    • Nerve to obturator internus
    • Sciatic nerve with
      • posterior femoral cutaneous nerve on its surface &
      • nerve to quadratus femoris deep to it

Superior Gluteal Nerve (L45S1)

  • Disappears under gluteus medius & runs forward between medius & minimus supply both of them & tensor fasciae latae
  • No cutaneous distribution

Superior Gluteal Artery

  • Superficial branch
    • Enters deep surface of maximus supplying it & the skin above it
  • Deep branch
    • Passes laterally between medius & minimus & divides into upper & lower branches
      • Upper – anastomosis at ASIS
      • Lower – supplies the medius, minimus, & joins trochanteric anastomosis

Inferior Gluteal Nerve (L5,S12)

  • Gluteus maximum, no cutaneous distribution

Inferior Gluteal Artery

  • Muscular branches – piriformis, obturator internus, gluteus maximus
  • Anastomotic branches – trochanteric & cruciate anastomoses
  • Artery to sciatic nerve
  • Cutaneous branches – buttock & back of thigh

Pudendal nerve (S234)

  • Brief appearance in buttock
  • Turns forward around the back of sacrospinous ligament, passing between sacrotuberous & sacrospinous ligaments (lesser sciatic foramen) to enter the pudendal canal

Internal pudendal artery

  • Similar path to nerve, lying on its lateral side
  • It crosses the tip of the ischial spine, against which it can be comprssed to control arterial bleeding in the perineum

Nerve to obturator internus (L5, S12)

  • More laterally, loops around the base of the ischial spine to pass forward in the side wall of ischianal fossa
  • supplies:
    • ob internus and
    • sup gemellus

Sciatic Nerve (L45S123)

  • More lateral
  • Lies in the ischium over the posterior part of the acetabulm
  • It is in contact with the bone at a point 1/3 up from the ischial tuberosity & PSIS – also surface marking to entry into gluteal region
  • Passes vertically down over the posterior surface of obturator internus & quadratus femoris to the hamstring compartment of the thigh where it is crossed posteriorly by the long head of biceps femoris
  • Surface marking
    • at top of thigh – midway between greater trochanter & ischial tuberosity
  • Note – if tibial & common peroneal components have high division in pelvis, then common peroneal usually pierces piriformis whilst tibial nerve emerges beneath piriformis

Posterior Femoral Cutaneous Nerve (S123)

  • Lies ontop of sciatic nerve
  • May pass down as far as mid calf
  • In thigh, the hamstrings separate it from the sciatic nerve
  • Branches
    • Gluteal branches – convexity of buttock
    • Long perineal branch – winds between gracilis & fascia lata supply posterior part of scrotum/labia majus
    • Pelvic Parasympathetic Nerves – S23 supply pelvic viscera – therefore referred pain from pelvic disease that is similar to sciatica

Nerve to Quadratus Femoris (L45S1)

  • Deep to sciatic nerve
  • Articular branch to hip joint
  • Supplies
    • quadratus femoris
    • inferior gemellus

Trochanteric anstomosis

  • Main supply to head of femur
  • Lies near trochanteric fossa
  • Formed by
    • Descending branch of superior gluteal artery
    • Ascending branch of medial circumflex artery
    • Ascending branch of lateral circumflex artery
    • Inferior gluteal artery

Cruciate anastomosis

  • Located at middle of lesser trochanter, lower border of insertion of quad fem
  • Formed by
    • Transverse branch of medial circumflex femoral artery
    • Transverse branch of lateral circumflex femoral
    • Ascending branch of first perforating artery
    • Descending branch of inferior gluteal artery