L8.3 Joints of the Hip & Pelvis

Question 1

Lumbosacral

Answer 1

• 2o cartilaginous IV joint (L5/S1) - hyaline on either side, fibrous cartilage in between
  
  • Also have synovial zygopophyseal joints (btw articular facets)
• Sup L5 facet: sagittal
• Inf L5 facet: transition to coronal → entire weight of body stopped here
• Curvature of backbone most prominent here
  
  • Disc wide (ANT), narrow (POS)
• Body weight goes ANT to joint → transferred to head of femur
  
  • Head of trabeculae vertically oriented → most dense ∴ weight bearing
  • Least dense at the neck → most common fracture

Question 2

Lumbosacral ligaments

Answer 2

• Iliolumbar:
  
  • L5 TP → iliac crest
  • Also acts as passive accessory lig to sacroiliac joint
• Lumbosacral lig:
  
  • TP → sacrum

Question 3

Sacroiliac

Answer 3

• Synovial joint (ANT), fibrous syndesmosis (POS)
• Weight bearing
• Btw auricular surfaces of sacrum & ilium

Question 4

Sacroiliac ligaments

Answer 4

• Interosseous lig
  
  • Btw auricle and sacral tuberosity
  • Passive support → stops excessive nutation
• ANT/POS sacraliliac lig (interosseous in between the 2)
• Sacrotuberous: ANT surface of sacrum → ischial tuberosity
• Sacrospinous: INF sacrum → ischial spine
  
  • Both sacro ligs stops excessive nutation & forms foramen

Question 5

Nutation of the pelvis while standing?

Answer 5

• Pelvis is usually slightly tilted forward while standing → pubic symphysis becomes the floor
  
  • ↓pelvic inlet (SUP), ↑pelvic outlet (INF)
  • Promontory of sacrum prone to nutation into cavity due to weight bearing nature

Question 6

What is the reverse keystone concept for the sacroiliac joint?

Answer 6

• (sacrum opposite of a normal keystone)
• Arch (iliac bones) holds the keystone (sacrum) in place
• Sacrum is also wide inferiorly, narrow superiorly
• POS ligs, interosseous lig → pulls iliac bones tgt → stops sacrum from excessive nutation
  
  • Ligs lax during pregnancy

Question 7

Pubic symphysis

Answer 7

• 2o cartilaginous joint
• Fibro disc wider in females
• Works as a ‘tie-beam’ → prevents separation laterally + resisting compressive force via femur

Question 8

Pubic symphysis ligaments

Answer 8

• SUP pubic ligament: across pubic tubercle
• INF Arcuate ligament: Supports at sub-pubic levels
• ANT pubic ligament

Question 9

Sacrococcyxgeal

Answer 9

Apex of sacrum & base of coccyx

Question 10

Sacrococcyxgeal ligaments

Answer 10

ANT/POS sacroccocygeal ligaments

Question 11

Pelvic and lumbosacral fractures

Answer 11

• At pubic symphysis & rami
• Fractured at pars interarticularis
  
  • On 1 side: spondylolysis
  • On both sides: spondylolisthesis (may slide fwd)

Question 12

Hip joint

Answer 12

• Synovial ball & socket
• Btw acetabulum & head of femur
• Margins of capsule:
  
  • ANT intertrochanteric line
  • POS above intertrochanteric crest
    
    • INF exposed
• Vascular synovial membrane within capsule
• Avascular hyaline cartilage covers articular parts

Question 13

Hip Joint ligaments

Answer 13

• Iliofemoral (‘Y’) ligament of Bigelow:
  
  • Stops hyperextension
  • Strongest lig in the body, has 2 branches from bones ∴ a Y shape
• Pubofemoral: Blends with iliofemoral ligament
• Ischiofemoral: Acetabulum (POS) → spirals to ANT surface
  
  • All 3 tighten in hip during internal rotation & extension
    
    • ∴ max stability: slight extension, AB, In rotation
    • Bursae sits in the deficiency

Question 14

Other structures of the hip joint?

Answer 14

• Acetabular labrum
• Acetabular notch: transverse acetabular ligament spans length of notch
• Fat pads, in the centre of acetabular fossa
• Bursae: Psoas (ANT), trochanteric (POS)
• Ligamentum teres: sits in fovea → attach to labrum

Question 15

Hip joint dislocations & fractures

Answer 15

• POS (more common): Hip flexed, add, in rotated (lady cross leg)
• ANT (not common): Extend, ab, ex rotated
• Congenital dislocation: baby bound too tightly, epiphysis not fused yet
• Fractures: Neck of femur → ↓trabeculae, endangers sciatic N

Question 16

Hip movement and muscles involved

Answer 16