Proximal and medial migration of femoral head through the medial acetabular wall, defined radiologically as migration medial to kohler’s line

Clinical image

Radiographic appearance of protrusio acetabuli. Source: Wikimedia Commons — Fernando Ruiz Santiago et al.; CC BY 4.0. Image binary is embedded locally in this package; original source and licence are retained.

Key points

Hirst

• 5mm

• 10mm

• 15mm

• or CE angle >40 degree

Aethiology

• Decreased bone density
  • OI
  • Osteomalasia
  • Osteoporosis
  • Rheumatoid
  • Marfan
  • A Spondylitis
• Normal density
  • Otto
  • OA
• Increased density
  • Paget

Management

• Exclude causes
• Xray
• CT for bone defect
• MR arthrogram if preservation planned

Preservation

• Valgus ITO and triradiate closure: young
• Periacetabular osteotomy

Principles of THA

• Assess bone defect
• Template
• Sciatic nerve is closer to hip
• Difficult dislocation
• Bone graft the floor and lateralise the cup, use uncemented THA
• Baghdadi et al, 90% 15 year survival