Review Topic
  • Pelvic ring formed from 2 innominate bones  
    • articulate posteriorly with the sacrum and anteriorly through pubis symphysis
  • Each innominate bone is composed of three fused bones: ilium, ischium, and pubis
    • ilium - prominences
      • ASIS 
      • AIIS 
      • PSIS
      • iliopectineal eminence - region union between ilium and pubis
      • sciatic notch
    • ischium
    • pubis
Ligaments & Stability
  • Stability
    • no inherent stability of articulations
    • stability comes from ligament complexes
  • Ligament complexes
    • posterior complex  
      • sacroiliac ligaments
        • posterior stronger than anterior
      • iliolumbar ligaments
        • transverse process of L4/L5 to posterior ilium
    • anterior complex 
      • pubis syphysis
        • fibrocartilaginous disc between innominate bones
    • pelvic floor complex
      • sacrospinous ligament
        • transversely oriented
        • resists external rotation
      • sacrotuberous ligaments
        • longitudinally oriented
        • resists vertical translation
Blood Supply 
  • Abdominal aorta 
    • bifurcates at L4 into common iliac system
      • external iliac artery
        • courses along pelvic brim
        • branches into common femoral artery (distal to inguinal ligament)
      • internal iliac artery
        • divides distal and posterior near the SI joint into
        • posterior division
          • leads to superior guteal artery and other branches
        • anterior division
          • leads to obturator artery
  • Corona mortis 
    • connects iliac and obturator systems
  • Posterior venous plexus
    • injury in pelvic fractures can account for majority of blood loss
  • Lumbosacral plexus 
    • L1-S4 nerve roots
  • Lateral femoral cutanous nerve
    • L2-L3 nerve roots
    • deep to inguinal ligament near ASIS
  • Obturator nerve 
  • Femoral nerve 
  • Sciatic nerve 
  • AP pelvis 
    • standard radiograph for all trauma patients
  • Inlet view 
    • beam perpendicular to the S1 end plate (caudal tilt)
  • Outlet view 
    • cranial tilt
    • demonstrates cranial-caudal displacemnt of the pelvic ring and sacral morphology
  • CT
    • provides excellent detail of bony anatomy and can confirm pelvic ring / acetabular fractures that are not always visible on plain radigraphs.

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