Learning Radiology xray montage
Acetabular Protrusio
Protrusio Acetabuli

General Considerations

  • Intrapelvic displacement of the medial acetabular wall
  • Most common cause is osteoarthritis
  • Primary form – Otto pelvis
    • Marked female to male predominance
    • Usually occurs in young to middle-aged
    • Bilateral in 1/3 to 2/3 of patients
    • No underlying causative mechanism is demonstrated
  • Secondary form
    • Rheumatoid arthritis
    • Paget disease
    • Central fracture-dislocation
    • Hip implants
    • Marfan Syndrome
    • Osteomalacia

Clinical Findings

  • May be asymptomatic, or have
  • Limitation of motion
  • Joint stiffness
  • Pain

Imaging Findings

  • Bilateral axial migration of the femoral heads with or without moderate degenerative changes
  • Distance between the acetabulum and the ilioischial line should be >3 mm in males and >6 mm in females in protrusio
  • Femoral head should not project medial to a line joining the inner border of the pelvis and the lateral margin of the obturator foramen


  • Coxa vara and decreased femoral anteversion


  • Depends on age and degree of degenerative changes
  • Medial wall bone grafts
  • Joint replacement surgery may be necessary


Protrusio Acetabuli. CC Dunlop, CW Jones, and N Maffulli. Bulletin, Hospital for Joint DiseasesVolume 62, Numbers 3 & 4 2005