Please confirm topic selection

Are you sure you want to trigger topic in your Anconeus AI algorithm?

Please confirm action

You are done for today with this topic.

Would you like to start learning session with this topic items scheduled for future?

Updated: Aug 28 2021

SI Dislocation & Crescent Fractures

Images - AP - crescent fx (wheeless)_moved.jpg axial - crescent fx (wheeless)_moved.jpg
  • Summary
    • Sacroiliac (SI) dislocations and crescent fractures include a spectrum of injuries involving the pelvis which can lead to instability and pelvic malalignment. 
    • Diagnosis requires pelvic radiographs with CT scan.
    • Treatment is generally operative with reduction and fixation of both the anterior and posterior pelvis ring as needed.
  • Epidemiology
    • Spectrum of injuries that include
      • incomplete (Sacroiliac) SI dislocation
        • posterior SI ligaments remain intact
        • rotationally unstable
      • complete SI dislocations
        • posterior SI ligaments ruptured
        • vertically and rotationally unstable
      • SI fracture-dislocation (crescent fracture)
        • iliac wing fracture that enters the SI joint
        • injury to posterior ligaments vary
        • combination of vertical iliac fx and SI dislocation
        • posterior ilium remains attached to sacrum by posterior SI ligaments
        • anterior ilium dislocates from sacrum with internal rotation deformity
        • when ilium fragment remains with sacrum it is termed a crescent fracture
  • Pathophysiology
    • Mechanism of injury
      • lateral compression force
      • usually high energy
    • Pathoanatomy
      • degree of injury to posterior structures determines pelvic stability
      • Iliac wing fractures may be associated with open wounds and may involve bowel entrapment
  • Anatomy
    • Ligaments
      • the SI joint is stabilized by the posterior pelvic ligaments
        • sacrospinous
        • sacrotuberous
        • anterior sacroiliac
        • posterior sacroiliac
    • Nerves
      • the L5 nerve root crosses the sacral ala approximately 2 cm medial to SI joint
    • Blood supply
      • the superior gluteal artery runs across SI joint
      • exits pelvis via greater sciatic notch
  • Classification
    • No classification system specifically for SI injury
      • included in Young- Burgess and Tile classification of pelvic fractures
      • crescent fractures described as LC-2 injury according to Young-Burgess
  • Presentation
    • Symptoms
      • pelvic pain
    • Physical Exam
      • assess hemodynamic status
      • perform detailed neurological exam
      • abdominal assessment to look for distention
      • rectal exam
      • examine urethral meatus for blood
  • Imaging
    • Radiographs
      • recommended views
        • AP pelvis
        • inlet and outlet views
    • CT scan
      • evaluation of sacral fractures
      • posterior pelvis better delineated
  • Treatment
    • Operative
      • immediate skeletal traction
        • indications
          • vertical translation of the hemipelvis
      • anterior ring ORIF
        • indications
          • incomplete SI dislocations with pubic symphyseal diastasis
      • anterior and posterior ring ORIF
        • indications
          • complete SI dislocations
            • vertically unstable require anterior and posterior pelvic ring fixation
      • ORIF of ilium
        • indications
          • crescent fracture
            • required to restore posterior SI ligaments and pelvic stability
  • Techniques
    • Closed Reduction and Percutaneous Fixation
      • positioning
        • intraoperative traction may aid in reduction
        • small midline bump under sacrum may assist with SI screw placement
      • imaging
        • inlet view
          • shows anterior-posterior position of SI joint(s) for screw placement
        • outlet view
          • shows cephalad-caudad position of SI joint(s) for screw placement
        • lateral sacral view
          • ensures safe placement of SI or sacral screws relative to the anterior cortex of the sacral ala and the nerve root tunnel
      • complications
        • L5 nerve root at risk with anterior perforation of iliosacral screw as nerve goes inferiorly over sacral ala
    • ORIF
      • approach
        • anterior approach
          • lateral window with elevation iliacus back to SI joint
        • posterior approach
          • for fixation of crescent fragment to intact ilium
      • fixation
        • plates
        • iliosacral lag screws (SI screws)
  • Complications
    • DVT
      • 35%-50%
    • Neurological injury
    • Loss of reduction and failure of fixation
  • Prognosis
    • Primarily based on accurate and stable reduction of SI joint
1 of 0
1 of 4
Private Note

Attach Treatment Poll
Treatment poll is required to gain more useful feedback from members.
Please enter Question Text
Please enter at least 2 unique options
Please enter at least 2 unique options
Please enter at least 2 unique options